Aquaculture farmers’ perceptions of climate-related risks in the Mekong Region

Natural protected areas (NPA) are portions of the Mexican territory where the original environment has not been modified and which are protected in order t     

An integrated and quantitative vulnerability assessment for proactive hazard response and sustainability: a case study on the Chan May-Lang Co Gulf area,Central Vietnam

A natural factors-based approach was developed to examine proactive responses to hazards and improving sustainability on the Chan May-Lang Co Gulf area, Central Vietnam. The approach was based on a weight-of-evidence method within an integrated and quantitative vulnerability assessment in which the spatial relationship between a set of evidential factors (lithology, distance to the coastline, altitude, slope, aspect, drainage, wind speed during storms, and land use and cover) and a set of hazard locations was combined with the prior probability (total vulnerability) to obtain the posterior probability of hazard occurrence. The result showed that 44.3 % of the study area had high to very high total vulnerability, due to the high density of vulnerable objects and frequency of severe damage from typhoons, floods, landslides, and erosion. The result also demonstrated that the contribution of natural factors was directly proportional to total vulnerability in approximately 75 % of the study area, indicating a high dependence of vulnerability on natural factors. In the remaining areas, low contributions were found in the high and very high vulnerability areas dominated by high anthropogenic activities. In contrast, natural factors were important contributors to total vulnerability in areas characterized by dense vegetation, consolidated rocks, and altitude greater than 300 m, reflecting high natural resilience. The present study demonstrated that a proactive approach may provide appropriate measures to mitigate hazards and to increase the sustainability of the study area.     

Selected chloro and bromo derivatives of triclosan—syntheses and their occurrence in Canadian sewage and biosolid samples

The occurrence of triclosan (TCS), a general purpose antibacterial agent contained in numerous consumer and personal-care products, in the aquatic environment is well known. To a lesser degree, the formation of chlorinated and brominated derivatives of TCS during the chlorination of the antibacterial has also been reported. Presumably due to the lack of authentic standards, very few reports have been published on the levels of these halogenated TCSs in the environment. For this purpose, we have synthesized six selected halogenated derivatives of TCS, namely, 3-Cl-, 5-Cl-, 3,5-Cl₂-, 3-Br-, 5-Br-, and 3,5-Br₂- TCSs, with supporting ¹H-NMR (nuclear magnetic resonance) and GC–MS (gas chromatography–mass spectrometry) data for their structural assignments. Using these model compounds together with sensitive analytical methods, we were able to identify and quantify the above compounds together with their precursor compound TCS in Canadian municipal wastewater and biosolid samples for the first time. While detected in all influent (range from 1.4 to 24.1 ng L^?1) and biosolid (range from 7.7 to 274 ng g^?1) samples, the concentrations of these chlorinated TCS were generally from 100- to 1,000-fold lower than TCS in the same sample. Even lower levels (<20 ng/g in 85 % of the results) of brominated TCS were found in biosolids, and they were mostly undetected in sewage.     

In-use polybrominated diphenyl ether (PBDE) stocks and atmospheric emissions in Japan

We estimated the in-use stocks of polybrominated diphenyl ethers (PBDEs) in Japan using a population balance model. The estimation is based on the domestic demand of PBDEs and the assumed survival rate of these products. Two cases relevant to the future regulation of commercial deca-BDE are considered, namely (1) deca-BDE declines at the same rate as the current rate of decline, and (2) deca-BDE is discontinued after 2020. The estimates of the decreasing rates of in-use penta-, octa-, and deca-BDE stocks were proportional with the measured decreases in the atmospheric concentrations of these substances. The in-use penta- and octa-BDE stocks could be depleted in the near future (500 and 60 tonne in 2013, and an estimated 20 and <1 tonne in 2020, respectively). Relevant to case 1, the in-use stocks of deca-BDE-containing products would be 28,000 tonne in 2013 and an estimated 1900 tonne in 2040, providing an ongoing source of deca-BDE emission to the environment. On the other hand, relevant to case 2, most of the deca-BDE would be phased out by 2040. The atmospheric emissions of deca-BDE were predicted at 84–841 kg/year in 2013 and an estimated 43–425 kg/year in 2020.     

Air pollution modeling at road sides using the operational street pollution model--a case study in Hanoi, Vietnam

In many metropolitan areas, traffic is the main source of air pollution. The high concentrations of pollutants in streets have the potential to affect human health. Therefore, estimation of air pollution at the street level is required for health impact assessment. This task has been carried out in many developed countries by a combination of air quality measurements and modeling. This study focuses on how to apply a dispersion model to cities in the developing world, where model input data and data from air quality monitoring stations are limited or of varying quality. This research uses the operational street pollution model (OSPM) developed by the National Environmental Research Institute in Denmark for a case study in Hanoi, the capital of Vietnam. OSPM predictions from five streets were evaluated against air pollution measurements of nitrogen oxides (NO(x)), sulfur dioxide (SO2), carbon monoxide (CO), and benzene (BNZ) that were available from previous studies. Hourly measurements and passive sample measurements collected over 3-week periods were compared with model outputs, applying emission factors from previous studies. In addition, so-called "backward calculations" were performed to adapt the emission factors for Hanoi conditions. The average fleet emission factors estimated can be used for emission calculations at other streets in Hanoi and in other locations in Southeast Asia with similar vehicle types. This study also emphasizes the need to further eliminate uncertainties in input data for the street-scale air pollution modeling in Vietnam, namely by providing reliable emission factors and hourly air pollution measurements of high quality.     

