Chlorinated Hydrocarbon Pollutants Research Articles

Structure and Assembly Mechanism of Archaeal Communities in Deep Soil Contaminated by Chlorinated Hydrocarbons

Chlorinated hydrocarbons are typical organic pollutants in contaminated sites, and microbial remediation technology has attracted more and more attention. To study the structural characteristics and assembly mechanism of the archaeal community in chlorinated hydrocarbon-contaminated soil, unsaturated-zone soil within 2~10 m was collected. Based on high-throughput sequencing technology, the archaeal community was analyzed, and the main drivers, environmental influencing factors, and assembly mechanisms were revealed. The results showed that chlorinated hydrocarbon pollution altered archaeal community structure. The archaeal community composition was significantly correlated with trichloroethylene (r = 0.49, p = 0.001), chloroform (r = 0.60, p = 0.001), pH (r = 0.27, p = 0.036), sulfate (r = 0.21, p = 0.032), and total carbon (r = 0.23, p = 0.041). Under pollution stress, the relative abundance of Thermoplasmatota increased to 25.61%. Deterministic processes increased in the heavily polluted soil, resulting in reduced species richness, while positive collaboration among surviving species increased to 100%. These results provide new insights into the organization of archaeal communities in chlorinated hydrocarbon-contaminated sites and provide a basis for remediation activities.

Pollution characteristics of groundwater in an agricultural hormone-contaminated site and implementation of Fenton oxidation process.

The groundwater polluted by an agricultural hormone site was taken as the research object, and a total of 7 groundwater samples were collected at different locations in the plant. The main pollutants in the research area were determined to be extractable petroleum hydrocarbons (C10-C40); 1,2-dichloroethane; 1,1,2-trichloroethane; carbon tetrachloride; vinyl chloride, and chloroform; the maximum content of these pollutants can reach 271mg/L, 1.68 × 107µg/L, 1.56 × 104µg/L, 9.53 × 104µg/L, 6.58 × 104µg/L, and 4.81 × 104µg/L, respectively. Aiming at the problems of groundwater pollution in this area, two sets of oxidation experiments have been carried out. The addition of NaHSO3 modified Fenton oxidation system was used in this contaminated water, which enhanced (2.2 ~ 46.7%) chemical oxygen demand (COD) removal rate. The highest removal rate of extractable petroleum hydrocarbons (C10-C40) can reach 99%. And the degradation rate of chlorinated hydrocarbon pollutants can reach 99% to 100%, which almost achieved the purpose of complete removal. In the NaHSO3 modified Fenton oxidation system, the addition of NaHSO3 accelerates the cycle of Fe3+/Fe2+ and ensures the continuous existence of Fe2+ in the reaction system, thereby producing more ·OH and further oxidizing and degrading organic pollutants. Our work has provided important insights for this economically important treatment of this type water body and laid the foundation for the engineering of this method.

Migration and pollution control of chlorinated hydrocarbons in groundwater system of eastern Jinan

The groundwater system is polluted by chlorinated hydrocarbon pollution in eastern Jinan, Shandong province, China, exceeding the limit of pollutants concentration in class III of Groundwater Quality Standards (GQS, GB/T 14848-2017). In order to improve the current situation of chlorinated hydrocarbon pollutants in groundwater system of eastern Jinan, the optimization study of the pollution control is carried out. In this paper, the pollutant of carbon tetrachloride in groundwater system is taken as the main research object, and the solute transport model is established by using GMS numerical simulation software. The simulation results illuminate that with the passage of time, the concentration of carbon tetrachloride decreases, but the acreage of pollution plume in groundwater still has little change, and it is hard to reach the limit standard of 2.0 μg/L in class III of GQS within a short time. Sequentially, on the basis of simulation model, the optimization of pumping and injection wells is conducted in the pollution control field of research region. The results turn out that the layout of 8 pumping and 5 injection wells has the best control effect of carbon tetrachloride in groundwater system, the pollutant concentration reached the limit standard of 2.0 μg/L in only 1187 d, and the acreage of pollution plume in control field reduced from 21.80 km2 to 12.21 km2. In summary, through the optimal pollution control scheme of carbon tetrachloride, the time for pollutant concentration to reach 2.0 μg/L has been reduced, and the acreage of pollution plume has been effectively controlled.

