Publications by authors named "Ravi Naidu"

363 Publications

Applying Raman imaging to capture and identify microplastics and nanoplastics in the garden.

J Hazard Mater 2021 Nov 19:127788. Epub 2021 Nov 19.

Global Centre for Environmental Remediation (GCER), University of Newcastle, Callaghan, NSW 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE), University of Newcastle, Callaghan, NSW 2308, Australia. Electronic address:

The characterisation of microplastics is still a challenge, and the challenge is even greater for nanoplastics, of which we only have a limited knowledge so far. Herewith we employ Raman imaging to directly visualise microplastics and nanoplastics which are released from the trimmer lines during lawn mowing. The signal-noise ratio of Raman imaging is significantly increased by generating an image from hundreds or thousands of Raman spectra, rather than from a single spectrum, and is further increased by combining with the logic-based and PCA-based algorithms. The increased signal-noise ratio enables us to capture and identify microplastics and particularly nanoplastics, including plastic fragments or shreds (with diameters / widths of 80 nm - 3 µm) and nanoparticles (with diameters of < 1000 nm) that are released during the mimicked mowing process. Using Raman imaging, we estimate that thousands of microplastics (0.1-5 mm), and billions of nanoplastics (< 1000 nm), are released per minute when a line trimmer is used to mow lawn. Overall, Raman imaging provides effective characterisation of the microplastics and is particularly suitable for nanoplastics.
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http://dx.doi.org/10.1016/j.jhazmat.2021.127788DOI Listing
November 2021

Desorption and Migration Behavior of Beryllium from Contaminated Soils: Insights for Risk-Based Management.

ACS Omega 2021 Nov 2;6(45):30686-30697. Epub 2021 Nov 2.

Global Centre for Environmental Remediation (GCER), College of Engineering, Science and Environment; The University of Newcastle (UoN), University Drive, Callaghan Campus, Callaghan, New South Wales 2308, Australia.

Factors influencing the desorption, distribution, and vertical migration behavior of Be in contaminated soils are not fully understood. This study examined the desorption and migration of Be in a soil profile from a legacy radioactive waste disposal site using different batch leaching [monofilled waste extraction procedure (MWEP); synthetic precipitation leaching procedure (SPLP); simulated acid rain solution (SARS); and toxicity characteristic leaching procedure] and sequential leaching [community bureau of reference (BCR)] methods for insights relevant to the application of risk-based management. The results showed that Be desorption was higher in the presence of organic than the inorganic leachate composition (MWEP < SPLP < SARS < TCLP < BCR first-step). The desorption followed three diffusion control mechanisms, which resulted in three desorption rate constant estimates of 157, 87.1, and 40.4 Be/kg.h, and the estimated desorption maximum was 556 μg/kg. The desorption process was, spontaneous (Δ > 0), enthalpically and entropically influenced. Increasing the incubation period and heat treatment resulted in a decrease of Be desorption and migration. The soil clay content and pH were the primary factors influencing Be desorption, and the results suggested that Be was desorbed from metal oxyhydroxides and surfaces of silicates (e.g., reactive surfaces of clay minerals), organic matters, and soil pores. Because of high values, the mobility of Be was limited, and no exceedances of ecological or human health risk index or guidelines were determined for the current contamination levels at the site. However, Be released from the waste trenches has the ongoing potential to increase Be concentration in the soil.
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http://dx.doi.org/10.1021/acsomega.1c04572DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8600622PMC
November 2021

Dietary heavy metal(loid)s exposure and prevalence of chronic kidney disease of unknown aetiology (CKDu) in Sri Lanka.

Environ Geochem Health 2021 Oct 29. Epub 2021 Oct 29.

Global Centre for Environmental Remediation, The University of Newcastle, Callaghan, 2308, Australia.

Intake of heavy metals and metalloids through the diet is posing a big research challenge in Sri Lanka due to the increasing occurrence of chronic kidney disease of unknown aetiology (CKDu) among the farming communities pursuing their livelihoods in the North Central Province (NCP). Duplicated diet studies were conducted on a sample of 62 individuals comprising adult males, adult females, boys, and girls who were selected following a demographic survey in an area of the NCP where there was a high incidence of CKDu. A health risk assessment was made by analysing the heavy metal(loid)s content in the diet samples, by means of inductively coupled plasma mass spectrometry. Rice and vegetables constituted the main diet in the CKDu prevalent areas, with all gender and age categories adhering to similar daily diet patterns. Results of the heavy metal(loid) analysis of duplicated food intake samples indicated that the amounts of Pb in rice, As and Pb in vegetables, and Cd in fish exceeded the recommended daily limits. Because consumption of rice was much higher than the other food items, the estimated daily intake of Pb exceeded the permissible daily intake of 3.5 µg/kg/day. There were no significant differences between the age and gender categories in respect of estimated daily intake of Pb, which suggested that the entire population of the study area faced the risk of a high level of Pb exposure. Further, the hazard quotient of Pb was greater than 1. Influence of heavy metal(loid)s on the prevalence of CKDu cannot be understated, and as such interventions are required as a matter of urgency to reduce the local population's dietary exposure to heavy metal(loid)s.
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http://dx.doi.org/10.1007/s10653-021-01144-1DOI Listing
October 2021

Raman imaging and MALDI-MS towards identification of microplastics generated when using stationery markers.

J Hazard Mater 2021 Oct 9;424(Pt B):127478. Epub 2021 Oct 9.

Global Centre for Environmental Remediation (GCER), University of Newcastle, Callaghan, NSW 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE), University of Newcastle, Callaghan, NSW 2308, Australia. Electronic address:

The characterisation of microplastics is still a challenge, particularly when the sample is a mixture with a complex background, such as an ink mark on paper. To address this challenge, we developed and compared two approaches, (i) Raman imaging, combined with logic-based and principal component analysis (PCA)-based algorithms, and (ii) matrix-assisted laser desorption/ionisation-mass spectrometry (MALDI-MS). We found that, accordingly, (i) if the Raman signal of plastics is identifiable and not completely shielded by the background, Raman imaging can extract the plastic signals and visualise their distribution directly, with the help of a logic-based or PCA-based algorithm, via the "fingerprint" spectrum; (ii) when the Raman signal is shielded and masked by the background, MALDI-MS can effectively capture and identify the plastic polymer, via the "barcode" of the mass spectrum linked with the monomer. Overall, both Raman imaging and MALDI-MS have benefits and limitations for microplastic analysis; if accessible, the combined use of these two techniques is generally recommended, especially when assessing samples with strong background interference.
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http://dx.doi.org/10.1016/j.jhazmat.2021.127478DOI Listing
October 2021

Facile one pot preparation of magnetic chitosan-palygorskite nanocomposite for efficient removal of lead from water.

