Nitrated- and oxygenated-polycyclic aromatic hydrocarbon in urban soil from Nepal: Source assessment, air-soil exchange, and soil-air partitioning.

In contrast to more frequently investigated priority pollutants, such as polycyclic aromatic hydrocarbons (PAHs), only little is known about the fate and distribution of nitrated- and oxygenated-PAHs (NPAHs and OPAHs) in urban soils, particularly in Indian sub-continent. Moreover, experimental data on air-soil exchange and soil-air partitioning are also lacking, which is critical in assessing the partitioning, fugacity coefficient, and secondary emission of PAH-derivatives. Hence, this article provides an insight into the fate, sources, air-soil exchange, and soil-air partitioning of PAH-derivatives on a molecular basis. Prospective health risk due to their exposure has also been discussed. The result showed that PAH-derivatives had significantly polluted all four Nepalese cities. Æ©15NPAHs and Æ©2OPAHs in soil were 4 and 20 times lower than their parent-PAHs, and ranged 396-2530 ng/g (median 458 ng/g) and 91.9-199 ng/g (median 94.9 ng/g), respectively. Æ©15NPAHs was higher than a few global studies, while Æ©2OPAHs was lower than some of the less urbanized/remote areas worldwide. The 6-Nitobenzo[a]pyrene (6-NBaP) was most abundant in soil, and accounted for 10-12% of Æ©15NPAHs, while Benzanthrone (BZONE) exceeded among OPAHs, and represented 71-76% of Æ©2OPAHs, respectively. Source identification study indicated that direct emissions from domestic/residential cooking and heating and secondary formations are the essential sources of derivative chemicals in soil. Fugacity fraction ratio (fratio) indicated volatilization from the soil. The soil-air partitioning study showed sorption by soil organic matter/black carbon has little role in soil-air partitioning of PAH-derivatives in Nepal's urban soil. The toxicity equivalency quotients (TEQs) of NPAHs (314 ± 102 ng/g) was estimated slightly higher than their parent-PAHs (294 ± 121 ng/g) suggesting a relatively higher risk of soil toxicity in Nepal.

Airborne brominated, chlorinated and organophosphate ester flame retardants inside the buildings of the Indian state of Bihar: Exploration of source and human exposure.

Since many household products used by individuals contain flame retardants (FRs), there is more chance that these chemicals may be present in the various exhibit of the indoor environment. Despite being one of the fastest-growing economies worldwide, the contamination level, sources, products, and pathways of FRs in India, is either not known or limited. This inspired us to investigate the level, profile, spatial distribution, and sources of different classes of FRs in the indoor air. For this purpose, 15 brominated, 2 chlorinated, and 8 organophosphate FRs (OPFRs) were investigated in indoor air samples from urban and suburban sites of an Indian state of Bihar. Additionally, inhalation health risk exposure to children and the adult was estimated to predict the risk of these chemicals. Overall, ∑8OPFRs (median 351 pg/m3) was the most prominent in air, followed by novel brominated FR (∑6NBFRs) (median 278 pg/m3), polybrominated diphenyl ether (∑9PBDE) (median 5.05 pg/m3), and dechlorane plus (∑2DPs) (median 2.52 pg/m3), and accounted for 55%, 44%, 0.8% and 0.4% of ∑FRs, respectively. Generally, ∑9PBDEs (median 6.29 pg/m3) and ∑8OPFRs (median 355 pg/m3) were measured high at sub-urban sites, while urban sites had the highest level of ∑2DPs (median 2.81 pg/m3) and ∑6NBFRs (median 740 pg/m3). BDE-209 was most abundant among ∑9PBDEs, while syn-DP dominated in ∑2DPs. Likewise, DBDPE was most prevalent in ∑6NBFRs, while TMPP topped among ∑8OPFRs. The principal component analysis revealed contribution from household items, food packaging and paints, hydraulic fluid, a gasoline additive, and de-bromination of BDE-209 as the primary sources of FRs. The estimated daily inhalation exposure (DIE) indicated a relatively high risk to children than the adult. The DIE of individual FR was several folds lower than their corresponding oral reference dose (RfDs), suggesting minimal risk. However, exposure risk, especially to children, may still need attention because other routes of intake may always be significant in the case of Bihar.