Numerical simulation and prediction of chlorinated hydrocarbon migration in eastern Jinan

In this paper, the pollution of carbon tetrachloride in the Groundwater system is taken as the main research object. By selecting the monitoring sample points of shallow groundwater and using MT3DMS module in GMS numerical simulation software to establish the migration and transformation model of typical chlorinated hydrocarbons. Sequentially, predicting the development trend of carbon tetrachloride pollution. The results show that with the passage of time, the concentration of pollutants decreases due to the adsorption and attenuation of solid phase media, the pollution range of carbon tetrachloride decreases, and the overall pollution degree of carbon tetrachloride in karst water decreases. From the simulation results, the concentration time-duration curves of the typical points in different parts of the southern, central and northern parts of the pollution plume were extracted, and the linear equation was used for fitting. The fitting effect is good and conforms to the first-order attenuation equation, providing ideas for the prevention and treatment of chlorinated hydrocarbon pollution in the subsequent groundwater.

Electrocatalytic hydrodechlorination of 2,4-dichlorophenol over palladium nanoparticles and its pH-mediated tug-of-war with hydrogen evolution

Electrocatalytic hydrodechlorination (EHDC) is a promising environmental technology that can produce highly active atomic hydrogen (H∗ad) to detoxify chlorinated hydrocarbon pollutants in water via the hydrogenolysis of C–Cl bonds. However, its efficiency is hampered by hydrogen evolution reaction (HER) in aqueous media which competes with EHDC by consuming H∗ad. Here we report that, by controlling the solution pH, we can facilely tune the relative kinetics of EHDC of 2,4-dichlorophenol (2,4-DCP) and HER over palladium nanoparticles (Pd NPs) for an optimized EHDC reaction. The batch EHDC experiments with different starting pHs find that both the EHDC efficiency (conversion rate of 2,4-DCP to phenol) and H∗ad utilization efficiency (HUE%, the molar percentage of H∗ad used by EHDC) present a volcano-shaped relationship vs. starting solution pH, with the peak EHDC efficiency of 66.4% and HUE% of 35–40% achieved at pHs of 2.12 and 3.49, respectively. The mechanism study finds that this volcano relationship originates from the dual effect of pH on both the H∗ad production rate and the adsorption behavior of 2,4-DCP over Pd NPs. The overfast generation of H∗ad at very low pHs and the poor adsorption of 2,4-DCP on electrode under alkaline conditions will both favor the HER over EHDC. A solution condition of weak acid is thus ideal to optimize the EHDC performance. This work presents an efficient approach to improve the EHDC efficiency and energy selectivity by tuning the solution pH, which should advance the EHDC application in environmental remediation.

Pollution Removal Performance of Laboratory Simulations of Sydney’s Street Stormwater Biofilters

The City of Sydney is constructing more than 21,000 square metres of street biofilter units (raingardens) in terms of their Decentralised Water Master Plan (DWMP), for improving the quality of stormwater runoff to Port Jackson, the Cooks River, and the historical Botany Bay. Recharge of the Botany Sand Beds aquifer, currently undergoing remediation by extraction of industrial chlorinated hydrocarbon pollutants, is also envisaged. To anticipate the pollution removal efficiency of field biofilter designs, laboratory soil-column simulations were developed by Western Sydney University partnered with the City. Synthetic stormwater containing stoichiometric amounts of high-solubility pollutant salts in deionised water was passed through 104 mm columns that were layered to simulate monophasic and biphasic field designs. Both designs met the City’s improvement targets for total nitrogen (TN) and total phosphorus (TP), with >65% median removal efficiency. Prolonged release of total suspended solids (SS) on startup emphasised the need for specifications and testing of proprietary fills. Median removal efficiency for selected heavy metal ecotoxicants was >75%. The researchers suggested that Zinc be added to the targets as proxy for metals, polycyclic aromatic hydrocarbons (PAH) and oils/greases co-generated during road use. Simulation results suggested that field units will play an important role in meeting regional stormwater improvement targets.

