Environmental fate of Ra in cation-exchange regeneration brine waste disposed to septic tanks, New Jersey Coastal Plain, USA: migration to the water table

Fate of radium (Ra) in liquid regeneration brine wastes from water softeners disposed to septic tanks in the New Jersey Coastal Plain was studied. Before treatment, combined Ra (²²⁶Ra plus ²²⁸Ra) concentrations (maximum, 1.54 Bq L⁻¹) exceeded the 0.185 Bq L⁻¹ Maximum Contaminant Level in 4 of 10 studied domestic-well waters (median pH, 4.90). At the water table downgradient from leachfields, combined Ra concentrations were low (commonly ≤0.019 Bq L⁻¹) when pH was >5.3, indicating sequestration; when pH was ≤5.3 (acidic), concentrations were elevated (maximum, 0.985 Bq L⁻¹ - greater than concentrations in corresponding discharged septic-tank effluents (maximum, 0.243 Bq L⁻¹)), indicating Ra mobilization from leachfield sediments. Confidence in quantification of Ra mass balance was reduced by study design limitations, including synoptic sampling of effluents and ground waters, and large uncertainties associated with analytical methods. The trend of Ra mobilization in acidic environments does match observations from regional water-quality assessments.     

Environmental estrogens in an urban aquatic ecosystem: I. Spatial and temporal occurrence of estrogenic activity in effluent-dominated systems

The present study investigated occurrence of environmental estrogens (EEs) in waterways managed by the Metropolitan Water Reclamation District of Greater Chicago (‘District’) — one of the largest and most complex water districts in the United States. The objectives of the study were: (i) to document spatial and temporal occurrence of EEs in the Chicago Area Waterways (CAWs); (ii) to determine whether water reclamation plant (WRP) effluents contribute to estrogenic pollution of the receiving streams; (iii) to determine whether the mandated water quality monitoring data could be used to predict estrogenic pollution in the receiving streams; and (iv) to determine whether snow melt, storm runoff and combined sewer overflows may also be contributors of estrogenic activity to these systems. The estrogenic potency of the waterways was assessed using a cell-based reporter gene assay. The water quality data was readily available as part of the District's regular monitoring program. Our findings indicate that EEs are commonly found in the CAWs, and that WRP effluents are one of, but not the only important contributor to estrogenic activity. Mean estrogenic activities in CAWs (11 ng estradiol equivalents (EEQs/L)) are well within the values reported for other urban areas and WRP effluents. The estrogenic activity exhibited significant seasonal variation with highest values noted during the spring and summer months. When comparing the mean estrogenic activity of general use waters, secondary contact waters and WRP effluents, we found that general use waters had significantly lower estrogenic activity (ca 5 ng EEQ/L) than the other two matrices (ca 15 and 17 ng EEQ/L respectively). Our analyses indicate that estrogenic activity of the waterways was not reliably associated with mandated water quality parameters, and that such measurements may not be useful for predicting estrogenic activity, especially so in the complex urban systems. One of the prominent findings of this study is that EEs do not follow predictable spatial patterns — many of the upstream sites in the heavily urbanized areas had levels of estrogenic activity comparable to those found in the effluents and downstream locations. Our data suggest that surface runoff and snow melt are estrogenic (0–9 ng EEQ/L), and given that their estrogenic activities are similar to those of their receiving waterways (0–7 ng EEQ/L), we conclude that these non-WRP sources are important contributors to estrogenic activity of the CAWs.     

The removal of uranium from mining waste water using algal/microbial biomass

We describe a three step process for the removal of uranium (U) from dilute waste waters. Step one involves the sequestration of U on, in, and around aquatic plants such as algae. Cell wall ligands efficiently remove U(VI) from waste water. Growing algae continuously renew the cellular surface area. Step 2 is the removal of U-algal particulates from the water column to the sediments. Step 3 involves reducing U(VI) to U(IV) and transforming the ions into stable precipitates in the sediments. The algal cells provide organic carbon and other nutrients to heterotrophic microbial consortia to maintain the low E(H), within which the U is transformed. Among the microorganisms, algae are of predominant interest for the ecological engineer because of their ability to sequester U and because some algae can live under many extreme environments, often in abundance. Algae grow in a wide spectrum of water qualities, from alkaline environments (Chara, Nitella) to acidic mine drainage waste waters (Mougeotia, Ulothrix). If they could be induced to grow in waste waters, they would provide a simple, long-term means to remove U and other radionuclides from U mining effluents. This paper reviews the literature on algal and microbial adsorption, reduction, and transformation of U in waste streams, wetlands, lakes and oceans.     

