Spatio-temporal distribution of organochlorine pesticides in agricultural soils of southeast China during 2014-2019.

Organochlorine pesticides (OCPs) are organic pollutants that are persistent and undegradable in the environment. To investigate their residual concentrations, spatial and temporal distributions, and the relationship with the crops planted, 12 individual OCPs in 687 soil samples from Jiangsu, Zhejiang and Jiangxi provinces of southeast China were examined. The detection frequencies of OCPs in the studied areas were 1.89%-64.9%. The concentrations of dichloro-diphenyl-trichloroethanes (DDTs), hexachlorocyclohexanes (HCHs), and endosulfans ranged from 0.01 to 5659 µg/kg, 0.03-3.58 µg/kg, and 0.05-3235 µg/kg, respectively. Jiangsu was mainly contaminated by p,p'-DDT, p,p'-DDD and endosulfan sulfate, Zhejiang was more polluted by OCPs except δ-HCH, and Jiangxi was more vulnerable to the contamination of OCPs except o,p'-DDE. The partial least-squares discrimination analysis (PLS-DA) model with RX2 36.3-36.8% revealed that compounds with similar chemical properties tended to appear in the same year and month. All crop lands were polluted by DDTs and Endosulfans. The highest concentrations of DDTs and Endosulfans were found in citrus and vegetable fields, respectively. This study offers new insight into the layout and partitioning of OCPs in agricultural land and into insecticide management on public health and ecological safety.

National temporal trend for organophosphate pesticide DDT exposure and associations with chronic kidney disease using age-adapted eGFR model.

Whilst certain environmental organochlorine pesticide exposure may still pose significant burden, the associations between dichloro-diphenyl-trichloroethane (DDT) and chronic kidney disease (CKD) remain disputable notwithstanding the potentially inaccurate disease definition between age groups. National DDT exposure burden atlas was depicted from 92,061 participants by measuring their serum concentrations of DDT congeners and major metabolite in the US from 1999 to 2016. Temporal analyses of these toxicant exposure suggested that although serum DDT concentrations exhibited recent decline, the detection rates remain up to 99.8% every year, posing great concern for exposure risk. A total of 3,039 US adults were further included from these participants demonstrating the weighted CKD prevalence of 40.2% using the new age-adapted CKD-EPI40 model compared to 28.0% using the current CKD-EPI method. After adjustment for covariates, logistic regression model results showed individual metabolites and total DDT burden were positively, yet monotonically, associated with risk of CKD incidence (P-trend for all < 0.05), particularly among adults 40 years of age and older. Much heightened renal disease risk was also observed with high DDT exposure (OR, 1.55; 95 % CI, 1.11-2.15) in those who were hypertensive (P for heterogeneity < 0.001) but not with diabetes. The current high DDT exposure risk combined with elevated probability for CKD incidence call for health concerns and management for the environmentally persistent pollutants.

A Synergistic Platform for Continuous Co-removal of 1,1,1-Trichloroethane, Trichloroethene, and 1,4-Dioxane via Catalytic Dechlorination Followed by Biodegradation.

Groundwater co-contaminated with 1,4-dioxane, 1,1,1-trichloroethane (TCA), and trichloroethene (TCE) is among the most urgent environmental concerns of the U.S. Department of Defense (DoD), U.S. Environmental Protection Agency (EPA), and industries related to chlorinated solvents. Inspired by the pressing need to remove all three contaminants at many sites, we tested a synergistic platform: catalytic reduction of 1,1,1-TCA and TCE to ethane in a H2-based membrane palladium-film reactor (H2-MPfR), followed by aerobic biodegradation of ethane and 1,4-dioxane in an O2-based membrane biofilm reactor (O2-MBfR). During 130 days of continuous operation, 1,1,1-TCA and TCE were 95-98% reductively dechlorinated to ethane in the H2-MPfR, and ethane served as the endogenous primary electron donor for promoting 98.5% aerobic biodegradation of 1,4-dioxane in the O2-MBfR. In addition, the small concentrations of the chlorinated intermediate from the H2-MPfR, dichloroethane (DCA) and monochloroethane (MCA), were fully biodegraded through aerobic biodegradation in the O2-MBfR. The biofilms in the O2-MBfR were enriched in phylotypes closely related to the genera Pseudonocardia known to biodegrade 1,4-dioxane.

