A decision framework for possible remediation of contaminated sediments in the River Kymijoki, Finland

Background, aim, and scope  The paper describes the spatial contamination of the River Kymijoki, South-Eastern Finland, and the coastal region of the Gulf of Finland with PCDD/Fs and mercury. The findings of ecotoxicologial and human health studies are also reported, including environmental and human risk assessments. Sediments from the River Kymijoki, draining into the Gulf of Finland, have been heavily polluted by the pulp and paper industry and by chemical industries. A wood preservative, known as Ky-5, was manufactured in the upper reaches of the river between 1940 and 1984 causing severe pollution of river sediments with polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF). Moreover, the sediments have been polluted with mercury (Hg) from chlor-alkali production and the use of Hg as a slimicide in pulp and paper manufacturing. Materials and methods  An extensive sediment survey was conducted as well as sediment transport modeling, toxicity screening of sediment invertebrates, and a survey of contaminant bioaccumulation in invertebrates and fish. Studies on human exposure to PCDD/Fs and the possible effects on hypermineralization of teeth as well as an epidemiological study to reveal increased cancer risk were also conducted. An assessment of the ecological and human health risks with a null hypothesis (no remediation) was undertaken. Results  The sediment survey revealed severe contamination of river and coastal sediments with PCDD/Fs and Hg. The total volume of contaminated sediments was estimated to reach 5 × 10⁶ m³ and hot spots with extremely high concentrations (max 292,000 ng g⁻¹ or 1,060 ng I-TEQ g⁻¹ d.w.) were located immediately downstream from the pollution source (approximately 90,000 m³). Sediment contamination was accompanied by changes in benthic assemblages, but direct effects were masked by many factors. The fish showed only slightly elevated PCDD/F levels in muscle, but orders of magnitude higher in the liver compared with reference freshwater sites and the Baltic Sea. The concentrations in human fat did not reveal high human exposure in the Kymijoki area in general and was lower than in sea fishermen. The relative risk for total cancer among farmers was marginally higher (RR = 1.13) among those living close to the river, compared with farmers living further away, and the possibility of increased cancer risk cannot be ruled out. A conservative risk assessment revealed that the present probability of exceeding the WHO upper exposure limit of 4 pg WHO-TEQ kg⁻¹ d⁻¹ for PCDD/Fs and DL-PCBs was 6%. The probability of exceeding the WHO limit value of 0.23 μg kg⁻¹ d⁻¹ for methyl mercury was estimated to be notably higher at 62%. Based on these studies and the estimated risks connected with different remediation techniques a general remediation plan with cost benefit analysis was generated for several sub-regions in the river. Dredging, on-site treatment, and a close disposal of the most contaminated sediments (90,000 m³) was suggested as the first phase of the remediation. The decision regarding the start of remediation will be made during autumn 2008. Conclusions  The sediments in the River Kymijoki are heavily polluted with PCDD/Fs and mercury from earlier chlorophenol, chlor-alkali, and pulp and paper manufacturing. A continuous transport of contaminants is taking place to the Gulf of Finland in the Baltic Sea. The highly increased PCDD/F and Hg levels in river sediments pose an ecotoxicological risk to benthic fauna, to fish-eating predators and probably to human health. The risks posed by mercury exceed those from PCDD/Fs and need to be evaluated for (former) chlor-alkali sites and other mercury releasing industries as one basis for remediation decision making. Recommendations and perspectives  The studies form the basis of a risk management strategy and a plan for possible remediation of contaminated sediments currently under consideration in the Southeast Finland Regional Environment Centre. It is recommended that a detailed restoration plan for the most seriously contaminated areas should be undertaken. Based on current knowledge, the restoration of the whole river is not feasible, considering the current risk caused by the contaminated sediment in the river and the costs of an extensive restoration project. The experiences gained in the present case should be utilized in the evaluation of PCDD/F- and mercury-contaminated sites in other countries. The case demonstrates that the historic reservoirs are of contemporary relevance and should be addressed, e.g., in the national implementation plans of the Stockholm Convention. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Spatial distribution of uranium and thorium in the surface soil around proposed uranium mining site at Lambapur and its vertical profile in the Nagarjuna Sagar Dam

