Factors affecting trace-metal bioaccumulation in Finnish headwater lakes

Fourteen unpolluted Finnish headwater lakes with pH values varying from 4.8 to 7.0 were studied for trace-metal concentrations in water, sediment, aquatic plants (Nuphar luteum L., Sparganium sp.), aquatic insect larvae (Limnophilus sp., Phryganea sp.) and fish (Esox lucius L., Perca fluviatilis L., Coregonus sp., Salvelinus fontinalis L., Salmo trutta L.). Trace-metal deposition was estimated by analysing the snowpack. Non-parametric correlation analysis was carried out between trace metal concentrations in biota and pH, ANC, TOC, CA + Mg concentration in water and a given metal concentration in water and sediment. Bioaccumulation of several trace metals increased with increasing acidity and decreasing ANC in water. This was especially true for Pb and Cd. Aquatic plants were, in general, the best indicator group concerning differences in trace-metal bioaccumulation in lakes with different acidity. There was some evidence that a higher concentration of TOC in water may reduce bioaccumulation of Pb, Cd and Zn in aquatic plants and fish. The copper concentration in sediment was the only background variable explaining Cu concentration in aquatic insects. Multivariate analysis of the whole background data gave comparable preliminary results. Over 80% of the trace metal concentrations in biota of different lakes was explained by the background variables. In general, elevated concentrations of most of these trace metals can be expected to occur in the biota of acidified low calcareous lakes.     

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.     

Dioxin concentrations in sediments of the Baltic Sea--a survey of existing data

Recent survey results for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs, dioxins) in Baltic Sea sediments from Finland, Sweden and Denmark were merged with previously published Baltic Sea data. Regional distribution of concentration levels, differences in congener patterns, and temporal changes in sediment profiles were examined. One of the main objectives was to study if any major point sources for different PCDD/F congeners could be identified on a regional scale, based on sediment records. The survey confirmed the impact of chlorophenol production derived highly chlorinated PCDF-congeners on the total toxicity in sediments in the Gulf of Finland near the Kymijoki river estuary. Signatures of other point sources or combined point sources pertinent to specific industry branches or particular production processes (such as pulp bleaching, vinyl chloride production, thermal processes) may be discerned. However, the findings did not support any of the known point sources significantly influencing those congeners that are most abundant in Baltic herring and salmon. Instead, regional distributions in the Baltic Sea indicate that atmospheric deposition may act as a major source for those congeners and especially for 2,3,4,7,8-PeCDF. There were clear indications of declines in levels in sediment in some areas, but generally the levels of highly chlorinated PCDD/Fs on the northern coast of the Gulf of Finland were still high when compared with other areas of the Baltic Sea. Major areas with data gaps cover the south-eastern and eastern coastal regions of the Baltic Proper and the southern Gulf of Finland.     

Organohalogen pollutants in herring from the northern Baltic Sea: concentrations, congener profiles and explanatory factors

Organohalogen contaminants were investigated in Baltic herring caught from three catchment areas in the Baltic Sea, off the coasts of Finland. Pools of both small and large herring were analysed for polychlorinated biphenyls (PCB), dibenzo-p-dioxins, dibenzofurans, naphthalenes, camphenes (toxaphene), polybrominated diphenyl ethers and the pesticide DDT and its metabolites. PCB concentrations per fresh weight in small herring were at the same level in all catchment areas, i.e. the Bothnian Bay, the Bothnian Sea and the Gulf of Finland, revealing no hot spots and reflecting most likely long term emissions and atmospheric deposition. Differences in the levels and/or congener profiles of other contaminants between catchment areas may be explained by point sources. Similar concentrations in small and large herring in the Gulf of Finland were possibly due to their common nutrition. In the other areas, differences between small and large herring most likely reflected their different food sources.     