Sequential coupling of bio-augmented permeable reactive barriers for remediation of 1,1,1-trichloroethane contaminated groundwater.

Sequential coupling of high-density luffa sponge (HDLS) immobilized microorganism and permeable reactive barriers (IM Bio-PRBs) was superior to intimate coupling of free microorganism and permeable reactive barriers (FM Bio-PRBs) for remediation of 1,1,1-trichloroethane contaminated groundwater. IM Bio-PRBs had much better performance to removal 1,1,1-trichloroethane (1,1,1-TCA) and prevent the transport of 1,1,1-TCA and inorganic ions (NO3-, PO43-, and SO42-). The majority of them were prevented and accumulated in upgradient of IM Bio-PRBs. 1,1,1-TCA and inorganic ions in there contributed to the much faster growth of microorganism in upgradient aquifer. Therefore, the removal of 1,1,1-TCA and consumption of inorganic ions in upgradient of Bio-PRBs played a constructive role in reducing the processing load of following zero-valent iron (ZVI) PRBs and the negative effect of free microorganism cells (biological clogging) and inorganic ions (chemical clogging) on Bio-PRB permeability. In addition, IM Bio-PRBs were more conducive to accelerate the removal of 1,1,1-TCA in long-term remediation and 1,1,1-TCA residual concentration significantly lower than the safety standard of 0.2 mg L-1. The change of terminal by-products of 1,1,1-TCA contaminated groundwater in Bio-PRBs showed that 1,1,1-TCA could be effectively de-chlorinated and mineralized in Bio-PRBs. The reductant H2S (prolong the service life of ZVI-PRBs) was much more produced and utilized in IM Bio-PRBs. Taken together, sequentially coupled IM Bio-PRBs had a better overall performance, and its service life could be prolonged. It was a different design and idea to update conventional PRB remediation technology and theory.

Effects of biological clogging on 1,1,1-TCA and its intermediates distribution and fate in heterogeneous saturated bio-augmented permeable reactive barriers.

Biological clogging in porous media was an important concern in the design of bio-augmented permeable reactive barriers (Bio-PRBs) that were used to remediate groundwater with dense non-aqueous phase liquids (DNAPLs). Here, we used laboratory sandbox experiments to develop and calibrate reactive transport models (C1 and C2) simulating 1,1,1-trichloroethane (1,1,1-TCA) change in heterogeneous saturated porous media. The routine (1,1,1-TCA chain kinetic reactions) and subroutine (the relationship between hydraulic conductivity (K) and time (t)) were included in the model computer code. The simulation results suggested that the model C1 had the applicability for simulating contaminant transport and fate in bio-augmented flow field. By using the model C1 which was suitable for constant K condition, the performance of different types of Bio-PRBs was evaluated, and the regularity of contaminants chain kinetic reactions in different heterogeneous saturated porous media was obtained. The results demonstrated that Bio-PRBs in immobilized microorganism (IM) protocol were more superior to Bio-PRBs in free microorganism (FM) protocol. In addition, by using the model C2 (updated model C1) which was suitable for decreasing K condition, the different and optimized regularity of contaminants transport and transformation was obtained. The results showed that microbial growth which further decreased K was beneficial to preventing the transport of contaminants and accelerating the transformation of contaminants. However, the negative effects of biological clogging on hydraulic conductivity and relative hydraulic conductivity ratio in FM Bio-PRBs were significantly stronger than that in IM Bio-PRBs. Deploying IM Bio-PRBs for groundwater remediation would be much more efficient and meet the design criteria. The research work had guiding significance to engineering and provided consultation for designing and optimizing Bio-PRBs system. To make the design and optimization of Bio-PRBs system convenient, it was very essential to choose the suitable mathematical model (C1 or C2).

Human Health Risk from Consumption of Marine Fish Contaminated with DDT and Its Metabolites in Maputo Bay, Mozambique.

Many countries with incidence of malaria, including those surrounding Maputo Bay, use dichloro-diphenyl-trichloroethane (DDT) to reduce mosquitoes. This study is the first to estimate the human health risk associated with consumption of marine fish from Maputo Bay contaminated with DDTs. The median for ∑DDTs was 3.8 ng/g ww (maximum 280.9 ng/g ww). The overall hazard ratio for samples was 1.5 at the 75th percentile concentration and 28.2 at the 95th percentile. These calculations show increased potential cancer risks due to contamination by DDTs, data which will help policy makers perform a risk-benefit analysis of DDT use in malaria control programs in the region.