Theoretical study on the hydrolytic step in the biotransformation of β-hexachlorocyclohexane degraded by haloalkane dehalogenase LinB

The hydrolytic process of LinB-catalyzed biotransformation of a notorious contaminant β-HCH was investigated in atomistic detail with a combined quantum mechanics/molecular mechanics approach. The Boltzmann-weighted averaging method amended by disproportionate effect analysis was showed to capture the fluctuation of a single molecule enzyme reaction. With the potential barriers of 18.7 and 2.6 kcal/mol, two elementary steps that refer to formation and decomposition of a tetrahedral intermediate are involved in the hydrolytic reaction, respectively. Polarized by Glu132, His272 serves as a proton carrier along the whole hydrolysis reaction. The electrostatic influence analysis highlighted residue Leu248 as a possible mutation target for rational design of LinB in enzyme modification. Further spatial location analysis provided explanation for the opposite effect of Asn38 toward the two elementary steps. Getting insight into the catalytic details and the structure and function of LinB can enrich the knowledge of it and promote its application in bioremediation of chlorinated hydrocarbon pollutants.

Microbial transformations of selenite by methane-oxidizing bacteria

Methane-oxidizing bacteria are well known for their role in the global methane cycle and their potential for microbial transformation of wide range of hydrocarbon and chlorinated hydrocarbon pollution. Recently, it has also emerged that methane-oxidizing bacteria interact with inorganic pollutants in the environment. Here, we report what we believe to be the first study of the interaction of pure strains of methane-oxidizing bacteria with selenite. Results indicate that the commonly used laboratory model strains of methane-oxidizing bacteria, Methylococcus capsulatus (Bath) and Methylosinus trichosporium OB3b, are both able to reduce the toxic selenite (SeO32−) but not selenate (SeO42−) to red spherical nanoparticulate elemental selenium (Se0), which was characterized via energy-dispersive X-ray spectroscopy (EDXS), X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). The cultures also produced volatile selenium-containing species, which suggests that both strains may have an additional activity that can transform either Se0 or selenite into volatile methylated forms of selenium. Transmission electron microscopy (TEM) measurements and experiments with the cell fractions cytoplasm, cell wall and cell membrane show that the nanoparticles are formed mainly on the cell wall. Collectively, these results are promising for the use of methane-oxidizing bacteria for bioremediation or suggest possible uses in the production of selenium nanoparticles for biotechnology.

Source apportionment of groundwater pollution in a city’s eastern part using multivariate statistical techniques

This study was carried out to assess the overall water quality and identify major chlorinated hydrocarbon variables affecting the groundwater quality. The source apportionment of groundwater pollution is important for the efficient management of groundwater resources.Based on 13 variables surveyed at 43 monitoring sites,the comprehensive application of different multivariate methods were used for determining source apportionment of groundwater chlorinated hydrocarbon pollutants in study area. Factor analysis and cluster analysis were applied to the identification of pollution sources and four potential pollution sources that explained 92.810% of the total variance were identified.The absolute principal component score-multiple linear regression was adopted to calculate the contribution of each pollution source. Regression results revealed that most variables were primarily influenced by chemical industry,electrical manufacturing,chemical fiber and agricultural source.The contributions of each pollution source to the entire study area were 43%, 32%, 14% and 11% respectively.

Residential exposure to chlorinated hydrocarbons from groundwater contamination and the impairment of renal function-An ecological study