Dioxin- and POP-contaminated sites—contemporary and future relevance and challenges

BACKGROUND, AIM AND SCOPE: Once they have been generated, polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) and other persistent organic pollutants (POPs) can persist in soils and sediments and in waste repositories for periods extending from decades to centuries. In 1994, the US EPA concluded that contaminated sites and other reservoirs are likely to become the major source of contemporary pollution problems with these substances. With this in mind, this article is the first in a new series in ESPR under the title 'Case Studies on Dioxin and POP Contaminated Sites--Contemporary and Future Relevance and Challenges', which will address this important issue. The series will document various experiences from sites contaminated with PCDD/F and other POPs. This article provides an overview of the content of the articles comprising the series. In addition, it provides a review of the subject in its own right and identifies the key issues arising from dioxin/POP-contaminated sites. Additionally, it highlights the important conclusions that can be drawn from these examples. The key aim of this article and of the series as a whole is to provide a comprehensive overview of the types of PCDD/F contaminated sites that exist as a result of historical activities. It details the various processes whereby these sites became contaminated and attempts to evaluate their contemporary relevance as sources of PCDD/Fs and other POPs. It also details the various strategies used to assess these historical legacies of contamination and the concepts developed, or which are under development, to effect their remediation. MAIN FEATURES: Special sessions on 'Contaminated sites--Cases, remediation, risk and policy' were held at the DIOXIN conferences in 2006 and 2007, and this theme will be continued at DIOXIN 2008 to be held in Birmingham. Selected cases from the approximately 70 contributions made to these sessions, together with some additional invited case studies are outlined together with the key issues they raise. By evaluating these cases and adding details of experiences published in the current literature, an overview will be given of the different features and challenges of dioxin and POP-contaminated sites. RESULTS: This article provides a systematic categorisation of types of PCDD/F and POP-contaminated sites. These are categorised according to the chemical or manufacturing process, which generated the PCDD/Fs or POPs and also includes the use and disposal aspects of the product life cycle in question. The highest historical PCDD/F and dioxin-like polychlorinated biphenyl (PCB) contamination burdens have arisen as a result of the production of chlorine and of chlorinated organic chemicals. In particular, the production of chlorinated pesticides, PCBs and the related contaminated waste streams are identified being responsible for historical releases of toxic equivalents (TEQs) at a scale of many tonnes. Along with such releases, major PCDD/F contaminated sites have been created through the application or improper disposal of contaminated pesticides, PCBs and other organochlorine chemicals, as well through the recycling of wastes and their attempted destruction. In some extreme examples, PCDD/F contaminated sites have also resulted from thermal processes such as waste incinerators, secondary metal industries or from the recycling or deposition of specific waste (e.g. electronic waste or car shredder wastes), which often contain chlorinated or brominated organic chemicals. The examples of PCDD/F and dioxin-like PCB contamination of fish in European rivers or the impact of contaminated sites upon fishing grounds and upon other food resources demonstrate the relevance of these historical problems to current and future human generations. Many of the recent food contamination problems that have emerged in Europe and elsewhere demonstrate how PCDD/F and dioxin like PCBs from historical sources can directly contaminate human and animal feedstuffs and indeed highlight their considerable contemporary relevance in this respect. Accordingly, some key experiences and lessons learnt regarding the production, use, disposal and remediation of POPs from the contaminated sites are summarised. DISCUSSION: An important criterion for evaluating the significance and risks of PCDD/Fs and other POPs at contaminated sites is their present or future potential for mobility. This, in turn, determines to a large degree their propensity for off-site transport and environmental accessibility. The detailed evaluation of contaminated site cases reveals different site-specific factors, which influence the varied pathways through which poor water-soluble POPs can be mobilised. Co-contaminants with greater water solubility are also typically present at such sites. Hence, pumping of groundwater (pump and treat) is often required in addition to attempting to physically secure a site. At an increasing number of contaminated sites, securing measures are failing after relatively short time spans compared to the time horizon, which applies to persistent organic pollutant contamination. Due to the immense costs and challenges associated with remediation of contaminated sites 'monitored natural attenuation' is increasingly gaining purchase as a conceptual remediation approach. However, these concepts may well prove limited in their practical application to contaminated sites containing persistent organic pollutants and other key pollutants like heavy metals. CONCLUSIONS: It is inevitable, therefore, that dioxin/POP-contaminated sites will remain of contemporary and future relevance. They will continue to represent an environmental issue for future generations to address. The securing and/or remediation of dioxin/POP-contaminated sites is very costly, generally in the order of tens or hundreds of millions of dollars. Secured landfills and secured production sites need to be considered as constructions not made for 'eternity' but built for a finite time scale. Accordingly, they will need to be controlled, supervised and potentially repaired/renewed. Furthermore, the leachates and groundwater impacted by these sites will require ongoing monitoring and potential further remediation. These activities result in high maintenance costs, which are accrued for decades or centuries and should, therefore, be compared to the fully sustainable option of complete remediation. The contaminated site case studies highlight that, while extensive policies and established funds for remediation exist in most of the industrialised western countries, even these relatively well-regulated and wealthy countries face significant challenges in the implementation of a remediation strategy. This highlights the fact that ultimately only the prevention of contaminated sites represents a sustainable solution for the future and that the Polluter Pays Principle needs to be applied in a comprehensive way to current problems and those which may emerge in the future. RECOMMENDATIONS AND PERSPECTIVES: With the continuing shift of industrial activities in developing and transition economies, which often have poor regulation (and weak self-regulation of industries), additional global challenges regarding POPs and other contaminated sites may be expected. In this respect, a comprehensive application of the "polluter pays principle" in these countries will also be a key to facilitate the clean-up of contaminated areas and the prevention of future contaminated sites. The threats and challenges of contaminated sites and the high costs of securing/remediating the problems highlight the need for a comprehensive approach based upon integrated pollution prevention and control. If applied to all polluting (and potentially polluting) industrial sectors around the globe, such an approach will prove to be both the cheapest and most sustainable way to underpin the development of industries in developing and transition economies.     