Effectiveness of centralized bilge water treatment — a field study

Instrumentation and procedures were developed for gross and detailed characterization of oily wastewaters. The methodology was applied to the assessment of effectiveness of a centralized oily waste treatment facility. Generated data included total, dissolved, and suspended organic content and detailed chemical characteristics of oily water samples.The usefulness of the methodology was demonstrated in a real-life field study involving operation of a centralized oily waste treatment facility operated by the U.S. Army at Fort Eustis, Virginia, in 1976. It was found that the concentration of suspended organics ranged between 5 and 335 ppm and dissolved organics between 14 and 156 ppm in untreated bilge water.Treated bilge waste effluents contained essentially no suspended oil, but rather high (769–1262 ppm) amounts of dissolved organic matter.It was determined that physical methods of waste treatment based on gravity separation and coalescence are effective in removal of suspended petroleum, and that prolonged contact between an oil film and water results in water solubilization of petroleum, leading to very high concentrations of dissolved organic material in the treated effluent.     

丹江口库区典型小流域地表径流氮素动态变化

探明面源污染特征对制定丹江口水库水质保障体系具有重要意义。以胡家山小流域为研究对象,对村落和林 耕复合两种典型土地利用类型和流域各集水区出口地表径流氮浓度进行了连续监测。结果表明：村落降雨径流中总氮、硝态氮浓度较高,其中总氮均值超过20 mg/L,变化幅度都不大;氨氮浓度较低,但变化剧烈,这种氮浓度演变过程和降雨强度关系密切。硝态氮是村落氮输出的主要形态,占总氮输出的6031%～9655%,与总氮输出变化过程具有显著的相关性。林 耕地的氮浓度相对较低,总氮表现出上升—下降—平稳—上升的变化过程,硝态氮和总氮变化有着显著的相关性。在空间传输过程中,小流域下游氮浓度表现出稀释和富集两种效应,其中村落的氮输出对两种效应影响较大;在时间上,受耕作制度和气象变化,各集水区的氮浓度季节性变化明显,总氮浓度表现出春季>夏季>秋季>冬季,硝氮浓度表现出秋季>夏季>春季>冬季。胡家山小流域径流中氮素的含量均高于水库水体氮素含量,总氮高于地表水Ⅴ类水质标准,需要加强对小流域污染源的控制与处理,尤其是对村落径流的处理。
     

Sulfide production during anaerobic lagoon treatment of tapioca wastewater

Laboratory-scale experiments on anaerobic lagoon treatment of tapioca wastewater were conducted under ambient, tropical conditions. The objectives of this study were to investigate factors that affect hydrogen sulfide production and to propose means to control the formation of hydrogen sulfide in lagoon effluents. The concentrations of sulfides were found to increase with increasing organic loading from 2.76 to 5.77 kg COD/m³.d, decreasing hydraulic retention time; and increasing pH from 3 to 7. The maximum total sulfide concentration of 18.8 mg/L occurred at the organic loading of 5.77 kg COD/ m³.d and neutral pH. the maximum H₂S concentration was calculated to be 13.3 mg/L which occurred in the laggoon operated at an organic loading of 5.77 kg COD/m³.d and a pH of 5. The control of odour problems due to the H₂S formation should be possible by raising pH of the lagoon water to be more than 8 or operating the lagoon at low organic loadings.     

浙江北部低洼田湿地农业种养结合模式的环境效应

浙江北部地区地势低洼,种粮易涝,严重制约当地农业的发展。2010年以来,作为湿地农业农作制度的创新,“水生作物 鱼类”种养结合模式在当地得到迅速发展。为了完善种养高效综合配套技术,在嘉兴市秀洲区3个农场开展了不同种养模式（藕 鱼和菱 鱼模式）的对比试验,对池塘水质、底质特征以及大气负氧离子浓度进行了分析。结果表明种养结合模式对池塘水质有一定改善作用。虽然养殖鱼类后水体有机污染有一定程度加重,但由于水生作物的吸收作用,使得水体氮磷含量明显降低。与菱 鱼模式相比,鱼塘种植莲藕后,对水质的改善效果更为明显。对底质的分析表明,鱼塘种植水生作物后,底泥中速效钾含量增加明显,尤其是在种植莲藕后。另外,由于施用化肥以及当年不收割引起的藕叶、茎杆等腐烂分解,使得藕 鱼模式池塘底泥中速效磷和总氮含量大幅增加,分别增加329.1% 和361.9%。对种养结合区域大气负氧离子浓度测定结果表明,种养结合开发利用有利于改善周边区域空气质量     

