No description available.

Black Creek is a small watershed located in Wise County, Virginia, west of the town of Norton. At the time of this survey, the watershed encompassed approximately 929 hectares of mine and forest lands with a small recreational area. Black Creek proper is a third-order stream approximately 6.7 km in length from its headwaters to its confluence with the Powell River in Kent Junction. Black Creek and several of the tributaries within the watershed were previously identified as areas impacted by acid mine drainage. The watershed was used in a study to identify sources of acid mine drainage and the best methods for its evaluation. The acid mine drainage sources were first identified using visual inspection and field chemistry. Additional stream segments were then included in the assessment process using metal (aluminum, copper, iron, magnesium, manganese, and zinc) analyses of both overlying water column and sediments. Using an upstream reach of Black Creek as a reference, short-term toxicity testing was employed, as well as a long-term purge study. The pH at sampling locations ranged from 2.75 to 7.87 SU, and conductivity ranged from 196 μmhos/cm to 2040 μmhos/cm. All metals were elevated when compared to the reference. Water column samples collected from locations with low pH were acutely toxic to Daphnia magna and Pimephales promelas. Mortality was high in the elutriant test at locations where pH was low, conductivity was elevated, metals were high, or a combination of these. In the initial sediment tests, all sampling locations were significantly different than the reference for survival of Chironomus tentans and reproduction of D. magna. One location was significantly different than the reference for survival of D. magna. In the sediment tests completed after two months, survival of C. tentans was only different from the control in three locations but was significantly different for growth at all locations. Reproduction by D. magna was again significantly less than the reference at all locations. At eight months, only two locations were significant for survival of C. tentans and after 15 months, no significant differences occurred between any stations. The study indicates that stream segments that are severely impaired by acid mine drainage are easy to identify using visual inspection and field water chemistry. Those that are moderately impaired require more investigation and may not be responsive to short-term toxicity tests. Benthic macroinvertebrates, leaf packs, and periphyton were evaluated in the field. Benthic macroinvertebrate communities and leaf-pack breakdown were evaluated at nine locations, while periphyton was evaluated at the mouth of Black Creek, as well as five sites in the Powell River receiving system. While leaf-pack information and benthic macroinvertebrate samples yielded similar information, benthic sampling was much simpler and less time consuming. Additionally, benthic macroinvertebrate sampling, particularly over several sampling events, was more sensitive at the most severely impacted AMD stations. The stations were broken down into five different categories in order to better determine which evaluation techniques were most sensitive and cost-effective. The five categories were Non-Impaired, Slightly Impaired, Moderately Impaired, Severely Impaired, and Severely pH impaired. Once the locations were categorized, each method used to evaluate toxicity was examined to determine which methods best identified acid mine drainage impairment in the Black Creek watershed. The methods utilized include the following: basic water chemistry; metals analysis of sediments and water column; acute toxicity testing using both D. magna and P. promelas; short-term elutriant and sediment tests; chronic sediment test using C. tentans and D. magna; a purge study; benthic macroinvertebrate sampling; leaf-pack and algal-tile studies. After evaluating these methods, it was determined that using basic water chemistry and benthic macroinvertebrate sampling were the best methods for evaluating acid mine drainage impairment in this watershed. The reference station was identified as Non-Impaired. Two stations located in the lower portions of Black Creek (L11 and L1) were also Non-Impaired or only Slightly Impaired with the benthic macroinvertebrate results indicating little impairment. Stations U2, U6, U7, and BBM were also found to be Slightly Impaired. The station on the margin of the wetland, U5, was Moderately Impaired. Two previously identified areas of impairment, U9 and U10, (Cherry et al. 1995) were identified as Severely pH Impaired and Severely Impaired, respectively. / Master of Science

On August 29, 2005 Hurricane Katrina struck the Gulf Coast and storm surges breached levees flooding much of New Orleans, Louisiana. One month after the storm, sediment was collected and toxicity was tested using Japanese medaka (Oryzias latipes) embryos. Sediments with the highest contaminant levels showed the highest embryonic mortality and most delayed development. However, no sediment caused an increased mutant frequency. When the most contaminated site was resampled in February, 2006 contaminant levels and toxicity decreased. During toxicity testing, approximately 20% of embryos incubated with sediment from one of these sites died and turned red. A red bacterium was isolated that is Gram-negative, cocco-baccilus, non-motile, and most similar to Hahella chejuensis based on genetic and metabolic tests. This bacterium caused 100% infection at 108 bacterial cells per ml and variable infection at lower doses. This study was the first to examine biological effects of exposure to post-Hurricane Katrina sediments.

