Publications by authors named "Wenlai Xu"

10 Publications

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Characteristics of Inorganic Phosphate-Solubilizing Bacteria from the Sediments of a Eutrophic Lake.

Int J Environ Res Public Health 2019 06 17;16(12). Epub 2019 Jun 17.

State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu 610059, China.

Inorganic phosphate-solubilizing bacteria (IPB) are an important component of microbial populations in lake sediments. The phosphate that they decompose and release becomes an important source of phosphorus for eutrophic algae. The IPB strains were screened and isolated from the sediments of Sancha Lake using National Botanical Research Institute's phosphate (NBRIP) plates. Their taxonomy was further determined by the 16S rDNA technique. The tricalcium phosphate-solubilizing ability of obtained IPB strains was evaluated using NBRIP- bromophenol blue (BPB) plates and Pikovskaya (PVK) liquid medium. Then, the ability of IPB strains to release phosphorus from the sediments were investigated by mimicking the lake environment. In this study, a total of 43 IPB strains were screened and isolated from the sediments of Sancha Lake, belonging to three phyla, eight families, and ten genera. Among them, two potentially new strains, SWSI1728 and SWSI1734, belonged to genus Bacillus, and a potentially new strain, SWSI1719, belonged to family Micromonosporaceae. Overall, the IBP strains were highly diverse and Bacillus and Paenibacillus were the dominant genera. In the tricalcium phosphate-solubilizing experiment, only 30 of the 43 IPB strains exhibited clear halo zones on plates, while in the liquid culture experiment, all strains were able to dissolve tricalcium phosphate. The phosphate-solubilizing abilities of the strains varied significantly, and the strain SWSI1725 of the genus showed the strongest ability with a phosphate-solubilizing content of 103.57 mg/L. The sterilized systems demonstrated significantly elevated phosphorus hydrochloride (HCl-P) decomposition and release from the sediments after the inoculation of IPB strains, whereas no significant effect was demonstrated on the phosphonium hydroxide (NaOH-P). Thus, the IPB strains in the sediments of Sancha Lake possessed rich diversity and the ability to release phosphorus in sediments.
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http://dx.doi.org/10.3390/ijerph16122141DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6617373PMC
June 2019

Rapid Sequestration of Ecosystem Carbon in 30-year Reforestation with Mixed Species in Dry Hot Valley of the Jinsha River.

Int J Environ Res Public Health 2019 05 31;16(11). Epub 2019 May 31.

State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu 610059, China.

Reforestation plays an important role in the carbon cycle and climate change. However, knowledge of ecosystem carbon sequestration through reforestation with mixed species is limited. Especially in dry hot valley of the Jinsha River, no studies cover total ecosystem carbon sequestration level in mature mixed plantations for a limited area of mixed plantations and difficulty in the sampling of plant roots and deep soil. In this study, carbon sequestration of seven mixed plantations of different ages in dry hot valley of the Jinsha River was investigated with analogous sites method. The results are as follows: 1) Deep soil organic carbon (SOC) storage significantly increased with stand age ( = 0.025), possibly due to fine root exudates and dissolved organic carbon transportation into deep soil and retention. 2) Total biomass carbon storage in the 30-year-old mixed plantation was 77.78 t C ha, 54 times reference wasteland and 9 times reference natural recovery shrub-grassland. However, total biomass carbon storage of 30-year-old mixed plantation was insignificantly lower than that of reference natural forest ( = 0.429). After 30 years of reforestation, plantation biomass carbon storage recovered to reference level, and its sequestration rate was 2.54 t C ha yr. 3) The total ecosystem carbon storage of 30-year-old mixed plantation was 185.50 t C ha, 2.38 times reference wasteland, 2.29 times reference natural recovery shrub grassland, and 29% lower than reference natural forest. It indicated that niche complementary, good stand structure, and characteristics of dominant species in mixed plantations facilitate more rapid carbon sequestration, especially biomass carbon in the dry hot valley.
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http://dx.doi.org/10.3390/ijerph16111937DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6604323PMC
May 2019

Microbial Community Structure in the Sediments and Its Relation to Environmental Factors in Eutrophicated Sancha Lake.

Int J Environ Res Public Health 2019 05 31;16(11). Epub 2019 May 31.

State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu 610059, China.

