Publications by authors named "Nguyen Manh Khai"

9 Publications

  • Page 1 of 1

Polycyclic aromatic hydrocarbons in airborne particulate matter samples from Hanoi, Vietnam: Particle size distribution, aryl hydrocarbon ligand receptor activity, and implication for cancer risk assessment.

Chemosphere 2021 Apr 30;280:130720. Epub 2021 Apr 30.

Centre for Environmental Technology and Sustainable Development (CETASD), University of Science, Vietnam National University, Hanoi, 334 Nguyen Trai, Hanoi, 11400, Viet Nam. Electronic address:

Concentrations and profiles of unsubstituted and methylated polycyclic aromatic hydrocarbons (PAHs and Me-PAHs) were analyzed in airborne particulate matter (PM) samples collected from high-traffic roads in Hanoi urban area. Levels of PAHs and Me-PAHs ranged from 210 to 660 (average 420) ng/m in total PM, and these pollutants were mainly associated with fine particles (PM) rather than coarser ones (PM and PM). Proportions of high-molecular-weight compounds (i.e., 5- and 6-ring) increased with decreasing particle size. Benzo[b+k]fluoranthene, indeno[1,2,3-cd]pyrene, and benzo[ghi]perylene were the most predominant compounds in the PM samples. In all the samples, Me-PAHs were less abundant than unsubstituted PAHs. The PAH-CALUX assays were applied to evaluate aryl hydrocarbon receptor (AhR) ligand activities in crude extracts and different fractions from the PM samples. Benzo[a]pyrene equivalents (BaP-EQs) derived by the PAH-CALUX assays for low polar fractions (mainly PAHs and Me-PAHs) ranged from 300 to 840 ng/m, which were more consistent with theoretical values derived by using PAH-CALUX relative potencies (270-710 ng/m) rather than conventional toxic equivalency factor-based values (22-69 ng/m). Concentrations of PAHs and Me-PAHs highly correlated with bioassay-derived BaP-EQs. AhR-mediated activities of more polar compounds and interaction effects between PAH-related compounds were observed. By using PAH-CALUX BaP-EQs, the ILCR values ranged from 1.0 × 10 to 2.8 × 10 for adults and from 6.4 × 10 to 1.8 × 10 for children. Underestimation of cancer risk can be eliminated by using effect-directed method (e.g., PAH-CALUX) rather than chemical-specific approach.
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http://dx.doi.org/10.1016/j.chemosphere.2021.130720DOI Listing
April 2021

Impact of Covid-19 partial lockdown on PM, SO, NO, O, and trace elements in PM in Hanoi, Vietnam.

Environ Sci Pollut Res Int 2021 Apr 8. Epub 2021 Apr 8.

Department of Environmental Water Quality Analysis, Institute of Environmental Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam.

Covid-19 lockdowns have improved the ambient air quality across the world via reduced air pollutant levels. This article aims to investigate the effect of the partial lockdown on the main ambient air pollutants and their elemental concentrations bound to PM in Hanoi. In addition to the PM samples collected at three urban sites in Hanoi, the daily PM, NO, O, and SO levels were collected from the automatic ambient air quality monitoring station at Nguyen Van Cu street to analyze the pollution level before (March 10th-March 31st) and during the partial lockdown (April 1st-April 22nd) with "current" data obtained in 2020 and "historical" data obtained in 2014, 2016, and 2017. The results showed that NO, PM, O, and SO concentrations obtained from the automatic ambient air quality monitoring station were reduced by 75.8, 55.9, 21.4, and 60.7%, respectively, compared with historical data. Besides, the concentration of PM at sampling sites declined by 41.8% during the partial lockdown. Furthermore, there was a drastic negative relationship between the boundary layer height (BLH) and the daily mean PM in Hanoi. The concentrations of Cd, Se, As, Sr, Ba, Cu, Mn, Pb, K, Zn, Ca, Al, and Mg during the partial lockdown were lower than those before the partial lockdown. The results of enrichment factor (EF) values and principal component analysis (PCA) concluded that trace elements in PM before the partial lockdown were more affected by industrial activities than those during the partial lockdown.
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http://dx.doi.org/10.1007/s11356-021-13792-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8032319PMC
April 2021

Kinetics of Organic Biodegradation and Biogas Production in the Pilot-Scale Moving Bed Biofilm Reactor (MBBR) for Piggery Wastewater Treatment.

J Anal Methods Chem 2021 5;2021:6641796. Epub 2021 Jan 5.

Faculty of Environmental Sciences, VNU University of Science, Vietnam National University, Hanoi, Vietnam.

