Pyrite-activated persulfate to degrade 3,5,6-trichloro-2-pyridyl in water: Degradation and Fe release mechanism.

TCP (3,5,6-trichloro-2-pyridinol), the main recalcitrant degradation product of chlorpyrifos, poses a high risk to human health and ecological systems. This study provided a comprehensive exploration of the pyrite-activated persulfate (PS) system for the removal of TCP in water and placed particular emphasis on the pyrite oxidation process that releases Fe. The results showed that the pyrite-activated PS system can completely degrade TCP within 300 min at 5.0 mmol/L PS and 1000 mg/L pyrite at 25 °C, wherein small amounts of PS (1 mmol/L) can effectively facilitate TCP removal and the oxidation of pyrite elements, while excessive PS (>20 mmol/L) can lead to competitive inhibitory effects, especially in the Fe release process. Aimed at the dual effects, the evident positive correlation (R2 > 0.90) between TCP degradation (kTCP) and Fe element release (kFe), but the value of k (0.00237) in the pyrite addition variable experiment was less than that in the PS experiment (k = 0.00729), further indicating that the inhibition effect of excessive addition consists of PS but not notably pyrite. Moreover, the predominant free radicals and non-free radicals produced in the pyrite/PS system were tested, with the order of significance being •OH < Fe (Ⅳ) < SO4•- < â€¢O2- < 1O2, wherein 1O2 emerged as the principal player in both TCP degradation and Fe release from the pyrite oxidation process. Additionally, CO32- can finitely activate PS but generally slows TCP degradation and inhibit pyrite oxidation releasing Fe process. This study provides a theoretical basis for the degradation of TCP using pyrite-activated PS.

Optimizing soil tetrabromobisphenol A remediation through iron-based activation of persulfate: A comparative analysis of homogeneous and heterogeneous systems.

Tetrabromobisphenol A (TBBPA) that widely exists in soil and poses a potential threat to ecological environment urgently needs economically efficient remediation techniques. This study utilized both homogeneous Fe2⁺ solution and heterogeneous iron-based nanomaterials (chemically synthesized nano zero-valence iron (nZVI) and green-synthesized iron nanoparticles (G-Fe NPs)) to activate persulfate (PS) and assess their efficacy in degrading TBBPA in soil. The results demonstrate the superior performance of heterogeneous catalytic systems (WG-Fe NPs/PS (82.07%) and WnZVI/PS (78.32%)) over homogeneous catalytic system (WFe2+/PS (71.69%)), In addition, G-Fe NPs and nZVI effectively controlled the slow release of Fe2+. The optimization analysis using response surface methodology (RSM) reveal the remarkable significance of the experimental model based on the box-behnken design. RSM show that G-Fe NPs/PS exhibited optimal process parameters and predicted the maximum soil TBBPA degradation efficiency reaching 98.77%. The results of density functional theory calculations suggest that C-Br are the primary targets for electrophilic substitution reactions. Based on the f0 value and △G, the degradation pathway of TBBPA is inferred to involve a sequential debromination process, followed by the cleavage of intermediate carbon-carbon bonds and subsequent oxidation reactions. Hence, G-Fe NPs/PS not only facilitate waste resource utilization but also hold significant application potential.

Persulfate activation with sodium alginate/sulfide coated iron nanoparticles for degradation of tetrabromobisphenol a in soil.