As cidades e as atividades industriais e agrícolas geram uma infinidade de substâncias, muitas vezes desconhecidas, que quando lançadas nos corpos de água receptores podem por em risco a biota local e até mesmo a saúde humana. O presente trabalho avaliou o estado de degradação ambiental nas bacias dos rios Piracicaba, Mogi Guaçu (ambas no estado de São Paulo) e Tibagi (estado do Paraná), tendo como ferramentas os testes de toxicidade de sedimentos com peixes, em laboratório e in situ, análises histopatológicas dos animais expostos e análises físicas e químicas da água e do sedimento. Foram realizadas, ainda, análises das alterações histológicas em peixes expostos ao efluente final de indústria de papel e celulose, atividade presente nas três bacias estudadas. Os organismos-teste selecionados foram a espécie nativa de peixe Serrapinnus notomelas (Characiformes, Characidae) e a espécie padronizada, exótica, Danio rerio (Cypriniformes, Cyprinidae). As preparações histológicas foram realizadas com os peixes inteiros, possibilitando a análise dos órgãos-alvo brânquias, rim e fígado, em um mesmo corte. Nenhum organismo morreu após 96 horas de exposição às amostras de sedimento. No entanto, as análises histológicas revelaram alterações importantes, as quais foram sistematizadas para o cálculo do Índice de Alterações Histológicas (IAH) e do Valor Médio de Alterações (VMA), por órgão e por espécie, para cada localidade estudada. Os sedimentos provenientes das localidades de Sumaré (rio Atibaia) e de Piracicaba (rio Piracicaba) foram os mais tóxicos a ambas as espécies, de acordo com os índices calculados, seguidos pelos sedimentos de Campinas (rio Atibaia), Limeira (rio Jaguari) e Americana (rio Piracicaba). Os sedimentos da bacia do rio Mogi Guaçu foram menos tóxicos, mas aqueles provenientes das localidades Mogi Guaçu e Luiz Antônio (ambos a jusante de indústrias de papel e celulose) provocaram alterações renais e hepáticas significativas em D. rerio. Apesar de terem sido observadas alterações importantes nos peixes de ambas as espécies, expostas aos sedimentos da bacia do rio Tibagi, estas não foram tão intensas e freqüentes como aquelas observadas nos peixes expostos aos sedimentos das localidades das outras bacias hidrográficas. As análises físicas e químicas comprovaram a crítica situação de degradação do ambiente aquático na bacia do rio Piracicaba e alertam para os cuidados que deverão ser tomados com relação a esta e às bacias dos rios Mogi-Guaçu e Tibagi, cujos recursos estão sendo cada dia mais explorados. As graves alterações observadas nas brânquias, rim e fígado dos peixes expostos ao efluente de indústria de papel e celulose indicaram que o monitoramento da toxicidade desse tipo de efluente deve ser realizado por ferramentas mais sensíveis, tais como as análises histopatológicas em peixes. / Urban and industrial activities generate a large number of substances, frequently unknown, that if discharged into water body receptors can put at risk the whole aquatic biota, as well as human health. The present work evaluated the state of environmental degradation in the basins of rivers Piracicaba, Mogi Guaçu (both in São Paulo state) and Tibagi (Paraná state), using as tools the toxicity tests with sediments and fishes as test-organisms, for both laboratory and in situ evaluations, together with histopathological analyses of exposed animals and chemical and physical analysis of sediments and water. Also, histological alterations in fishes exposed to the final pulp-mill effluent were analyzed. The species selected as test-organisms were the native species of fish Serrapinnus notomelas (Characiformes, Characidae) and the standard exotic species Danio rerio (Cypriniformes, Cyprinidae). Hystological preparations were performed with whole fish specimens, what allowed the analysis of the target-organs: gills, kidney and liver in the same section. No fish mortality was found after 96 hours exposition to the sediment samples. Nevertheless histological analyses revealed important alterations, which were used to calculate the histological alteration index (IAH) and the mean value of alterations (VMA), for each organ and species, in each locality evaluated. Sediments coming from Sumaré (Atibaia river) and