In this research, the kinetics of COD biodegradation and biogas production in a moving bed biofilm reactor (MBBR) at pilot scale (10 m) for piggery wastewater treatment were investigated. Polyethylene (PE) was used as a carrying material, with organic loading rates (OLRs) of 10, 15, and 18 kgCOD/m day in accordance to hydraulic retention times (HRTs) of 0.56, 0.37, and 0.3 day. The results showed that a high COD removal efficiency was obtained in the range of 68-78% with the influent COD of 5.2-5.8 g/L at all 3 HRTs. About COD degradation kinetics, in comparison to the first- and second-order kinetics and the Monod model, Stover-Kincannon model showed the best fit with 0.98 and a saturation value constant ( ) and a maximum utilization rate () of 52.40 g/L day and 82.65 g/L day, respectively. The first- and second-order kinetics with all 3 HRTs and Monod model with the HRT of 0.56 day also obtained high values. Therefore, these kinetics and models can be further considered to be used for predicting the kinetic characteristics of the MBBR system in piggery wastewater treatment process. The result of a 6-month operation of the MBBR was that biogas production was mostly in the operating period of days 17 to 80, around 0.2 to 0.3 and 0.15-0.20 L/gCOD, respectively, and then reduction at an OLR of 18 kgCOD/m. After the start-up stage, day 35 biogas cumulative volume fluctuated from 20 to 30 m/day and reached approximately 3500 m for 178 days during the whole digestive process. Methane is accounted for about 65-70% of biogas with concentration around 400 mg/L.
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http://dx.doi.org/10.1155/2021/6641796DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7803399PMC
January 2021

Renewable energy from biomass surplus resource: potential of power generation from rice straw in Vietnam.

Sci Rep 2021 Jan 12;11(1):792. Epub 2021 Jan 12.

Faculty of Environmental Sciences, VNU University of Science, Vietnam National University (VNU), 334 Nguyen Trai, Thanh Xuan, Hanoi, Vietnam.

Biomass, one of the renewable resources, is expected to play an important role in the world's energy future. In Asia, rice straw is an abundant agricultural surplus because rice is one of the leading staple food crops in the region. Often, rice straw is burned directly in the field via uncontrolled combustion methods that emit large amounts of short-lived air pollutants, greenhouse gases, and other pollutants. In Vietnam, the energy and environment protection sectors are facing great challenges because of rapid urbanisation and industrialisation. A national strategic choice is to exploit renewable energy, including biomass-derived energy, to achieve energy security and CO emission reduction. This study investigates the potential of rice straw as an energy source for power plants at a local scale in Vietnam using data derived from satellite Sentinel-1 images. The results show that Vietnam can produce 2,565 MW from rice straw, for which 24 out of 63 provinces have a potential capacity higher than 30 MW, and the Kien Giang province has the highest capacity (245 MW). The study also analyses limitations and obstacles overcoming which can promote the biomass energy sector in the country.
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http://dx.doi.org/10.1038/s41598-020-80678-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7804265PMC
January 2021

Insights of environmental impact assessment reports for industrial parks: wastewater quantity prediction aspect.

Environ Monit Assess 2020 Mar 28;192(4):252. Epub 2020 Mar 28.

Faculty of Environmental Sciences, VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Hanoi, Vietnam.

While the contribution of industrial parks to the socio-economic aspect has been widely acknowledged over the past two decades in Vietnam, the problem of environmental pollution due to the wastes generated from industrial parks, especially wastewater, has still been an emerging issue, which places a great pressure on the Government. The wastewater generation from industrial parks was ordinarily required to report in all environmental impact assessment (EIA) reports as a base for the construction of on-site wastewater treatment plants within the industrial park. In Vietnam, this data was, however, often higher than the actual generated number due to inaccurate technical guidelines on predicting wastewater generation and many different methods to be applied. This study aimed to evaluate different approaches used to calculate the effluent in the industrial parks. The results showed that all of the four approaches (i.e., previous operation-based, water-based, wastewater-based, or experience-based methods) rendered significant gaps between predicted and actual values. None can be acceptable for use at present. A revision of technical guideline should be conducted to provide more detailed instruction for the better prediction. This shall minimize the investment capital and increase the efficiency of industrial parks in pollution control.
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http://dx.doi.org/10.1007/s10661-020-8217-2DOI Listing
March 2020

Esterification of sugarcane bagasse by citric acid for Pb adsorption: effect of different chemical pretreatment methods.

Environ Sci Pollut Res Int 2021 Mar 17;28(10):11869-11881. Epub 2020 Jan 17.

Department of Chemical Engineering, Laboratory for Process Engineering for Sustainable Systems, KU Leuven, Celestijnenlaan 200F, 3001, Leuven, Belgium.

In this study, different pretreatment strategies of sugarcane bagasse prior to citric acid modification were investigated in terms of Pb adsorption capacity. Pretreatment strategies included the use of NaOH, HCl, and CHOH in various concentrations. In order to fundamentally understand how these pretreatment methods affect the modification of sugarcane bagasse by citric acid as well as the Pb adsorption capacity of sugarcane bagasse, three main components of sugarcane bagasse namely cellulose, hemicellulose, and lignin were isolated and esterified by citric acid under the same conditions. ATR-FTIR, XPS, SEM, and an analysis of the number of carboxylic acid groups were used to investigate the physicochemical and chemical properties of the materials. These three components were proved to participate in adsorption and induce the esterification with citric acid. Hence, pretreatment with ethanol and 0.01 M NaOH which could retain cellulose, hemicellulose, and lignin in sugarcane bagasse achieved a high Pb adsorption capacity, i.e., 122.4 and 97 mg/g after the esterification with citric acid. In contrast, pretreatment with 0.5 M NaOH and 0.1 M HCl removed lignin and hemicellulose, leading to the lowest value of approximately 45 mg/g for citric acid esterified-pretreated sugarcane bagasse. XPS analysis and number of carboxylic group measurement confirmed the esterification between bagasse and citric acid. To understand the adsorption mechanism of adsorbent, two kinetic models including pseudo-first-order model and pseudo-second-order model were applied. The experimental data were well described by the pseudo-second-order model. The adsorption isotherm data were fitted Langmuir and Freundlich.
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http://dx.doi.org/10.1007/s11356-020-07623-9DOI Listing
March 2021

Removal of As (V) from the aqueous solution by a modified granular ferric hydroxide adsorbent.