Spectroscopic methods for aqueous cyclodextrin inclusion complex binding measurement for 1,4-dioxane, chlorinated co-contaminants, and ozone.

Recalcitrant organic contaminants, such as 1,4-dioxane, typically require advanced oxidation process (AOP) oxidants, such as ozone (O3), for their complete mineralization during water treatment. Unfortunately, the use of AOPs can be limited by these oxidants' relatively high reactivities and short half-lives. These drawbacks can be minimized by partial encapsulation of the oxidants within a cyclodextrin cavity to form inclusion complexes. We determined the inclusion complexes of O3 and three common co-contaminants (trichloroethene, 1,1,1-trichloroethane, and 1,4-dioxane) as guest compounds within hydroxypropyl-ß-cyclodextrin. Both direct (ultraviolet or UV) and competitive (fluorescence changes with 6-p-toluidine-2-naphthalenesulfonic acid as the probe) methods were used, which gave comparable results for the inclusion constants of these species. Impacts of changing pH and NaCl concentrations were also assessed. Binding constants increased with pH and with ionic strength, which was attributed to variations in guest compound solubility. The results illustrate the versatility of cyclodextrins for inclusion complexation with various types of compounds, binding measurement methods are applicable to a wide range of applications, and have implications for both extraction of contaminants and delivery of reagents for treatment of contaminants in wastewater or contaminated groundwater.

Biochar supported Ni/Fe bimetallic nanoparticles to remove 1,1,1-trichloroethane under various reaction conditions.

In this study, Ni/Fe nanoparticles supported by biochar to stimulate the reduction of 1,1,1-trichloroethane (1,1,1-TCA) in groundwater remediation was investigated. In order to enhance the reactivity of ZVI (zero valent iron) nanoparticles, surface modification of ZVI was performed using nickel and biochar. The removal efficiency of 1,1,1-TCA increased from 42.3% to 99.3% as the biochar-to-Ni/Fe mass ratio increased from 0 to 1.0. However a higher biochar-to-Ni/Fe ratio showed little difference in the 1,1,1-TCA degradation efficiency. In the presence of Ni, atomic hydrogen generated by ZVI corrosion could be absorbed in the metal additive's lattice and then produce a hydride-like species (H) that represented the primary redox-active entity. The effects of various factors were evaluated, including pH, humic acid (HA) and inorganic matters (Cl-, CO32-, HCO3-, NO3- and SO42-). The degradation of 1,1,1-TCA was greatly affected by pH. The presence of Cl-, CO32-, HCO3- and SO42- had negligible effects, but NO3- and HA showed a significant inhibitory effects on 1,1,1-TCA degradation. In conclusion, biochar supported Ni/Fe nanoparticles could be highly effective for 1,1,1-TCA degradation.

Concentration effects on biotic and abiotic processes in the removal of 1,1,2-trichloroethane and vinyl chloride using carbon-amended ZVI.

A permeable reactive barrier, consisting of both zero valent iron (ZVI) and a biodegradable organic carbon, was evaluated for the remediation of 1,1,2-trichloroethane (1,1,2-TCA) contaminated groundwater. During an 888 day laboratory column study, degradation rates initially stabilized with a degradation half-life of 4.4±0.4 days. Based on the accumulation of vinyl chloride (VC) and limited production of 1,1-dichloroethene (1,1-DCE) and 1,2-dichloroethane (1,2-DCA), the dominant degradation pathway was likely abiotic dichloroelimination to form VC. Degradation of VC was not observed based on the accumulation of VC and limited ethene production. After a step reduction in the influent concentration of 1,1,2-TCA from 170±20 mg L(-1) to 39±11 mg L(-1), the degradation half-life decreased 5-fold to 0.83±0.17 days. The isotopic enrichment factor of 1,1,2-TCA also changed after the step reduction from -14.6±0.7‰ to -0.72±0.12‰, suggesting a possible change in the degradation mechanism from abiotic reductive degradation to biodegradation. Microbiological data suggested a co-culture of Desulfitobacterium and Dehalococcoides was responsible for the biodegradation of 1,1,2-TCA to ethene.

nZVI injection into variably saturated soils: Field and modeling study.