Groundwater pollution from the petrochemical industry causes serious deterioration of soil and groundwater quality and impacts on human health worldwide. However, few studies have examined the effect of residential exposure to petrochemical chlorinated hydrocarbon-contaminated groundwater on renal function impairment in humans. We conducted an ecological study to investigate the two. A polyvinyl chloride (PVC) plant was located in one of the six villages, the study area, in Kaohsiung city of southwestern Taiwan. Based on the direction of groundwater flow and previous groundwater measurements of chlorinated hydrocarbons from Taiwan Environmental Protection Bureau, we divided the six villages into highly-polluted villages, moderately-polluted villages, and a non-polluted village. All inhabitants in those six villages were invited to receive free health examinations between May-June, 2010. In total, 4,432 study subjects ≥18 yrs old were analyzed. Compared to those in the non-polluted village, subjects in highly-polluted villages had 1.89- and 1.46-fold the risk of impaired estimated glomerular filtration rate (eGFR) and proteinuria (95% CI = 1.15–1.85 and 1.09–3.28, respectively) after adjusting for other covariates. Given this relative large sample size, we found that groundwater chlorinated hydrocarbon pollution can cause kidney damage in adults.

Degradation of chlorinated hydrocarbons by UV/H2O2: The application of experimental design and kinetic modeling approach

The aim of the study was to develop a detail mathematical model describing the degradation of chlorinated hydrocarbon pollutants in water by UV/H2O2 process. As a model representative of chlorinated hydrocarbons para-chlorophenol (p-CP) was chosen. A degradation mechanism of parent pollutant to its aromatic and aliphatic by-products, as well as the mineralization of simulated wastewater, was included in the model. The optimal values of operating parameters of UV/H2O2 process influencing the treatment efficiency were established by the means of the two-factor three-level Box–Behnken experimental design combining with response surface modeling (RSM) and quadratic programming. The results of such experimental design using different statistical tools showed that pH 6.8 and pollutant/oxidant ratio 1:199 maximize the performance of oxidative treatment system. The model was tested to evaluate accuracy in predicting system behavior at different process conditions and pollutant concentrations. Rather high accuracy of developed model was demonstrated at all tested conditions. Good accordance of the data predicted by model and the empirically obtained data was confirmed by calculated standard deviation (SD) for each experimentally monitored parameter. Hence, the developed mathematical model describing the kinetic of p-CP degradation by UV/H2O2 can be characterized as interpretable, transparent and accurate, and therefore can be used as a tool for maximizing efficiency of wastewater treatment process.

Chlorinated hydrocarbon pollution in caviar samples

In this study the levels of chlorinated hydrocarbons in caviar samples were investigated in relation to the information available about the origin of the samples. The organochlorine pesticides such as 1,1,1-trichloro-2,2-bis(p-chlorophenyl)-ethane (p,p'-DDT), its metabolites (ΣDDT) and γ-hexachlorocyclohexane (Lindane), its isomers (ΣHCH), as well as some polychlorinated biphenyls (ΣPCB) were studied. The values for ΣDDT ranged from 21 ng/gram fresh weight (gfw) to 3622 ng/gfw, for ΣHCH from 8 ng/gfw to 133 ng/gfw, and for ΣPCB from 9 ng/gfw to 388 ng/gfw. The relationships between hydrocarbon concentrations in caviar samples and the parameters geographical origin, type of sturgeon, and spawning season were examined using cluster analysis and the Hasse diagram technique. A number of typical compositions of organochlorines in caviar samples originating in the Black Sea and the Caspian Sea were found. The ranking of sturgeon species according to the chlorinated hydrocarbon pollution found in their caviar fits their ranking in trophic level: Huso huso (highest trophic level and organochlorine concentration) > Acipenser gueldenstaedti > Acipenser stellatus.

Persistent organochlorine pesticides detected in blood and tissue samples of vultures from different localities in South Africa

Gaschromatography was used to establish the presence of quantifiable residues of 14 persistent chlorinated hydrocarbon pollutants in whole blood, clotted blood, heart, kidney, liver and muscle samples obtained from individual African whitebacked ( Pseudogyps africanus), Cape griffon ( Gyps coprotheres) and Lappetfaced ( Torgos tracheliotos) vultures from different localities in South Africa. The levels of pesticides measured in whole blood samples of live specimens were compared between nestlings from two natural breeding colonies, adults from a wildlife area and birds held in captivity. Statistically significant ( P<0.05) differences between populations were detected in geometric means calculated for γ-BHC (lindane), α(cis)-chlordane and α-endosulfan. Five of the organochlorine contaminants displayed significant variations between concentrations detected in the clotted blood, organs and muscles excised from vulture carcasses. This includes residues of γ-BHC, α-chlordane, dieldrin, β-endosulfan and heptachlor epoxide. Values of the respective biocides measured in vulture samples were generally low in comparison to results documented for a number of avian species. Although no threat is posed by any of the organochloride pesticides, continual monitoring of especially breeding colonies is recommended. Furthermore, the suitability of African whitebacked vulture nestlings as basic bioindicators is highly advocated.