J Colloid Interface Sci 2021 Sep 22;608(Pt 1):575-587. Epub 2021 Sep 22.

Global Centre for Environmental Remediation, The University of Newcastle, Callaghan, NSW 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment, ATC Building, Callaghan, NSW 2308, Australia.

Development of polymeric magnetic adsorbents is a promising approach to obtain efficient treatment of contaminated water. However, the synthesis of magnetic composites involving multiple components frequently involves tedious preparation steps. In the present study, a magnetic chitosan-palygorskite (MCP) nanocomposite was prepared through a straight-forward one pot synthesis approach to evaluate its lead (Pb) removal capacity from aqueous solution. The nano-architectural and physicochemical properties of the newly-developed MCP composite were described via micro- and nano-morphological analyses, and crystallinity, surface porosity and magnetic susceptibility measurements. The MCP nanocomposite was capable to remove up to 58.5 mg Pb g of MCP from water with a good agreement of experimental data to the Langmuir isotherm model (R = 0.98). The Pb adsorption process on MCP was a multistep diffusion-controlled phenomenon evidenced by the well-fitting of kinetic adsorption data to the intra-particle diffusion model (R = 0.96). Thermodynamic analysis suggested that the adsorption process at low Pb concentration was controlled by chemisorption, whereas that at high Pb concentration was dominated by physical adsorption. X-ray photoelectron and Fourier transform infrared spectroscopy results suggested that the Pb adsorption on MCP was governed by surface complexation and chemical reduction mechanisms. During regeneration, the MCP retained 82% Pb adsorption capacity following four adsorption-desorption cycles with ease to recover the adsorbent using its strong magnetic property. These findings highlight the enhanced structural properties of the easily-prepared nanocomposite which holds outstanding potential to be used as an inexpensive and green adsorbent for remediating Pb contaminated water.
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http://dx.doi.org/10.1016/j.jcis.2021.09.109DOI Listing
September 2021

Photodegradation of modified petroleum impregnated bentonite mulch under the effects of solar radiation simulating the outdoor condition.

Environ Sci Pollut Res Int 2021 Oct 7. Epub 2021 Oct 7.

Global Centre for Environmental Remediation, Research and Innovation Division, University of Newcastle, Callaghan, NSW, 2308, Australia.

The objectives of this study were investigating the photodegradation of the polycyclic aromatic hydrocarbons (PAHs) in modified petroleum impregnated bentonite mulch through solar radiation, determining PAHs' translocation in the soils that underlay the mulch and finding a solution to prevent the uncontrolled release of petroleum into the environment. For this research, various formulated mulches were prepared: mulch no. 1 was a mixture of 5:1 sandy soil: natural bentonite + petroleum; mulch no. 2 composed a mixture of 5:1 sandy soil: modified bentonite + natural bentonite + petroleum; and mulch no. 3 composed a mixture of 5:1:0.5 ratio of sandy soil: natural bentonite: modified bentonite mixed with petroleum at a ratio of 1:1. PAHs in surface mulches and subsurface sandy soil were monitored over 5, 20, 40 and 80 days. The results demonstrated that PAHs undergo numerous changes over time because of sunlight. Photodegradation is the most dominant process for low molecular weight (LMW) PAHs (≤ 3 fused aromatic rings) and high molecular weight (HMW) PAHs (≥ 4 fused aromatic rings). HMW PAHs could be sequestrated strongly within the soil particles because of their higher aromaticity and lower polarity; they were more resilient in the soil matrices than LMW PAHs. Mulch no. 2 retained more PAHs compounds (p > 95%) than mulch nos. 1 and 3, which could be attributed to the retention of numerous PAHs in its interlayers, preventing its movement into the underlying soil, environment and atmosphere.
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http://dx.doi.org/10.1007/s11356-021-16714-0DOI Listing
October 2021

Minimizing hazardous impact of food waste in a circular economy - Advances in resource recovery through green strategies.

J Hazard Mater 2021 08 19;416:126154. Epub 2021 May 19.

Biorefining and Advanced Materials Research Center, Scotland's Rural College (SRUC), Kings Buildings, West Mains Road, Edinburgh EH9 3JG, UK; Center for Safe and Improved Food, Scotland's Rural College (SRUC), Kings Buildings, West Mains Road, Edinburgh EH9 3JG, UK. Electronic address:

Recent trends in food waste and its management have increasingly started to focus on treating it as a reusable resource. The hazardous impact of food waste such as the release of greenhouse gases, deterioration of water quality and contamination of land areas are a major threat posed by food waste. Under the circular economy principles, food waste can be used as a sustainable supply of high-value energy, fuel, and nutrients through green techniques such as anaerobic digestion, co-digestion, composting, enzymatic treatment, ultrasonic, hydrothermal carbonization. Recent advances made in anaerobic co-digestion are helping in tackling dual or even multiple waste streams at once with better product yields. Integrated approaches that employ pre-processing the food waste to remove obstacles such as volatile fractions, oils and other inhibitory components from the feedstock to enhance their bioconversion to reduce sugars. Research efforts are also progressing in optimizing the operational parameters such as temperature, pressure, pH and residence time to enhance further the output of products such as methane, hydrogen and other platform chemicals such as lactic acid, succinic acid and formic acid. This review brings together some of the recent progress made in the green strategies towards food waste valorization.
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http://dx.doi.org/10.1016/j.jhazmat.2021.126154DOI Listing
August 2021

Predicting the thresholds of metals with limited toxicity data with invertebrates in standard soils using quantitative ion character-activity relationships (QICAR).

J Hazard Mater 2022 Feb 21;423(Pt A):126982. Epub 2021 Aug 21.

Global Centre for Environmental Remediation, The University of Newcastle, Callaghan, NSW 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE), Callaghan, NSW 2308, Australia.

