Partitioning of polychlorinated biphenyls in octanol/water, triolein/water, and membrane/water systems

The use of the octanol/water partition constant (Kow) as a surrogate parameter for lipid/water partitioning of persistent organic pollutants (POPs) was reassessed by comparing the measured Kow of 12 selected polychlorinated biphenyl congeners (PCBs) with partition constants in triolein/water (Ktw) and membrane/water (Kmw) systems. Kow and Ktw were measured by the slow-stirring method. Kmw was measured by an adaptation of the slow-stirring method using suspensions of phosphatidylcholine and phosphatidylserine liposomes. Partitioning of POPs to octanol, triolein, and liposomes is similar but not equal. The log-log correlation for Kow and Ktw is excellent (r2 = 0.982) and that for Kow and Kmw is somewhat weaker (r2 = 0.856). Ktw values are greater than Kow by a factor of 1.6. Kmw of some PCB congeners exceed both Kow and Ktw by an order of magnitude. The differences are attributed to different PCB activity coefficients in the different lipid phases. The results imply that Kow can be used as a reasonable conservative estimate of lipid/water partitioning. But the observed differences between Kow and Kmw also indicate that using Kow to predict accumulation of POPs, particularly highly hydrophobic ones, in the polar lipids of organisms will underestimate their concentrations at equilibrium.     

Selective removal of organochlorine pesticides (OCPs) from aqueous solution by triolein-embedded composite adsorbent

A novel composite adsorbent (CA-T) was used for the selective removal of organochlorine pesticides (OCPs) from aqueous solution. The adsorbent was composed of the supporting activated carbon and the surrounding triolein-embedded cellulose acetate membrane. Scanning electron microscopy (SEM), N2 adsorption isotherms and fluorescence methods were used to characterize the physicochemical properties of CA-T. Triolein was perfectly embedded in the cellulose acetate membrane and deposited on the surface of activated carbon. The adsorbent was stable in water and no triolein leakage was detected during the test periods. Some organochlorine pesticides (OCPs), such as dieldrin, endrin, aldrin, and heptachlor epoxide, were used as model contaminants and removed by CA-T in laboratory batch experiments. The adsorption isotherm followed the Freundlich equation and the kinetic data fitted well to the pseudo-second-order reaction model. Results also indicated that CA-T appeared to be a promising adsorbent with good selectivity and satisfactory removal rate for lipophilic OCPs from aqueous solutions when present in trace amounts. The adsorption rate and removal efficiency for lipophilic OCPs were positively related to their octanol-water partition coefficients (log K(ow)). Lower residual concentrations of OCPs were achieved when compared to granular activated carbon (GAC).     

Reliable QSAR for estimating Koc for persistent organic pollutants: correlation with molecular connectivity indices

Several recent studies have shown that n-octanol/water partition coefficients may not be a good predictor for estimating soil sorption coefficients of persistent organic pollutants (POPs), defined here as chemicals with log Kow greater than 5. Thus, an alternative QSAR model was developed that seems to provide reliable estimates for the soil sorption coefficients of persistent organic pollutants. This model is based on a set of calculated molecular connectivity indices and evaluated soil sorption data for 18 POPs. The chemical's size and shape, quantified by 1chi, 3chiC and 4chiC(v) indices, have a dominant effect on the soil sorption process of POPs. The developed QSAR model was rationalized in terms of potential hydrophobic interactions between persistent organic pollutants and soil organic matrix. Its high predictive power has been verified by an extensive internal and external validation procedure.     

Selective removal of organochlorine pesticides (OCPs) from aqueous solution by triolein-embedded composite adsorbent