Measurement of legacy and emerging flame retardants in indoor dust from a rural village (Kopawa) in Nepal: Implication for source apportionment and health risk assessment.

Under the Stockholm Convention, signatory countries are obliged to direct source inventories, find current sources, and provide ecological monitoring evidence to guarantee that the encompassing levels of persistent organic pollutants (POPs) are declining. However, such monitoring of different types of POPs are to a great degree constrained in most developing countries including Nepal and are primarily confined to suspected source area/ densely populated regions. In this study, 9 polybrominated diphenyl ethers (PBDEs), 2 dechlorane plus (DPs), 6 novel brominated flame retardants (NBFRs) and 8 organophosphate ester flame retardants (OPFRs) were investigated in indoor dust from a rural area (Kopawa) in Nepal in order to evaluate their occurrence/level, profile, spatial distribution and their sources. Additionally, health risk exposure was estimated to anticipate the possible health risk to the local population. The results showed that OPFRs was the most abundant FR measured in the dust. The concentration of ∑8OPFRs was about 2, 3 and 4 orders of magnitude higher than the ∑6NBFRs, ∑9PBDEs, and ∑2DPs, respectively. Tris (methylphenyl) phosphate (TMPP) and Tris (2-ethylhexyl) phosphate (TEHP) were the most abundant OPFRs analyzed in the dust; while decabromodiphenyl ethane (DBDPE) exceeded among NBFRs. Likewise, 2,2',3,3',4,4',5,5',6,6'-decabromodiphenylether (BDE-209) was the most identified chemical among PBDEs. The total organic carbon (TOC) content in dust was significantly and positively connected with octa-BDEs (Rho = 0.615, p < 0.01), BTBPE (Rho = 0.733, p < 0.01), TPHP (Rho = 0.621, p < 0.01), TEHP (Rho = 0.560, p < 0.01) and TMPPs (Rho = 0.550, p < 0.01), while black carbon (BC) was either weakly related or not related, suggesting little or no impact of BC in the distribution of FRs. Principal component analysis indicated the contribution from commercial penta-, octa- and deca-BDEs formulation, the adhesive substance, food packaging and paints, and degradation of BDE-209 as the essential sources of FRs. Health risk exposure estimates showed that dermal absorption via dust as the primary route of FRs intake. The estimated daily exposure of PBDEs, NBFRs and OPFRs were 2-10 orders of magnitude lower than their corresponding reference dose (RfD), suggesting insignificant risk. However, other routes such as inhalation and dietary intake might still be significant in the case of Kopawa which should be tested in future.

Polychlorinated Biphenyls in Surface Soil from North-East India: Implication for Sources Apportionment and Health-Risk Assessment.

Although India never manufactured polychlorinated biphenyls (PCBs), evidence suggests the prevalence of PCBs in multi-environmental matrices. Despite the high level of PCBs that has been detailed in the major urban areas of India, little is known about the fate and sources of PCBs in Northeast India (NEI). This motivated us to investigate the contamination level and sources of PCBs in the surface soil. In this study, the environmental concentration and sources of 25 PCBs were investigated in surface soil (n = 60) from three states of NEI (lower Assam, Manipur, and Tripura). Additionally, the relationship between soil organic carbon (SOC) and PCBs was studied to investigate the role of SOC in the distribution of PCBs. Overall, the concentration of ∑25PCBs ranged from 2950 to 16,700 pg/g dw (median 7080 pg/g dw), 3580-21,100 pg/g dw (median 11,500 pg/g dw), and 2040-11,000 pg/g dw (median 4270 pg/g dw) in Assam, Manipur, and Tripura, respectively. Low-chlorinated PCBs were more prevalent than highly chlorinated PCBs. PCB-49 was identified as the most abundant in soil, followed by PCB-52, and accounted for 13% and 12.9% of ∑25PCBs, respectively. With respect to land use categories, high ∑25PCBs were related to grassland areas and proximity to the roadside soil. The principal component analysis indicated emissions from technical PCB mixtures, combustion of municipal wastes/residential wood, incineration of hospital wastes, and e-waste recycling/disposal sites are the real sources of PCBs. Marginally, a moderate-to-weak correlation of SOC with ∑25PCBs (R2 = 0.144, p < 0.05) and their homologs (R2 = 0.280-0.365, p < 0.05) indicated the little role of SOC in the dispersion of PCBs. The estimated toxic equivalency of dioxin-like PCBs suggested that PCB-126 is the most toxic contaminant to endanger the human population.