To study the microbial community structure in sediments and its relation to eutrophication environment factors, the sediments and the overlying water of Sancha Lake were collected in the four seasons. MiSeq high-throughput sequencing was conducted for the V3-V4 hypervariable regions of the 16S rRNA gene and was used to analyze the microbial community structure in sediments. Pearson correlation and redundancy analysis (RDA) were conducted to determine the relation between microbial populations and eutrophic factors. The results demonstrated four main patterns: (1) in the 36 samples that were collected, the classification annotation suggested 64 phyla, 259 classes, 476 orders, 759 families, and 9325 OTUs; (2) The diversity indices were ordered according to their values as with summer > winter > autumn > spring; (3) The microbial populations in the four seasons belonged to two distinct characteristic groups; (4) pH, dissolved oxygen (DO), total phosphorus (TP), and total nitrogen (TN) had significant effects on the community composition and structure, which further affected the dissolved total phosphorus (DTP) significantly. The present study demonstrates that the microbial communities in Sancha Lake sediments are highly diverse, their compositions and distributions are significantly different between spring and non-spring, and Actinobacteria and Cyanobacteria may be the key populations or indicator organisms for eutrophication.
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http://dx.doi.org/10.3390/ijerph16111931DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6603867PMC
May 2019

Mechanism and Kinetic Analysis of Degradation of Atrazine by US/PMS.

Int J Environ Res Public Health 2019 05 20;16(10). Epub 2019 May 20.

Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu 610031, China.

The degradation effect, degradation mechanism, oxidation kinetics, and degradation products of Atrazine (ATZ) by Ultrasound/Peroxymonosulfate (US/PMS) in phosphate buffer (PB) under different conditions were studied. It turned out that the degradation rate of US/PMS to ATZ was 45.85% when the temperature of the reaction system, concentration of PMS, concentration of ATZ, ultrasonic intensity, and reaction time were 20 °C, 200 μmol/L, 1.25 μmol/L, 0.88 W/mL, and 60 min, respectively. Mechanism analysis showed that PB alone had no degradation effect on ATZ while PMS alone had extremely weak degradation effect on ATZ. HO• and SO• coexist in the US/PMS system, and the degradation of ATZ at pH7 is dominated by free radical degradation. Inorganic anion experiments revealed that Cl, HCO, and NO showed inhibitory effects on the degradation of ATZ by US/PMS, with Cl contributing the strongest inhibitory effect while NO showed the weakest suppression effect. According to the kinetic analysis, the degradation kinetics of ATZ by US/PMS was in line with the quasi-first-order reaction kinetics. ETA with concentration of 1 mmol/L reduced the degradation rate of ATZ by US/PMS to 10.91%. Product analysis indicated that the degradation of ATZ by US/PMS was mainly achieved by dealkylation, dichlorination, and hydroxylation, but the triazine ring was not degraded. A total of 10 kinds of ATZ degradation intermediates were found in this experiment.
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http://dx.doi.org/10.3390/ijerph16101781DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6572287PMC
May 2019

Gene Diversity of Quinoprotein Glucose Dehydrogenase in the Sediment of Sancha Lake and Its Response to the Environment.

Int J Environ Res Public Health 2018 12 20;16(1). Epub 2018 Dec 20.

State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu 610059, China.

Quinoprotein glucose dehydrogenase (GDH) is the most important enzyme of inorganic phosphorus-dissolving metabolism, catalyzing the oxidation of glucose to gluconic acid. The insoluble phosphate in the sediment is converted into soluble phosphate, facilitating mass reproduction of algae. Therefore, studying the diversity of genes which encode GDH is beneficial to reveal the microbial group that has a significant influence on the eutrophication of water. Taking the eutrophic Sancha Lake sediments as the research object, we acquired samples from six sites in the spring and autumn. A total of 219,778 high-quality sequences were obtained by DNA extraction of microbial groups in sediments, PCR amplification of the gene, and high-throughput sequencing. Six phyla, nine classes, 15 orders, 29 families, 46 genera, and 610 operational taxonomic units (OTUs) were determined, suggesting the high genetic diversity of . genes came mainly from the genera of (1.63⁻77.99%), (0.13⁻56.95%), (0.32⁻25.49%), and (0.16⁻11.88%) in the phylum of Proteobacteria (25.10⁻98.85%). The abundance of these dominant -harboring bacteria was higher in the spring than in autumn, suggesting that they have an important effect on the eutrophication of the Sancha Lake. The alpha and beta diversity of genes presented spatial and temporal differences due to different sampling site types and sampling seasons. Pearson correlation analysis and canonical correlation analysis (CCA) showed that the diversity and abundance of genes were significantly correlated with environmental factors such as dissolved oxygen (DO), phosphorus hydrochloride (HCl⁻P), and dissolved total phosphorus (DTP). OTU composition was significantly correlated with DO, total organic carbon (TOC), and DTP. GDH encoded by genes transformed insoluble phosphate into dissolved phosphate, resulting in the eutrophication of Sancha Lake. The results suggest that genes encoding GDH may play an important role in lake eutrophication.
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http://dx.doi.org/10.3390/ijerph16010001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6339069PMC
December 2018

Graphene-Modulated Removal Performance of Nitrogen and Phosphorus Pollutants in a Sequencing Batch Reactor.