The accumulation of tetrabromobisphenol A (TBBPA) in soil posed a serious threat to ecosystem and human health. Sodium alginate/sulfide coated iron nanoparticles (SA@S-Fe NPs) was synthesized by a two-step modification of Fe NPs prepared with tung tree leaves extracting solution, and utilized as a persulfate (PS) activator to degrade TBBPA in soil. Response surface methodology (RSM) optimization showed a theoretical maximum TBBPA degradation reaching 99.79% at the 34.28 °C, SA@S-Fe NPs and PS additions of 3.57 g kg-1 and 36.35 mM, respectively. The degradation mechanism of TBBPA suggested that the main reactive species produced in the SA@S-Fe NPs/PS system were •OH, SO4•-, and O2•-. Proposed mechanisms for the degradation of TBBPA in soil involved debromination, benzene rings split, hydroxylation, demethylation, and complete mineralization to CO2 and H2O. We also further studied the effect to soil physicochemical properties and morphology structure during TBBPA degradation in SA@S-Fe NPs/PS system, which showed that SOM, TN, C/N and TOC slightly reduced, the heavy metals Fe, Cu and Zn still existed in stable residue form, and the soil morphology showed a certain degree of aggregation. Therefore SA@S-Fe NPs/PS technology can effectively degrade soil TBBPA, maintain soil fertility, curb the migration of heavy metals, and environmental risks.

A meta-analysis of heavy metals pollution in farmland and urban soils in China over the past 20 years.

A total of 713 research papers about field monitor experiments of heavy metals in farmland and urban soils in China, published from 2000 to 2019, were obtained. A meta-analysis was conducted to evaluate the level of China's heavy metal pollution in soils, mainly focusing on eight heavy metals. It was found that the average concentrations of cadmium (Cd), lead (Pb), zinc (Zn), copper (Cu), mercury (Hg), chromium (Cr), nickel (Ni), and arsenic (As) in China were 0.19, 30.74, 85.86, 25.81, 0.074, 67.37, 27.77 and 8.89 mg/kg, respectively. Compared with the background value (0.097 mg/kg), the Cd content showed a twofold (0.19 mg/kg) rise in farmland soils and a threefold (0.29 mg/kg) rise in urban soils. The decreasing order of the mean Igeo was Cd (1.77) > Pb (0.62) > Zn (0.60) > Cu (0.58) > Hg (0.57) > Cr (0.54) > Ni (0.47) > As (0.28). Nearly 33.54% and 44.65% of sites in farmland and urban soils were polluted with Cd. The average concentrations of eight heavy metals were not sensitive change in recent two decades in farmland and urban soils. The average Pn values for urban (2.52) and farmland (2.15) soils showed that heavy metal pollution in urban soils was more serious than that in farmland, and the middle Yangtze River regions, where industrial activity dominates, were the most polluted. The meta-analysis comprehensively evaluated the current pollution situation of soil heavy metal, and provided important basis for soil management and environment prevention in China.

Air-soil exchange of organochlorine pesticides in a sealed chamber.

So far little is known about air-soil exchange under any sealed circumstances (e.g., in plastic and glass sheds), which however has huge implications for the soil-air-plant pathways of persistent organic pollutants including organochlorine pesticides (OCPs). A newly designed passive air sampler was tested in a sealed chamber for measuring the vertical concentration profiles of gaseous phase OCPs (hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs)). Air was sampled at 5, 15, and 30 cm above ground level every 10th day during a 60-day period by deploying polyurethane foam cylinders housed in acrylonitrile butadiene styrene-covered cartridges. Concentrations and compositions of OCPs along the vertical sections indicated a clear relationship with proximity to the mixture of HCHs and DDTs which escapes from the soils. In addition, significant positive correlations were found between air temperatures and concentrations of HCHs and DDTs. These results indicated revolatilization and re-deposition being at or close to dynamic pseudo-equilibrium with the overlying air. The sampler used for addressing air-soil exchange of persistent organic pollutants in any sealed conditions is discussed.

China action of "Cleanup Plan for Polychlorinated Biphenyls Burial Sites": emissions during excavation and thermal desorption of a capacitor-burial site.