Nano-scale zero valent iron (nZVI) has been used at a number of contaminated sites over the last decade. At most of these sites, significant decreases in contaminant concentrations have resulted from the application of nZVI. However, limited work has been completed investigating nZVI field-scale mobility. In this study, a field test was combined with numerical modeling to examine nZVI reactivity along with transport properties in variably saturated soils. The field test consisted of 142L of carboxymethyle cellulose (CMC) stabilized monometallic nZVI synthesized onsite and injected into a variably saturated zone. Periodic groundwater samples were collected from the injection well, as well as, from two monitoring wells to analyze for chlorinated solvents and other geochemistry indicators. This study showed that CMC stabilized monometallic nZVI was able to decrease tricholorethene (TCE) concentrations in groundwater by more than 99% from the historical TCE concentrations. A three dimensional, three phase, finite difference numerical simulator, (CompSim) was used to further investigate nZVI and polymer transport at the variably saturated site. The model was able to accurately predict the field observed head data without parameter fitting. In addition, the numerical simulator estimated the mass of nZVI delivered to the saturated and unsaturated zones and distinguished the nZVI phase (i.e. aqueous or attached). The simulation results showed that the injected slurry migrated radially outward from the injection well, and therefore nZVI transport was governed by injection velocity and viscosity of the injected solution. A suite of sensitivity analyses was performed to investigate the impact of different injection scenarios (e.g. different volume and injection rate) on nZVI migration. Simulation results showed that injection of a higher nZVI volume delivered more iron particles at a given distance; however, the travel distance was not proportional to the increase in volume. Moreover, simulation results showed that using a 1D transport equation to simulate nZVI migration in the subsurface may overestimate the travel distance. This is because the 1D transport equation assumes a constant velocity while pore water velocity radially decreases from the well during injection. This study suggests that on-site synthesized nZVI particles are mobile in the subsurface and that a numerical simulator can be a valuable tool for optimal design of nZVI field applications.

Detection of persistent OCPs and PCBs congeners in the near-shore coastal waters of Alexandria, Egypt.

The residues of 19 EPA-organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were determined in water samples collected from the near-shore surface water of Alexandria coast, Egypt, using gas chomatograph-electron capture detector (GC-ECD) and gas chromatograph-mass spectometer (GC-MS). Higher concentrations of hexachlorocyclohexane (HCH)s, TC, and 2,2-bis (p-chlorophenyl)-1,1,1-trichloroethane (DDT)s with 1.36, 0.556, and 36.97 ngl(-1) were recorded, respectively, with a maximum of 165.46 ngl(-1) of PCBs during June 2014, which was clearly affected by higher sewage activities during summer season. Among DDTs metabolites, p,p-DDT was the most dominant with a maximum of 36.31 ngl(-1) recorded at El-Montazah station during June 2014.

Evidence of 1,4-dioxane attenuation at groundwater sites contaminated with chlorinated solvents and 1,4-dioxane.

There is a critical need to develop appropriate management strategies for 1,4-dioxane (dioxane) due to its widespread occurrence and perceived recalcitrance at groundwater sites where chlorinated solvents are present. A comprehensive evaluation of California state (GeoTracker) and Air Force monitoring records was used to provide significant evidence of dioxane attenuation at field sites. Temporal changes in the site-wide maximum concentrations were used to estimate source attenuation rates at the GeoTracker sites (median length of monitoring period = 6.8 years). While attenuation could not be established at all sites, statistically significant positive attenuation rates were confirmed at 22 sites. At sites where dioxane and chlorinated solvents were present, the median value of all statistically significant dioxane source attenuation rates (equivalent half-life = 31 months; n = 34) was lower than 1,1,1-trichloroethane (TCA) but similar to 1,1-dichloroethene (1,1-DCE) and trichloroethene (TCE). Dioxane attenuation rates were positively correlated with rates for 1,1-DCE and TCE but not TCA. At this set of sites, there was little evidence that chlorinated solvent remedial efforts (e.g., chemical oxidation, enhanced bioremediation) impacted dioxane attenuation. Attenuation rates based on well-specific records from the Air Force data set confirmed significant dioxane attenuation (131 out of 441 wells) at a similar frequency and extent (median equivalent half-life = 48 months) as observed at the California sites. Linear discriminant analysis established a positive correlation between dioxane attenuation and increasing concentrations of dissolved oxygen, while the same analysis found a negative correlation with metals and CVOC concentrations. The magnitude and prevalence of dioxane attenuation documented here suggest that natural attenuation may be used to manage some but not necessarily all dioxane-impacted sites.