Terrestrial invertebrates are often used as indicator organisms in ecological risk assessments. However, determining the risk of metals to invertebrates is laborious and time-consuming due to the lengthy testing and ethical approval procedures. In this study, a review of the literature was conducted to provide toxicity data for two standard soils (OECD and LUFA 2.2). An attempt was made to establish models for predicting the toxicity of elements to invertebrates using quantitative ion character-activity relationships (QICARs). In OECD soil, the element toxicity of four groups (Enchytraeus albidus mortality and reproduction, Folsomia candida and Eisenia fetida reproduction) showed significant correlations with atomic number, atomic mass and atomic ionization potential (0.852 ≤ R ≤ 0.989, P < 0.05). For LUFA 2.2 soil, polarization force parameters and boiling point were most significant parameters for toxicity values of F. candida and Enchytraeus crypticus, respectively (0.866 ≤ R ≤ 0.962, P < 0.05). Finally, QICAR models were established, and LC or EC of elements were predicted. Then, models were verified using standard and natural soils, and showed that errors between observed and predicted logLC/EC were mostly < 0.5 orders of magnitude. Thus, the developed QICAR models have potential for predicting the toxicity of elements for soils.
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http://dx.doi.org/10.1016/j.jhazmat.2021.126982DOI Listing
February 2022

Spatial distribution, partitioning, ecological risk and source apportionment of potential toxic elements in water and sediments of the Hoor Al-Azim wetland and their bioaccumulation in selected commercial fish species.

Mar Pollut Bull 2021 Nov 25;172:112875. Epub 2021 Aug 25.

Khuzestan Environmental Protection Office, Khuzestan, Iran.

The potentially toxic elements (PTEs) concentrations in water and sediments were measured in the Hoor Al-Azim wetland to evaluate the spatial distribution, pollution rate, fate, partitioning, and ecological risk and also to recognize the PTEs sources in sediments using MLR-APCs (multiple linear regression-absolute principal component scores) receptor model. The human health risk was investigated based on the seven fish species consumed in the study area. Based on the results, water and sediment contamination was observed at some stations in the southern part of the wetland where agricultural water drains. Also, the sediments of oil well drilling disposal site was polluted by PTEs. Based on the MLR-APCs model, 80.8% of Mo and 81.5% of Se originated from agricultural source. Total target hazard quotients (TTHQ) values suggested that the children could experience adverse health effects due to consumption of Coptodon zillii, Aspius vorax, Carassius auratus and Carasobarbus luteus.
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http://dx.doi.org/10.1016/j.marpolbul.2021.112875DOI Listing
November 2021

Mechanistic insights of hexavalent chromium remediation by halloysite-supported copper nanoclusters.

J Hazard Mater 2022 01 4;421:126812. Epub 2021 Aug 4.

Global Centre for Environmental Remediation (GCER), College of Engineering, Science and Environment, The University of Newcastle, Callaghan, NSW 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE), The University of Newcastle, Callaghan, NSW 2308, Australia. Electronic address:

Chromium (Cr) pollution is a significant environmental concern with remediation challenge. Hexavalent chromium (Cr(VI)) is more toxic than trivalent chromium (Cr(III)) due to its mutagenicity and oncogenicity. In this investigation, a multi-functional material, copper nanoclusters (CuNCs)-halloysite nanotubes (HNT) composite ([email protected]), has been synthesised in an eco-friendly manner and utilised for Cr(VI) remediation. Advanced analytical tools confirmed the seeding of ultra-fine CuNCs onto HNT surfaces. The maximum adsorption capacity of [email protected] is 79.14 ± 6.99 mg/g at pH 5 ± 0.1 with an increment at lower pHs. This performance was comparable for real surface stream water as well as other reported materials. The pseudo-second-order kinetic-, intra-particle diffusion- and Freundlich isotherm models well fit the experimental data implying that the chemisorption, multiphase diffusion and multi-molecular layer distribution occurred during adsorption. The Fourier-transform infrared and the x-ray photoelectron spectra also ensured the transformation of Cr(VI) to Cr(III) indicating the material's suitability for concurrent adsorption and reduction of Cr(VI). While coexisting cations and anions did not overwhelm this adsorption, [email protected] was regenerated and reused five successive times in adsorption-desorption cycles without significant loss of adsorption capacity and material's integrity. Therefore, this multi-functional, biocompatible, low-cost and stable [email protected] composite may have practical application for similar toxic metals remediation.
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http://dx.doi.org/10.1016/j.jhazmat.2021.126812DOI Listing
January 2022

Impact of Nitrate and Ammonium Concentrations on Co-Culturing of Tetradesmus obliquus IS2 with Variovorax paradoxus IS1 as Revealed by Phenotypic Responses.

Microb Ecol 2021 Aug 7. Epub 2021 Aug 7.

Global Centre for, Environmental Remediation (GCER), School of Engineering, Science and Environment, The University of Newcastle, ATC Building, University Drive, NSW, 2308, Callaghan, Australia.

Mutual interactions in co-cultures of microalgae and bacteria are well known for establishing consortia and nutrient uptake in aquatic habitats, but the phenotypic changes in terms of morphological, physiological, and biochemical attributes that drive these interactions have not been clearly understood. In this novel study, we demonstrated the phenotypic response in a co-culture involving a microalga, Tetradesmus obliquus IS2, and a bacterium, Variovorax paradoxus IS1, grown with varying concentrations of two inorganic nitrogen sources. Modified Bold's basal medium was supplemented with five ratios (%) of NO-N:NH-N (100:0, 75:25, 50:50, 25:75, and 0:100), and by maintaining N:P Redfield ratio of 16:1. The observed morphological changes in microalga included an increase in granularity and a broad range of cell sizes under the influence of increased ammonium levels. Co-culturing in presence of NO-N alone or combination with NH-N up to equimolar concentrations resulted in complete nitrogen uptake, increased growth in both the microbial strains, and enhanced accumulation of carbohydrates, proteins, and lipids. Total chlorophyll content in microalga was also significantly higher when it was grown as a co-culture with NO-N and NH-N up to a ratio of 50:50. Significant upregulation in the synthesis of amino acids and sugars and downregulation of organic acids were evident with higher ammonium uptake in the co-culture, indicating the regulation of carbon and nitrogen assimilation pathways and energy synthesis. Our data suggest that the co-culture of strains IS1 and IS2 could be exploited for effluent treatment by considering the concentrations of inorganic sources, particularly ammonium, in the wastewaters.
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http://dx.doi.org/10.1007/s00248-021-01832-6DOI Listing
August 2021

Identification and visualisation of microplastics via PCA to decode Raman spectrum matrix towards imaging.

Chemosphere 2022 Jan 30;286(Pt 2):131736. Epub 2021 Jul 30.

Global Centre for Environmental Remediation (GCER), University of Newcastle, Callaghan, NSW, 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE), University of Newcastle, Callaghan, NSW, 2308, Australia.