Scarce data are available so far on emissions in a given scenario for excavation and thermal desorption, a common practice, of soils contaminated with polychlorinated biphenyls (PCBs). As part of China action of "Cleanup Plan for PCBs Burial Sites", this study roughly estimated PCBs emissions in the scenario for a capacitor-burial site. The concentrations of total PCBs (22 congeners) in soils were in the range of 2.1-16,000µg/g with a mean of 2300µg/g, among the same order of magnitude as the highest values obtained in various PCBs-contaminated sites. Only six congeners belonging to Di-, Tri-, and Tetra-CBs were observed above limits of detection in air samples in the scenario, partially which can be estimated by the USEPA air emission model. Comparing concentrations and composition profiles of PCBs in the soil and air samples further indicated a leaked source of commercial PCBs formulations of trichlorobiphenyl (China PCB no. 1). The measures taken if any to mitigate the volatilization and movement of PCBs and to minimize worker exposure were discussed for improvements of the excavation practice.

Risk assessment and sources of polycyclic aromatic hydrocarbons in agricultural soils of Huanghuai plain, China.

The profiles and sources of polycyclic aromatic hydrocarbons (PAHs) were analyzed in 227 agricultural surface soils from the Huanghuai plain, China. The total concentrations of 16 PAHs varied from 15.7 to 1247.6 µg/kg, with an average of 129.5 µg/kg. Compared with pollution level and carcinogenic potential risk in other research, the soil PAH concentrations in this study fell within low to middle level. Unexpectedly, a significant correlation was not observed between the PAH concentration in soils and the corresponding content of the soil organic matter. This is partly interpreted for our sampling sites located in agricultural area where fresh input of organic fertilizers is expected. Principal component analysis-multiple linear regression suggests that low temperature combustion, coal combustion and traffic emissions could be the primary PAH contributors in soils from the Huanghuai plain, accounting for 46.7 percent, 42.1 percent and 11.2 percent of PAH concentrations, respectively.

Degradation of TBBPA by nZVI activated persulfate in soil systems.

Tetrabromobisphenol A (TBBPA) greatly impacts on ecosystems and human health due to its high environmental toxicity and persistence. Persulfate (PS) advanced oxidation technology to remove organic pollutants in soils has received intense attention. In this study, nanoscale zero-valent iron (nZVI) was synthesized through the borohydride reduction method to explore its activating potential towards PS to accelerate the degradation of TBBPA in soils. The degradation behaviors of TBBPA in soils were investigated by batch experiments. The degradation efficiency of TBBPA (5 mg kg-1) was 78.32% within 12 h under the following reaction conditions: 3 g kg-1 nZVI, 25 mM PS, and pH 5.5 at 25 °C. Notably, PS can be used effectively, and the pH changed slightly in the reaction system. Oxidative degradation of TBBPA is favored at higher temperatures and lower pH values, while it is inhibited when the amount of catalyst increases significantly. The coexisting heavy metal ions such as Zn(II) and Ni(II) inhibit TBBPA degradation, while Cu(II) accelerates the degradation. Radical scavenging and electron spin resonance (ESR) tests further confirmed the generation of SO4·-, ·OH, and O2·- in nZVI activated PS. The intermediates identified by gas chromatograph-mass spectrometry analysis indicated that TBBPA via debromination and the cleavage between the isopropyl group and one of the benzene rings complete degradation. These findings provide new insight into the mechanism of nZVI activation of PS and will promote its application in the degradation of refractory organic compounds.

[Simultaneous determination of tetracyclines, fluoroquinolones, and sulfonamides in chicken manure using solid-phase extraction and high performance liquid chromatography].

A highly efficient and economic method for the simultaneous determination of six common antibiotics (two tetracyclines, two quinolones, and two sulfonamides) in chicken manure was developed by using solid-phase extraction and high performance liquid chromatography (SPE-HPLC). The samples were extracted by using a mixture of the EDTA-McIlvaine buffer and a mixed organic extractant (methanol-acetonitrile-acetone, 2:2:1, v/v/v), cleaned by a hydrophile-lipophile balance (HLB) cartridge, eluted by methanol-dichloromethane (7:3, v/v), and separated by HPLC with an acetonitrile-0.7% (v/v) H3PO4 aqueous solution as the mobile phase. The detection wavelength and temperature of the chromatographic column were 270 nm and 32℃, respectively. All antibiotics showed great linear relationships in the range of 0.5-100 mg/L; the correlation coefficients (r2) of the standard curves were between 0.9999 and 1; the recoveries of antibiotics were between 70.0% and 116.3%; and the relative standard deviations were between 1.2% and 16.6%. The limits of detection were 1.3-6.7 µg/kg; and the limits of quantity were 3.5-9.2 µg/kg. This method was used to detect antibiotics in chicken manure from a hennery in Fushun, Liaoning Province. The contents of norfloxacin and enrofloxacin (quinolones) were from not detected to 9.23 mg/kg and 1.57-7.69 mg/kg, respectively, that of sulfamethazine (sulfonamides) were 2.02-13.05 mg/kg, while sulfamethoxazole, oxytetracycline, and tetracycline were undetectable.

