Low volatile chlorinated hydrocarbons in aquatic sediments in Berlin and surrounding areas

Low volatile chlorinated hydrocarbons, especially DDT and HCH, have been used as indicators of the level of pollution in aquatic sediments. These compounds were present in all the sediment samples analysed in this study by gas chromatography. Enrichment factors between the water and sediment were high (K^d = 85-108 for DDT), documenting the strong geoaccumulation of toxic chlorinated hydrocarbons. in contrast with the generally held view, no linear relationship was observed between the concentration of HCH and PCBs and the organic matter content of the sediment. the application of the EVOLON model to determine the kinetics of sorption clearly showed a saturation value. the sorbed amount of low volatile chlorinated hydrocarbons depends to a large extent on the amount of organic matter on the surface of the sediment particles.     

挥发性氯代烃在土壤中的吸附行为研究进展

挥发性氯代烃(Volatile chlorinated hydrocarbons,VCHs)是工业污染场地的常见污染物,在非饱和带存在于土壤气相、水相、固相或以高密度非水相液体(Dense non-aqueous phase liquids,DNAPL)的形式存在,形成一个动态平衡系统。土壤对VCHs的吸附不仅影响土壤中的污染物浓度,而且极大地影响VCHs的迁移转化行为。根据VCHs在土壤中的吸附机制,可以对土壤中的VCHs浓度进行预测,优化各种模型参数,指导污染修复及管理工作。本文总结了VCHs在非饱和带土壤中的相间分配特征,吸附机制及其影响因素,特别探讨了土壤有机碳、矿物及水分对吸附的影响,提出了当前研究中存在的问题,并对将来研究进行了展望。     

Modelling of colloid leaching from unsaturated, aggregated soil

The migration of colloids in soils can enhance the leaching of strongly sorbing contaminants. We present a model for the simulation of colloid leaching from unsaturated, aggregated soil media under stationary flow. Transport in the intra-aggregate pores is simulated by convection–dispersion, and transport in the interaggregate pores, and a stagnant layer of water surrounding the aggregates, is simulated by diffusion. The model describes the release of colloids from soil aggregates, sorption and desorption processes at the air–water interfaces, and flocculation and subsequent straining from the flowing water. All three processes were simulated as functions of ionic strength. Transport of ions in intra-aggregate pores was simulated by Fickian diffusion. The model was calibrated against experimental results of colloid leaching from columns packed with natural soil aggregates. The aggregates were of two soils differing in organic matter content. On each soil a single calibrated parameter set could describe the experiments with the three ionic strengths. The parameters for release of colloids from the aggregate surface and the sorption properties of the air–water interface were different for the two soils. The key parameters for leaching were the thickness of the stagnant layer of water surrounding the aggregates, the mechanical dispersion, the maximum concentration of colloids at the surface of the aggregates, the sorption capacity and rate coefficient of the colloids at the air–water interface, and the colloid diffusion coefficient. Simulations were also done with two additional irrigation intensities at one ionic strength. Simulated leaching was greater than measured leaching at both irrigation intensities, but the diffusion-controlled release of colloids from the aggregates was simulated correctly.     

Trace metals and chlorinated hydrocarbons in sewage sludges of Kuwait

Levels of trace metals and chlorinated hydrocarbons were determined in sludge produced at the three main wastewater treatment plants in Kuwait (Ardhiya, Jahra, and Reqqa). Over the 6 mo study period (October 1984 to March 1985) levels at the three plants showed the following ranges (μg g^?1 dry weight); Cd, 0.5 to 5.0; Cu, 90 to 270; Zn, 1100 to 3000; Pb, 80 to 300; Ni, 25 to 60; Hg, 1.8 to 3.6; Ag, 1 to 35; PCBs, 0.1 to 3.6; lindane, 0.4 to 7.4; EDDT (i.e., DDT + DDD + DDE), 0.07 to 0.20; aldrin, below detection to 0.07; endrin, below detection to 0.27; dieldrin, 0.005 to 0.04). Mean levels were generally close or lower than mean concentrations reported in the United Kingdom and the United States. They were also lower than suggested concentration limits for application of sludge on agricultural land, which is one of the most cost-effective and attractive techniques for sludge disposal. For Kuwait to adopt this application, however, the characteristics of the local soil and prevailing environmental conditions, notably the frequent occurrence of severe dust storms, should be considered.     