To visualise microplastics and nanoplastics via Raman imaging, we need to scan the sample surface over a pixel array to collect Raman spectra as a matrix. The challenge is how to decode this spectrum matrix to map accurate and meaningful Raman images. This study compares two decoding approaches. The first approach is used when the sample contains several known types of microplastics whose standard spectra are available. We can map the Raman intensity at selected characteristic peaks as images. In order to increase the image certainty, we employ a logic-based algorithm to merge several images that are simultaneously mapped at several characteristic peaks to one image. However, the rest of the signals other than the selected peaks are ignored, meaning a low signal-noise ratio. The second approach for decoding is used when samples are complicated and standard spectra are not available. We employ principal component analysis (PCA) to decode the spectrum matrix. By selecting principal components (PC) and generating PC score curves to mimic the Raman spectrum, we can justify and assign the suspected items to microplastics and other materials. By mapping the PC loadings as images, microplastics and other materials can be simultaneously visualised. We analyse a sample containing two known microplastics to validate the effectiveness of the PCA-based algorithm. We then apply this method to analyse "unknown" microplastics printed on paper to extract Raman spectra from the complicated background and individually assign the images to paper fabric/additive, black carbon and microplastics, etc. Overall, the PCA-based algorithm shows some advantages and suggests a further step to decode Raman spectrum matrices towards machine learning.
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http://dx.doi.org/10.1016/j.chemosphere.2021.131736DOI Listing
January 2022

Beryllium in contaminated soils: Implication of beryllium bioaccessibility by different exposure pathways.

J Hazard Mater 2022 01 28;421:126757. Epub 2021 Jul 28.

Global Centre for Environmental Remediation, College of Engineering, Science and Environment, The University of Newcastle, Callaghan Campus, NSW 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment, The University of Newcastle, Callaghan Campus, NSW 2308, Australia.

Inhalation exposure and beryllium (Be) toxicity are well-known, but research on bioaccessibility from soils via different exposure pathways is limited. This study examined soils from a legacy radioactive waste disposal site using in vitro ingestion (Solubility Bioaccessibility Research Consortium [SBRC], physiologically based extraction test [PBET], in vitro gastrointestinal [IVG]), inhalation (simulated epithelial lung fluid [SELF]) and dynamic two-stage bioaccessibility (TBAc) methods, as well as 0.43 M HNO extraction. The results showed, 70 ± 4.8%, 56 ± 16.8% and 58 ± 5.7% of total Be were extracted (gastric phase [GP] + intestinal phase [IP]) in the SBRC, PBET, and IVG methods, respectively. Similar bioaccessibility of Be (~18%) in PBET-IP and SELF was due to chelating agents in the extractant. Moreover, TBAc-IP showed higher extraction (20.8 ± 2.0%) in comparison with the single-phase (SBRC-IP) result (4.8 ± 0.23%), suggesting increased Be bioaccessibility and toxicity in the gastrointestinal tract when the contamination derives from the inhalation route. The results suggested Be bioaccessibility depends on solution pH; time of extraction; soil reactive fractions (organic-inorganic); particle size, and the presence of chelating agents in the fluid. This study has significance for understanding Be bioaccessibility via different exposure routes and the application of risk-based management of Be-contaminated sites.
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http://dx.doi.org/10.1016/j.jhazmat.2021.126757DOI Listing
January 2022

Bioavailability of arsenic, cadmium, lead and mercury as measured by intestinal permeability.

Sci Rep 2021 07 19;11(1):14675. Epub 2021 Jul 19.

Global Centre for Environmental Remediation, University of Newcastle, Callaghan, NSW, Australia.

In this study, the intestinal permeability of metal(loid)s (MLs) such as arsenic (As), cadmium (Cd), lead (Pb) and mercury (Hg) was examined, as influenced by gut microbes and chelating agents using an in vitro gastrointestinal/Caco-2 cell intestinal epithelium model. The results showed that in the presence of gut microbes or chelating agents, there was a significant decrease in the permeability of MLs (As-7.5%, Cd-6.3%, Pb-7.9% and Hg-8.2%) as measured by apparent permeability coefficient value (P), with differences in ML retention and complexation amongst the chelants and the gut microbes. The decrease in ML permeability varied amongst the MLs. Chelating agents reduce intestinal absorption of MLs by forming complexes thereby making them less permeable. In the case of gut bacteria, the decrease in the intestinal permeability of MLs may be associated to a direct protection of the intestinal barrier against the MLs or indirect intestinal ML sequestration by the gut bacteria through adsorption on bacterial surface. Thus, both gut microbes and chelating agents can be used to decrease the intestinal permeability of MLs, thereby mitigating their toxicity.
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http://dx.doi.org/10.1038/s41598-021-94174-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8289861PMC
July 2021

Insights into vapour intrusion phenomena: Current outlook and preferential pathway scenario.

Sci Total Environ 2021 Nov 6;796:148885. Epub 2021 Jul 6.

Global Centre for Environmental Remediation, The University of Newcastle, University Dr, Callaghan, NSW 2308, Australia; CRC CARE, ATC Building, The University of Newcastle, University Dr, Callaghan, NSW 2308, Australia. Electronic address:

Vapour intrusion (VI) is the phenomenon by which volatile organic compounds (VOCs) migrate from the subsurface source through the soil and enter into the overlying buildings, affecting the indoor air quality and ultimately causing health hazards to the occupants. Health risk assessments associated with hydrocarbon contaminated sites and recommendations of site closure are often made by quantifying the VI risks using mathematical models known as 'vapour intrusion models' (VIM). In order to predict the health risk, various factors such as the lithological and geochemical conditions of the subsurface, environmental conditions, building operational conditions etc. are commonly evaluated using VIMs. Use of these models can overlook the role of preferential pathways like highly permeable subsurface layers and utility lines which act as the path of least resistance for vapour transport, which can increase the VI risks. The extensive networks of utility lines and sanitary sewer systems in urban areas can significantly exacerbate the uncertainty of VI investigations. The backfill materials like sand and gravel surrounding the utility lines can allow the vapours to easily pass through due to their high porosity as compared to natural formations. Hence, failure to understand the role of preferential pathways on the fate and transport of VOC in the vadose zone can result in more conservative predictions of indoor air vapour concentrations and wrong clean up approaches. This comprehensive review outlines the vapour transport mechanisms, factors influencing VI, VIMs and the role of preferential pathways in predicting indoor air vapour concentrations.
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http://dx.doi.org/10.1016/j.scitotenv.2021.148885DOI Listing
November 2021

Mesoporous Biopolymer Architecture Enhanced the Adsorption and Selectivity of Aqueous Heavy-Metal Ions.