Occurrence of endocrine-disrupting pesticide residues in wetland sediments from Beijing, China.

Wetlands are important habitats and spawning grounds to a diverse wildlife population and are particularly vulnerable to adverse effects of endocrine disruptors. Many pesticides possess hormonal activity and have thus been classified as endocrine disruptors. A new analytical method based on ultrasonic-assisted extraction, solid-phase extraction, and gas chromatography technologies was developed for analysis of selected potential endocrine-disrupting pesticide residues in wetland sediment samples from northern Beijing, China. The newly developed method was a less time-consuming and less solvent-consuming way of analyzing residues without an air-drying process prior to extraction. The selected pesticides included the compounds hexachlorocyclohexane, cyclodiene, DDTs, chlordane, hexachlorobenzene, heptachlor, endrin aldehyde, heptachlor epoxide, dicofol, acetochlor, alachlor, metolachlor, chlorpyrifos, nitrofen, trifluralin, cypermethrin, fenvalerate, and deltamethrin. Characterization and identification of the selected endocrine-disrupting pesticide residues in sediments may help to assess current pollution status of endocrine-disrupting pesticides in the area. Total concentrations of pesticides ranged from 15.4 to 38.1 ng/g (dry weight) with a mean concentration of 23.7 ng/g (dry weight) for sediment samples. Although levels of all detected pesticides were below the New York State Department of Environmental Conservation, USA, sediment quality criteria, considering the potential health effects of endocrine disruptors even in a trace level, the use of the pesticides in the agricultural system should be minimized and regular monitoring is needed in the area.

Removal of five fluoroquinolone antibiotics during broiler manure composting.

Composting is a cost-effective approach for the removal of antibiotics from the environment; however, the consequence of this approach on fluoroquinolone antibiotics is limited. The fate of five representative fluoroquinolone antibiotics, namely ciprofloxacin, enrofloxacin, lomefloxacin, norfloxacin, and sarafloxacin, was investigated in a pilot-scale composting of broiler manure over 42 days. The effect of antibiotic concentrations (at a dose of 15, 30, or 60 mg/kg for each and a control without antibiotic addition) on the composting process was also assessed. The 42-day composting showed 45.3-75.4% of antibiotic removal with species-specific patterns. However, the observed variations in such removal among both antibiotics concentrations and composting times were not significant in most cases, possibly indicating a slight side-effect of the tested antibiotic concentrations on the composting process. To the best of our knowledge, this study is among few studies with a focus on the persistence of fluoroquinolone antibiotics during a pilot-scale composting, which warrants further study in regards to the mechanism underlying the removal of these compounds during composting.

Distribution and removal of organochlorine pesticides in waste clay bricks from an abandoned manufacturing plant using low-temperature thermal desorption technology.

The distribution of pollutants in waste clay bricks from an organochlorine pesticide-contaminated site was investigated, and removal of the pollutants using a thermal desorption technology was studied. The results showed that the contents of HCHs in both the surface and the inner layer of the bricks were slightly higher than those of DDTs. The total pore volume of the bricks was 37.7 to 41.6% with an increase from external to internal surfaces. The removal efficiency by thermal treatment was within 62 to 83% for HCHs and DDTs in bricks when the temperature was raised from 200 to 250 °C after 1 h. HCHs were more easily removed than DDTs with a higher temperature. Either intraparticle or surface diffusion controls the desorption processes of pollutants in bricks. It was feasible to use the polluted bricks after removal of the pollutants by low-temperature thermal desorption technology.