Piracicaba (Piracicaba river) were the most toxic to both species, according to the calculated index, followed by the sediments from Campinas (Atibaia river), Limeira (Jaguari river) and Americana (Piracicaba river). The sediments of Mogi Guaçu riber basin had a lower toxicity, but those coming from Mogi Guaçu and Luiz Antônio (both localities placed downstream pulp-mill plants) have caused significant alterations in kidney and liver of D. rerio. Although important alterations were found for both species of fish exposed to the sediments from Tibagi river basin, these were not as intense and frequent as those observed in the fishes exposed to the sediment from the other localities studied. Physical and chemical analysis corroborated the critical degree of environmental degradation of Piracicaba river basin and must be considered as an early warning for the measures that must be taken in relation to this and also to Mogi-Guaçu and Tibagi basins, where resources are increasingly being overexploited. The severe damage found in gills, kidney and liver of fishes exposed to the pulp-mill effluent suggest that monitoring this type of effluent must include a high sensibility tool, as the histopatological analysis on fish.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2007. / Härtill 4 uppsatser.

As cidades e as atividades industriais e agrícolas geram uma infinidade de substâncias, muitas vezes desconhecidas, que quando lançadas nos corpos de água receptores podem por em risco a biota local e até mesmo a saúde humana. O presente trabalho avaliou o estado de degradação ambiental nas bacias dos rios Piracicaba, Mogi Guaçu (ambas no estado de São Paulo) e Tibagi (estado do Paraná), tendo como ferramentas os testes de toxicidade de sedimentos com peixes, em laboratório e in situ, análises histopatológicas dos animais expostos e análises físicas e químicas da água e do sedimento. Foram realizadas, ainda, análises das alterações histológicas em peixes expostos ao efluente final de indústria de papel e celulose, atividade presente nas três bacias estudadas. Os organismos-teste selecionados foram a espécie nativa de peixe Serrapinnus notomelas (Characiformes, Characidae) e a espécie padronizada, exótica, Danio rerio (Cypriniformes, Cyprinidae). As preparações histológicas foram realizadas com os peixes inteiros, possibilitando a análise dos órgãos-alvo brânquias, rim e fígado, em um mesmo corte. Nenhum organismo morreu após 96 horas de exposição às amostras de sedimento. No entanto, as análises histológicas revelaram alterações importantes, as quais foram sistematizadas para o cálculo do Índice de Alterações Histológicas (IAH) e do Valor Médio de Alterações (VMA), por órgão e por espécie, para cada localidade estudada. Os sedimentos provenientes das localidades de Sumaré (rio Atibaia) e de Piracicaba (rio Piracicaba) foram os mais tóxicos a ambas as espécies, de acordo com os índices calculados, seguidos pelos sedimentos de Campinas (rio Atibaia), Limeira (rio Jaguari) e Americana (rio Piracicaba). Os sedimentos da bacia do rio Mogi Guaçu foram menos tóxicos, mas aqueles provenientes das localidades Mogi Guaçu e Luiz Antônio (ambos a jusante de indústrias de papel e celulose) provocaram alterações renais e hepáticas significativas em D. rerio. Apesar de terem sido observadas alterações importantes nos peixes de ambas as espécies, expostas aos sedimentos da bacia do rio Tibagi, estas não foram tão intensas e freqüentes como aquelas observadas nos peixes expostos aos sedimentos das localidades das outras bacias hidrográficas. As análises físicas e químicas comprovaram a crítica situação de degradação do ambiente aquático na bacia do rio Piracicaba e alertam para os cuidados que deverão ser tomados com relação a esta e às bacias dos rios Mogi-Guaçu e Tibagi, cujos recursos estão sendo cada dia mais explorados. As graves alterações observadas nas brânquias, rim e fígado dos peixes expostos ao efluente de indústria de papel e celulose indicaram que o monitoramento da toxicidade desse tipo de efluente deve ser realizado por ferramentas mais sensíveis, tais como as análises histopatológicas em peixes. / Urban and industrial activities generate a large number of substances, frequently unknown, that if