Chemometric evaluation of heavy metal pollutions in Patna region of the Ganges alluvial plain, India: implication for source apportionment and health risk assessment.

While metal pollution and distribution in soil are well documented for many countries, the situation is more serious in developing countries because of the rapid increase in industrialization and urbanization during last decades. Although it is well documented in developed countries, data about substantial metal pollution in Indian soil, especially in eastern Ganges alluvial plain (GAP), are limited. In this study, eight different blocks of Patna district located in eastern GAP were selected to investigate the contamination, accumulation, and sources of metals in surface soil considering different land use types. Additionally, human health risk assessment was estimated to mark the potential carcinogenic and non-carcinogenic effect of metals in soil. The concentration of all metals (except Pb) in soil was below the Indian standard limit of the potential toxic element for agricultural soil. Pb was the most abundant in soil, followed by Zn and Cu, and accounted for 52, 33 and 8% of the total metal. In terms of land use types, roadside soil detected higher concentrations of all metals, followed by park/grassland soil. Principal component analysis results indicated traffic pollution and industrial emissions are the major sources of heavy metals in soil. This was further confirmed by strong inter-correlation of heavy metals (Cd, Cr, Ni, Cu and Pb). Human health risk assessment results indicated ingestion via soil as the primary pathway of heavy metal exposure to both adults and children population. The estimated hazard index was highest for Pb, suggesting significant non-carcinogenic effect to both adults and children population. The children were more prone to the non-carcinogenic effect of Pb than adults. However, relatively low cancer risk value estimated for all metals suggested non-significant carcinogenic risk in the soil.

A Review on the Abundance, Distribution and Eco-Biological Risks of PAHs in the Key Environmental Matrices of South Asia.

Polycyclic aromatic hydrocarbons (PAHs) are consistently posing high risks to human/biota in developing countries of South Asia where domestic areas are exposed to biomass burning and commercial/industrial activities. This review article summarized the available data on PAHs occurrence, distribution, potential sources and their possible risks in the key environmental matrices (i.e., Air, Soil/Sediments, Water) from South Asian Region (SAR). Available literature reviewed suggested that PAHs concentration levels were strongly influenced by the monsoonal rainfall system in the region and it has been supported by many studies that higher concentrations were measured during the winter season as compared to summer. Biomass burning (household and brick kilns activities), open burning of solid wastes and industrial and vehicular emissions were categorized as major sources of PAHs in the region. Regional comparison revealed that the contamination levels of PAHs in the water bodies and soil/sediments in SAR remained higher relatively to the reports from other regions of the world. Our findings highlight that there is still a general lack of reliable data, inventories and research studies addressing PAHs related issues in the context of environmental and human health in SAR. There is therefore a critical need to improve the current knowledge base, which should build upon the research experience from other regions which have experienced similar situations in the past. Further research into these issues in South Asia is considered vital to help inform future policies/control strategies as already successfully implemented in other countries.

Polychlorinated biphenyls in Nepalese surface soils: Spatial distribution, air-soil exchange, and soil-air partitioning.

Regardless of the ban on the polychlorinated biphenyls (PCBs) decade ago, significant measures of PCBs are still transmitted from essential sources in cities and are all inclusive ecological contaminants around the world. In this study, the concentrations of PCBs in soil, the air-soil exchange of PCBs, and the soil-air partitioning coefficient (KSA) of PCBs were investigated in four noteworthy urban areas in Nepal. Overall, the concentrations of ∑30PCBs ranged from 10 to 59.4ng/g dry weight; dw (mean 12.2ng/g ±11.2ng/g dw). The hexa-CBs (22-31%) was most dominant among several PCB-homologues, followed by tetra-CBs (20-29%), hepta-CBs (12-21%), penta-CBs (15-17%) and tri-CBs (9-19%). The sources of elevated level of PCBs discharge in Nepalese soil was identified as emission from transformer oil, lubricants, breaker oil, cutting oil and paints, and cable insulation. Slightly strong correlation of PCBs with TOC than BC demonstrated that amorphous organic matter (AOM) assumes a more critical part in holding of PCBs than BC in Nepalese soil. The fugacity fraction (ff) results indicated the soil being the source of PCB in air through volatilization and net transport from soil to air. The soil-air partitioning coefficient study suggests the absorption by soil organic matter control soil-air partitioning of PCBs. Slightly weak but positive correlation of measured Log KSA with Log KOA (R2 = 0.483) and Log KBC-A (R2 = 0.438) suggests that both Log KOA and Log KBC-A can predict soil-air partitioning to lesser extent for PCBs.