乌江中上游新建水库水体甲基汞的时空分布

为了弄清新修建的水库是否造成水体甲基汞浓度升高，以贵州省乌江流域2座新建水库洪家渡水库和索风营水库为研究对象，采用蒸馏 乙基化结合（GC CVAFS）法测定了不同季节水库水体中甲基汞的浓度，最低检出限为 0.009 ng/L。探讨了水质参数对甲基汞分布的影响以及水库水体甲基汞的分布特征。结果显示:洪家渡水库总甲基汞浓度夏季平均值为 0.11 ng/L，秋季平均值为 0.08 ng/L，冬季平均值为 0.10 ng/L；索风营水库总甲基汞浓度夏季平均值为 0.11 ng/L，秋季平均值为 0.07 ng/L，冬季平均值为 0.09 ng/L。数据表明2座水库水体甲基汞含量均较低，低于目前我国环境质量标准规定的一类地表水汞含量标准限值，与世界上其他未受污染的水体基本相当。水库水体甲基汞浓度随水体深度的增加没有明显的变化规律，且夏季略高于冬季、秋季，这与夏季降雨量和温度有关，在入库处与大坝前没有明显的变化趋势。这与水库中被淹没土壤有机质含量偏低且流域内基岩为碳酸盐有关，还与其他环境因素有关(如pH值较高，DOC含量偏低等)。通过研究发现目前库区环境汞的甲基化率低，但随着水库生态系统的不断演化，内源和外源营养物的输入及水体在温度分层其间自身甲基汞的形成，导致水体甲基汞含量的逐渐增加，但仍需进一步的研究证实。     

Spatial and temporal variability of composition of urban effluents in the island of Lesvos, Greece

The spatial and temporal variability in the composition of effluents of the coastal town of Mytilene, island of Lesvos, Greece, was investigated in 8 sewers of the town. Differences were found in the quality of effluents between the old and new parts of the town and were attributed mainly to the different design and construction of the sewers, as well as to the occasional discharge of septage into the sewerage network in parts of the town. During summer the population and water consumption increase, leading to partial dilution of the organic load. However, in the same period (July), the concentrations of dissolved Zn and particulate Pb were enriched. The reasons for such an increase are not clear. At present the seasonal metal peaks (Pb and Zn) are attributed to the increased traffic (Pb and Zn) and to increased corrosion under the prevailing weather conditions of the water supply network, which includes a very large number of galvanized storage tanks (Zn).     

Unraveling the causes of the toxicity of extremely acid waters of volcanic origin

A river ecosystem in East Java, Indonesia, fed by a volcanic lake with high concentrations of dissolved metals and a low pH, was found to support only few macroinvertebrates. To unravel the causes of toxicity and to determine the level of dilution necessary to obtain non-toxic water, a bioassay was conducted with the fairy shrimp Thamnocephalus platyurus. A partial toxicity identification evaluation (TIE) approach was used with EDTA as a chelating agent to relate toxicity to pH and metal concentrations. Three water samples were tested, with pHs ranging from 0.72 to 4.5, and diluted with water from a neutral river to different degrees. The dilution factor necessary to achieve no more than 50% mortality in the Thamnotox test (Ldf(50)) varied from >300 at the most acidic site, to 7 for water of pH 2.6 and 1.5 for water of pH 4.5. Toxicity was best explained from both low pH and high concentrations of metals, especially Al and Fe. The key role of Al and Fe in the toxicity was confirmed by relating concentrations of the different compounds in the river water to toxicity data from the literature. EDTA addition did not significantly influence Ldf(50) or the lethal pH 50% (LpH(50)), suggesting a large effect, besides cationic components and pH, of anions (F, SO(4) and Cl).     

