Kwik en chroom in het milieu. Verschijningsvormen, gedrag en toxiciteit Literatuurstudie

Kwik is een metaal dat door zijn toxische eigenschappen al jaren in de aandacht staat van milieumonitoring. Het metaal werd en wordt gebruikt voor vele toepassingen, en door zowel de natuurlijke als menselijke emissie komt het overal in het milieu voor. De voornaamste bronnen van kwikverontreiniging van water en land bestaan uit atmosferische depositie, aanvoer via zwevend stof in waterstromen en door specifieke industriële bronnen. Meer specifiek wordt ingegaan op die parameters die van invloed kunnen zijn in het beheer van het Zwarte Water en waterbodems in het algemee

BIOACCUMULATION OF POLYCHLORINATED BIPHENYL COMPOUNDS AND MERCURY IN A MINING IMPACTED AQUATIC ECOSYSTEM

The Keweenaw area continues to be influenced by the century of copper mining that ended nearly 50 years ago. This project is focused on Torch Lake, an aquatic ecosystem that has been heavily impacted by mining waste disposal. The watershed has been impaired by mine discharge and tailings, smelter and smokestack plumes, and poor waste disposal practices. The lake is listed as a Great Lakes Area of Concern with beneficial use impairments of restrictions on fish consumption and a degraded benthic community. Polychlorinated biphenyl compounds (PCBs) and methylmercury (MeHg) are persistent, bioaccumulative, and toxic substances (PBTs). These contaminants pose threats to human and environmental health primarily via fish consumption. The use impairment of restricted fish consumption is a result of elevated concentrations of PCBs and MeHg in Torch Lake. In this research, kinetic bioaccumulation models were developed using MATLAB to estimate steady state concentrations in each trophic level of the Torch Lake food chain. The model links the contaminated environment to the bioaccumulation in a single organism. The model is most sensitive to the dietary uptake rate constants, and Monte Carlo simulations indicate that the uncertainty (95% confidence interval) is approximately 0.13 ng/g ww for PCBs and 0.02 mg/g ww for MeHg. Model-predicted concentrations agree with the steady-state model, AQUAWEB, and with concentrations measured in walleye (Sander vitreus). The kinetic model coupled with a mass balance model is used to predict the extent of recovery of the ecosystem following remediation actions, such as removal of local contaminant sources to the lake. Removal of contaminated sediments is predicted to reduce the PCB congener concentrations by a factor of 2-14, and elimination of in-lake methylation was predicted to reduce fish Hg concentrations by a factor of 2. Thus, the model suggests that the planned remediation under the Legacy Act will significantly reduce PCB concentrations in fish. The model indicates that adult fish entering Torch Lake from the Keweenaw Waterway could reach the observed PCB contaminant concentrations in fish within 62 days to over 10 years, but other studies have indicated that immigration of fish to Torch Lake is uncommon

Distribuição, bioacumulação e avaliação de risco do mercúrio em diferentes áreas climáticas no Oceano Atlântico Norte