High resolution gas chromatographic analysis of nonpolar chlorinated hydrocarbons in human milk

A gas chromatographic method is described for the analysis of human milk to determine polychlorinated biphenyls (PCBs) as 72 congeners plus p,p'-DDE, mirex, hexachlorobenzene, and octachlorostyrene. The detection limit for individual compounds is about 0.05 ng/g when 30 g milk is analyzed. Total PCBs can be estimated with a detection limit of 1-5 ng/mL milk. Analytical precision is better than +/- 10% for all compounds at 20-50 ng/mL whole milk.     

Metals and chlorinated hydrocarbons in surficial sediments of three nile Delta lakes,Egypt

Water, Air, & Soil Pollution - Surficial sediment samples from three shallow Nile Delta lakes (Lake Mariut, Hozha hydrodrome, andke Manzalah) were analyzed for PCBs, DDT-group pesticides, and...     

砂质多孔介质中土壤颗粒的迁移

通过室内模拟试验,研究了不同土壤悬液浓度和不同多孔介质组成条件下土壤颗粒在砂质多孔介质中的截留和迁出特征,以揭示土壤颗粒在砂质多孔介质中的迁移特征。结果表明,土壤颗粒在砂质多孔介质中迁移时会受到土壤颗粒粒级、浓度和介质组成的影响。截留作用在土壤颗粒通过砂质多孔介质时起主导作用,土壤颗粒截留比例随着土壤颗粒浓度的增大逐渐增加;而随着多孔介质中粗砂比例的增大,其逐渐降低。土壤总颗粒、50μm和1~50μm土壤颗粒迁出量分别与该粒级相应投入量呈幂函数增加趋势,而1μm土壤颗粒的迁出量与其投入量呈线性增加趋势。土壤总颗粒迁出量与介质中粗砂比例之间存在线性增加关系。因此,多孔介质组成、颗粒粒径和浓度在土壤颗粒迁移过程中起着重要作用,在多孔介质中土壤颗粒和污染物迁移研究方面需要充分考虑这些因素。     

Solute transport in aggregated porous media: Comparing model independent and dependent parameter estimation

In many studies on solute transport soil column experiments arc used to obtain the transport characteristics for Convection-Dispersion-Models. Early breakthrough of the solute pulse has been attributed to a non-equilibrium in phase exchange. It is a standard procedure to determine several model parameter values from such breakthrough curves (BTC). This investigation is focused on the physical significance of simultaneously fitted parameter values used in the convection and diffusion-controlled mass transfer model (mobile — immobile phase concept). Saturated column experiments were conducted with solid phases consisting of porous and solid glass beads. One set of model parameter values was obtained from the breakthrough curves by simultaneous optimization and a second set was determined by independent measurements of individual parameter values. Both sets of parameter values described the BTCs equally well but deviated substantially from each other. These discrepancies were analysed in terms of local parameter sensitivities.     

Levels of some high molecular chlorinated hydrocarbons in sediment samples from the eastern Adriatic coastal waters

It is well documented that synthetic chlorinated hydrocarbon residues are widespread through the oceanic ecosystem. The Adriatic Sea, as semi-enclosed body of water, is of special interest for an evaluation of the entry, extent and fate of the pollution by chlorinated hydrocarbons. Sediments samples were collected from 1976 to 1990 at seven areas and over forty stations located on the eastern Yugoslav coastal waters. Concentrations of chlorinated insecticides and polychlorinated biphenyls in surface sediment samples ranged from <0.1 to 93.9 for DDTs and from <0.5 to 294 μg kg^?1 for PCBs on dry weight basis. It is very important to stress that all these samples were analyzed from a single analytical group (mostly by the same analyst), using a uniform methodology. Total DDT and PCB concentration do not exhibit Gausian distribution in the investigated area and collecting period, so it is necessary to be very careful in interpreting the concentration data using parametric statistics. Very often, the pollutant levels in sediment samples differ significantly in samples collected at the same time at nearby stations.     