鄱阳湖枯水期水体营养浓度及重金属含量分布研究

通过监测鄱阳湖枯水期的主湖区、五河入湖口以及碟形湖表层水体氮、磷等营养浓度以及重金属含量变化,对鄱阳湖全湖的营养状况以及重金属污染现状进行了系统分析。结果表明：2010年枯水期的鄱阳湖流域表层水体总氮、总磷、化学需氧量等含量较高,达富营养化水平,湖泊水质受总氮、氨态氮、总磷和pH的影响较大。且鄱阳湖水域的氮、磷等营养存在明显的空间差异。研究结果进一步显示,饶河入湖口水体N、P污染最严重（TN 314 mg/L;TP 025 mg/L）,修河入湖口污染程度次之（TN 134 mg/L;TP 009 mg/L）,而南矶山碟形湖水体污染最小（TN 049 mg/L;TP 005 mg/L）。鄱阳湖表层水体重金属Pb、Cd的含量较低,符合国家渔业水质标准要求,尤其是湖泊Cd含量低于地表水Ｉ类标准。但鄱阳湖流域Cu、Zn污染较严重     

Aquatic mosses as a monitoring tool for 137Cs contamination in streams and rivers-a field study from central southern Norway

Mosses are frequently used as biomonitors for trace element pollution in the aquatic environment. The purpose of this study was to assess their usefulness as a tool in monitoring and in regional surveys of radioactive contamination. Specimens of the aquatic mosses, Fontinalis antipyretica and F. dalecarlica, were transplanted from non-contaminated areas to streams and rivers in the Norwegian Jotunheimen Mountains and neighbouring lowland areas that had received radioactive fallout after the Chernobyl accident. Equilibrium concentrations of 137Cs in the exposed mosses were reached after a few weeks. Two series from 20 streams in 1994 and 1996 show linear correlations between activities in water and moss samples and biomagnification ratios of 10(4) - 10(5). We conclude that mosses are better suited for monitoring purposes than water samples, because they provide values integrated over weeks while the radioactivity in surface waters can be subject to rapid variations according to hydrological events. The activity concentrations in aquatic mosses can be easily measured with good precision even when aqueous concentrations are below the limit of detection. Use of aquatic mosses also reduces the logistic problems of transporting large volumes of water, especially in areas inaccessible by road.     

Contamination of settling ponds and rivers as a result of discharge of radium-bearing waters from Polish coal mines

Saline waters from underground coal mines in Poland often contain natural radioactive isotopes, mainly 226Ra from the uranium decay series and 228Ra from the thorium series. Approximately 40% of the total amount of radium remains underground as radioactive deposits, but 225 MBq of 226Ra and 400 MBq of 228Ra are released daily into the rivers along with the other mine effluents from all Polish coal mines. Technical measures such as inducing the precipitation of radium in gobs, decreasing the amount of meteoric inflow water into underground workings, etc. have been undertaken in several coal mines, and as a result of these measures, the total amount of radium released to the surface waters has diminished by about 60% during the last 5-6 years. Mine water can have a severe impact on the natural environment, mainly due to its salinity. However, associated high levels of radium concentration in river waters, bottom sediments and vegetation have also been observed. Sometimes radium concentrations in rivers exceed 0.7 kBq/m3, which is the permitted level for waste waters under Polish law. The extensive investigations described here were carried out for all coal mines and on this basis the total radium balance in the effluents has been calculated. Measurements in the vicinity of mine settling ponds and in rivers have given us an opportunity to study radium behaviour in river waters and to assess the degree of contamination. Solid waste materials with enhanced natural radioactivity have been produced in huge amounts in the power and coal industries in Poland. As a result of the combustion of coal in power plants, low-radioactive waste materials are produced, with 226Ra concentration seldom exceeding a few hundreds of Bq/kg. A different situation is observed in coal mines, where, as a result of precipitation of radium from radium-bearing waters, highly radioactive deposits are formed. Sometimes the radioactivity of such materials is extremely high; precipitates from coal mines may have radium concentrations of 400,000 Bq/kg--equivalent to 3% uranium ore. Usually, such deposition takes place underground, but sometimes co-precipitation of radium with barium takes place on the surface, in settling ponds and in rivers. Therefore management of solid waste with technologically enhanced natural radioactivity (TENR) is a very important subject.     