Aqueous oxidation of trichloroethene (TCE): a kinetic analysis

An empirical kinetic rate law appropriate for many ground waters (neutral pH, aerobic) has been determined for the aqueous oxidation of trichloroethene (TCE), one of the most volumetrically important chlorinated hydrocarbon pollutants. Mass balances were monitored by measuring both the rate of disappearance of TCE and the rate of appearance of CO 2 and Cl −. Dilute buffer solutions were used to fix pH and stoichiometrically sufficient amounts of dissolved O 2 were used to make the reactions pseudo zero-order in O 2. Using a standard chemical kinetic approach, two orders-of-magnitude in initial TCE concentration were spanned and the resulting double-log plot (log concentration vs. log initial rate) was used to determine the rate constant ( k=5.77±1.06×10 −7 s −1) and “true” (i.e., with respect to concentration, not time) reaction order ( n c=0.85±0.03) for the rate law. By determining rate constants over the temperature interval 343–373 K, the Arrhenius activation energy (E a) for the reaction was determined to be 108.0±4.5 kJ/mol. The rate law and derived kinetic parameters may be used in reactive transport simulators in order to account for aqueous oxidation of TCE as a function of temperature.

Detoxification of Trichloroethylene in a Low-Pressure Surface Wave Plasma Reactor

Application of surface wave plasmas as an alternative technology for the destruction and removal of chlorinated hydrocarbon pollutants is demonstrated. The destruction of parts per thousand concentrations of trichloroethylene in air/water or oxygen mixtures has been investigated in a low-pressure reactor at 5 Torr. Effluent analysis included the determination of destruction and removal efficiencies by electron capture gas chromatography and product distribution by Fourier transform infrared spectroscopy, mass spectrometry, and titrimetric analysis. TCE conversions of up to 99.998% were achieved using radio frequency power densities ranging from 1.6 to 7.5 kJ/L and millisecond range residence times within the plasma. Product analysis indicated that trichloroethylene conversion was limited to light gases, primarily CO2, CO, HCl, and Cl2.

Biological effects of polychlorinated dibenzo‐p‐dioxins, dibenzofurans, and biphenyls in bald eagle (Haliaeetus leucocephalus) chicks

AbstractDuring the1992 breeding season, eggs of bald eagles (Haliaeetus leucocephalus) were collected within a gradient of exposure to chlorinated hydrocarbon pollutants, particularly from pulp mill point sources, on the southern coast of British Columbia, Canada. Twenty‐five eggs were placed in a laboratory incubator, of which 18 hatched; chicks were sacrificed within 24 h. Hatching success was not significantly different between eggs taken from pulp mill sites and reference sites. A hepatic cytochrome P4501A (CYP1A) cross‐reactive protein was induced nearly sixfold in chicks from near a pulp mill at Powell River compared to those from a reference site (p &lt; 0.05). Hepatic ethoxyresorufin‐O‐deethylase (EROD) and benzyloxyresorufin O‐dealkylase (BROD) activities were also significantly elevated in chicks from nests located near pulp mills compared to reference sites (p &lt; 0.0005 and p &lt; 0.02, respectively). A hepatic CYP2B cross‐reactive protein was threefold higher in chicks from pulp mill versus reference sites, but the difference was not significant. Residual yolk sacs of eggs collected near pulp mill sites contained greater concentrations of 2,3,7,8‐substituted polychlorinated dibenzo‐p‐dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) compared to reference areas. No significant differences in concentrations of polychlorinated biphenyls (PCBs), non‐ortho congeners, and organochlorine pesticides occurred among sites. Regressions showed that the hepatic CYP1A cross‐reactive protein and EROD and BROD activities were positively correlated with 2,3,7,8‐TCDD, 2,3,7,8‐TCDF, and toxic equivalents (TEQsWHO—Wrld Health Organization toxic equivalence factors) in yolk sacs. No significant concentration‐related effects were found for morphological, physiological, or histological parameters, such as chick growth, edema, or density of thymic lymphocytes. Using hepatic CYP1A induction as a biomarker, a no‐observed‐effect‐level (NOEL) of 100 ng/kg and a lowest‐observed‐effect‐level (LOEL) of 210 ng/kg TEQsWHO on a whole egg (wet weight basis) are suggested for bald eagle chicks.