ACS Omega 2021 Jun 31;6(23):15316-15331. Epub 2021 May 31.

Discipline of Chemistry, University of Newcastle, Callaghan, NSW 2308, Australia.

Halloysite nanotubes (HNT) and ball-milled biochar (BC) incorporated biocompatible mesoporous adsorbents ([email protected]) were synthesized for adsorption of aqueous heavy-metal ions. [email protected] outperformed the BC, HNT, and [email protected] in removing cadmium (Cd), copper (Cu), nickel (Ni), and lead (Pb). Mesoporous structure (∼7.19 to 7.56 nm) of [email protected] was developed containing an abundance of functional groups induced from encapsulated BC and tubular HNT, which allowed heavy metals to infiltrate and interact with the adsorbents. Siloxane groups from HNT, oxygen-containing functional groups from BC, and hydroxyl and carboxyl groups from alginate polymer play a significant role in the adsorption of heavy-metal ions. The removal percentage of heavy metals was recorded as Pb (∼99.97 to 99.05%) > Cu (∼95.01 to 90.53%) > Cd (∼92.5 to 55.25%) > Ni (∼80.85 to 50.6%), even in the presence of 0.01/0.001 M of CaCl and NaSO as background electrolytes and charged organic molecule under an environmentally relevant concentration (200 μg/L). The maximum adsorption capacities of Ni, Cd, Cu, and Pb were calculated as 2.85 ± 0.08, 6.96 ± 0.31, 16.87 ± 1.50, and 26.49 ± 2.04 mg/g, respectively. [email protected] has fast sorption kinetics and maximum adsorption capacity within a short contact time (∼2 h). Energy-dispersive X-ray spectroscopy (EDS) elemental mapping exhibited that adsorbed heavy metals co-distributed with Ca, Si, and Al. The reduction of surface area, pore volume, and pore area of [email protected] (after sorption of heavy metals) confirms that mesoporous surface (2-18 nm) supports diffusion, infiltration, and interaction. However, a lower range of mesoporous diameter of the adsorbent is more suitable for the adsorption of heavy-metal ions. The adsorption isotherm and kinetics fitted well with the Langmuir isotherm and the pseudo-second-order kinetic models, demonstrating the monolayer formation of heavy-metal ions through both the physical sorption and chemical sorption, including pore filling, ion exchange, and electrostatic interaction.
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http://dx.doi.org/10.1021/acsomega.1c01642DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8210456PMC
June 2021

Extracellular Polymeric Substances Drive Symbiotic Interactions in Bacterial‒Microalgal Consortia.

Microb Ecol 2021 Jun 16. Epub 2021 Jun 16.

Global Centre for Environmental Remediation (GCER), College of Engineering, Science and Environment, The University of Newcastle, ATC Building, University Drive, Callaghan, NSW, 2308, Australia.

The importance of several factors that drive the symbiotic interactions between bacteria and microalgae in consortia has been well realised. However, the implication of extracellular polymeric substances (EPS) released by the partners remains unclear. Therefore, the present study focused on the influence of EPS in developing consortia of a bacterium, Variovorax paradoxus IS1, with a microalga, Tetradesmus obliquus IS2 or Coelastrella sp. IS3, all isolated from poultry slaughterhouse wastewater. The bacterium increased the specific growth rates of microalgal species significantly in the consortia by enhancing the uptake of nitrate (88‒99%) and phosphate (92‒95%) besides accumulating higher amounts of carbohydrates and proteins. The EPS obtained from exudates, collected from the bacterial or microalgal cultures, contained numerous phytohormones, vitamins, polysaccharides and amino acids that are likely involved in interspecies interactions. The addition of EPS obtained from V. paradoxus IS1 to the culture medium doubled the growth of both the microalgal strains. The EPS collected from T. obliquus IS2 significantly increased the growth of V. paradoxus IS1, but there was no apparent change in bacterial growth when it was cultured in the presence of EPS from Coelastrella sp. IS3. These observations indicate that the interaction between V. paradoxus IS1 and T. obliquus IS2 was mutualism, while commensalism was the interaction between the bacterial strain and Coelastrella sp. IS3. Our present findings thus, for the first time, unveil the EPS-induced symbiotic interactions among the partners involved in bacterial‒microalgal consortia.
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http://dx.doi.org/10.1007/s00248-021-01772-1DOI Listing
June 2021

Chronic and Transgenerational Effects of Polystyrene Microplastics at Environmentally Relevant Concentrations in Earthworms (Eisenia fetida).

Environ Toxicol Chem 2021 Aug 22;40(8):2240-2246. Epub 2021 Jun 22.

Global Centre for Environmental Remediation, College of Engineering, Science and Environment, University of Newcastle, Callaghan, NSW, Australia.

Recently, soil contamination with microplastics has emerged as a serious global environmental concern that has necessitated more research on their potential impacts on soil biota. We investigated the acute and chronic toxicity of 2 different polystyrene microplastics, pure versus commercial (0-0.5% w/w in soil; sized 65-125 µm) on earthworm mortality, reproduction, and genotoxicity. Whereas the microplastics showed no acute toxicity in terms of mortality, reproduction was adversely affected in both parents (F0) and first filial generation (F1) of earthworms, with >50% reduction in juvenile production at 0.5% microplastics concentration in soil. Also, significant genotoxicity in terms of DNA damage was observed in the F0 and F1 earthworms. Chemical analysis of microplastic-exposed soils showed the presence of several benzene derivatives that are associated with polystyrene particles. Our study, for the first time to our knowledge, demonstrated the long-term adverse effects on earthworms of polystyrene microplastics even at environmentally relevant concentrations. The results have significant implications for risk assessment of polystyrene microplastics to soil biota. Environ Toxicol Chem 2021;40:2240-2246. © 2021 SETAC.
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http://dx.doi.org/10.1002/etc.5072DOI Listing
August 2021

Capture and characterisation of microplastics printed on paper via laser printer's toners.

Chemosphere 2021 Oct 13;281:130864. Epub 2021 May 13.

Global Centre for Environmental Remediation (GCER), University of Newcastle, Callaghan, NSW, 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE), University of Newcastle, Callaghan, NSW, 2308, Australia.