A novel composite adsorbent (CA-T) was used for the selective removal of organochlorine pesticides (OCPs) from aqueous solution. The adsorbent was composed of the supporting activated carbon and the surrounding triolein-embedded cellulose acetate membrane. Scanning electron microscopy (SEM), N₂ adsorption isotherms and fluorescence methods were used to characterize the physicochemical properties of CA-T. Triolein was perfectly embedded in the cellulose acetate membrane and deposited on the surface of activated carbon. The adsorbent was stable in water and no triolein leakage was detected during the test periods. Some organochlorine pesticides (OCPs), such as dieldrin, endrin, aldrin, and heptachlor epoxide, were used as model contaminants and removed by CA-T in laboratory batch experiments. The adsorption isotherm followed the Freundlich equation and the kinetic data fitted well to the pseudo-second-order reaction model. Results also indicated that CA-T appeared to be a promising adsorbent with good selectivity and satisfactory removal rate for lipophilic OCPs from aqueous solutions when present in trace amounts. The adsorption rate and removal efficiency for lipophilic OCPs were positively related to their octanol-water partition coefficients (log K _ow). Lower residual concentrations of OCPs were achieved when compared to granular activated carbon (GAC).     

中国持久性有机污染物嫌疑物质的计算机辅助筛选研究

按照《关于持久性有机污染物的斯德哥尔摩公约》中持久性有机污染物（POPs)的确定标准，借鉴荷兰建设规划和环境部开发的持久的生物富集性有毒化学物质（PBTs)筛选流程，利用计算机辅助工具《中国现有化学物质名录》最新版中收录的所有26707种化学物质进行了初步筛选，最后得到111种POPs嫌疑物质。对结果的深入讨论表明计算机工具用于持久性有机污染物初步筛选是可行的。     

Accumulation of organochlorine pesticides by semipermeable membrane devices using composite complex

Semipermeable membrane devices (SPMDs) were developed for passive in situ monitoring of organochlorine pesticides (OCPs) in aqueous solution in both laboratory and field (Pearl River Delta, China) studies. The device consisted of a thin film of neutral lipid triolein, enclosed in thin-walled tubing made of composite cellulose acetate membrane (CA) supported by linear low density polyethylene (LLDPE) (CAPE). Results from the laboratory and field application indicated that triolein-CAPE (TCAPE) could quickly and efficiently accumulate hydrophobic OCPs in water and uptake equilibrium could reached within 20h in the laboratory. Some mathematical relationships of TCAPE-water partition coefficient (logK(sw)), triolein-water partition coefficient (logK(tw)) and octanol-water partition coefficient (logK(ow)) were developed under the laboratory conditions. A good correlation of accumulation in TCAPE with r(2) values ranging from 0.55 to 0.86 for individual OCPs (n=8) and an excellent correlation of logK(sw) and logK(ow) was also obtained under the field conditions. The average OCPs concentration in the surface water could be estimated by measuring OCPs concentration in the device under the field conditions.     

持久性有机污染物的环境分布与生物危害

介绍了国内外持久性有机物的研究进展,分析了中国典型地区中的持久性有机污染物的分布情况,其中淮河中下游的PAHs含量较高,而大连湾检测出的DDTs和PCBs含量均高于其他地区。持久性有机污染物可以在动植物体内不断富集,据分析,有机污染物在鱼类的富集因子可高达1124．1,持久性有机污染物通过食物链的富集逐级放大,对全球生态构成潜在巨大的威胁。近年来,由于持久性有机污染物的影响,在世界各地出现了动物的死亡、甚至灭绝的现象,而且有机污染物在人体内的蓄积,会对人体产生极大的的影响。最后,就当前存在的问题,提出了对策与建议,指出了该领域的发展方向。     

Estimating K(oc) for persistent organic pollutants: limitations of correlations with K(ow)

The n-octanol/water partition coefficient (K(ow)) is commonly used to predict the soil or aquatic particle water partition coefficient normalized to organic carbon (K(oc)). Many correlations are available covering several chemical classes and ranges of hydrophobicity. This work indicates the K(ow) may not be a strong predictor for persistent organic pollutants (POPs) which are defined here as chemicals with logK(ow) > 5.0. In addition, the correlation developed in this work for POPs will still result in a predicted value which is of by a factor of 15. Accordingly, care must be taken when applying K(oc) estimations using K(ow) for POPs until more suitable correlations are developed.     