Microbial interactions in the arsenic cycle: adoptive strategies and applications in environmental management.

Arsenic (As) is a nonessential element that is often present in plants and in other organisms. However, it is one of the most hazardous of toxic elements globally. In many parts of the world, arsenic contamination in groundwater is a serious and continuing threat to human health. Microbes play an important role in regulating the environmental fate of arsenic. Different microbial processes influence the biogeochemical cycling of arsenic in ways that affect the accumulation of different arsenic species in various ecosystem compartments. For example, in soil, there are bacteria that methylate arsenite to trimethylarsine gas, thereby releasing arsenic to the atmosphere.In marine ecosystems, microbes exist that can convert inorganic arsenicals to organic arsenicals (e.g., di- and tri-methylated arsenic derivatives, arsenocholine,arsenobetaine, arsenosugars, arsenolipids). The organo arsenicals are further metabolized to complete the arsenic cycle.Microbes have developed various strategies that enable them to tolerate arsenic and to survive in arsenic-rich environments. Such strategies include As exclusion from cells by establishing permeability barrier, intra- and extracellular sequestration,active efflux pumps, enzymatic reduction, and reduction in the sensitivity of cellular targets. These strategies are used either singly or in combination. In bacteria,the genes for arsenic resistance/detoxification are encoded by the arsenic resistance operons (ars operon).In this review, we have addressed and emphasized the impact of different microbial processes (e.g., arsenite oxidation, cytoplasmic arsenate reduction, respiratory arsenate reduction, arsenite methylation) on the arsenic cycle. Microbes are the only life forms reported to exist in heavy arsenic-contaminated environments. Therefore,an understanding of the strategies adopted by microbes to cope with arsenic stress is important in managing such arsenic-contaminated sites. Further future insights into the different microbial genes/proteins that are involved in arsenic resistance may also be useful for developing arsenic resistant crop plants.

Spatial distribution of arsenic in groundwater of southern Nepal.

Groundwater is an important source of both drinking water and of irrigation in the Terai region of Nepal. Although thousands of tubewells have been drilled in this region, the distribution of those that have been sampled and analyzed for As contamination is not consistent across the region. Based on a recent blanket tubewell testing program conducted in Nepal in 2007, preliminary data are available that allows us to provide a perspective on the As-contamination situation in drinking water of the six southern the Terai districts of Nepal. Arsenic concentrations detected in drinking water of tubewells and dug wells in these districts ranged from 0 to 770 jg L-'. It was found that the majority of the tested wells contained water that had As level below 10 jg L-', which is the WHO guideline value for exposure to As. The mean As levels detected varied from 2 jtg L-' in the Sunsari, Dhanusha, and Rupandehi districts, to 6.27 pg L-' in the Kailali district. The distribution of As levels detected, based on the NIS guideline, and expressed as a percentage thereof, was highest in the tubewells of the Bara district (3.8%), followed by the Kailali district (3.4%). Wells that were between 0- and 20-m deep contained water that had the highest percentage of As residues that exceeded both the WHO and NIS guideline values. In shallow tubewells of all six tested districts, the highest As contamination levels were found at depths of <50-m. The proportion of the population that was most often exposed to As levels >50 jig L-' occurred in the Kailali district (4%), followed by the Bara district (3.6%). Using a system developed to classify the relative vulnerability of inhabitants to As through drinking water only the Kailali and Bara districts were classified as "highly vulnerable" to As exposure. The Kota Tulsipur VDC of the Kailali district was found to be the most prominent As hotspot, wherein the majority of tubewells contained more than 50 jtg L-1 of As.

Legacy and emerging flame retardants in indoor and outdoor dust from Indo-Gangetic Region (Patna) of India: implication for source apportionment and health risk exposure.