discharged into water body receptors can put at risk the whole aquatic biota, as well as human health. The present work evaluated the state of environmental degradation in the basins of rivers Piracicaba, Mogi Guaçu (both in São Paulo state) and Tibagi (Paraná state), using as tools the toxicity tests with sediments and fishes as test-organisms, for both laboratory and in situ evaluations, together with histopathological analyses of exposed animals and chemical and physical analysis of sediments and water. Also, histological alterations in fishes exposed to the final pulp-mill effluent were analyzed. The species selected as test-organisms were the native species of fish Serrapinnus notomelas (Characiformes, Characidae) and the standard exotic species Danio rerio (Cypriniformes, Cyprinidae). Hystological preparations were performed with whole fish specimens, what allowed the analysis of the target-organs: gills, kidney and liver in the same section. No fish mortality was found after 96 hours exposition to the sediment samples. Nevertheless histological analyses revealed important alterations, which were used to calculate the histological alteration index (IAH) and the mean value of alterations (VMA), for each organ and species, in each locality evaluated. Sediments coming from Sumaré (Atibaia river) and Piracicaba (Piracicaba river) were the most toxic to both species, according to the calculated index, followed by the sediments from Campinas (Atibaia river), Limeira (Jaguari river) and Americana (Piracicaba river). The sediments of Mogi Guaçu riber basin had a lower toxicity, but those coming from Mogi Guaçu and Luiz Antônio (both localities placed downstream pulp-mill plants) have caused significant alterations in kidney and liver of D. rerio. Although important alterations were found for both species of fish exposed to the sediments from Tibagi river basin, these were not as intense and frequent as those observed in the fishes exposed to the sediment from the other localities studied. Physical and chemical analysis corroborated the critical degree of environmental degradation of Piracicaba river basin and must be considered as an early warning for the measures that must be taken in relation to this and also to Mogi-Guaçu and Tibagi basins, where resources are increasingly being overexploited. The severe damage found in gills, kidney and liver of fishes exposed to the pulp-mill effluent suggest that monitoring this type of effluent must include a high sensibility tool, as the histopatological analysis on fish.

Several sediment characteristics were analyzed to determine their suitability for use as potential normalization factors for the bioavailability of neutral organic compounds sorbed to sediments. Percent organic carbon, cation exchange capacity and particle surface area were measured sediment characteristics that varied sufficiently to encompass the range in observed sediment toxicity. Laboratory sediment toxicity test data using fluoranthene suggest that there is no biologically significant correlation between sediment toxicity and sediment characteristics (organic carbon, cation exchange capacity, particle size distribution, particle surface area). Fluoranthene amended sediments with similar organic carbon contents do not yield similar toxicities due to sorbed fluoranthene and thus do not support the organic carbon normalization approach for evaluating sediment quality or for sediment criteria development.

Concern over sediment toxicity has increased the need for toxicity test information with organisms that inhabit sediments. Oligochaetes are exposed to toxicants through feeding and direct body contact with aquatic sediments. Chronic testing with oligochaetes has historically focused on tubificids with test lengths of one year or more to encompass several generations. Most naidid oligochaetes have generation times of three to seven days and could provide chronic information in a matter of weeks. The cosmopolitan distributed naidid, Pristina leidyi, was evaluated for use as a toxicity test organism. Results of research conducted includes culture methods, effects of temperature on reproduction, growth rates in a reference sediment, acute toxicity tests, and chronic toxicity tests.