Evaluation of aquatic plants for removing polar microcontaminants: a microcosm experiment

Microcosm wetland systems (5 L containers) planted with Salvinia molesta, Lemna minor, Ceratophyllum demersum, and Elodea canadensis were investigated for the removal of diclofenac, triclosan, naproxen, ibuprofen, caffeine, clofibric acid and MCPA. After 38 days of incubation, 40-99% of triclosan, diclofenac, and naproxen were removed from the planted and unplanted reactors. In covered control reactors no removal was observed. Caffeine and ibuprofen were removed from 40% to 80% in planted reactors whereas removals in control reactors were much lower (2-30%). Removal of clofibric acid and MCPA were negligible in both planted and unplanted reactors. The findings suggested that triclosan, diclofenac, and naproxen were removed predominantly by photodegradation, whereas caffeine and naproxen were removed by biodegradation and/or plant uptake. Pseudo-first-order removal rate constants estimated from nonlinear regressions of time series concentration data were used to describe the contaminant removals. Removal rate constants ranged from 0.003 to 0.299 d(-1), with half-lives from 2 to 248 days. The formation of two major degradation products from ibuprofen, carboxy-ibuprofen and hydroxy-ibuprofen, and a photodegradation product from diclofenac, 1-(8-Chlorocarbazolyl)acetic acid, were followed as a function of time. This study emphasizes that plants contribute to the elimination capacity of microcontaminants in wetlands systems through biodegradation and uptake processes.     

Occurrence and source characterization of perfluorochemicals in an urban watershed

Perfluorochemicals (PFCs) are used in numerous applications, mainly as surfactants, and occur ubiquitously in the environment as complex mixtures. This study was undertaken to characterize the occurrence and sources of commonly detected PFC compounds in surface waters of the Marina catchment, a watershed that drains an urbanized section of Singapore. Of the 19 target PFCs, 13 were detected with perfluorooctanoic acid (PFOA) (5-31 ng L⁻¹) and perfluorooctane sulfonate (PFOS) (1-156 ng L⁻¹) being the dominant components. Other compounds detected included perfluoroalkyl carboxylates (C7-C12) and perfluoroalkyl sulfonates (C6 and C8). Sulfonamide compounds detected 2-(N-ethylperfluorooctanesulfonamido) acetic acid (N-EtFOSAA), 2-(N-methylperfluorooctanesulfonamido) acetic acid (N-MeFOSAA), perfluorooctanesulfonamido acetic acid (FOSAA) and perfluorooctanesulfonamide (FOSA) were putative transformation products of N-EtFOSE and N-MeFOSE, the N-ethylated and N-methylated ethyl alcohol derivatives, respectively. Surface water concentrations were generally higher during dry weather than during storm water flow: the median concentrations of total PFCs in dry and wet weather were 57 and 138 ng L⁻¹ compared to 42 and 79 ng L⁻¹, respectively, at Stamford and Alexandra canal, suggesting the presence of a continuous source(s) which is subject to dilution during storm events. In rain water, median concentrations were 6.4 ng L⁻¹, suggesting rain contributed from 12-25% to the total PFC load for non-point source sites. The longitudinal concentration profile along one of the canals revealed a point source of sulfonated PFCs (PFOS), believed to originate from aqueous film-forming foam (AFFF). Sources were characterized using principal component analysis (PCA) and by plotting PFHxS/PFOA against PFOS/PFOA. Typical surface waters exhibit PFOS/PFOA and PFHxS/PFOA ratios below 0.9 and 0.5, respectively. PCA plots reveal waters impacted by “non-typical” PFC sources in Alexandra canal.     

Utilizing waste corn-cob in biosynthesis of noble metallic nanoparticles for antibacterial effect and catalytic degradation of contaminants

Environmental Science and Pollution Research - In the present study, cost-effective, and environmentally friendly fabrication of silver and gold nanoparticles was performed by using aqueous extract...     

Potential health risks of toxic heavy metals and nitrate via commonly consumed bivalve and vegetable species in Ho Chi Minh City,Vietnam

Environmental Science and Pollution Research - This study aimed to evaluate the health risks of cadmium (Cd), lead (Pb), inorganic arsenic (As), and nitrate exposure through the consumption of...