The understanding and evaluation of the possible interactions of various naturally occurring radionuclides in the world's third largest man-made dam, Nagarjuna Sagar located in Andhra Pradesh, India and built on river Krishna assumed significance with the finding of uranium deposits in locations near the dam. For the present work, surface soil samples from the mineralized area of Lambapur, Mallapuram, Peddagattu and sediment core samples from the Nagarjuna Sagar dam were analyzed for naturally occurring radionuclides namely uranium and thorium using gamma spectrometric technique. Also toxic elements lead and chromium were analysed by the Energy Dispersive X-ray Fluorescence Spectrometer (EDXRF) technique. Surface soil samples show a variation from 25 to 291 Bq/kg (2.02–23.5 mg/kg) for ²³⁸U and 32–311 Bq/kg (7.9–76.9 mg/kg) for ²³²Th. U/Th concentration ratio in surface soil samples ranged from 0.19 to 0.31 and was found comparable with the nation wise average of 0.26. The study of sediment core samples reflected higher U/Th concentration ratio of 0.30–0.33 in the bottom section of the core as compared to 0.22–0.25 in the upper section. The concentration ratio in the upper section of the core was similar to the ratio 0.23 found in the western Deccan Basalt region through which the river originates. A higher concentration of lead and chromium was observed in the upper section of the core compared to bottom section indicating the impact of river input on the geochemical character of dam sediment.     

Heavy metals in water, sediment and tissues of Liza saliens from Esmoriz–Paramos lagoon, Portugal

Esmoriz–Paramos lagoon is an ecosystem of great ecological importance that is located on the northwest coast of Portugal and has been degraded as a result of industrial and anthropogenic activities. Concentrations of heavy metals (Cr, Cu, Pb and Zn) were measured in water, sediment and in tissues (liver and muscle) of Liza saliens, which is the dominant fish from the lagoon. Comparisons between metal concentrations in water and sediments were made with those in tissues of fish caught at the lagoon. Metals in water were quantified predominantly bound to particulate and equalled or exceeded the limit of chronic reference values. Metal concentrations in sediments varied among sampled sites. The relative order of concentrations was “Zn > Cu ∼ Pb > Cr” the same pattern observed for metals in water. Metals in fish tissues showed higher concentrations in liver (262 mg Cu·Kg⁻¹ and 89 mg Zn·Kg⁻¹) than in muscle (<3 mg Cu·Kg⁻¹ and 26 mg Zn·Kg⁻¹), while Pb and Cr were not detected. These results suggest that Cu and Zn are the metals of major concern in the lagoon. Mullet detritivorous feeding habits, bioaccumulation pattern and the high sediment metals concentrations relative to the water suggest that sediments can be the most important source of contamination in this ecosystem. The positive relationship found between Cu in liver and fish length demonstrates that time of exposure is a crucial factor in bioaccumulation. Condition indices (K and HSI) in mullets from the lagoon were higher compared to mullets from sea, suggesting abnormal condition in the lagoon population. We conclude that metals chronic exposure in the lagoon can impose considerable fish stress. The results also show that the lagoon is an area of environmental concern.     

太湖沉积物重金属污染及生态风险性评价

对1993年～1999年所采集的太湖表层沉积物中重金属含量进行了统计分析和生态风险性评价.结果表明,太湖沉积物的pH值呈中性至弱碱性,较适合于沉积物中粘土矿物及腐殖质对重金属的吸附;太湖大部分地区沉积物未受到重金属污染,且沉积物中重金属处于安全状态.沉积物生态风险性指数评价结果也表明,太湖大部分地区目前无重金属生态危害.     

Determination of toxic elements in waters and sediments from River Subin in the Ashanti Region of Ghana

Waters and sediments of Subin River, which flows through the industrial and commercial areas of Kumasi in the Ashanti region of Ghana, were geochemically investigated to ascertain heavy metal pollution levels due to anthropogenic activities. The study shows preoccupying pollution levels that constitute a threat to public and ecological systems. The waters of Subin River are neutral to slightly basic, inferred from pH values of 6.89–7.65). Electric conductivity (EC) of the waters ranges from 822 to 1,821 μs/cm and the range of total dissolved solids (TDS) is from 409 to 913 mg/l. Toxic elements contents of sediments and waters from 10 sites along the river were analysed by instrumental neutron activation analysis (INAA), and Al, As, Cd, Cr, Cu and Zn were determined. The concentrations of Al, As, Cd, Cr, Cu and Zn in the waters range between 4.02–15.18, 0.007–0.16, 0.002–0.05, 0.001–0.019, 1.32–7.04 and 4.28–10.2 mg/l, respectively. The contamination factors (CF) computed for the elements indicate that with the exception of sampling site S10, the sediments are polluted with Cd. Chromium contamination in the sediments is observed at S6 and S7, where the CF values were 1.39 and 1.52, respectively. The pollution load indices (PLI) were low (<1) and ranged from 0.14 to 0.75, suggesting that the overall sediment column of the river is not polluted.     