Existing ecotoxicity data for chemicals vary to a high extent between the environmental compartments water and sediment, since the evaluation of contaminants has historically focused on water exposition. Many anthropogenic chemicals and waste materials, including toxic organic and inorganic chemicals, adsorb to particulate matter and accumulate in sediments, and may thus be a threat to organisms living in the sediment. The invertebrates Chironomus riparius and Lumbriculus variegatus were selected as representatives of endobenthic living organisms. Acute toxicity tests, via water-only exposure, and sediment toxicity tests were conducted with the two endobenthic invertebrates. In sediment toxicity tests, organisms are mainly exposed to sediment- and particle-bound chemicals and dissolved chemical in the pore water. Toxicity data for algae, daphnids, and fish (via water-only exposure) are available for many substances, whereas the existing sediment toxicity data are rather rare. Thus, the interest arises to predict sediment toxicity for sediment-dwelling invertebrates from existing acute toxicity data of tests with water-only exposure. The main emphasis of this work was placed on one metal compound and seven organic chemicals. The objective of this study was fivefold: (1) develop methods and improve existing procedures on acute and sediment toxicity testing of the two invertebrates; (2) conduct both acute toxicity tests via water exposure and long-term sediment toxicity tests for the selected model substances to generate data for comparative discussion; (3) assess correlations among acute toxicity data of the organisms exposed via water-only and correlations among sediment toxicity data of the two endobenthic invertebrates for the eight tested chemicals; (4) assess possible forecasting for sediment toxicity from acute toxicity (via water-only exposure) and (5) assess exposure effects to determine the main exposure route. Acute toxicity data of the eight tested chemicals of D. magna significantly correlated with data of L. variegatus and C. riparius (p<0.05). However, a prediction of toxicity based on D. magna data bears high uncertainty, due to the small data set and high variation in sensitivity of the organisms. Existing sediment toxicity test methods were improved to meet the demand for artificial sediments containing organic matter that serves sufficiently as internal food source for the test organisms, and thus representing natural exposure conditions. However, the sediments that were used for the two organisms to test the selected model substances differed in sediment composition. Therefore, a sediment with the same sediment composition and the same water-to-sediment ratio for both invertebrates was developed, to have similar exposure conditions. In sediment toxicity tests, C. riparius was observed to be more sensitive than L. variegatus and no correlation was observed among data of the invertebrates. For the selected substances, lowest effect concentrations were observed for 3,4-dichloroaniline, whereas effect concentrations were the highest for benzo[a]pyrene. No correlations were found between the acute toxicity data of exposure via the water phase and sediment toxicity data, thus making a prediction of sediment toxicity data impossible. From analytical measurements of chemicals concentration in the compartments overlying, pore water, and bulk sediment, partition coefficients on sediment water partitioning were calculated. The highest partition coefficient ratios for sediment water partitioning were found for the high lipophilic organic substances 4,4-dichlorodiphenyltrichloroethan (DDT) and benzo[a]pyrene. Further, it was found that the main exposure routes in the 28-day sediment toxicity tests were not only chemical but species-dependent. As a result of very differing exposure routes for the tested chemicals and the absence of correlations from the acute to sediment toxicity data, sediment toxicity tests are necessary to assess the toxicity of chemicals on sediment inhabiting