The fate of legacy and emerging flame retardants are poorly reported in developing countries, including India. Also, the positive matrix factorization (PMF) application-based source apportionment of these pollutants is less comprehensive. This study analyzed the contamination level and sources of 25 flame retardants in dust from India's central Indo-Gangetic Plain (Patna city) using the PCA and PMF model. Dust samples were collected from various functional areas of indoor (n = 22) and outdoor (n = 16) environments. The sum of four groups of FRs in indoor dust (median 8080 ng/g) was 3-4 times greater than the outdoor dust (median 2410 ng/g). The novel-brominated flame retardants (NBFRs) and organophosphate esters (OPFRs) were more dominant than polybrominated diphenyl ethers (PBDEs), indicating the influence of worldwide elimination of PBDEs. The median concentration of ∑NBFRs in indoor and outdoor dust was 1210 ng/g and 6820 ng/g, while the median concentration of ∑OPFRs was measured to be 383 ng/g and 1210 ng/g, respectively. Likewise, ∑9PBDEs in indoor and outdoor dust ranged from 2-1040 ng/g (median 38.8 ng/g) to 0.62-249 ng/g (median 10.7 ng/g), respectively. Decabromodiphenylethane (DBDPE) was identified as the most abundant NBFR in dust, comprising 99.9% of ∑6NBFR, while tri-cresyl phosphates (TMPPs) showed the highest concentration among OPFR and accounted for 75% ∑8OPFRs. The PMF analysis indicated that a significant fraction of FRs in the dust (80%) could derive from plastics, textiles, polyurethane foam, anti-foam agents, PVC, paint, and coatings. In comparison, debromination of higher PBDE congeners contributed 20% in the dust environment. FR's estimated daily exposure risk in dust showed dermal absorption as the main route of FR's intake to adult and children populations. Children were more vulnerable to the risk of FRs than the adult population. The estimated daily exposure risk for selected FRs in this study was 4-6 orders of magnitude lesser than the respective reference dose (RfD), proposing negligible health risk.

Physicochemical characteristics of paper industry effluents--a case study of South India Paper Mill (SIPM).

Pulp and paper mills generate varieties of pollutants depending upon type of the pulping process being used. This paper presents the characteristics of wastewater from South India Paper Mill, Karnataka, India which is using recycled waste paper as a raw material. The raw wastewater consists of 80-90 mg L( - 1) suspended solid and 1,010-1,015 mg L( - 1) dissolved solid. However, pH varied from 5.5-6.8. The biochemical oxygen demand and chemical oxygen demand ranged from 200-210 and 1,120-1,160 mg L( - 1), respectively. Aerobic treatment of raw effluent attribute to significant reduction in suspended solid (range between 25 to 30 mg L( - 1)) and total dissolved solid (range between 360 to 390 mg L( - 1)). However, pH, temperature, and electrical conductivity were found superior after treatment. Copper, cadmium, iron, lead, nickel, and zinc were found in less quantity in raw effluent and were almost completely removed after treatment. The dendrogram of the effluent quality parameters clearly indicate that South India Paper Mill does not meet Minimal National Standard set by central Pollution Control Board to discharge in agricultural field.

Passive air sampling of organochlorine pesticides in a northeastern state of India, Manipur.

Thirty-six polyurethane foam disk passive air samplers (PUF-PAS) were deployed over a year during January to December, 2009 at three locations, i.e., Imphal (urban site), Thoubal (rural site) and Waithou (alpine site) of Manipur, to assess the seasonal local atmospheric emission of selected organochlorine pesticides (OCPs). The average concentration of HCHs monitored at mountain site during hot season (Mar, Apr, and May) and rainy seasons (Jun, Jul, Aug, and Sep) were 403 and 349 pg/m3, respectively. DDTs had a high concentration with 384 pg/m3 at rural site and 379 pg/m3 at urban site during hot seasons. Endosulfans and chlordane were found high in concentration during hot seasons (260 pg/m3) and low during retreating monsoon seasons (44 pg/m3) at rural site. Most of the OCPs concentrations were high during cultivation period. The OCP concentrations of rainy season were highly correlated (p < 0.01) with OCPs of hot seasons. Further, positive correlation (p < 0.05) was also obtained between cold seasons and retreating monsoon. Principal component analysis showed a significant correlation among the four seasons and distribution pattern of OCPs in air. Back trajectory analysis by using HYPSLIT model showed a long range air transport of OCPs to the present study area. Present OCP levels at Manipur is an outcome of both local emission and also movement of air mass by long range atmospheric transport.