Wet weather impact on trihalomethane formation potential in tributaries to drinking water reservoirs

During rain storm events, land surface runoff and resuspension of bottom sediments cause an increase in Trihalomethane (THM) precursors in rivers. These precursors, when chlorinated at water treatment facilities will lead to the formation of THMs and hence impact drinking water resources. In order to evaluate the wet weather impact on the potential formation of THMs, river samples were collected before, during and after three rain storms ranging from 15.2 to 24.9 mm precipitation. The samples were tested for THM formation potential and other indicators including UV254 absorbance, turbidity and volatile suspended solid (VSS). Average levels of THMs increased from 61 μg/l during dry weather to 131 μg/l during wet weather, and then went back to 81 μg/l after rain ended. Wet weather values of THM are well above the maximum contaminant level (MCL) 80 μg/l, set by EPA for drinking water. THM indicators also exhibited similar trends. Average levels increased from 0.6 to 1.8 abs; 2.6 to 6 ntu; and 7.5 to 15 mg/l respectively for UV254, turbidity and VSS. A positive correlation was observed between THM formation and THM indicators. The t-test of significance (p-value) was less than 0.05 for all indicators, and R values ranged from 0.85 to 0.92 between THMs and the indicators, and 0.72 to 0.9 among indicators themselves.     

An evaluation of selenium concentrations in water, sediment, invertebrates, and fish from the Solomon River Basin

The Solomon River Basin is located in north-central Kansas in an area underlain by marine geologic shales. Selenium is an indigenous constituent of these shales and is readily leached into the surrounding groundwater. Portions of the Basin are irrigated primarily through the pumping of selenium-contaminated groundwater from wells onto fields in agricultural production. Water, sediment, macroinvertebrates, and fish were collected from various sites in the Basin in 1998 and analyzed for selenium. Selenium concentrations were analyzed spatially and temporally and compared to reported selenium toxic effect thresholds for specific ecosystem components: water, sediments, food-chain organisms, and wholebody fish. A selenium aquatic hazard assessment for the Basin was determined based on protocol established by Lemly. Throughout the Basin, water, macroinvertebrate, and whole fish samples exceeded levels suspected of causing reproductive impairment in fish. Population structures of several fish species implied that successful reproduction was occurring; however, the influence of immigration of fish from low-selenium habitats could not be discounted. Site-specific fish reproduction studies are needed to determine the true impact of selenium on fishery resources in the Basin. The U.S. Government’s right to retain a non-exclusive, royalty free license in and to any copyright is acknowledged.     

渭河干流(宝鸡段)表层沉积物Cu、Zn、Pb污染特征与评价

对渭河干流（宝鸡段）表层沉积物中重金属Cu、Zn、Pb含量进行了调查,用潜在生态危害系数法对其污染水平进行了评价,并与松花江（吉林市段）、淮河（江苏段）、长江（下游）、苏州河、珠江（广州段）5条河流表层沉积物中Cu、Zn、Pb的含量做了对比研究。结果表明,3种重金属元素平均含量均超出相应的土壤背景值,出现了一定程度上的富集;生态危害系数均〈40,属轻微生态危害。重金属含量水平在国内诸河中处于中间位置。     

广州大学城珠江水域多环芳烃的污染特征

利用GC-MS对广州大学城珠江水域的地表水及表层沉积物中多环芳烃(PAHs)的含量进行了分析。结果表明,广州大学城珠江水域及表层沉积物中均可检出PAHs,水体优控PAHs总量在1061.7~6577.8ng/L之间,沉积物中优控PAHs总量分布在896.1~7248ng/g之间。广州大学城珠江水域的PAHs属混合来源,主要有石油类产品的输入(漏油泄油)和化石燃料的燃烧(大气沉降)。     

基于临水区域化工园区的整体安全研究

针对临水区域化工园区的生产特点及在整体安全方面存在的普遍问题,提出在临水区域化工园区内要进行合理布局,做到功能分区明确;同时需建立园区安全生产管理、监测预警及应急处置系统,主要是由固定危险源和移动危险源动态安全管理子系统、安全生产监测预警系统、突发事故应急处置平台等所组成;坚持安全监控信息化与标准化,对化工园区的整体安全性的提高将发挥巨大的作用,为建设"平安园区"打下坚实的基础。