A mathematical model for removing volatile subsurface hydrocarbons by miscible displacement

A mathematical model is developed for analyzing the forced venting method of controlling hazardous vapors escaping from underground spills. Equations for predicting concentration profiles are derived from the fundamental laws governing the isothermal flow and dispersion of two-component, miscible, compressible fluids in a porous medium. The resulting equations are solved numerically by finite difference methods to predict concentration profiles for a two-dimensional venting process. Concentration profiles were found to be more sensitive to the dispersion coefficient than to porosity or permeability for the flow rates examined. A comparison of the model profiles with laboratory measurements indicated that realistic predictions are feasible.     

Simplified fat extraction with sulfuric acid as cleanup procedure for residue determination of chlorinated hydrocarbons in butter

A new cleanup procedure is described for chlorinated hydrocarbon residues in butterfat. The method is based on the dropwise addition of H2SO4 to a fat solution column and continuous removal of the lipids and the acid. The cleanup of 0.25-2.0 g fat requires only 10-40 ml sulfuric acid and 12-17 ml petroleum ether. There is no need for any further cleanup step, solvent evaporation, or centrifugation. The method is easy to standardize and is suitable for automation. At least 30 fat samples can be cleaned up manually by one analyst in one day. Recoveries were complete (greater than 90%) for polychlorinated biphenyl compounds and for 13 chlorinated pesticides of 16 examined. The method was tested on chlorinated hydrocarbon residues in commercial butter and the results were compared with those obtained with the acetonitrile method. The versatility and limitations of the method were investigated by varying the sulfuric acid strength, initial fat solution concentration, and column dimensions.     

Statistical models for the accumulation of PAH,chlorinated hydrocarbons and trace metals in epiphytic Hypnum cupressiforme

Concentrations of PAH (1.12-benzoperylene, 3.4-benzopyrene, fluoranthene), chlorinated hydrocarbons (α-BHC, lindane, PCB) and trace metals (Zn, Pb, Cu) in bulk precipitation, as well as PAH and trace metal concentrations in atmospheric dust samples from 14 sites in Bavaria, F.R.G. are presented for two vegetation periods (1979 and 1980). The same substances were also analyzed in epiphytic moss (Hypnum cupressiforme var. filiforme) sampled from tree trunks in October 1979 and 1980. Using mean immission values and the amount of precipitation as predictors and concentrations of pollutants in moss samples as criteria, a number of multiple regression models were computed in order to quantify the relationships between absolute air pollution data and accumulated trace substance values. Beta values of all variables help to determine whether bulk precipitation or atmospheric particulate matter has dominant influence on the uptake of trace substances by mosses. The study shows that epiphytic mosses can be used to monitor both heavy-metal, PAH and chlorinated hydrocarbons.     

Transport of polycyclic aromatic hydrocarbons through a partly urbanized river basin

The PAH-pollutant loads resulting from storm runoff to a receiving stream are associated with high concentrations of suspended sediments. This is explained by the sorption coefficients and isotherms on street dust, suspended solids, bedload and other sorbents. Pollutographs for a stream with storm runoff mainly from storm water overflows from a combined sewered medium sized town show strong ‘first-flush’ phenomena. Rainfall and bedload contribute only to a lesser extent to the overall transport which stems from street dust washoff. High correlation between total PAH load and maximum flow, but no relation between total PAH load and the number of days since the previous storm, indicates a ‘low washoff case’ under ‘transport limited’ conditions. 3.4-Benzopyrene load was modeled by a pollutant washoff function analoguous to that of the EPA storm water model.     

Transport of commercial endosulfan through a column of aggregated vineyard soil by a water flux simulating field conditions

Endosulfan is a potentially harmful, degradation resistant pesticide that is found in soils where it has been used. Despite being hydrophobic and having high affinity for soil matrix components, it has also been found in groundwater. To investigate this behavior, we studied the passage of a commercial emulsified formulation through a column of aggregated vineyard soil under simulated light rain. Breakthrough data were obtained using gas chromatography with electron capture detection to determine the concentration of endosulfan in samples extracted from the column periodically at several depths. These data, and analogous data obtained previously for the passage of bromide, were analyzed using the program CXTFIT v.2. Analysis of the bromide data strongly suggested the existence of preferential flow paths in the column. The endosulfan data were adequately accounted for by a model in which the preferential flow and nonpreferential flow regions are almost isolated from each other. These regions differ also as regards both the partition of endosulfan between soil and soil solution and the rate at which reversibly adsorbed endosulfan is transformed into irreversibly adsorbed endosulfan. The "irreversibility" sink term accounts also for biological and chemical degradation of endosulfan. The findings imply that soil humidity favors the transport of commercial endosulfan by the formation and maintenance of preferential flow paths in soil, controlling both the presence of endosulfan in groundwater and its high persistence in soil.     