Organochlorinated pesticide multiresidues in surface sediments from Beijing Guanting reservoir.

For the analysis of organochlorine pesticides (OCPs) in sediments and water, a multiresidue analysis method based on gas chromatography with electron capture detection (GC/ECD) was developed. Solid-phase extraction (SPE) using Oasis HLB cartridges was also applied in sample extraction. Mean recoveries were satisfactory with 72-103% and 71-103% for water and sediment, respectively. Twenty-one OCPs were analyzed in water and surface sediment samples from Beijing Guanting reservoir. Total concentrations of 21 OCPs were 16.7-791 ng/l (mean 234 ng/l), 275-1,600 ng/l (mean 644 ng/l), 5250-33,400 ng/kg (mean 13,000 ng/kg) in surface water, pore water and sediment (dry weight), respectively. P, p'-DDE, delta-HCH, aldrin, gamma-HCH and beta-HCH are the most abundant compounds in water while p, p'-DDE, o, p'-DDT, beta-HCH, delta-HCH, p, p'-DDT and aldrin accounted for about 85% of total 21 OCPs in sediment in Beijing Guanting reservoir. Concentrations of OCPs were high both in water and sediment samples in Beijing Guanting reservoir for municipal water supply. The data provides information on the levels and sources of OCPs in Guanting reservoir. The study indicated that measures should be taken to decrease OCPs residues in order to improve the quality of municipal water supply in Beijing.

Distribution of Al-, Fe- and Mn-pools and their correlation in soils from two acid deposition small catchments in Hunan, China.

Distribution of Al-, Fe- and Mn-pools was investigated in five forest soil profiles (consisting of four horizons) in each of two Hunan catchments (BLT and LKS) where acid deposition has been considered critical. Al- and Fe-pools were higher in BLT than those in LKS, but Mn-pools much lower in BLT. Mn-pools vary from topsoils to bottom soils, but there are different trends for different Mn speciation. Al- and Fe-pools, except amorphous Fe(ox), were positively correlated to contents of soil organic matter (OM) showed by the loss on ignition in the two catchments. Accumulation of Al- and Fe-pools may occur in the area where soil organic matter was enriched (e.g. in top soil and rhizosphere soil). However, no direct correlation is observed between Mn and OM. Acidic atmospheric deposition may affect transforming among speciations of Al-, Fe- and Mn-pools and leaching of soil Al, Fe and Mn through formation of soluble organo-metal dissolved Al which was potentially toxic, increased. There were significant correlations between Al-pools complexes or change of oxidation-reduction conditions. Mn(ex) (exchangeable Mn) and Mn(ox) (amorphous and organic Mn) were highly linearly correlation with soil pH values at LKS but at BLT. Under acid deposition, the availability of the nutrient Fe increased with the amount of dissolved Al, which was potentially toxic, in the two catchments. There are no significant correlations between Al(ex) (exchangeable Al) and Mn(ex), Fe(ex) (exchangeable Fe) and Mn(ex) in this work, indicating potentially toxic Mn increase seldom accompanying with Al increase in the two catchments.

Enhanced adsorption of benzene vapor on granular activated carbon under humid conditions due to shifts in hydrophobicity and total micropore volume.