Concentrations of polychlorinated dibenzo-p-dioxins and furans in fish downstream from a Ky-5 manufacturing

Concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were studied in seven fish species, burbot (Lota lota), pike (Esox lucius), perch (Perca fluviatilis), pikeperch (Stizopedion lucioperca), bream (Abramis brama), salmon (Salmo salar) and Baltic herring (Clupea harengus membras) in River Kymijoki and its estuary polluted by Ky-5 manufacturing. The fish were caught at 14 localities along the river and its estuary. The selected species represent different trophic levels and/or inhabit different environments. The concentrations of PCDD/Fs were low, in most samples below 1 pg g(-1) ITEQ (NATO/CCMS 1988) fresh weight (fw) in muscle, except salmon and Baltic herring. These two species graze at the open sea and consequently accumulate contaminants at a large area in the Baltic Sea. The lipid content in salmon and Baltic herring was an order of magnitude higher than in other species. PCDD/Fs in fish muscle showed only slightly elevated levels in the Kymijoki area and its estuary as compared to the levels in the same species in Finnish freshwaters and sea areas. The concentration of the main impurities of the fungicide Ky-5 was higher in the Kymijoki River downstream the Ky-5 manufacturing place compared to the up-stream locations. The PCDD/F concentrations in fish liver and spawn were 10-100 times higher than the concentration in muscle, because of the much higher lipid concentrations of these organes. Consequently, the tolerable daily intake values could be as much as 100 times smaller (M. Korhonen, M. Verta, T. Vartiainen, Organohalog. Comp. 32 (1997) 305-310; P. Mikkelson, J. Paasivirta, H. Kiviranta, Organohalog. Comp. 39 (1998) 59-62).     