Microplastics are among the ubiquitous contaminants in our environment. As emerging contaminants, microplastics are still facing with lots of challenges on the characterisation, including their capture, identification and visualisation, particularly from a complex background. For example, when we print documents using a laser printer, we are printing microplastics onto paper, because the plastics are the main ingredient of the toner powder mixture. Characterisation of these microplastic mixture meets an even more complicated challenge, because plastic's signals might be shielded by other toner powder ingredients such as the pigments, the dyes, the black carbon, and the paper fabrics as well. To solve this challenge, we employ various techniques, including SEM, TEM, XPS, FT-IR, TGA and Raman, to characterise the microplastics printed via the toner powders. Interestingly, we show that Raman can distinguish and visualise the distribution of the microplastics from the complex background of the mixture. We estimate the millions of toner powders, each of which is ~4-6 μm in size, are printed out per A4 sheet as microplastics. The findings send a strong warning that millions of microplastics might be generated from the printing activities in our daily lives.
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http://dx.doi.org/10.1016/j.chemosphere.2021.130864DOI Listing
October 2021

Chemical pollution: A growing peril and potential catastrophic risk to humanity.

Environ Int 2021 11 12;156:106616. Epub 2021 May 12.

Faculty of Health and Medicine, The University of Newcastle, Callaghan, NSW 2308, Australia; Priority Research Centre for Reproductive Science, The University of Newcastle, Callaghan, NSW 2308, Australia.

Anthropogenic chemical pollution has the potential to pose one of the largest environmental threats to humanity, but global understanding of the issue remains fragmented. This article presents a comprehensive perspective of the threat of chemical pollution to humanity, emphasising male fertility, cognitive health and food security. There are serious gaps in our understanding of the scale of the threat and the risks posed by the dispersal, mixture and recombination of chemicals in the wider environment. Although some pollution control measures exist they are often not being adopted at the rate needed to avoid chronic and acute effects on human health now and in coming decades. There is an urgent need for enhanced global awareness and scientific scrutiny of the overall scale of risk posed by chemical usage, dispersal and disposal.
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http://dx.doi.org/10.1016/j.envint.2021.106616DOI Listing
November 2021

Heavy metal(loid)s and health risk assessment of Dambulla vegetable market in Sri Lanka.

Environ Monit Assess 2021 Mar 27;193(4):230. Epub 2021 Mar 27.

Global Centre for Environmental Remediation (GCER), The University of Newcastle, Callaghan, NSW, 2308, Australia.

Vegetables are essential for a healthy diet in humans. However, vegetables can carry harmful metal(loid) contaminants such as As, Cd and Pb which are deleterious to health in the long term. It has been postulated that long-term heavy metal(loid) exposure by vegetable consumption is associated with chronic kidney disease of unknown aetiology (CKDu) that prevails in North Central Province of Sri Lanka. We performed a human health risk assessment to identify if there is any link between heavy metal(loid) exposure from vegetable consumption and the prevalence of CKDu. The study includes a survey of food consumption in CKDu-impacted areas and determination of the heavy metal(loid) contents of market vegetables. We found that Solanum tuberosum (potato) and Momordica charantia (bitter gourd) accumulated Pb to a greater extent than other vegetables and exceeded the permissible concentration for foodstuffs. The Cd content of Solanum melongena (Brinjal) also exceeded permissible levels. However, the As content was below permissible levels for all the vegetables tested. The weekly total heavy metal(loid) intake of Cd, As and Pb in vegetables in CKDu-impacted areas was lower than permissible limits. The consumption of an average amount of vegetables does not pose a chronic health risk to the consumers. There was no evidence of a link between the consumption of heavy metal(loid)s in vegetables and CKDu. Since, few vegetables showed marked heavy metal(loid) accumulation, periodical monitoring of heavy metal(loid) concentrations in vegetables will be beneficial for avoidance of future possible health risks.
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http://dx.doi.org/10.1007/s10661-021-09020-2DOI Listing
March 2021

[Combined Remediation of Eutrophic Water by Phoslock and Aerobic Denitrifying Bacteria].

Huan Jing Ke Xue 2021 Apr;42(4):1861-1869

School of Environmental Science & Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.

Nitrogen and phosphorus are the leading causes of water eutrophication, and it is challenging to remove nitrogen and phosphorus effectively through a single water remediation method. In this study, an aerobic denitrifying bacterium (AD-19) isolated from eutrophic water was used to construct an immobilized biofilm and combined with Phoslock to remove nitrogen and phosphorus from the water. The phosphorus control efficiency of Phoslock, nitrogen removal performance of the denitrifying bacteria, and combined remediation performance for the eutrophic water were studied. The results demonstrated that the removal rate of PO-P in the simulated eutrophic water reached 95% with a dosing ratio of 80 (mass ratio of Phoslock to PO-P), and phosphorus release from sediment was effectively inhibited at the same time. Strain AD-19, which was identified as sp. Using the 16S rDNA method, had a good heterotrophic nitrification and aerobic denitrification ability, and more than 97% of the nitrogen was removed when NH-N or NO-N was used as the nitrogen source. The feasibility of the combined remediation of the eutrophic water was demonstrated using a lake simulation device. Furthermore, this technique was used to restore a eutrophic pond in a park in Wuhan city. After 16 days of treatment, the water quality indices for nitrogen and phosphorus were improved from worse than Grade Ⅴ to Grade Ⅲ (GB 3838-2002, Ministry of Environmental Protection of China, 2002) and remained stable for more than 270 days, indicating that Phoslock combined with the immobilized biofilm could quickly and effectively restore eutrophic water as well as maintain the water quality for long periods.
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http://dx.doi.org/10.13227/j.hjkx.202008232DOI Listing
April 2021

In situ decomposition of crop residues using lignocellulolytic microbial consortia: a viable alternative to residue burning.

Environ Sci Pollut Res Int 2021 Feb 24. Epub 2021 Feb 24.

ICAR-Indian Institute of Soil Science, Bhopal, 462038, India.