Chemical exposure levels in printing workers with cholangiocarcinoma.

OBJECTIVE: This study aimed to identify chemicals used by printing workers with cholangiocarcinoma, as well as the levels of exposure to the chemicals. METHODS: Information necessary to identify chemicals used by printing workers with cholangiocarcinoma and to estimate chemical exposure concentrations was obtained from the Ministry of Health, Labour and Welfare, Japan. Working environment concentrations of the chemicals in the printing rooms were estimated using a well-mixed model, and exposure concentrations during the ink removal operation were estimated using a near-field and far-field model. Shift time- weighted averages (TWA) of exposure concentrations were also calculated. RESULTS: Two workers from each of three small printing plants examined suffered from cholangiocarcinoma, and all six of these workers had been exposed to 1,2-dichloropropane (1,2-DCP) for 10-16 years. The estimated working environment concentrations of 1,2-DCP in the printing rooms were 17-180 ppm and estimated exposure concentrations during the ink removal operation were 150-620 ppm. Shift TWA values were estimated to be 62-240 ppm. Four of the six workers had also been exposed to dichloromethane (DCM) at estimated working environment concentrations of 0-98 ppm and estimated exposure concentrations during the ink removal operation of 0-560 ppm. Shift TWA values were estimated to be 0-180 ppm. Other chlorinated organic solvents (1,1,1-trichloroethane, 1,1-dichloro-1-fluoroethane) and petroleum solvents (gasoline, naphtha, mineral spirit, mineral oil, kerosene) were also used in the ink removal operation. CONCLUSIONS: All six printing workers with cholangiocarcinoma were exposed to very high levels of 1,2-DCP for a long term.

A gated atmospheric pressure drift tube ion mobility spectrometer-time-of-flight mass spectrometer.

Identifying the compounds of an unknown gas mixture by using an ion mobility spectrometer (IMS) is a difficult task, because several ion species can be generated in the ionization process. One method to analyze the occurring peaks in an IMS spectrum is coupling an IMS to a mass spectrometer (MS). In our setup we coupled a (3)H drift tube IMS to a Bruker micrOTOF II. Therefore, the detector plate of the IMS is pierced and a transfer capillary is inserted. The ions are transferred via gas flow and electric fields into the MS. The transmission of the ions through the transfer capillary can be shuttered very precisely by increasing the electric potential of the detector generating a repulsive electric field. Thus, it is possible to transfer single ion clouds of generated IMS spectra into the mass spectrometer where a corresponding mass spectrum is generated. In this work we analyze the positive and negative IMS spectra of single analytes as well as gas mixtures and characterize the occurring ion species.

Behavior of nine selected emerging trace organic contaminants in an artificial recharge system supplemented with a reactive barrier.

Artificial recharge improves several water quality parameters, but has only minor effects on recalcitrant pollutants. To improve the removal of these pollutants, we added a reactive barrier at the bottom of an infiltration basin. This barrier contained aquifer sand, vegetable compost, and clay and was covered with iron oxide dust. The goal of the compost was to sorb neutral compounds and release dissolved organic carbon. The release of dissolved organic carbon should generate a broad range of redox conditions to promote the transformation of emerging trace organic contaminants (EOCs). Iron oxides and clay increase the range of sorption site types. In the present study, we examined the effectiveness of this barrier by analyzing the fate of nine EOCs. Water quality was monitored before and after constructing the reactive barrier. Installation of the reactive barrier led to nitrate-, iron-, and manganese-reducing conditions in the unsaturated zone below the basin and within the first few meters of the saturated zone. Thus, the behavior of most EOCs changed after installing the reactive barrier. The reactive barrier enhanced the removal of some EOCs, either markedly (sulfamethoxazole, caffeine, benzoylecgonine) or slightly (trimethoprim) and decreased the removal rates of compounds that are easily degradable under aerobic conditions (ibuprofen, paracetamol). The barrier had no remarkable effect on 1H-benzotriazole and tolyltriazole.