Total and methyl mercury concentrations and fluxes from small boreal forest catchments in Finland

Total mercury (TotHg) and methyl mercury (MeHg) concentrations were studied in runoff from eight small (0.02-1.3 km2) boreal forest catchments (mineral soil and peatland) during 1990-1995. Runoff waters were extremely humic (TOC 7-70 mg l-1). TotHg concentrations varied between 0.84 and 24 ng l-1 and MeHg between 0.03 and 3.8 ng l-1. TotHg fluxes from catchments ranged from 0.92 to 1.8 g km-2 a-1, and MeHg fluxes from 0.03 to 0.33 g km-2 a-1. TotHg concentrations and output fluxes measured in runoff water from small forest catchments in Finland were comparable with those measured in other boreal regions. By contrast, MeHg concentrations were generally higher. Estimates for MeHg output fluxes in this study were comparable at sites with forests and wetlands in Sweden and North America, but clearly higher than those measured at upland or agricultural sites in other studies. Peatland catchments released more MeHg than pure mineral soil or mineral soil catchments with minor area of peatland.     

Mobility and Methylation of Mercury in Forest Soils Development of an In-Situ Stable Isotope Tracer Technique and Initial Results

A method for investigating in-situmethylation and mobility of mercury has beendeveloped and applied to forest soil. The methodis based on additions of stable ¹⁹⁹Hgisotopes to forest soil plots followed bysampling and analysis of isotope ratios of totalmercury and MeHg using ICP-MS. Initial resultsindicate that a fraction (30%) of the mercuryadded to the forest soils is immobilised over atime scale of 16 months. A small but significantfraction of the mercury is methylated during thesame time scale. Higher methylation rates werefound in wetland soil than in dry forest podzolsoil.     

Sedimentation of PCDD/Fs and PCBs in the Gulf of Finland and the Gulf of Bothnia,the Baltic Sea

Sediment trap material was collected during May–December in the period 1996–2008 in three coastal areas and four open sea stations in the Finnish territory of the Baltic Sea. The highest sedimentation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) with a typical source-related congener profile from chlorophenol production dominated by highly chlorinated dibenzofurans was found close to a historical source in the Kymijoki estuary. This was an order of magnitude higher than in other river estuaries and two orders of magnitude higher than in the open sea stations. The sedimentation of polychlorinated biphenyls (PCBs) was also higher in river estuaries than in other areas. No significant decrease over a 12 year period of monitoring was found in concentration or in sedimentation in the Kymijoki estuary. In the western Gulf of Finland, the Archipelago Sea and the Gulf of Bothnia, the dominating congeners, calculated as toxic equivalent (TEQ) in sedimentation were 1, 2, 3, 7, 8-PeCDD and 2, 3, 4, 7, 8-PeCDF, often reported as the main congeners in deposition.     

Polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) in Finnish semi-domesticated reindeer (Rangifer tarandus tarandus L.)

To explore the concentrations and dynamics of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in Finnish semi-domesticated reindeer (Rangifer tarandus tarandus L.) the reindeer milk and tissue samples were collected from the sub-arctic northern Finland. Reindeer milk's PCB sum (1.20 ng g(-1) wet weight) and PCDD/F sum (0.70 pg g(-1) ww) in autumn were higher than in summer (PCBs 0.50 ng g(-1) ww and PCDD/Fs 0.20 pg g(-1) ww). The mean fat content in autumn milk (26%) was significantly higher than in summer (10%). Concentrations in reindeer milk were generally far below 50% of that in adult reindeer body burden. However, the bioaccumulation factors were multiple in milk/reindeer calf ratio and that aroused the question of other important exposure routes than lactation. The muscle and liver of reindeer calves had higher PCDD/F and PCB concentrations than adult animals that possibly indicate the significance of transfer of these compounds from dam to calf through lactation and placenta. However, PBDE concentrations were higher in adult reindeer, especially in liver. In addition, reindeer liver seems to have a special feature to collect highly toxic PCDD/Fs, although the PCB sum concentrations (range from 0.33 to 1.69 ng g(-1) wet weight) were clearly higher than the sums of PCDD/Fs (range from 3.78 to 39.2 pg g(-1) ww). Stillborn reindeer calves represented individuals who had got their PCDD/F, PCB and PBDE load only via the placenta. Concentrations in muscle and brown adipose tissue samples did not indicate dependency on fat content. Obviously effective placental transfer of PCBs and PBDEs from reindeer dam to foetus was seen in this study.