Sci Total Environ 2020 Mar 5;706:135947. Epub 2019 Dec 5.

Faculty of Environmental Sciences, VNU University of Science, Vietnam National University, Hanoi, Viet Nam.

A novel adsorbent was prepared in granular form from iron (III) hydroxide and other additives to remove arsenate (As (V)) from aqueous solution. Adsorption of As (V) onto the adsorbent in batch experiments was analyzed to understand the adsorption mechanism, affecting factors, and adsorption isotherms. The optimal working conditions for the developed adsorbent were at pH 3, 30 °C and 50 g/L. The adsorption of arsenate onto the adsorbent occurred rapidly in the first 10 min and reached equilibrium in 2 h. The Langmuir isotherm was found to be best fitted the adsorption. The pre- and post-adsorption adsorbents were characterized by SEM, BET, FTIR, XRD, and Zeta potential techniques. Experimental results clearly demonstrated the potential impact of elemental composition, crystallinity, surface morphology, and other physico-chemical properties of the adsorbent on the adsorption performance variety. The experimental results with the pilot scale treatment system revealed that the adsorbent can be applied successfully and lead to a very efficient drinking water treatment system, at a competitive cost compared to the water market in Hanoi, Vietnam.
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http://dx.doi.org/10.1016/j.scitotenv.2019.135947DOI Listing
March 2020

Assessing dietary exposure to cadmium in a metal recycling community in Vietnam: age and gender aspects.

Sci Total Environ 2012 Feb 9;416:164-71. Epub 2012 Jan 9.

Vietnamese Academy of Agriculture Sciences, Soils and Fertilizers Research Institute, Tu Liem, Hanoi, Viet Nam.

This study estimates the dietary exposure to cadmium (Cd), and associated potential health risks, for individuals living and working in a metal recycling community (n=132) in Vietnam in comparison to an agricultural (reference) community (n=130). Individual-level exposure to Cd was estimated through analysis of staple foodstuffs combined with information from a food frequency questionnaire. Individual-level exposure estimates were compared with published 'safe' doses to derive a Hazard Quotient (HQ) for each member of the study population. Looking at the populations as a whole, there were no significant differences in the diets of the two villages. However, significantly more rice was consumed by working age adults (18-60 years) in the recycling village compared to the reference village (p<0.001). Rice was the main staple food with individuals consuming 461±162g/d, followed by water spinach (103±51kg/d). Concentrations of Cd in the studied foodstuffs were elevated in the metal recycling village. Values of HQ exceeded unity for 87% of adult participants of the metal recycling community (39% had a HQ>3), while 20% of adult participants from the reference village had an HQ>1. We found an elevated health risk from dietary exposure to Cd in the metal recycling village compared to the reference community. WHO standard of 0.4mg Cd/kg rice may not be protective where people consume large amounts of rice/have relatively low body weight.
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http://dx.doi.org/10.1016/j.scitotenv.2011.11.068DOI Listing
February 2012

Modeling of metal binding in tropical Fluvisols and Acrisols treated with biosolids and wastewater.

Chemosphere 2008 Feb 7;70(8):1338-46. Epub 2007 Nov 7.

Department of Soil Sciences, Swedish University of Agricultural Sciences (SLU), P.O. Box 7014, SE-750 07 Uppsala, Sweden.

There is growing concern about the accumulation of metals in tropical agricultural soils. In this study, experimental results from batch studies were used to test whether multi-surface geochemical models could describe metal binding in selected Vietnamese soils. The multi-surface models considered metal binding to iron hydroxides (using the diffuse layer model), organic matter (Stockholm Humic model and NICA-Donnan model), and phyllosilicate clay (Gaines-Thomas equation) as well as complexation to dissolved organic and inorganic ligands in the solution phase. We found that for total dissolved Cd, Cu and Zn the two multi-surface models being tested provided very good model fits for all soils, as evidenced by low root-mean square errors between model predictions and observations. These results suggest that organic matter is an important sorbent for many metals in these soils. However, poor fits were obtained for Cr(III), Mn and Pb for all soils. The study also suggests that the pH is the main factor that controls the solubility of metals in tropical Fluvisols and Acrisols subjected to application of biosolids and wastewater, and that advanced multi-surface models can be used to simulate the binding and release of many trace metals.
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http://dx.doi.org/10.1016/j.chemosphere.2007.09.046DOI Listing
February 2008