organisms. / In den meisten standardisierten ökotoxikologischen Untersuchungen zur Abschätzung des Gefährdungspotentials von Chemikalien für Gewässer erfolgt die Exposition der Organismen über die Wasserphase. Viele Schadstoffe, die in die aquatische Umwelt gelangen, adsorbieren aufgrund ihrer physikalisch-chemischen Eigenschaften an die Oberflächen von Schwebstoffen, sedimentieren und erreichen Sedimentkonzentrationen, die möglicherweise eine Gefahr für sedimentbewohnende Organismen darstellen. Im Rahmen dieser Arbeit wurden für benthische Invertebraten Testverfahren etabliert, bei denen eine Exposition der Organismen über das Sediment, hier hauptsächlich über die an ingestierte Sedimentbestandteile gebundene oder über die im Porenwasser gelöste Chemikalie (28-Tage Sedimenttoxizitätstest), und über dieWasserphase (Akuttoxizitätstest) erfolgte. Die Invertebraten Chironomus riparius und Lumbriculus variegatus wurden als typische Vertreter endobenthischer Organismen ausgewählt. Für viele Chemikalien liegen Daten zur akuten Toxizität für Algen, Daphnien und Fische für die Wasserexposition vor. Demgegenüber sind nur wenige Daten zur Toxizität für benthische Organismen weder mit einer Wasser- noch mit einer Sedimentexposition vorhanden. Als Modellsubstanzen wurden eine anorganische und sieben organische Substanzen für die Untersuchungen ausgewählt. Ziele dieser Arbeit waren: (1) die Entwicklung und Verbesserung von bestehenden Methoden zur Bestimmung der akuten Toxizität mitWasserexposition und der Sedimenttoxizität für die beiden Invertebraten; (2) die Durchführung der Tests mit den acht ausgewählten Modellsubstanzen zur vergleichenden Betrachtung; (3) die Beurteilung einer Korrelation der Daten zur Akuttoxizität innerhalb der verschiedenen Organismen mit Wasserexposition und einer Korrelation der Daten zwischen den beiden benthischen Organismen bei Sedimentexposition; (4) die Beurteilung einer Korrelation zwischen Daten der benthischen Invertebraten zur Akuttoxizität mit Wasserexposition und Sedimenttoxizität und (5) die Ermittlung und Bewertung der Expositionspfade. Die Akuttoxizitätsdaten von D. magna korrelieren significant (p<0.05) mit den Daten der beiden Invertebraten. Jedoch ist eine Vorhersage aufgrund des kleinen Datensatzes und der großen Unterschiede in der Empfindlichkeit der Arten abzulehnen. Um einer möglichst natürlichen Expositionssituation in Sedimenten zu entsprechen, wurden künstliche Sedimente mit interner Futterquelle, die auch mit der zu testenden Chemikalie kontaminiert wurde, entwickelt und für die Tests mit den Modellsubstanzen verwendet. Ein Nachteil war die unterschiedliche Sedimentzusammensetzung für die beiden Organismen. Um gleiche Expositionsbedingungen für beide Testorganismen zu gewährleisten, wurde ein artifizielles Sediment mit gleicher Zusammensetzung und gleichem Volumenverhältnis zwischen Sediment und Überstandswasser entwickelt. In den Sedimenttoxizitätstests reagierte C. riparius empfindlicher als L. variegatus. Die Effektkonzentrationen waren am niedrigsten für 3,4-Dichloraniline und am höchsten für Benzo[a]pyren. Die Korrelationen zwischen den Ergebnissen aus Akut- und Sedimenttoxizitstests waren nicht signifikant (p>0.05). Folglich läßt sich die Sedimenttoxizität nicht aus Daten zur akuten Toxizität mit Wasserexposition abschätzen. Aus den analytischen Messungen von Sediment-, Porenwasser- und Überstandswasserproben wurden die Koeffizienten für die Verteilung zwischen Sediment und Wasser berechnet. Für die stark lipophilen Stoffe, 4-Dichlorodiphenyltrichloroethan (DDT) und Benzo[a]pyren wurden die höchsten Koeffizienten errechnet. Weiterhin wurde festgestellt, daß die Hauptexpositionspfade in Sedimenttoxizitätstests einerseits von der Chemikalie und andererseits von der verwendeten Spezies abhängen. Aufgrund der Ergebnisse dieser Arbeit und der Tatsache, daß Sedimente “Senken” für viele Schadstoffe sind, müssen zur Erfassung und Bewertung des Gefährdungspotentials von Chemikalien gegenüber Sedimentbewohnern weiterhin Sedimenttoxizitätstests durchgeführt werden.