Exposure assessment of the pharmaceutical diclofenac based on long-term measurements of the aquatic input

Although various single-concentration measurements of the pharmaceutical diclofenac are available in literature, detailed information on the mass flux in the aquatic environment is often missing. Therefore, the overall load of diclofenac was obtained by recording each concentration in nine effluents of sewage treatment plants (STP) and at three river sites located in the area of the river Main (Germany) over a time period of six weeks.In STP effluents, concentrations of up to 2200 ng/L were obtained. In combination with flow rates and connected population an average specific load per capita and day of 0.28 mg (+/? 0.11 mg) diclofenac reaches the receiving water course. This average specific load per capita is an expressive parameter to assess main diclofenac exposure to the aquatic environment avoiding uncertainties of estimated data commonly used in exposure assessment. Accordingly, predicted environmental concentrations (PEC) of 140 ng/L for a realistic worst case scenario and 2 to 52 ng/L based on water quality modeling were derived. Since concentrations of up to 140 ng/L were observed in surface water, the obtained PEC is in perfect agreement with measured concentrations. Hence, comparing the PEC with published predicted no effect concentrations (PNEC), chronic adverse effects in fish populations may occur.     

三峡库区172 m蓄水位实现后干流水体溶解态重金属含量变化特征

从2008年至2010年连续两年,对三峡库区涪陵至巴东段水体溶解态重金属含量进行监测,分析三峡水库自2008年首次以172 m高水位试验性蓄水以来水体溶解态重金属含量变化特征及其影响因素。结果表明：水体溶解态重金属含量在丰水期低水位时含量较高,而在平水期和枯水期高水位蓄水时,水体重金属含量较低,丰水期时水体溶解态重金属含量虽然相对较高,但仍然达到《地表水环境质量标准》(GB 3838 2002)Ⅰ类水域标准。重金属在水体与沉积物和消落带土壤中含量并无明显相关性,沉积物和消落带土壤重金属对水体溶解态重金属含量分布影响较小。库区水环境因素在丰水期和平水期、枯水期呈现出明显差异特征,特别是汛后水体悬浮物SS含量远低于丰水期。三峡水库水环境因素的变化对重金属的分配有着重要作用,丰水期过后三峡库区水体pH值和DO升高,水温和Eh降低,SS含量显著下降,水环境因素、气象条件、水位调度等因素的变化致使水体溶解态重金属含量降低     

土壤物理质量指标研究进展及在矿区环境中的应用展望

对土壤物理质量指标在国内外的研究进展进行了系统总结,在矿区环境中的应用进行了展望,构建了矿区环境土壤物理质量指标体系。常规指标的研究集中于耕作或人为干扰对指标影响的定量研究及物理、化学和生物学指标的相互影响。国外提出并应用了许多非常规指标来对土壤物理质量进行评价,结合常规指标,可以对自然或人为扰动情况下,土壤损伤及退化问题进行深入研究。采煤沉陷对土壤物理质量的影响是一个系统和复杂的过程,我国矿区土壤环境的研究,应该基于不同的研究目的,选择正确的常规和非常规指标来对矿区土壤物理质量进行系统的评价、表征及定量化。构建的矿区环境土壤物理质量指标体系,具有一定的参考和应用价值。     

Abnormal high natural radium concentration in surface waters

Unexpected high 228Ra concentrations, up to 2 Bq 1(-1), were found in waters of a coastal lagoon close to a monazite sand separation plant. Due to their use as process waters in this plant, the initial supposition was a contamination related to its operation. However, it was concluded that these abnormal radium concentrations had a natural origin, springs at the lagoon head area with high 228Ra and 226Ra concentrations. The strong relationship among radium and light rare-earth elements (LREEs), the observed 228Ra/226Ra activity ratio and the rare-earth element pattern in the spring waters suggested that monazite is the main source of nuclides for water, indicating the disturbance of monazite chemical stability by the combined effects of low pH and high salinity. Both factors combined allow relatively low mobility of thorium, but, on the other hand, a relatively high mobility of radium and LREEs.     

Distributions of zinc, copper, cadmium and lead in a tropical ultisol after long-term disposal of sewage sludge