Mercury (Hg) is classified as a priority hazardous substance by the Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR Convention), the European Union Water Framework Directive (EU-WFD) due to the combination of its frequency, toxicity and potential effects on human health and wildlife. In the environment, Hg can be converted into other forms of Hg (e.g. methylmercury – MeHg). MeHg is a potent neurotoxin, which can accumulate in the organism’s tissues due to its high rate of absorption by the gastrointestinal tract and its affinity for thiol groups of proteins. The human exposure to Hg occurs mainly through the consumption of fish. Despite being essential for a healthy balanced diet owing to a high content of protein and fatty acids, fish ingestion can result in the intake of large amounts of Hg since some species have high Hg levels in their tissues. Thus, this study presents as central question the evaluation of the distribution, bioaccumulation and exposure to Hg in different geographic areas located in the North Atlantic (Portuguese northwest coast, Azores archipelago and Mexican southwest coast). In this sense, the following specific objectives were outlined: (i) to determine the presence of Hg in the sediment of coastal areas from different geographic areas; (ii) to evaluate a potential transfer of the Hg present in the sediment to the marine food chain; (iii) to assess the effect of different sea water temperature scenarios on the bioaccumulation and toxicity of the Hg; (iv) to evaluate the [Hg] present in marine species of commercial interest in the different coastal areas (fish and squid) and (v) to understand the contribution of each species to human exposure to Hg. The results revealed that the Hg concentration in the sediments in the different areas reflect the proximity to possible sources of contamination by Hg. The fine fraction is the one with the higher levels of Hg when compared to the fraction of coarser sediments (sand). However, although in some places these Hg levels exceed the values established by international agencies through the criteria for the quality of sediments, the fine fraction represents less than 1% of the total sediment fraction. Therefore, the Hg concentration present in the total sediment fraction was found to be below the limits established by the different agencies. Regarding the transfer of Hg from sediments to the marine trophic chain, the results showed that levels of Hg present in the studied species do not seem to be related to the transfer of Hg present in sediments, but rather to the ingestion of Hg through food. abstract (cont.) This study also concludes that even in a short-term exposure to low Hg concentrations, the increase of water temperature can promote the Hg accumulation in fish. The accumulation was is most evident in the liver. This increase in the Hg concentration in tissues, as well as the increase of water temperature, can induce the production of reactive oxygen species (ROS) by the organisms. However, the antioxidant defenses of the liver seem to act efficiently in combating these ROS, preventing cells damage by oxidative stress. On the other hand, in the muscle, the fight against ROS was not so efficient resulting in damage at the proteins’ level and decreased energy consumption. Regarding the Hg concentration in different fish species with commercial value, it was observed that characteristics such as feeding habits and lifestyle, have an influence on Hg accumulation. Carnivorous fish species are those that have higher concentrations of Hg, which reinforces the notion that Hg can biomagnify along the food chain. Finally, considering the Hg accumulation in the different species of commercial interest and the maximum limit of Hg allowed for human consumption (of 0.5 µg g-1 ), only two fish species (Mora moro and Zeus faber) showed a Hg concentration above this limit. Despite this, consumption of 14 of the studied fish species may lead to a weekly intake of Hg greater than 1.3 µg kg body weight-1 week-1 suggested by JECFA (Joint FAO/WHO Expert Committee on Food Additives). From these 14 species, 9 concern the Azores archipelago and 4 the Northwest Portuguese coast, which are areas with a fish consumption per capita estimated by the FAO three times higher than the southeast coast of Mexico. In fact, data from the Azores archipelago demonstrated that the species that contributed the most to human exposure in this area were those that presented low Hg concentration but were captured in larger quantities. Even though Hg is a widely studied contaminant, the results obtained in the framework of this thesis allowed us to obtain knowledge regarding the presence of Hg in the North Atlantic coastal areas that provide multiple ecosystem services and have until now been poorly studied. It also contributes to the state of the art regarding human exposure to Hg through the consumption of fish and seafood in risk analysis, since Hg concentration usually receives greater importance regardless of the fish consumption per capita.Devido à da sua frequência, toxicidade e potenciais efeitos para a saúde humana e da vida selvagem, o mercúrio (Hg) está classificado como uma substância perigosa prioritária pela Convenção para a Proteção do Meio Ambiente Marinho do Atlântico Nordeste (Convenção OSPAR) e pela DiretivaQuadro da Água da União Europeia (UE-WFD). Uma vez presente no meio ambiente, o Hg pode ser convertido em diferentes formas de Hg (por exemplo, metilmercúrio – MeHg). O MeHg é uma potente neurotoxina que devido à sua alta taxa de absorção pelo trato gastrointestinal e afinidade pelos grupos tiol das proteínas, tem a capacidade de acumular nos organismos. Nos humanos, a exposição ao Hg ocorre principalmente através do consumo de peixe. Apesar ser indispensável para uma dieta equilibrada e saudável, devido ao elevado teor em proteína e ácidos gordos, os peixes podem apresentar elevados níveis de Hg nos seus tecidos. Assim, este estudo teve como questões centrais avaliar a distribuição, bioacumulação e exposição ao Hg em diferentes áreas geográficas localizadas no Atlântico Norte (costa noroeste Portuguesa, arquipélago dos Açores e costa sudeste Mexicana), tendo sido delineados os seguintes objetivos específicos de modo a avaliar: (i) a presença de Hg no sedimento em zonas costeiras das diferentes áreas geográficas, (ii) uma possível transferência do Hg presente no sedimento para a cadeia trófica marinha, (iii) o efeito da temperatura da água do mar dos diferentes locais na bioacumulação e toxicidade do Hg, (iv) a concentração de Hg presente em espécies marinhas de interesse comercial nas diferentes áreas costeiras (peixe e lula) e (v) a contribuição de cada espécie para a exposição humana ao Hg. Os resultados revelaram que as concentrações de Hg presente nos sedimentos das diferentes áreas refletem a proximidade a possíveis focos de contaminação por Hg. A fracção fina é aquela que apresenta maiores níveis de Hg em comparação à fracção de sedimentos mais grosseiros (areia). Contudo, apesar de em alguns locais estes níveis de Hg ultrapassarem os valores estabelecidos pelas agências internacionais através dos critérios para a qualidade dos sedimentos, a fracção fina representa menos de 1% da fracção total do sedimento, o que faz com que a concentração de Hg presente na fracção total do sedimento se situe abaixo dos limites estabelecidos pelas diversas agências. Relativamente à transferência do Hg para a cadeia trófica marinha, os resultados demostraram que os níveis de Hg presente nas espécies estudadas não parecem estar relacionados com a transferência do Hg presente nos sedimentos, mas sim com ingestão de Hg através da alimentação. resumo (cont.) Este estudo também conclui que mesmo numa exposição de curta duração a baixas concentrações de Hg, o aumento da temperatura da água pode promover a acumulação de Hg em peixes, sendo que é no fígado que essa acumulação é mais evidente. Este aumento da concentração de Hg nos tecidos, assim como o aumento da temperatura da água, podem induzir a produção de espécies reactivas de oxigénio (ROS) por parte do organismo. Contudo, as defesas antioxidantes do fígado parecem actuar de forma eficiente no combate a esses ROS, evitando danos nas células por stress oxidativo. Por outro lado, no músculo, o combate contra os ROS não foi tão eficiente resultando em danos ao nível das proteínas e diminuição do consumo de energia. No que diz respeito à concentração de Hg nas diferentes espécies de peixe com valor comercial, observou-se que características como hábitos alimentares e estilo de vida influenciam a acumulação de Hg, sendo que as espécies de peixes carnívoras são aquelas que apresentam maiores concentrações de Hg, reforçando a ideia de que o Hg tem a capacidade de biomagnificar ao longo da cadeia trófica. Finalmente, considerando a acumulação de Hg das diferentes espécies com interesse comercial e o limite máximo de 0,5 µg g-1 de Hg permitido para consumo humano, apenas duas espécies de peixes (Mora moro e Zeus faber) apresentaram uma concentração de Hg acima deste limite. Apesar disso, o consumo de 14 das espécies de peixes estudadas podem levar a uma ingestão semanal de Hg maior do que 1,3 µg kg de peso corporal-1 semana-1 sugerido pelo JECFA (Comité Conjunto de Especialistas FAO/OMS sobre Aditivos Alimentares). Destas 14 espécies, 9 dizem respeito ao arquipélago dos Açores e 4 à costa noroeste de Portugal, áreas que segundo a FAO, tem um consumo de peixe per capita três vezes superior ao da costa sudeste do México. De facto, dados relativos ao arquipélago dos Açores demonstraram que as espécies que mais contribuem para a exposição humana ao Hg nesta área são as que apresentam baixo [Hg] mas que são capturadas em maiores quantidades. Embora o Hg seja um contaminante amplamente estudado, os resultados obtidos no âmbito desta tese permitiram obter conhecimento sobre a presença de Hg em áreas costeiras do Atlântico Norte, que além de fornecerem múltiplos serviços de ecossistema são áreas até agora pouco estudadas. Ao mesmo tempo contribuem com mais informações sobre a exposição humana ao Hg por meio do consumo de peixes e derivados na análise de risco, uma vez que a concentração de Hg costuma receber maior importância independente do consumo per capita.Programa Doutoral em Biologia e Ecologia das Alterações Globai