Existing ecotoxicity data for chemicals vary to a high extent between the environmental compartments water and sediment, since the evaluation of contaminants has historically focused on water exposition. Many anthropogenic chemicals and waste materials, including toxic organic and inorganic chemicals, adsorb to particulate matter and accumulate in sediments, and may thus be a threat to organisms living in the sediment. The invertebrates Chironomus riparius and Lumbriculus variegatus were selected as representatives of endobenthic living organisms. Acute toxicity tests, via water-only exposure, and sediment toxicity tests were conducted with the two endobenthic invertebrates. In sediment toxicity tests, organisms are mainly exposed to sediment- and particle-bound chemicals and dissolved chemical in the pore water. Toxicity data for algae, daphnids, and fish (via water-only exposure) are available for many substances, whereas the existing sediment toxicity data are rather rare. Thus, the interest arises to predict sediment toxicity for sediment-dwelling invertebrates from existing acute toxicity data of tests with water-only exposure. The main emphasis of this work was placed on one metal compound and seven organic chemicals. The objective of this study was fivefold: (1) develop methods and improve existing procedures on acute and sediment toxicity testing of the two invertebrates; (2) conduct both acute toxicity tests via water exposure and long-term sediment toxicity tests for the selected model substances to generate data for comparative discussion; (3) assess correlations among acute toxicity data of the organisms exposed via water-only and correlations among sediment toxicity data of the two endobenthic invertebrates for the eight tested chemicals; (4) assess possible forecasting for sediment toxicity from acute toxicity (via water-only exposure) and (5) assess exposure effects to determine the main exposure route. Acute toxicity data of the eight tested chemicals of D. magna significantly correlated with data of L. variegatus and C. riparius (p<0.05). However, a prediction of toxicity based on D. magna data bears high uncertainty, due to the small data set and high variation in sensitivity of the organisms. Existing sediment toxicity test methods were improved to meet the demand for artificial sediments containing organic matter that serves sufficiently as internal food source for the test organisms, and thus representing natural exposure conditions. However, the sediments that were used for the two organisms to test the selected model substances differed in sediment composition. Therefore, a sediment with the same sediment composition and the same water-to-sediment ratio for both invertebrates was developed, to have similar exposure conditions. In sediment toxicity tests, C. riparius was observed to be more sensitive than L. variegatus and no correlation was observed among data of the invertebrates. For the selected substances, lowest effect concentrations were observed for 3,4-dichloroaniline, whereas effect concentrations were the highest for benzo[a]pyrene. No correlations were found between the acute toxicity data of exposure via the water phase and sediment toxicity data, thus making a prediction of sediment toxicity data impossible. From analytical measurements of chemicals concentration in the compartments overlying, pore water, and bulk sediment, partition coefficients on sediment water partitioning were calculated. The highest partition coefficient ratios for sediment water partitioning were found for the high lipophilic organic substances 4,4-dichlorodiphenyltrichloroethan (DDT) and benzo[a]pyrene. Further, it was found that the main exposure routes in the 28-day sediment toxicity tests were not only chemical but species-dependent. As a result of very differing exposure routes for the tested chemicals and the absence of correlations from the acute to sediment toxicity data, sediment toxicity tests are necessary to assess the toxicity of chemicals on sediment inhabiting