A series of hydrophobic-modified (polydimethylsiloxane (PDMS) coating) activated carbons (ACs) were developed to answer a fundamental question: what are the determinants that dominate the adsorption on ACs under humid conditions? Using column experiments, an inter-comparison among bare-AC and PDMS-coated ACs was conducted regarding the association of surface characteristics and adsorption capacity. Primary outcomes occurred in two dominating markers, hydrophobicity and total micropore volume, which played a key role in water adsorption on ACs. However, their contributions to water adsorption on ACs substantially differed under different Pwater/Pair conditions. Hydrophobicity was the only contributor in Pwater/Pair=0.1-0.6, while the two markers contributed equally in Pwater/Pair=0.7-1.0. Furthermore, PDMS-coated AC had a significant increase in benzene adsorption capacities compared to bare-AC at 0-90% relative humidity, while these differences were not significant among PDMS-coated ACs. It is thus presumed that the balance between the two markers can be shifted to favor almost unchanged benzene adsorption capacities among PDMS-coated ACs over a large range of relative humidity. These findings suggest potential benefits of PDMS coating onto ACs in enhancing selective adsorption of hydrophobic volatile organic compounds under high humid conditions. To develop new porous materials with both high total micropore volume and hydrophobicity should thus be considered.

[Effects of Acidic and Basic Modification on Activated Carbon for Adsorption of Toluene].

Activated carbons (ACs) were modified by acidic solutions (H2SO4, HNO3, or H3PO4) and basic solutions (NaOH or NH3·H2O), then H2SO4modified ACs were re-modified by basic solutions, respectively, in order to investigate the key factors of physico-chemical properties that mainly affected the adsorption of ACs. BET surface area, micropore volume, and surface functional groups were characterized and the adsorption capacity of toluene on the modified ACs was measured. Results showed that BET area,micropore area and micropore volume decreased and the acidic functional groups increased by the acidic treatment, while the basic treatment showed the opposite changing trend in the physico-chemical properties of ACs. Such changes might be associated with the acidity/alkaline and oxidizability/reducibility of experimental solutions. The acidic treatment led to a reduce in toluene adsorption capacities by 9.6%-20.0%, while the capacity increased by 29.2%-39.2% using the basic treatment, compared to those in original ACs. Correlation analysis revealed that there was a positive relationship between toluene adsorption capacities and BET area, as well as micropore area and micropore volume, and a negative relationship between toluene adsorption capacities and acidic functional groups. Multiple regression analysis showed that micorpore volume and acidic functional groups were key factors influencing the toluene adsorption capacity. Furthermore, the adsorption capacity of toluene on re-modified ACs was influenced by the amount of acidic functional groups (-COOH, C=O, and -OH), of which -COOH was the most important factor affecting the adsorption capacity. It is generally suggested that the modification of ACs should focus on an increase in micorpore volume and a decrease in surface functional groups, especially the amount of -COOH, in order to gain the improvement of toluene adsorption capacities.

[Transfer and Fate of Polybrominated Diphenyl Ethers in an Electrical Equipment Dismantling Area Using a Multimedia Fugacity Model].

The multimedia fugacity model (Ⅲ) was used to simulate the distribution, transfer and fate of typical polybrominated diphenyl ethers (PBDEs) in air, water, soil and sediment in an electrical equipment dismantling area in eastern China. The modeling data were compared with monitored values in air, soil and sediment for validation purpose. Moreover, the transfer fluxes between different compartments were analyzed in order to infer the main transfer process. Parameters of the model were tested and the key parameters were identified using sensitivity analysis method for BDE47 and BDE209.The results of sensitivity analysis indicated that vapor pressure, the lgKow value and half-life had significant influence on concentrations of PBDEs in different media. The results showed that when the system reached equilibrium, most of the PBDEs would be accumulated in soil and sediment. The air advection outflow and soil degradation were the major routes for PBDEs to disappear in the area. The results will provide the basis for the risk management of PBDEs contamination.

[Toluene, Benzene and Acetone Adsorption by Activated Carbon Coated with PDMS].