A fiber-optic sensor system for monitoring chlorinated hydrocarbon pollutants

We have developed and field-tested a fiber-optic chemical sensor system for use in environmental monitoring and remediation. The system detects chlorinated hydrocarbon pollutants with colorimetry, and is based on an irreversible chemical reaction between the target compound and a specific reagent. The reaction products are detected by their absorption at 560 nm and can be monitored remotely with optical fibers. Continuous measurements are made possible by renewing the reagent from a reservoir with a miniature pumping system. The sensor has been evaluated against gas chromatography standards and has demonstrated accuracy and sensitivity (5 ppbw) sufficient for the environmental monitoring of trichloroethylene and chloroform. Successful preliminary field tests have been conducted in a variety of contamination monitoring scenarios.

Adsorption of Chlorinated Hydrocarbon Pollutants on Silica Gel

Abstract A survey of indoor air pollutants was conducted. The removal of six chlorinated hydrocarbons, including methyl chloride, methylene chloride, chloroform, carbon tetrachloride, 1,1,1-trichloroethane, and tetrachloroethylene was performed using adsorption methods. The equilibrium uptakes of the six indoor pollutants on silica gel were determined gravimetrically at 25°C and at pressures up to saturation. The modified potential theory proposed by Dubinin and coworkers was used to correlate the adsorption data.

Halogenated hydrocarbon environmental pollution: The special case of halogenated anesthetics

For several years, there has been concern about the adverse environmental consequences accruing from the use of chlorinated hydrocarbon compounds, although information regarding effects on humans has been relatively sparse (see reference to NRC-Canada). However, there are several similarities between chlorinated hydrocarbon pollutants (e.g., DDT or PCBs, etc.) and modern-day halogenated hydrocarbon anesthetics; the similarities include their respective chemical structure, their bioaccumulation in adipose tissue, and their dependence on the liver for metabolic transformation and partial excretion. Moreover, several halogenated hydrocarbon anesthetics have been in widespread clinical use during the past three-or-so decades, and this has led to a substantial accumulation of knowledge bearing on the toxicological cause/effect aspects in humans. Aside from the likelihood that the various halogenated hydrocarbon compounds in the human environment may have similar metabolic effects, there is also the very real possibility that diverse exposures to a variety of these compounds might lead to “cross-sensitization” phenomena among susceptible humans.

Approaches and initial findings of a state-sponsored research programme on population exposure to toxic substances

Summary Population exposure to toxic chemicals in the environment has become one of the most important, if not the most important, environmental issue of the 1980's. In response to finding high cancer mortality rates, the State of New Jersey organized an extensive program of research to determine public exposure to toxic substances in the environment. Three parts of that research are described. One focusing on toxic substances in the water has detected very low concentrations of many substances. These substances tend to be found in three distinct chemical groups: pesticides, light chlorinated hydrocarbons, and heavy metals. Gross pesticide contamination tends to occur in agricultural and forest areas; gross light chlorinated hydrocarbon pollution is in urban areas. The second component of the research is toxic substances in the air. Like the water studies, low levels of contamination have been found. Limited sampling to date has found groupings of ubiquitous organic chemicals in urban areas, two groups of specialized organic chemicals near industrial sites, and high lead levels near major highways. The third project is developing a computerized information bank about the use and disposal of 155 chemicals and will look for associations between industrial disposal practices and contamination of the environment.