Environmental risk assessment of inorganic chemicals in mining environment.

Mining is one of the human‟s earliest industrial activities. Indeed early civilizations such as the Bronze Age and Iron Age are named according to their use of metals; the importance of metals is still central to industrialization and urbanization. The enormous quantities of mine waste and tailings generated by mining every year however, are also of concern. The relocation and removal of large quantities of mineral and waste can also release chemicals into the environment especially surface water, groundwater and soil during the mining lifecycle if good mining engineering and mitigation are not performed. To optimise this risk management based on excellent risk analysis is required. The study analysed the mining life cycle, chemicals in the mining environment, current regulations on chemicals in the environment and the development of environmental risk assessment framework with particular focus on the inorganic substances. Chemicals in the mining environment were then grouped into a) the minor constituents of the ore deposits; b) chemicals used in mining such as explosives, leaching chemicals and froth flotation reagents. c) chemicals generated by mining, milling and smelting including Acid mine drainage (AMD) and emissions from smelting and refining. The natural and anthropogenic sources, potential pathways to environmental and human receptors and the implications on human health of key toxic metals and metalloids in the mining context were then evaluated. A new two-tier risk assessment was developed based on the four-step conventional risk assessment framework by the U.S.National Research Council (NRC). Tier 1 involved analysing and evaluating existing data using two new semi-quantitative risk screening and prioritisation procedures, namely Chemicals of Greatest Concern (CGC) and Media of Greatest Concern (MGC). CGC was developed using specific hazardous properties of the inorganic chemicals and their eco-toxicities in the environment. MGC was a system of decomposition using a combination of various decision-making tools such as Multi-criteria decision making (MCDM) and Hierarchical holographic modelling (HHM) to facilitate hazard identification and assessment. Tier 2 involved quantitative toxicity assessment, exposure assessment and risk characterisation which were used to quantify the total risk to human health using Monte Carlo simulations (MCS). The tiered risk-based approach developed was evaluated using three cases studies, viz, the Rustenburg platinum (Pt) mine, South Africa; the Lisheen lead (Pb) – zinc (Zn) mine, Ireland and the Richmond copper (Cu) smelter. The results from them were evaluated and compared as a basis for Anglo American plc‟s global strategic decision making. Finally, the strengths and weakness of the methodology developed were evaluated in relation to the application at current operational level. Future methodology refinement and incorporation of organic chemicals were also discussed