In this study, the combined effects of pH, water hardness, and dissolved organic carbon (DOC) concentration and type on the chronic (72-h) effect of copper on growth inhibition of the green alga Pseudokirchneriella subcapitata were investigated. Natural dissolved organic matter (DOM) was collected at three sites in Belgium and The Netherlands using reverse osmosis. A full central composite test design was used for one DOM and a subset of the full design for the two other DOMs. For a total number of 35 toxicity tests performed, 72-h effect concentration resulting in 10% growth inhibition (EbC10s) ranged from 14.2 to 175.9 micrograms Cu/L (factor 12) and 72-h EbC50s from 26.9 to 506.8 micrograms Cu/L (factor 20). Statistical analysis demonstrated that DOC concentration, DOM type, and pH had a significant effect on copper toxicity; hardness did not affect toxicity at the levels tested. In general, an increase in pH resulted in increased toxicity, whereas an increase of the DOC concentration resulted in decreased copper toxicity. When expressed as dissolved copper, significant differences of toxicity reduction capacity were noted across the three DOM types tested (up to factor 2.5). When expressed as Cu2+ activity, effect levels were only significantly affected by pH; linear relationships were observed between pH and the logarithm of the effect concentrations expressed as free copper ion activity, that is, log(EbC50Cu2+) and log(EbC10Cu2+): (1) log(EbC50Cu2+)= - 1.431 pH + 2.050 (r2 = 0.95), and (2) log(EbC10cu2+) = -1.140 pH -0.812 (r2 = 0.91). A copper toxicity model was developed by linking these equations to the WHAM V geochemical speciation model. This model predicted 97% of the EbC50dissolved and EbC10dissolved values within a factor of two of the observed values. Further validation using toxicity test results that were obtained previously with copper-spiked European surface waters demonstrated that for 81% of tested waters, effect concentrations were predicted within a factor of two of the observed. The developed model is considered to be an important step forward in accounting for copper bioavailability in natural systems.

The protective effect of dissolved organic matter (DOM) on metal toxicity to aquatic organisms has been reported by numerous authors. Bioavailability models such as the biotic ligand model (BLM) thus account for this factor to predict metal toxicity to aquatic organisms. Until now, however, few attempts have been made to assess the effect of the DOM source on metal speciation and toxicity and, accordingly, on BLM predictions. The aims of this study were to investigate to what extent DOMs differ in their ability to decrease acute copper toxicity to the cladoceran Daphnia magna and to evaluate if ultraviolet (UV) absorbance measurements may be a simple and effective method to incorporate DOM variability into the acute Cu-BLM for D. magna. Acute toxicity tests were carried out in artificial test water enriched with DOMs isolated from six locations in Europe and North America and in seven natural European surface waters. The acute Cu-BLM for D. magna was then used to estimate the copper complexing capacity of each DOM (expressed as % active fulvic acid, %AFA). A factor of 6 difference was observed between the lowest and the highest copper complexing capacity. A significant linear relationship was observed between the UV-absorbance coefficient at 350 nm (epsilon350) and the %AFA. Linking this relationship to the acute Cu-BLM resulted in a significant improvement of the predictive capacity of this BLM. Without accounting for this relationship, 90% of the predicted 48-h 50% effective concentrations (EC50) were within a factor of 2 of the observed EC50s; taking this relationship into account, 90% of the EC50s were predicted with an error of less than factor 1.3. The present study and other studies seem to indicate that UV absorbance may be a good measure of biologically and toxicologically relevant differences in copper binding behavior of DOM.

comum e tem sido alvo de diversas pesquisas com o objetivo de determinar o impacto ambiental desse tipode contaminação. Sabe-se hoje que somente a concentração total de metais nos sedimentos não é um bomparâmetro para a avaliação da toxicidade de metais em sedimentos. Além de ensaios de eco toxicidade érecomendável a realização de ensaio de caracterização geoquímica da concentração de sulfetos voláteispor acidificação e de metais simultaneamente extraídos (AVS/SEM) que é utilizada para a determinação dafração potencialmente biodisponível de metais em sedimento. Sete amostras em duplicada foram coletadasnas margens do rio São Francisco próximo a uma planta metalúrgica de zinco no município de Três MariasMG. Os ensaios de caracterização geoquímica do tipo AVS/SEM dessas amostras sugerem que apesarda concentração de metais totais (Zn, Cd, Pb, Cu e Ni) estarem acima do Nível 1 da norma ambiental dequalidade de sedimentos, o potencial de biodisponibilidade de metais nessas amostras é relativamente baixopara seis dentre sete amostras.Palavras chaves: metais; contaminação; biodisponibilidade; sedimentos. ABSTRACT: In countries with intense industrial activities, sediment contamination by metals is relatively common and ithas being the target of several researches with the goal of investigating the environmental impact assessmentof this type of contamination. It is well known that using only the bulk metal concentration in sediment is notsufficient for estimating the metal toxicity in this media. Besides ecotoxicological tests it is recommended thedetermination acid volatile sulfides and simultaneously extracted metals (AVS/SEM) for the estimation ofthe fraction of potential bioavailability of metal in the sediment. Seven samples in duplicate were collectedfrom the edges of the São Francisco River near a zinc metallurgical plant in the town of Três Marias MG. Thesediment AVS/SEM geochemical characterization test results of these samples suggest that although the metalbulk concentrations (Zn, Cd, Pb, Cu e Ni) from these samples are above the Level 1 of the environmentalregulation for sediment quality, six out of seven samples presented low potential for metal bioavailability.Keywords: metals; contamination; bioavailability; sediments.

Hydrogeological and geochemical studies were conducted on historic tailings located along the Cardoso Creek near the municipality of Nova Lima, in the state of Minas Gerais, Brazil. These tailings, which contain elevated arsenic levels, date from the first half of the twentieth century and are currently owned by AngloGold Ashanti Ltd. The investigations had three principal components: a) environmental, hydrogeological and geochemical assessment, including monitoring wells installation, field and laboratory tests and dynamic modeling; b) preliminary risk analysis; and c) development of conceptual remediation solutions and management practices to prevent adverse impacts to human health and the environment.