Degradation half-life times of PCDDs, PCDFs and PCBs for environmental fate modeling

Literature search of the knowledge on the degradation of persistent organic pollutants (POPs) in environmental compartments air, water, soil and sediment was done in purpose to find properties of POPs of interest for modeling. One degradation process, hydrolysis (chemical degradation), was omitted as negligibly slow for POPs studied. The other two, photolysis and biodegradation processes, were considered separately in purpose to develop estimation procedures. The estimates can be given as pseudo first-order rate constants kP for photolysis and kB for biodegradation. For each compartment, an overall degradation rate is k(tot) = kP + kB and lifetime t(1/2) = ln 2/k(tot). The latter values, lifetimes in each compartment, will be used as input parameters to the Baltic Sea model.     

Modification of UNIFAC parameter table Revision 5 for representation of aqueous solubility and 1-octanol/water partition coefficient for POPs

In order to represent aqueous solubility and 1-octanol/water partition coefficient for POPs (persistent organic pollutants) by the UNIFAC model, two pairs of group interaction parameters in Revision 5 of the UNIFAC parameter table were modified. First, the pair of interaction parameters between the aromatic carbon-chloride (ACCl) and water (H2O) groups were corrected by minimizing the deviation between the experimental and calculated values of these properties for chlorinated benzenes, polychlorinated biphenyls, and polychlorinated dibenzo-p-dioxins and dibenzofurans. The corrected interaction parameters provided a better representation of both properties than the calculation results obtained in early works using the UNIFAC model. Second, the unknown pair of interaction parameters between the chloroalkene (Cl(C=C)) and H2O groups, which are required for calculating those properties of the other five POPs (aldrin, chlordane, endrin, dieldrin, and heptachlor), were newly determined from the experimental data on their properties. Finally, this study shows that Revision 5 could also predict solubility of POPs in some organic solvents. The modified parameter table is first suggested as the UNIFAC parameter table applicable to various phase equilibria including aqueous or nonaqueous solubility and partition coefficient of POPs.     

Testing common sediment-porewater distribution models for their ability to predict dissolved concentrations of POPs in The Grenlandsfjords, Norway

This study compares in situ observed porewater concentration of persistent organic pollutants (POPs) with predictions by common solid-water phase distribution models. Bottom sediments were sampled in The Grenlandsfjords, Norway, and the interstitial porewater was isolated from the solids by centrifugation and filtration. Both phases were analysed for polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F), polycyclic aromatic hydrocarbons (PAH), and organic carbon. Based on the sediments' solid phase content of POPs, organic carbon, and soot carbon, we used the organic matter partitioning (OMP), and also the soot and organic matter partitioning (SOMP) model to estimate the porewater concentration. The OMP model gave better agreement to observations than the SOMP model for both PCDD/Fs and PAHs. The observed concentration of the PCDD/Fs in the sediments' porewater was much higher than in the deep water of the fjord. The logarithm of the organic matter-water partitioning coefficent (log K(OC)) in the porewater had positive linear regression on the logarithm of the octanol-water partitioning coefficient (log K(OW)). The slope of the regression model was indistinguishable from 1, except for the PAHs as a group which had a slope less than 1. This contrasts to previous studies undertaken in The Grenlandsfjords water column, where the slopes were higher than 1 for PCDD/Fs, and the K(OC) were much higher than the K(OW). One explanation may be that the influence of POPs adsorption to soots decrease because competitive sorption by other compounds in the sediment are higher than in the water column. This indicates that the sorption isotherms for these POPs need better understanding in order to be applicable in both the water column and the porewater.     

Persistent organic pollutants (POPs) in the conventional activated sludge treatment process: model predictions against experimental values

The FATE and treatibility estimator (FATE) model, developed by the United States Environmental Protection Agency was used for the prediction of the FATE of 26 persistent organic pollutants (POPs), i.e. 7 PCBs and 19 organochlorine compounds (OCs), during the conventional activated sludge treatment process applied in the waste water treatment plant (WWTP) of Thessaloniki, Greece. The removal rates predicted by the model for the primary and the secondary treatment stages were found to differ substantially from those experimentally measured. When the overall treatment was considered, the differences between measured and model predicted removals were within acceptable limits of confidence. Possible reasons that might cause deviations from experimental values were suggested to be the wastewater content in dissolved organic carbon (DOC), and/or the low concentrations of POPs in untreated wastewater.     