Open field burning of crop residue causes severe air pollution and greenhouse gas emission contributing to global warming. In order to seek an alternative, the current study was initiated to explore the prospective of lignocellulolytic microbes to expedite in situ decomposition of crop residues. Field trials on farmers' field were conducted in the state of Haryana and Maharashtra, to target the burning of rice and wheat residue and sugarcane trash, respectively. A comparative study among crop residue removal (CRR), crop residue burning (CRB) and in situ decomposition of crop residues (IND) revealed that IND of rice and wheat residues took 30 days whereas IND of sugarcane trash took 45 days. The decomposition status was assessed by determining the initial and final lignin to cellulose ratio which increased significantly from 0.23 to 0.25, 0.21 to 0.23 and 0.24 to 0.27 for rice, wheat residues and sugarcane trash, respectively. No yield loss was noticed in IND for both rice-wheat system and sugarcane-based system; rather IND showed relatively better crop yield as well as soil health parameters than CRB and CRR. Furthermore, the environmental impact assessment of residue burning indicated a substantial loss of nutrients (28-31, 23-25 and 51-77 kg ha of N+PO+KO for rice, wheat and sugarcane residue) as well as the emission of pollutants to the atmosphere. However, more field trials, as well as refinement of the technology, are warranted to validate and establish the positive potential of in situ decomposition of crop residue to make it a successful solution against the crop residue burning.
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http://dx.doi.org/10.1007/s11356-021-12611-8DOI Listing
February 2021

Identification and visualisation of microplastics / nanoplastics by Raman imaging (iii): algorithm to cross-check multi-images.

Water Res 2021 Apr 8;194:116913. Epub 2021 Feb 8.

Global Centre for Environmental Remediation (GCER), University of Newcastle, Callaghan NSW 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE), University of Newcastle, Callaghan NSW 2308, Australia.

We recently developed the Raman mapping image to visualise and identify microplastics / nanoplastics (Fang et al. 2020, Sobhani et al. 2020). However, when the Raman signal is low and weak, the mapping uncertainty from the individual Raman peak intensity increases and may lead to images with false positive or negative features. For real samples, even the Raman signal is high, a low signal-noise ratio still occurs and leads to the mapping uncertainty due to the high spectrum background when: the target plastic is dispersed within another material with interfering Raman peaks; materials are present that exhibit broad Raman peaks; or, materials are present that fluoresce when exposed to the excitation laser. In this study, in order to increase the mapping certainty, we advance the algorithm to combine and merge multi-images that have been simultaneously mapped at the different characteristic peaks from the Raman spectra, akin imaging via different mapping channels simultaneously. These multi-images are merged into one image via algorithms, including colour off-setting to collect signal with a higher ratio of signal-noise, logic-OR to pick up more signal, logic-AND to eliminate noise, and logic-SUBTRACT to remove image background. Specifically, two or more Raman images can act as "parent images", to merge and generate a "daughter image" via a selected algorithm, to a "granddaughter image" via a further selected algorithm, and to an "offspring image" etc. More interestingly, to validate this algorithm approach, we analyse microplastics / nanoplastics that might be generated by a laser printer in our office or home. Depending on the toner and the printer, we might print and generate millions of microplastics and nanoplastics when we print a single A4 document.
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http://dx.doi.org/10.1016/j.watres.2021.116913DOI Listing
April 2021

Variability in plant trace element uptake across different crops, soil contamination levels and soil properties in the Xinjiang Uygur Autonomous Region of northwest China.

Sci Rep 2021 01 22;11(1):2064. Epub 2021 Jan 22.

Institute of Resources and Environment Science, Xinjiang University, Urumqi, 830046, China.

This study investigated contamination status of eight trace elements (As, Cd, Cr, Hg, Pb, Cu, Zn and Ni) in farmland soils and crops at 535 sites across the Xinjiang Uygur Autonomous Region, Northwest China. Land use types of the sampling sites included vegetable patch, grain field and orchard. Our experimental results indicated all farmland soils were considered as trace element contamination based on the Nemerow comprehensive pollution index (NCPI > 1). However, 91.97% of the crop samples were uncontaminated according to the Chinese Risk Control Standard. Soils from the vegetable patch showed higher pollution level comparison with that from grain field and orchard. Health risks for both non-carcinogenic and carcinogenic risks were calculated through crop ingestion exposure pathway. Grain samples showed highest health risks, followed by melon and fruit, and vegetables. The health risks of crops were mainly driven by Cr and Cd. Crop consumption may pose risks for children but not adults. The source of trace element contamination in the different farmland soils varied and may be attributed to the different agricultural activities. Plant type had a greater influence on the trace element accumulation in crops compared with soil trace element contents and physicochemical properties.
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http://dx.doi.org/10.1038/s41598-021-81764-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7822888PMC
January 2021

Exposure to perfluorooctanesulfonate (PFOS) but not perflurorooctanoic acid (PFOA) at ppb concentration induces chronic toxicity in Daphnia carinata.

Sci Total Environ 2021 May 9;769:144577. Epub 2021 Jan 9.

Global Centre for Environmental Remediation, Faculty of Science, The University of Newcastle, Callaghan, NSW 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment, The University of Newcastle, Callaghan, NSW 2308, Australia. Electronic address:

Widespread environmental contamination of per- and polyfluoroalkyl substances (PFAS) is well established. Nevertheless, few studies have reported on the aquatic toxicity of PFAS, especially in indicator species such as Daphnia. In this study, the toxicity of two major PFAS, namely perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS), was investigated on water flea (Daphnia carinata) using a battery of comprehensive toxicity tests, including a 48 h acute and a 21-day chronic assays. The survival, growth, and reproduction of D. carinata were monitored over a 21-day life cycle. PFOS exhibited higher toxicity than PFOA. The 48 h LC values (confidence interval) based on acute toxicity for PFOA and PFOS were 78.2 (54.9-105) mg L and 8.8 (6.4-11.6) mg L, respectively. Chronic exposure to PFOS for 21 days displayed mortality and reproductive defects in D. carinata at a concentration as low as 0.001 mg L. Genotoxicity assessment using comet assay revealed that exposure for 96 h to PFOS at 1 and 10.0 mg L significantly damaged the organism's genetic makeup. The results of this study have great implications for risk assessment of PFOS and PFOA in aquatic ecosystems, given the potential of PFOS to pose a risk to Daphnia even at lower concentrations (1 μg L).
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http://dx.doi.org/10.1016/j.scitotenv.2020.144577DOI Listing
May 2021

Microalgal-bacterial consortia unveil distinct physiological changes to facilitate growth of microalgae.

FEMS Microbiol Ecol 2021 03;97(3)

Global Centre for Environmental Remediation (GCER), Faculty of Science, The University of Newcastle, ATC Building, Callaghan, NSW 2308, Australia.