Effect of soil pH on the sorption capacity of soil organic matter for polycyclic aromatic hydrocarbons in unsaturated soils

Sorption by soil organic matter (SOM) is considered the most important process affecting the bioavailability of hydrophobic organic chemicals (HOCs)in soil.The sorption capacity of SOM for HOCs is affected by many environmental factors.In this study,we investigated the effects of soil pH and water saturation level on HOC sorption capacity of SOM using batch sorption experiments.Values of soil organic carbon-water partition coefficient (K_OC) of six selected polycyclic aromatic hydrocar...     

Effect of reduced iron on the degradation of chlorinated hydrocarbons in contaminated soil and ground water: A review of publications

Chlorinated hydrocarbons are among the most hazardous organic pollutants. The traditional remediation technologies, i.e., pumping of contaminated soil- and groundwater and its purification appear to be costly and not very efficient as applied to these pollutants. In the last years, a cheaper method of destroying chlorine-replaced hydrocarbons has been used based on the construction of an artificial permeable barrier, where the process develops with the participation of in situ bacteria activated by zerovalent iron. The forced significant decrease in the redox potential (Eh) down to ?750 mV provides the concentration of electrons necessary for the reduction of chlorinated hydrocarbons. A rise in the pH drastically accelerates the dechlorination process. In addition to chlorine-organic compounds, ground water is often contaminated with heavy metals. The influence of the latter on the effect of zerovalent iron may be different: both accelerating its degradation (Cu) and inhibiting it (Cr). Most of the products of zerovalent iron corrosion, i.e., green rust, magnetite, ferrihydrite, hematite, and goethite, weaken the efficiency of the Fe⁰ barrier by mitigating the dechlorination and complicating the water filtration. However, pyrrhotite FeS, on the contrary, accelerates the dechlorination of chlorine hydrocarbons.     

Aspects of transport processes in aggregated soils

The way in which water and solutes move in aggregated soils depends on the mode of saturation of the pore space that is made up of the micropore region within the aggregates and the macropores surrounding them. When both regions are saturated, a hydraulic-head gradient causes water to flow preferentially in the macropores with little flow within the aggregates, so that movement of solutes into or out of the aggregates is mainly by diffusion caused by the difference between the solute concentrations of the water in the two regions. When macropores full of water surround unsaturated aggregates, water is imbibed by the aggregates giving rise to convective movement of solutes with the moving water. When the macropores are empty, the aggregates become almost isolated so that redistribution of water and solutes occurs only within the aggregates with very little transport of water and solutes between them. The movement of water and solutes in the micropore region within the aggregates can be considered to behave as if in a continuum, and can be described by Darcy's law and the dispersion equation, with boundary conditions imposed by conditions in the macropores. These physical considerations of transport behaviour in aggregated soils can be used to give guidance on soil management practices concerning drainage and leaching.     

Biodegradation of chlorinated phenols in subsurface soils

Microcosm studies were employed to determine the subsurface biodegradation rates of phenol, 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), and pentachlorophenol (PCP). Soil samples were taken from sites in Pennsylvania and Virginia from depths up to 31 m, and all samples contained significant microbial populations. Soil from both sites readily biodegraded all five compounds. Biodegradation rates increased as initial concentrations increased, and all biodegradation rates appeared to follow first-order kinetics with regard to the initial compound concentrations. Biodegradation rates for the five compounds followed the order: phenol = 2-CP > 2,4,6-TCP > 2,4-DCP. PCP was degraded more slowly than phenol or 2-CP, but similarly to 2,4,6-TCP and 2,4-DCP. Different soils exhibited different degradation rates, and the soil characteristics that may influence the rates are discussed. The data suggest that biological degradation is a significant attenuation mechanism for phenol and its chlorinated derivatives in subsurfaces saturated and unsaturated zones.