organisms. / In den meisten standardisierten ökotoxikologischen Untersuchungen zur Abschätzung des Gefährdungspotentials von Chemikalien für Gewässer erfolgt die Exposition der Organismen über die Wasserphase. Viele Schadstoffe, die in die aquatische Umwelt gelangen, adsorbieren aufgrund ihrer physikalisch-chemischen Eigenschaften an die Oberflächen von Schwebstoffen, sedimentieren und erreichen Sedimentkonzentrationen, die möglicherweise eine Gefahr für sedimentbewohnende Organismen darstellen. Im Rahmen dieser Arbeit wurden für benthische Invertebraten Testverfahren etabliert, bei denen eine Exposition der Organismen über das Sediment, hier hauptsächlich über die an ingestierte Sedimentbestandteile gebundene oder über die im Porenwasser gelöste Chemikalie (28-Tage Sedimenttoxizitätstest), und über dieWasserphase (Akuttoxizitätstest) erfolgte. Die Invertebraten Chironomus riparius und Lumbriculus variegatus wurden als typische Vertreter endobenthischer Organismen ausgewählt. Für viele Chemikalien liegen Daten zur akuten Toxizität für Algen, Daphnien und Fische für die Wasserexposition vor. Demgegenüber sind nur wenige Daten zur Toxizität für benthische Organismen weder mit einer Wasser- noch mit einer Sedimentexposition vorhanden. Als Modellsubstanzen wurden eine anorganische und sieben organische Substanzen für die Untersuchungen ausgewählt. Ziele dieser Arbeit waren: (1) die Entwicklung und Verbesserung von bestehenden Methoden zur Bestimmung der akuten Toxizität mitWasserexposition und der Sedimenttoxizität für die beiden Invertebraten; (2) die Durchführung der Tests mit den acht ausgewählten Modellsubstanzen zur vergleichenden Betrachtung; (3) die Beurteilung einer Korrelation der Daten zur Akuttoxizität innerhalb der verschiedenen Organismen mit Wasserexposition und einer Korrelation der Daten zwischen den beiden benthischen Organismen bei Sedimentexposition; (4) die Beurteilung einer Korrelation zwischen Daten der benthischen Invertebraten zur Akuttoxizität mit Wasserexposition und Sedimenttoxizität und (5) die Ermittlung und Bewertung der Expositionspfade. Die Akuttoxizitätsdaten von D. magna korrelieren significant (p<0.05) mit den Daten der beiden Invertebraten. Jedoch ist eine Vorhersage aufgrund des kleinen Datensatzes und der großen Unterschiede in der Empfindlichkeit der Arten abzulehnen. Um einer möglichst natürlichen Expositionssituation in Sedimenten zu entsprechen, wurden künstliche Sedimente mit interner Futterquelle, die auch mit der zu testenden Chemikalie kontaminiert wurde, entwickelt und für die Tests mit den Modellsubstanzen verwendet. Ein Nachteil war die unterschiedliche Sedimentzusammensetzung für die beiden Organismen. Um gleiche Expositionsbedingungen für beide Testorganismen zu gewährleisten, wurde ein artifizielles Sediment mit gleicher Zusammensetzung und gleichem Volumenverhältnis zwischen Sediment und Überstandswasser entwickelt. In den Sedimenttoxizitätstests reagierte C. riparius empfindlicher als L. variegatus. Die Effektkonzentrationen waren am niedrigsten für 3,4-Dichloraniline und am höchsten für Benzo[a]pyren. Die Korrelationen zwischen den Ergebnissen aus Akut- und Sedimenttoxizitstests waren nicht signifikant (p>0.05). Folglich läßt sich die Sedimenttoxizität nicht aus Daten zur akuten Toxizität mit Wasserexposition abschätzen. Aus den analytischen Messungen von Sediment-, Porenwasser- und Überstandswasserproben wurden die Koeffizienten für die Verteilung zwischen Sediment und Wasser berechnet. Für die stark lipophilen Stoffe, 4-Dichlorodiphenyltrichloroethan (DDT) und Benzo[a]pyren wurden die höchsten Koeffizienten errechnet. Weiterhin wurde festgestellt, daß die Hauptexpositionspfade in Sedimenttoxizitätstests einerseits von der Chemikalie und andererseits von der verwendeten Spezies abhängen. Aufgrund der Ergebnisse dieser Arbeit und der Tatsache, daß Sedimente “Senken” für viele Schadstoffe sind, müssen zur Erfassung und Bewertung des Gefährdungspotentials von Chemikalien gegenüber Sedimentbewohnern weiterhin Sedimenttoxizitätstests durchgeführt werden.