Data on fate and distribution of organophosphate esters in the soil - sediments from Kathmandu Valley, Nepal.

Globally, soil and sediments are known as the likely sinks of various organic pollutants, such as organophosphate esters (OPEs). However, the fate of OPEs in soil/sediment matrices is limited in the whole of South Asia, especially if there should be an occurrence of Nepal. This data article elucidates the fate and distribution of OPEs in soil and sediment samples from the capital city of Nepal (Kathmandu). A total of eight different compounds of OPE was measured in soil (N = 19) and sediment (N = 20) samples collected during October 2014. The median concentration and composition of the individual OPE have been discussed. Additionally, health risk exposure due to ingestion and dermal contact of OPE was assessed to mark the endanger of OPE. Moreover, risk quotient (RQ) for fish, Daphnia, and algae was calculated to forecast the risk of OPEs on aquatic organisms.

Spatial distribution, source analysis, and health risk assessment of heavy metals contamination in house dust and surface soil from four major cities of Nepal.

Raising population, deteriorating environmental conditions and limiting natural resources to handle the key environmental health problems have critically affected human health and the environment. Policy makers and planners in Nepal are more concerned today than at any other time in the past about the deterioration of the environmental condition. Therefore, understanding the connection between pollution and human wellbeing is fundamental endeavors to control pollution exposures and secure human wellbeing. This ability is especially critical for countries like Nepal where the issues of environmental pollution have customarily taken a second place to request for economic development. In this study, spatial distribution and sources of 12 heavy metals (HMs) were investigated in surface soils (n = 24) and house dust (n = 24) from four major urban areas of Nepal in order to mark the pollution level. Additionally, a health risk was estimated to establish the link between HMs pollution and human health. Results showed that the median concentration of Ag, Cd, Co, Cr, Cu, Ni, Pb, Sb, Mn and Zn in soil and dust were 2-13 times greater than the background value. The As, Zn, Cu, Cd, and Pb showed a relatively higher spatial variability in soil and dust. Zn was the most abundant metal measured in dust and soil and accounted for 59% and 55% of ∑7HMs, respectively. The HMs in soil and dust were poorly correlated with total organic carbon (TOC) and black carbon (BC), suggesting little or no influence on HMs contamination. Source analysis study indicated the distribution of Cr, Ni, Sb, Ag, Pb, Cu, and Zn in soil and dust are mainly affected by anthropogenic sources, particularly traffic emissions, industrial source, and domestic households materials, while Co, Fe, As, Mn and Cd were from natural sources. The estimated carcinogenic risk (CR) of HMs in soil and dust exceeded the acceptable level of human exposure, recommending significant CR to the local population.

Modeling of runoff water and runoff pesticide concentrations in upland bare soil using improved SPEC model.

The SPEC model (Predicted Environmental Concentrations in agricultural Soils) was developed and improved for the simulation of pesticide runoff. The model was applied to the Sakaecho upland bare soil field (Tokyo, Japan) to predict runoff water, sediment concentration in runoff water, pesticide concentrations in runoff water, and runoff sediment (clothianidin and imidacloprid) under artificial rainfall conditions. The results showed that the simulated time to first runoff agreed very well with the observed data. The simulated cumulative runoff, sediment yield, and imidacloprid concentration in sediment agreed well with the observed data (Nash-Sutcliffe Efficiency (NSE)>0.75). The simulated runoff rate agreed reasonably well with the observed data (NSE >0.5). The predicted clothianidin concentrations in sediment and in runoff water had acceptable agreement with the observed data (NSE >0). The results implied the model's potential to predict runoff water, sediment yield, and pesticide runoff.

Soil erosion and transport of Imidacloprid and Clothianidin in the upland field under simulated rainfall condition.