Materials (Basel) 2018 Nov 4;11(11). Epub 2018 Nov 4.

Haitian Water Grp. Co. Ltd., Chengdu 610059, China.

In this work, the influence of graphene on nitrogen and phosphorus in a batch reactor was studied. The impact of graphene on the removal performance of was investigated in a home-built sewage treatment system with seven identical sequencing batch reactors with graphene contents of 0 mg/L (T1), 0.05 mg/L (T2), 0.1 mg/L (T3), 0.2 mg/L (T4), 0.4 mg/L (T5), 0.8 mg/L (T6) and 10 mg/L (T7). The influence of graphene concentration and reaction time on the pollutant removal performance was studied. The malondialdehyde (MDA) and total superoxide dismutase (SOD) concentrations in each reactor were measured, and optical microscopy and scanning electron microscopy (SEM) characterizations were performed to determine the related mechanism. The results show that after 168 h, the total nitrogen (TN), ammonia nitrogen (AN) and total phosphorus (TP) removal rates of reactors T1⁻T7 become stable, and the TN, AN and TP removal rates were gradually reduced with increasing graphene concentration. At 96 h, the concentrations of both MDA and SOD in T1⁻T7 gradually increased as the graphene concentration increased. In optical microscopy and SEM measurements, it was found that graphene was adsorbed on the surface of , and entered cells, deforming and reducing . Through the blood plate count method, we estimated an average reduction of 16%. According to the water quality and microscopic experiments, it can be concluded that the addition of graphene causes oxidative damage to microalgae and destruction of the cell wall and cell membrane, inhibiting the nitrogen and phosphorus removal in reactors. This study provides theoretical and practical support for the safe use of graphene.
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http://dx.doi.org/10.3390/ma11112181DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6266974PMC
November 2018

Treatment of Sewage Using a Constructed Soil Rapid Infiltration System Combined with Pre-Denitrification.

Int J Environ Res Public Health 2018 09 14;15(9). Epub 2018 Sep 14.

State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu 610059, China.

The activated sludge process of the anaerobic/oxic (A/O) process has a good denitrification performance because it can make full use of the carbon source in the original sewage, and the denitrification can provide alkalinity for aerobic nitrification. The traditional constructed soil rapid infiltration (CSRI) system, on the other hand, has a poor nitrogen removal effect. Dividing the traditional CSRI system into two sections, one performs denitrification as an anoxic section, while the other performs nitrification as an aerobic section and is placed after the anoxic section. The nitrification liquid of the effluent from the aerobic section is mixed with the original wastewater and enters the anoxic section for denitrification. We expected that this would be improved by combining CSRI with a pre-denitrification step that would make full use of the carbon source in the original sewage. In a small-scale experimental model, the removal efficiencies of nitrogen, in the form of ammonium, nitrate, and total nitrogen (TN), as well as chemical oxygen demand (COD), were determined. The hydraulic load was varied, while the backflow reflux capacity was kept constant, to determine the effect on the pre-denitrification process. An average removal rate of 95.4% for NH₄⁺-N and 96% for COD could be obtained when a hydraulic load of 80 cm³(cm²·d) and a reflux ratio of 75% were applied. Under these conditions, the average removal rate of TN was 77.4%, which is much higher than what can be typically achieved with conventional CSRI systems.
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http://dx.doi.org/10.3390/ijerph15092005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6163630PMC
September 2018

Effect of C/N Ratio on the Removal of Nitrogen and Microbial Characteristics in the Water Saturated Denitrifying Section of a Two-Stage Constructed Rapid Infiltration System.

Int J Environ Res Public Health 2018 07 12;15(7). Epub 2018 Jul 12.

Haitian Water Grp Co Ltd., Chengdu 610059, China.

The aim of this study was to improve the removal of nitrogen pollutants from artificial sewage by a modeled two-stage constructed rapid infiltration (CRI) system. The C/N ratio of the second stage influent was elevated by addition of glucose. When the C/N ratio was increased to 5, the mean removal efficiency of total nitrogen (TN) reached up to 75.4%. Under this condition, the number of denitrifying bacteria in the permanently submerged denitrifying section (the second stage) was 22 times higher than that in the control experiment without added glucose. Elevation of the C/N ratio resulted in lower concentrations of nitrate and TN in the second stage effluent, without impairment of chemical oxygen demand removal. The concentration of nitrate and TN in effluent decreased as the abundance of denitrifying bacteria increased. Moreover, the bacterial biofilms that had formed in the sand of the second stage container were analyzed. The secretion of extracellular polymeric substances, a major constituent of biofilms, was enhanced as a result of the elevated C/N ratio, which lead to the improved protection of the bacteria and enhanced the removal of pollutants.
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http://dx.doi.org/10.3390/ijerph15071469DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6069465PMC
July 2018

Effect of Potassium Chlorate on the Treatment of Domestic Sewage by Achieving Shortcut Nitrification in a Constructed Rapid Infiltration System.