Stable carbon isotope analysis to distinguish biotic and abiotic degradation of 1,1,1-trichloroethane in groundwater sediments.

The fate and treatability of 1,1,1-TCA by natural and enhanced reductive dechlorination was studied in laboratory microcosms. The study shows that compound-specific isotope analysis (CSIA) identified an alternative 1,1,1-TCA degradation pathway that cannot be explained by assuming biotic reductive dechlorination. In all biotic microcosms 1,1,1-TCA was degraded with no apparent increase in the biotic degradation product 1,1-DCA. 1,1,1-TCA degradation was documented by a clear enrichment in (13)C in all biotic microcosms, but not in the abiotic control, which suggests biotic or biotically mediated degradation. Biotic degradation by reductive dechlorination of 1,1-DCA to CA only occurred in bioaugmented microcosms and in donor stimulated microcosms with low initial 1,1,1-TCA or after significant decrease in 1,1,1-TCA concentration (after∼day 200). Hence, the primary degradation pathway for 1,1,1-TCA does not appear to be reductive dechlorination via 1,1-DCA. In the biotic microcosms, the degradation of 1,1,1-TCA occurred under iron and sulfate reducing conditions. Biotic reduction of iron and sulfate likely resulted in formation of FeS, which can abiotically degrade 1,1,1-TCA. Hence, abiotic degradation of 1,1,1-TCA mediated by biotic FeS formation constitute an explanation for the observed 1,1,1-TCA degradation. This is supported by a high 1,1,1-TCA (13)C enrichment factor consistent with abiotic degradation in biotic microcosms. 1,1-DCA carbon isotope field data suggest that this abiotic degradation of 1,1,1-TCA is a relevant process also at the field site.

DDTs in mothers' milk, placenta and hair, and health risk assessment for infants at two coastal and inland cities in China.

This study is a one of the very few investigating the dichloro-diphenyl-trichloroethanes (DDTs) (summation of o,p'-DDE, p,p'-DDE, o,p'-DDD, p,p'-DDD, o,p'-DDT, and p,p'-DDT) in multiple human matrices in mothers' milk, placenta and hair collected from residents from two coastal cities: Guiyu (GY) and Taizhou (TZ) and one inland city: Lin'an (LA). TZ (milk: 360±319ng/g lipid wt.) showed significantly higher concentrations of DDTs than those from LA (milk: 190±131ng/g lipid wt.), whereas, concentrations of DDTs in GY (milk: 305±109ng/g lipid wt.) were in between TZ and LA. In addition, levels of DDTs in the human tissues from TZ (placenta: 122±109ng/g lipid wt.; hair: 79.9±215ng/g dry wt.) were significantly higher than those from Lin'an (placenta: 49.2±30.2ng/g lipid wt.; hair: 10.8±7.09ng/g dry wt.). The above concentrations of DDTs in milk exceeded the Codex Maximum Residue Limits/Extraneous Maximum Residue Limits for milk (20ng/g lipid wt. whole milk), indicating that the human milk samples were grossly polluted. The present study revealed that human specimens collected from the coastal city (TZ) were more contaminated with inland one (LA), based on the levels of DDTs contained in samples which may be due to the higher dietary exposure to DDTs via consumption of contaminated seafood. The estimated daily intakes of DDTs by GY, TZ and LA infants were 1.69±1.86, 1.48±0.79, and 0.95±0.73µg/kg body wt./day, respectively which did not exceed 10µg/kg body wt./day, the provisional tolerable daily intake proposed by the Food and Agriculture Organization/World Health Organization.

Comprehensive screening and priority ranking of volatile organic compounds in Daliao River, China.