Surface runoff has been recognized as an important medium of pesticides transport to surface water and groundwater causing critical risk to the aquatic ecosystem. Although total pesticide transport in surface runoff in most cases reported being below 1% of applied mass, much larger losses may occur in extreme cases. In this study, surface runoff potential of Imidacloprid and Clothianidin was investigated in an upland field with 5% slope under two simulated rainfall experiments of 70 mm/h intensity. Additionally, the downward movement of the pesticides was determined in soil (n = 87) taken at several depths on different time scales. The result showed that the second rainfall experiment caused more surface runoff than first rainfall experiment, and accounted 30.0 mm and 21.2 mm of applied rainfall, respectively. The cumulative surface runoff developed during first and second rainfall experiments was equal to 30% and 44% of the applied rainfall, respectively. The sediment transport in runoff was relatively higher in second rainfall than first rainfall, and was mostly stable after 30 min of rainfall. The chemical masses of Imidacloprid and Clothianidin were primarily transported in runoff sediments than runoff water and accounted for 10.8% and 7.93% of the applied mass, respectively. The transport of Imidacloprid both in runoff water and sediment was 1-2 times greater than that of Clothianidin. The concentrations of both pesticides were measured highest in the second fraction of runoff (10 min) collected during the first experiment. In soil, the transport of both pesticides prior to rainfall experiment was 1-2 times greater than post-rainfall experiments. The concentration of these pesticides decreased continuously with the time in the upper layer of soil; while a gradual increase of the pesticides mass was observed in the second soil layer. The cumulative mass transport of both pesticides was directly proportional to the cumulative runoff depth.

Polycyclic aromatic hydrocarbons in house dust and surface soil in major urban regions of Nepal: Implication on source apportionment and toxicological effect.

Urban centers have turned to be the provincial store for resource consumptions and source releases of different types of semi-volatile organic compounds (SVOCs) including polycyclic aromatic hydrocarbons (PAHs), bringing about boundless environmental pollutions, among different issues. Human prosperity inside urban communities is unambiguously dependent on the status of urban soils and house dusts. However, environmental occurrence and sources of release of these SVOCs are challenging in Nepalese cities, as exceptionally very limited data are accessible. This motivated us to explore the environmental fate, their source/sink susceptibilities and health risk associated with PAHs. In this study, we investigated the contamination level, environmental fate and sources/sink of 16 EPA's priority pollutants in surface soil and house dusts from four major cities of Nepal. Additionally, the toxicological effect of individual PAH was studied to assess the health risk of PAHs. Generally, the concentrations of ∑16PAHs in surface soil were 1.5 times higher than house dust, and ranged 767-6770ng/g dry weight (dw) (median 1810ng/g dw), and 747-4910 dw (median 1320ng/g dw), respectively. High molecular weight-PAHs both in soil and dust were more abundant than low molecular weight-PAHs, suggesting the dominance of pyrogenic source. Moderate to weak correlation of TOC and BC with PAHs in soil and dust suggested little or no role of soil organic carbon in sorption of PAHs. Source diagnostic ratio and principal component analysis indicated fossil fuel combustion, traffic/vehicular emissions and combustion of biomass are the principal sources of PAHs contamination in Nepalese urban environment. The high average TEQ value of PAHs in soil than dust suggested high risk of soil carcinogenicity compared to dust.

Organophosphate ester flame retardants in Nepalese soil: Spatial distribution, source apportionment and air-soil exchange assessment.

Despite soil being the major terrestrial environmental reservoir and one of the significant sinks for many hydrophobic organic compounds including organophosphate ester flame retardants (OPFRs), limited information is available about concentration and fate of OPFRs contamination in urban soil in general and especially in case of Nepal. This study investigates the environmental concentration, spatial distribution and source apportionment of eight OPFRs in surface soil (n = 28) from four major cities of Nepal with special interest on air-soil exchange. Overall, significantly high concentrations of ∑8OPFR were measured in soil ranging from 25-27,900 ng/g dw (median 248 ng/g dw). In terms of compositional pattern, tris(methyl phenyl) phosphate (TMPP) was the most abundant phosphorus chemical in soil, followed by tris(2-chloroisopropyl) phosphate (TCIPP), and accounted for 35-49% and 8-25% of ∑8OPFRs, respectively. The high level of these OPFRs was attributed to local sources as opposed to transboundary influence from remote areas. A Spearman's rank correlation analysis exhibited weak correlation of ∑8OPFRs with TOC (Rho = 0.117, p < 0.05) and BC (Rho = 0.007, p < 0.05), suggesting little or no influence of TOC and BC on the concentration of ∑8OPFRs. The fugacity fraction (ff) results indicated a strong influence of soil contamination on atmospheric level of OPFRs via volatilization.