Contaminant concentrations in breeding and non-breeding northern fulmars (Fulmarus glacialis L.) from the Canadian high arctic

Persistent organic pollutants (POPs) were measured in livers of male and female northern fulmars (Fulmarus glacialis) shortly after egg-laying on northern Devon Island, NU, Canada. Breeding females had lower hepatic POPs (lipid normalised) than breeding males, but non-breeding males and females had similar concentrations. We suspect that breeding females are eliminating some of their POPs during egg formation. Concentrations of measured POPs were lower than those associated with avian health concerns, and there was no evidence that POPs in the birds were contributing to additional breeding stress.     

Distribution of PCNs, PCBs, and other POPs together with soot and other organic matter in the marine environment of the Grenlandsfjords, Norway

The apparently dissolved concentration of polychlorinated naphthalenes (PCNs) and three planar polychlorinated biphenyls (pPCBs) were sampled and analysed in the water column of a marine fjord system. We also measured how much of these persistent organic pollutants (POPs) were associated with suspended particles. The field observations showed that an unexpectedly high portion of the pollutants were particle-associated. The factor of deviation from model predictions had positive linear regression on the soot carbon:particulate organic carbon ratio of the particles, and on estimates of the soot-water distribution coefficient for the PCNs. The spatial distribution of surface sediment concentrations of PCNs and polycyclic aromatic hydrocarbons (PAH) were found to consistently follow the sediment content of soot (f(SC)) to a larger extent than the bulk organic matter (f(OC)). There were no systematic differences in the strength of correlation of sediments concentrations of other POPs, i.e. octachlorostyrene and organochlorine pesticides with sediment concentration to f(SC) and f(OC). Mechanisms possible of generating these types of observations, e.g. adsorption to soot carbon in the marine particle, are discussed.     

The deep-sea as a final global sink of semivolatile persistent organic pollutants? Part I: PCBs in surface and deep-sea dwelling fish of the north and south Atlantic and the Monterey Bay Canyon (California)

The understanding of the global environmental multiphase distribution of persistent organic pollutants (POPs) as a result of the physico-chemical properties of the respective compounds is well established. We have analysed the results of a vertical transport of POPs from upper water layers (0-200 m) to the deepwater region (> 800 m) in terms of the contamination of the biophase in both water layers. The contents of persistent organochlorine compounds like polychlorinated biphenyls (PCBs) in fish living in the upper water layers of the North Atlantic and the South Atlantic, and at the continental shelf of California (Marine Sanctuary Monterey Bay and its deep-sea Canyon) are compared to the levels in deep-sea or bottom dwelling fish within the same geographic area. The deep-sea biota show significantly higher burdens as compared to surface-living species of the same region. There are also indications for recycling processes of POPs--in this case the PCBs--in the biophase of the abyss as well. It can be concluded that the bio- and geo phase of the deep-sea may act similarly as the upper horizons of forest and grasslands on the continents as an ultimate global sink for POPs in the marine environment.     

The deep-sea as a final global sink of semivolatile persistent organic pollutants? Part II: Organochlorine pesticides in surface and deep-sea dwelling fish of the north and south Atlantic and the Monterey Bay Canyon (California)

The understanding of the global environmental multiphase distribution of persistent organic pollutants (POPs) as a result of the physico-chemical properties of the respective compounds is well established. We have analysed the results of a vertical transport of POPs from surface water to deepwater in terms of the contamination of the biota living in the respective environmental compartments. Samples were taken from the North and the South Atlantic and from the uprising water region of the continental shelf of California (Marine Sanctuary Monterey Bay and its Canyon). The contents of persistent organochlorine pesticides (DDTs, chlordanes, toxaphenes, HCHs, and HCB) in surface-living fish are compared to those in deepwater fish of the same geographic area. The deepwater biota show significantly higher burdens as compared to surface-living species of the same region. There are also indications for recycling processes of POPs of the class of organochlorine pesticides in the biophase of the abyss as well. It can be concluded that the bio- and geophase of the deep-sea may act as an ultimate global sink for persistent semivolatile contaminants in the marine environment like the soil on the continents.     