Int J Environ Res Public Health 2018 04 4;15(4). Epub 2018 Apr 4.

State Environmental Protection Key Laboratory of Synergetic Control and Joint Remediation for Soil and Water Pollution, Chengdu University of Technology, Chengdu 610059, China.

A constructed rapid infiltration (CRI) system is a new type of sewage biofilm treatment technology, but due to its anaerobic zone it lacks the carbon sources and the conditions for nitrate retention, and its nitrogen removal performance is very poor. However, a shortcut nitrification–denitrification process presents distinctive advantages, as it saves oxygen, requires less organic matter, and requires less time for denitrification compared to conventional nitrogen removal methods. Thus, if the shortcut nitrification–denitrification process could be applied to the CRI system properly, a simpler, more economic, and efficient nitrogen removal method will be obtained. However, as its reaction process shows that the first and the most important step of achieving shortcut nitrification–denitrification is to achieve shortcut nitrification, in this study we explored the feasibility to achieve shortcut nitrification, which produces nitrite as the dominant nitrogen species in effluent, by the addition of potassium chlorate (KClO₃) to the influent. In an experimental CRI test system, the effects on nitrogen removal, nitrate inhibition, and nitrite accumulation were studied, and the advantages of achieving a shortcut nitrification–denitrification process were also analysed. The results showed that shortcut nitrification was successfully achieved and maintained in a CRI system by adding 5 mM KClO₃ to the influent at a constant pH of 8.4. Under these conditions, the nitrite accumulation percentage was increased, while a lower concentration of 3 mM KClO₃ had no obvious effect. The addition of 5mM KClO₃ in influent presumably inhibited the activity of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), but inhibition of nitrite-oxidizing bacteria (NOB) was so strong that it resulted in a maximum nitrite accumulation percentage of up to over 80%. As a result, nitrite became the dominant nitrogen product in the effluent. Moreover, if the shortcut denitrification process will be achieved in the subsequent research, it could save 60.27 mg CH₃OH per litre of sewage in the CRI system compared with the full denitrification process.
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http://dx.doi.org/10.3390/ijerph15040670DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5923712PMC
April 2018

Characteristics and management of domestic waste in a rural area of the Tibetan Plateau.

J Air Waste Manag Assoc 2015 Nov;65(11):1365-75

a State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, College of Environment and Civil Engineering , Chengdu University of Technology , Chengdu , People's Republic of China.

Unlabelled: In the rural area of the Tibetan Plateau (RATP), the characteristics of domestic waste, people's environmental awareness, people's willingness to pay and their influence factors were firstly studied by questionnaires, field samplings and laboratory tests. The results showed that, in the RATP, the generation of domestic waste was 85 g•d-1 per capita and it was mainly composed of plastics, inert waste, kitchen waste, glass and paper. The waste bulk density, moisture content, ash, combustible and low calorific value were 65 kg•m-3, 19.25%, 44.90%, 35.85% and 10,520 kJ•kg-1 respectively. These characteristics are influenced by income sources and geographical position to some extent. Classified collection should be promoted widely on the household and the village basis. Compost, fermentation, landfill, bioreactor landfill and semi-aerobic landfill have been approved as effective techniques to treat domestic waste, except incineration. The distance of 50-800 m between each collection facility and the disposal fee of around $0.8 per month per household are suggested. For suburbs or large population villages, it's better to treat domestic waste by the centralized way. But for the remote rural areas, a decentralized way is proposed. Significantly, the educational and economic influence should be considered into an effective domestic waste management program.

Implications: The current situatio n of the environment in the rural areas of the Tibetan Plateau (RATP) was surveyed. There, the generation of organics and moisture of domestic waste were low but ash, recyclables, and combustibles were high. People's knowledge of domestic waste was absent but their participation in management was strong. Based on the current situation, compost, fermentation, and landfill were effective but incineration was inappropriate. Also, a localized mini landfill for a cluster of villages and or settlements was the best method there.
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http://dx.doi.org/10.1080/10962247.2015.1078859DOI Listing
November 2015