To improve the adsorption selectivity of volatile organic compounds ( VOCs) , activated carbon ( AC) was modified by polydimethylsiloxane (PDMS) and characterized by BET analysis and Boehm titration. Dynamic adsorption column experiments were conducted and Yoon-Neslon(Y-N) model was used to identify adsorption effect for toluene, beuzene and acetone on AC when relative humidity was 0%, 50% and 90%, respectively. The results showed that the BET area, micropore volume and surface functional groups decreased with the PDMS modification, and surface hydrophobicity of the modified AC was enhanced leading to a lower water adsorption capacity. The results of dynamic adsorption showed that the adsorption kinetics and capacity of Bare-AC decreased with the increase of relative humidity, and the adsorption capacities of PDMS coated AC were 1.86 times (toluene) and 1.92 times (benzene) higher than those of Bare-AC, while a significant improvement of adsorption capacity for acetone was not observed. These findings suggest that polarity of molecule can be an important influencing factor for adsorption on hydrophobic surface developed by PDMS.

Screening 31 endocrine-disrupting pesticides in water and surface sediment samples from Beijing Guanting reservoir.

For screening 31 potential or suspected endocrine-disrupting pesticides in water and surface sediments, a multiresidue analysis method based on gas chromatography with electron capture detection (GC/ECD) was developed. Solid phase extraction (SPE) technology with Oasis HLB cartridge was also applied in sample extraction. The relevant mean recoveries were 70-103% and 71-103% for water and sediment, respectively. Relative standard deviations (RSD) are 2.0-7.0%, 4.0-8.0% for water and sediment, respectively. Thirty one pesticides (alpha-HCH, beta-HCH, gamma-HCH, delta-HCH, hexachlorobenzene (HCB), aldrin, heptachlor, endosulfan I & II, p,p'-DDD, o,p'-DDT, p,p'-DDT, p,p'-DDE, endrin aldehyde, endosulfan sulphate, methoxychlor, hepachlor epoxide, alpha-chlordane, gamma-chlordane, dieldrin, endrin, dicofol, acetochlor, alachlor, metolachlor, chlorpyriphos, nitrofen, trifluralin, cypermethrin, fenvalerate, deltamethrin) in water and surface sediment samples from Beijing Guanting reservoir were analyzed. Concentrations of pesticides ranged from 7.59 to 36.0 ng g(-1) on a dry wt. basis for sediment samples, from 279.3 to 2740 ng l(-1) for pore waters and from 48.8 to 890 ng l(-1) for water samples, respectively, with a mean concentration of 10.7 ng g(-1) in sediment, 735 ng l(-1) in pore water and 295 ng l(-1) in water, respectively. The data obtained provides information on the levels and sources of endocrine-disrupting pesticides in Guanting reservoir. These results underscore the need to improved environmental protection measures in order to reduce the exposure of the population and aquatic biota to these endocrine-disrupting compounds.

[Distribution and health risk of HCHs and DDTs in a contaminated site with excavation].

Air samples were collected to analyze the distribution of HCHs and DDTs around a contaminated site during its excavation. The carcinogenic risks and non-carcinogenic risks through breath exposure were studied by health risk assessment modes. The results showed that, there was an obvious seasonal variation of HCHs and DDTs in air around the excavating area. The concentrations of HCHs and DDTs were higher in winter and autumn, lower in spring and summer. The Σ HCHs concentration ranged from 5.65 ng x m(-3) to 133 ng x m(-3), and the average value was 28.6 ng x m(-3); Σ DDTs concentration ranged from 4.48 ng x m(-3) to 2 800 ng x m(-3), and the average value was 457.3 ng x m(-3) in winter. However, the Σ HCHs concentration was between 6.23 ng x m(-3) and 26.4 ng x m(-3), and the average value was 15.1 ng x m(-3) in spring; the Σ DDTs concentration was between 3.17 ng x m(-3) and 8.1 ng x m(-3), and the average value was 6.1 ng x m(-3) in summer. So the pollution could be reduced by excavating in spring and summer. The concentrations of HCHs and DDTs in the residents area were negatively correlated to the height (P < 0.05, n = 33 ). The carcinogenic and non-carcinogenic risks of adult residents through respiration to residents near the excavating area were lower than the acceptable level, while the excavating process caused carcinogenic and non-carcinogenic risks to young residents to some extent. In order to decrease the risks, measures should be taken to restrain the pollutants in the excavation area diffusing into the air.