Physiological changes that drive the microalgal-bacterial consortia are poorly understood so far. In the present novel study, we initially assessed five morphologically distinct microalgae for their ability in establishing consortia in Bold's basal medium with a bacterial strain, Variovorax paradoxus IS1, all isolated from wastewaters. Tetradesmus obliquus IS2 and Coelastrella sp. IS3 were further selected for gaining insights into physiological changes, including those of metabolomes in consortia involving V. paradoxus IS1. The distinct parameters investigated were pigments (chlorophyll a, b, and carotenoids), reactive oxygen species (ROS), lipids and metabolites that are implicated in major metabolic pathways. There was a significant increase (>1.2-fold) in pigments, viz., chlorophyll a, b and carotenoids, decrease in ROS and an enhanced lipid yield (>2-fold) in consortia than in individual cultures. In addition, the differential regulation of cellular metabolites such as sugars, amino acids, organic acids and phytohormones was distinct among the two microalgal-bacterial consortia. Our results thus indicate that the selected microalgal strains, T. obliquus IS2 and Coelastrella sp. IS3, developed efficient consortia with V. paradoxus IS1 by effecting the required physiological changes, including metabolomics. Such microalgal-bacterial consortia could largely be used in wastewater treatment and for production of value-added metabolites.
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http://dx.doi.org/10.1093/femsec/fiab012DOI Listing
March 2021

Metagenomics analysis identifies nitrogen metabolic pathway in bioremediation of diesel contaminated soil.

Chemosphere 2021 May 7;271:129566. Epub 2021 Jan 7.

Global Centre for Environmental Remediation, Faculty of Science, University of Newcastle, Callaghan, NSW, 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment, Australia. Electronic address:

Nitrogen amendment is known to effectively enhance the bioremediation of hydrocarbon-contaminated soil, but the nitrogen metabolism in this process is not well understood. To unravel the nitrogen metabolic pathway(s) of diesel contaminated soil, six types of nitrogen sources were added to the diesel contaminated soil. Changes in microbial community and soil enzyme genes were investigated by metagenomics analysis and chemical analysis through a 30-day incubation study. The results showed that ammonium based nitrogen sources significantly accelerated the degradation of total petroleum hydrocarbon (TPH) (79-81%) compared to the control treatment (38%) and other non-ammonium based nitrogen amendments (43-57%). Different types of nitrogen sources could dramatically change the microbial community structure and soil enzyme gene abundance. Proteobacteria and Actinobacteria were identified as the two dominant phyla in the remediation of diesel contaminated soil. Metagenomics analysis revealed that the preferred metabolic pathway of nitrogen was from ammonium to glutamate via glutamine, and the enzymes governing this transformation were glutamine synthetase and glutamate synthetase; while in nitrate based amendment, the conversion from nitrite to ammonium was restrained by the low abundance of nitrite reductase enzyme and therefore retarded the TPH degradation rate. It is concluded that during the process of nitrogen enhanced bioremediation, the most efficient nitrogen cycling direction was from ammonium to glutamine, then to glutamate, and finally joined with carbon metabolism after transforming to 2-oxoglutarate.
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http://dx.doi.org/10.1016/j.chemosphere.2021.129566DOI Listing
May 2021

Sorption of PFOS in 114 Well-Characterized Tropical and Temperate Soils: Application of Multivariate and Artificial Neural Network Analyses.

Environ Sci Technol 2021 02 15;55(3):1779-1789. Epub 2021 Jan 15.

Australian Department of Defence, BP26-2-B009, Brindabella Business Park, Canberra Airport, Deakin ACT 2600, Australia.

The influence of soil properties on PFOS sorption are not fully understood, particularly for variable charge soils. PFOS batch sorption isotherms were conducted for 114 temperate and tropical soils from Australia and Fiji, that were well-characterized for their soil properties, including total organic carbon (TOC), anion exchange capacity, and surface charge. In most soils, PFOS sorption isotherms were nonlinear. PFOS sorption distribution coefficients () ranged from 5 to 229 mL/g (median: 28 mL/g), with 63% of the Fijian soils and 35% of the Australian soils showing values that exceeded the observed median . Multiple linear regression showed that TOC, amorphous aluminum and iron oxides contents, anion exchange capacity, pH, and silt content, jointly explained about 53% of the variance in PFOS in soils. Variable charge soils with net positive surface charges, and moderate to elevated TOC content, generally displayed enhanced PFOS sorption than in temperate or tropical soils with TOC as the only sorbent phase, especially at acidic pH ranges. For the first time, two artificial neural networks were developed to predict the measured PFOS ( = 0.80) in the soils. Overall, both TOC and surface charge characteristics of soils are important for describing PFOS sorption.
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http://dx.doi.org/10.1021/acs.est.0c07202DOI Listing
February 2021

The influence of soil properties on sorption-desorption of beryllium at a low level radioactive legacy waste site.

Chemosphere 2021 Apr 15;268:129338. Epub 2020 Dec 15.

Global Centre for Environmental Remediation (GCER), The University of Newcastle (UoN), Callaghan Campus, NSW, 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC-CARE), ATC Building, The University of Newcastle, University Drive, Callaghan, NSW, 2308, Australia. Electronic address:

This study examined the influence of soil physicochemical properties on the sorption, desorption and kinetics of beryllium (Be) uptake and release on soils from a legacy waste site in Australia. This information is needed to help explain the current distribution of Be at the site and evaluate potential future environmental risks. Sorption was determined by a batch study and key soil properties were assessed to explain Be retention. The soil was favourable for sorption of Be (up to 99%) due to organic content, negative surface charge, soil oxyhydroxides (Fe/Al/Mn-O/OH) and the porosity of the soil structure. Lesser sorption was observed in the presence of a background electrolyte (NaNO). Sorption closely followed pseudo second order kinetics and was best described by the Langmuir model. FTIR analysis suggested that chemisorption was the predominant mechanism of Be sorption. Desorption was very low and best described by the Freundlich model. The low desorption reflected the high K (up to 6624 L/kg), and the presence of hysteresis suggested partially irreversible binding of Be with active surfaces of the soil matrix (minerals, SOM, oxyhydroxides of Fe/Al/Mn etc.). Intra-particle diffusion of Be and entrapment in the pores contribute to the irreversible binding. The sorption behaviour of Be helped to explain the relative immobility of Be at the site despite the significant quantities of Be disposed. Soil physicochemical properties were significant for Be sorption, through influencing both the uptake and desorption, and this demonstrates the implications of these measurements for evaluating potential future risks to the environment.
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http://dx.doi.org/10.1016/j.chemosphere.2020.129338DOI Listing
April 2021
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