Fourth WHO-coordinated survey of human milk for persistent organic pollutants (POPs): Belgian results

Persistent organic pollutants (POPs) are chemicals that accumulate in the food chain and are toxic to humans and wildlife. The fourth World Health Organization (WHO) survey on POP levels in human milk (2006-2009) aims to provide baseline and trend information on human exposure to POPs. So far Belgium participated in all three previous rounds (1988, 1992, 2001). Whereas the first three rounds focused on determination of dioxins and PCBs in pooled (mixed) samples, the fourth survey comprised the analyses of individual milk samples for nine "basic POPs" (chlorinated pesticides and indicator PCBs) and of pooled milk samples for "basic POPs", "advanced POPs" (dioxins and dioxin-like PCBs) and "optional POPs" (polybrominated diphenylethers [PBDEs], polybrominated dioxins and dibenzofurans [PBrDD/F], mixed halogenated dioxins and dibenzofurans [PXDD/F] and hexabromocyclododecane [HBCD]). For the Belgian participation human milk samples were collected during the summer of 2006 from 197 women between 18 and 30 years old distributed over all Belgian provinces. The individual samples were analyzed in a Belgian Laboratory for "basic" POPs. A pooled sample was made from 178 individual samples and analyzed by the WHO Reference Laboratory for the "basic, advanced and optional" POPs. The results indicate that most organochlorinated pesticides banned 25-30 years ago were below or around detection limits in Belgian human milk samples although DDE was still found at low levels in all samples. Over the last five years the levels of marker PCBs and PCDD/Fs in Belgian human milk decreased, respectively, by 58% and 39%. For some of the other emerging or older compounds recent international data are needed to allow comparison. This shows the importance of international studies as run by WHO.     

Pollution sources and occurrences of selected persistent organic pollutants (POPs) in sediments of the Mekong River delta, South Vietnam

The Mekong River delta is one of the largest agricultural land in the Southeast Asia. It plays a very important role for agriculture and fisheries in South Vietnam. However, comprehensive studies on the environmental pollution of persistent organic pollutants (POPs) in Mekong River delta have not been carried out in recent years. In this study, we collected sediment samples from the Mekong River to evaluate the contamination and ecological risks caused by several POPs. The contamination pattern of POPs was DDT>PCBs>CHLs>HCHs>HCB. DDTs are the most abundant pollutants, their concentration ranging from 0.01 to 110 ng/g dry wt, followed by PCBs (0.039-9.2 ng/g dry wt). DDTs and PCBs concentrations were higher in sediment from adjacent to urban areas than those from rural and agricultural sites, suggesting urban areas as important point sources of DDTs and PCBs to the river. Ratio of p,p'-DDT/p,p'-DDE was lower compared to those previously reported. However, some samples still had the ratio higher than 0.5, indicating recent input of DDT into the aquatic environments. This result shows that although the magnitude of contamination decreased over time, recent inputs of DDTs to the river still occur. Some sediment samples had concentrations of DDT compounds higher than the standards from the Canadian Environmental Quality Guideline, suggesting continuous monitoring for POPs contamination in the Mekong River is necessary.     

Development of an in-line system for the analysis of 4,4'-DDT in water

An in-line system for trace persistent organic pollutants (POPs) in water was developed by using a laboratory-made hollow fiber membrane (HFM) unit connected with a high-resolution gas chromatograph-mass spectrometer (HRGC-MS). The semivolatile organic compound, 4,4'-Dichlorodiphenyl trichloroethane (4,4'-DDT), was chosen as a representative of a persistent organic compound. The synthetic water contaminated with 4,4'-DDT was passed through the HFM unit, the extraction occurred by the analyte pervaporated and permeated, then stripped into HRGC-MS. Several factors were investigated for the high extraction efficiency. The best performance was obtained at sample and stripping gas flow rates of 6 and 9 mLmin-1, respectively, and desorption temperature of 60 degrees C. At this temperature, the diffusion rate was enhanced by 15 times over 25 degrees C. A wide linear dynamic range was obtained, i.e., 0.10-1.0 mgL-1, with a limit of detection (LOD) of 90 microgL-1. The extraction efficiency of 4,4'-DDT in real water samples was in the range of 83-94%. Real water samples were analyzed and 0.6 microgL-1 of 4,4'-DDT was found in unregistered bottled water and 7.0 microgL-1 in tap water.