Heavy metals present in soils constitute serious environmental hazards from the point of view of polluting the soils and adjoining streams and rivers. The distribution of heavy metals in a sandy Ultisol (Arenic Kandiustult) in south eastern Nigeria subjected to 40 years disposal of sewage wastes (sludge and effluents) was studied using two profile pits (S/NSK/1 and S/NSK/2) sited in the sewage disposal area and one profile pit (NS/NSK) sited in the non-sewage disposal area. Soil samples were collected in duplicate from these soil horizons and analyzed for their heavy metal contents. The mean concentrations of Zn, Cu, Cd and Pb in the top- and sub-soil horizons of sewage soil were 79.3, 32, 0.29 and 1.15 mg/kg, respectively. These levels were high enough to constitute health and phytotoxic risks. All the metal levels were much higher in the AB horizon in the sewage than in the non-sewage soil profile, but Pb and Cu contents were also high down to the Bt1 horizon, indicating their apparent relatively high mobility in this soil. There was a significant correlation between organic matter (OM) and Zn (r=0.818**), and between OM and Cd (0.864**) in the sewage soil. The high OM status of the sewage sludge, together with its corresponding low pH, might have favoured metal-OM complexation that could reduce heavy metal mobility and phytotoxicity in this soil.     

Heavy metal contamination by Al-fabrication plants in Hong Kong

Leaf samples of six plant species collected from locations near the Al-fabrication plants in Sai Kung, Hong Kong were found to be heavily contaminated by Al, Cd, Pb, Ni, Cu and Zn, as determined by inductively — coupled plasma emission spectrophotometer (ICP). Studies using scanning electron microscope incorporated with X-ray microanalyzer showed that significant amounts of dust, with elevated concentrations of heavy metals, were deposited on the leaf surface. The stomatal pores were partially plugged and the guard cells were distorted. The amount of dust deposition and metal contamination varied significantly among different species. Lantana camara had the highest concentrations of all metals. Washing with deionized water could remove the surficial dust particles and reduce the metal contamination, with a degree of effectiveness depending on plant species and metal species. About 50% of Al and other metals were removed from leaves of L. camara and Fiscus variegata by washing, whereas only 20% removal was recorded in Bauhina variegata, the species had the least dust deposition. The soil samples and Al wastes collected from the same sites also exhibited higher values of total metal concentrations than the control. However, the contents of extractable metals were extremely low and were almost below the limits of detection. Experimental data further suggested that the source of leaf metals was mainly accumulated from metal-enriched aerosols, either from Al-fabrication plants or from automobile exhausts, and contribution from soil was relatively unimportant.     

Residues and source identification of persistent organic pollutants in farmland soils irrigated by effluents from biological treatment plants

Sewage and industrial effluents from biological treatment plant have been widely used for agricultural irrigation in north part of China. However, effluents after biological treatment still contain heavy metals and persistent organic contaminants. The persistent organic contaminants accumulated in soil may transfer through the food chains and cause adverse health effects on human or biological effects on soil fauna and flora after long-term application. In present study, field surveys were carried out in the farmlands irrigated by effluents from biological treatment plants that receive sewage wastewater and industrial discharges. Residues of polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) in the soils irrigated using both ground water and effluents were compared. The origins of PAHs in the soils were discussed. The results showed that wastewater irrigation could cause accumulation of PAHs in soils close to the pollution discharge. Significantly higher concentrations of PAHs were observed in the sampling sites close to the entrance of main channel in contrast to those along branches and the reference sites. There was no significant relationship between the accumulation of persistent organic pollutants and organic matter content in soil (TOC). Soil contamination of these persistent organic pollutants as affected by effluent irrigation was characterized by the dominant accumulation of high-molecular-weight PAHs (HMW-PAHs). In the case study, concentration of benzo[a]pyrane (BaP, 45.6 ng/g), indeno[1,2,3-cd]pyrene (IcP, 86.3 ng/g), benzo[g,h,i]perlene (BgP, 66.9 ng/g) could exceed the limits of the soil quality standard for biodegraded soils. In identification of the sources, the IcP/BgP values of PAHs in soils were more close to that in air particulates from coal/coke source (1.09+/-0.03 ng/g) [Dickhut RM, Canuel EA, Gustafson KE, Liu K, Arzayus KM, Walkers E, et al. Automotive sources of carcinogenic polycyclic aromatic hydrocarbons associated with particulate matter in the chesapeake bay region. Environ Sci Technol 2000;34:4635-40]. Therefore, both of the PAHs residues in effluents and emission from a nearby coal/coke plant were responsible. Also in this case study, low levels of the OCPs were observed and were not of significant concern in this wastewater irrigation area. Among the different OCPs analyzed, DDTs (mean 8.41 ng/g) and HCHs (mean 2.91 ng/g) were the major components. From the ratios of DDT/DDTs and beta-HCH/HCHs, it indicated that OCPs residues should be from historical usage.