An analytical strategy for comprehensive screening of target and non-target volatile organic compounds (VOCs) in surface water was developed, and it was applied to the analysis of VOCs in water samples from Daliao River. The target VOCs were quantified using purge and trap-gas chromatography-mass spectrometry (P&T-GC/MS). Among 20 water samples, 34 VOCs were detected at least once. For the screening of non-target VOCs, the double distillation apparatus was used for the pre-concentration of VOCs prior to P&T-GC/MS analysis. Subsequently, deconvolution software and NIST mass spectral library were applied for the identification of the non-target compounds. A total of 17 non-target VOCs were identified. The most frequently detected VOCs (detection frequencies >80 %) included toluene, benzene, naphthalene, 1,2-dichloroethane, 1,1,2-trichloroethane, and methyl tert-butyl ether. The distribution of VOCs obviously varied according to the sampling sites. The total concentrations of VOCs in water samples collected from the heavily industrialized cities (Anshan and Liaoyang) and the busy port city (Yingkou) were relatively high. The top ten priority VOCs, including naphthalene, 1,2-dichloroethane, o-xylene, 1,3-dichlorobenzene, tetrachloroethene, 1,2-dichlorobenzene, 1,2,4-trichlorobenzene, ethylbenzene, m-xylene, and p-xylene, were obtained by the ranking of the detected VOCs according to their occurrence and ecological effects. These compounds should be given more attention in monitoring and drainage control strategies.

The reductive degradation of 1,1,1-trichloroethane by Fe(0) in a soil slurry system.

Most studies on the treatment of chlorinated contaminants by Fe(0) focus on aqueous system tests. However, few is known about the effectiveness of these tests for degrading chlorinated contaminants such as 1,1,1-trichloroethane (TCA) in soil. In this work, the reductive degradation performance of 1,1,1-TCA by Fe(0) was thoroughly investigated in a soil slurry system. The effects of various factors including acid-washed iron, the initial 1,1,1-TCA concentration, Fe(0) dosage, slurry pH, and common constituents in groundwater and soil such as Cl(-), HCO3 (-), SO4 (2-), and NO3 (-) anions and humic acid (HA) were evaluated. The experimental results showed that 1,1,1-TCA could be effectively degraded in 12 h for an initial Fe(0) dosage of 10 g L(-1) and a soil/water mass ratio of 1:5. The soil slurry experiments showed two-stage degradation kinetics: a slow reaction in the first stage and a fast reductive degradation of 1,1,1-TCA in the second stage. The reductive degradation of 1,1,1-TCA was expedited as the mass concentration of Fe(0) increased. In addition, high pHs adversely affected the degradation of 1,1,1-TCA over a pH range of 5.4-8.0 and the reductive degradation efficiency decreased with increasing slurry pH. The initial 1,1,1-TCA concentration and the presence of Cl(-) and SO4(2-) anions had negligible effects. HCO3(-) anions had a accelerative effect on 1,1,1-TCA removal, and both NO3(-) and HA had inhibitory effects. A Cl(-) mass balance showed that the amount of Cl(-) ions released into the soil slurry system during the 1,1,1-TCA degradation increased with increasing reaction time, suggesting that the main degradation mechanism of 1,1,1-TCA by Fe(0) in a soil slurry system was reductive dechlorination with 1,1-DCA as the main intermediate. In conclusion, this study provides a theoretical basis for the practical application of the remediation of contaminated sites containing chlorinated solvent.

The impact of chlorinated solvent co-contaminants on the biodegradation kinetics of 1,4-dioxane.

1,4-Dioxane (dioxane), a probable human carcinogen, is used as a solvent stabilizer for 1,1,1-trichloroethane (TCA) and other chlorinated solvents. Consequently, TCA and its abiotic breakdown product 1,1-dichloroethene (DCE) are common co-contaminants of dioxane in groundwater. The aerobic degradation of dioxane by microorganisms has been demonstrated in laboratory studies, but the potential effects of environmentally relevant chlorinated solvent co-contaminants on dioxane biodegradation have not yet been investigated. This work evaluated the effects of TCA and DCE on the transformation of dioxane by dioxane-metabolizing strain Pseudonocardia dioxanivorans CB1190, dioxane co-metabolizing strain Pseudonomas mendocina KR1, as well as Escherichia coli expressing the toluene monooxygenase of strain KR1. In all experiments, both TCA and DCE inhibited the degradation of dioxane at the tested concentrations. The inhibition was not competitive and was reversible for strain CB1190, which did not transform the chlorinated solvents. For both strain KR1 and toluene monooxygenase-expressing E. coli, inhibition of dioxane degradation by chlorinated solvents was competitive and irreversible, and the chlorinated solvents were degraded concurrently with dioxane. These data suggest that the strategies for biostimulation or bioaugmentation of dioxane will need to consider the presence of chlorinated solvents during site remediation.