Environmental concentration and atmospheric deposition of halogenated flame retardants in soil from Nepal: Source apportionment and soil-air partitioning.

While various investigations have been driven on polybrominated diphenyl ethers (PBDEs) and other flame retardants (FRs) in different framework around the world, information about contamination and fate of PBDEs and other FRs in developing countries especially in the Indian subcontinent is uncommon. Nepal being located in the Indian subcontinent, very little is known about contamination level of semi-volatile organic pollutants discharged into the environment. This motivated us to investigate the environmental fate of halogenated flame retardant (HFRs) in Nepalese condition. In this study, we investigated the concentration, fate, and sources of 9 PBDEs, 2 dechlorane plus isomers (DPs), and 6 novel brominated flame retardants (NBFRs). Moreover, air-soil exchange and soil-air partitioning were also evaluated to characterize the pattern of air-soil exchange and environmental fate. In general, the concentrations of NBFRs in soil were more prevalent than PBDEs and DPs, and accounted 95% of ∑HFRs. By and large, the concentrations of NBFRs and DPs were measured high in Kathmandu, while PBDEs level exceeded in Pokhara. Principal component analysis (PCA) study suggested contributions from commercial penta-, octa-, and deca-BDEs products and de-bromination of highly brominated PBDEs as the significant source of PBDEs. Likewise, low fanti ratio suggested DPs in soil might have originated from long-range atmospheric transport from remote areas, while high levels of decabromodiphenyl ethane (DBDPE) in soil were linked with the use of wide varieties of consumer products. The estimated fugacity fraction (ff) for individual HFR was quite lower (<0.05) than equilibrium value, suggesting that deposition and net transport from air to the soil is overwhelming. Soil-air partitioning study revealed neither octanol-air partition coefficient (KOA) nor black carbon partition coefficient (KBC-A) is an appropriate surrogate for soil organic matter (SOM), subsequently, absorption by SOM has no or little role in the partitioning of HFRs.

Concentration and spatial distribution of organophosphate esters in the soil-sediment profile of Kathmandu Valley, Nepal: Implication for risk assessment.

Despite the fact that soil and sediments, which act as a sink or potential source of organic pollutants, have been polluted with organophosphate esters (OPEs) around the globe, extremely constrained data is accessible on environmental concentration and fate of OPEs in solid matrices in whole of the South Asia particularly if there should be an occurrence in Nepal. In this study, surface soil (N=19) and sediments samples (N=20) were analyzed for eight different OPE in Kathmandu Valley during October 2014. The concentration of ∑8OPE measured in sediments samples was 12 times higher than soil and ranged 983-7460ng/g dw (median 2210ng/g dw) and 65-27,500ng/g dw (186ng/g dw), respectively. TMPP was most abundant in soil followed by TCIPP, TEHP and EHDPHP and ranged 17-25,300ng/g dw (41.3ng/g dw), 11.2-911ng/g dw (31.7ng/g dw), 8.52-858ng/g dw (26.1ng/g dw) and 10.2-114ng/g dw (25.6ng/g dw), respectively. TEHP was most prevalent in sediments followed by TMPP and EHDPHP and were in the range of 657-3020ng/g dw (median 1140ng/g dw), 267-2630ng/g dw (median 815g/g dw), 34-418ng/g (median 131ng/g dw), respectively. The sources of the high level of OPEs in soil was related to the end point use of consumer materials, traffic emission, and close proximity to commercial and industrial areas; while domestic sewage discharges and effluents from carpet industry were identified as the possible entry of OPE in sediments. Total organic carbon (TOC) and black carbon (BC) content in soil were moderately and positively correlated with ∑8OPE indicating more or less influence of soil organic carbon. The health risk assessment suggested dermal absorption of OPEs via soil is the primary pathway of human exposure to the general population. The significantly high-risk quotient (RQ) estimated for ∑8OPEs especially TMPP and TPHP suggested significant potential adverse risk for aquatic organisms.