Seasonal variability of contaminants with specific modes ofaction in polluted river-basin
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Abstract:
River ecosystems represent dynamic system, where contamination
of river compartments exerts significant variability in space
and time. Chemical compounds occur in the environment as
complex mixtures that can act through specific modes of action
in organisms. Suitable tools for assessing specific biological
activities in environmental samples represent screening
bioassays. The present research focuses on contamination of a
model river ecosystem in south-eastern part of Czech Republic.
Aim of our one-year long study was to characterize temporal and
spatial variability of contamination and toxicity of complex
mixtures (sediments and water samples) collected from five
sampling sites.This research was supported by the Czech
Ministry of Education projects ENVISCREEN - NPVII 2B08036 and
INCHEMBIOL 0021622412.Keywords:
Christian ministry
Environmental Monitoring
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This chapter contains sections titled: Introduction Sediment quality issues and concerns Indicators of sediment quality conditions Integration of information on multiple indicators of sediment quality conditions Summary and conclusions References
Freshwater ecosystem
Marine ecosystem
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Sediments are components of marine and estuarine ecosystems. Toxicants most often
become sorbed to suspended particulate matter, then fall to the bottom to become
incorporated into bed sediments. The bioavailability of the toxicants is difficult to measure
chemically and the interpretation of biological significance is unclear. Toxicants stored in
sediments can be released due to physical and chemical changes in the environment. The
extent of the effects of these changes is also not well established and there is little
knowledge of what levels of contaminants may be mobilised, and the ecological effect of
that mobilisation.
Although recently, pore water toxicity and chemistry has been included in sediment testing,
there is a lack ofresearch characterising pore water from Australian marine sediments.
Further, there is a paucity of multidisciplinary research of the quality of marine sediments
in Australia to provide information on factors affecting quality and remediation of marine
sediments that will contribute to improved environmental management of marine sites and
allow for successful remediation practices.
The primary aim of this study was to apply a multidisciplinary approach to form a weight of
evidence assessment of sediment quality in northern Tasmanian estuaries. The technical
objectives associate with this aim were to:
• determine whether shallow subtidal sediments adjacent to a heavy metals industrial estate
was chemically contaminated relative to other northern Tasmanian locations, and relative to
numerical, effects-based guidelines
• determine ifbenthic communities exposed to chemical contamination differed relative to
benthic communities exposed to non-contaminated sediments
• establish whether the contaminated sediments were toxic relative to non-contaminated
sediments
• determine the relationships between toxicity, chemical composition and benthic
communities of the subtidal sediments at contaminated and non-contaminated sites
• generate background data for future assessment of sediment remediation.
The relationship between the toxicity, chemical composition and benthic communities was
investigated through a field program. Over two years, samples were collected at four
locations. One of these, Deceitful Cove in the Tamar River estuary, has been heavily
contaminated by past industrial effluents from aluminium refining and ferro-manganese
smelting industrial plants, another (East Ann in the Tamar River estuary) has intermediate
contamination, while the other two (Squeaking Point and North East Arm in the Port Sorell
estuary) are effectively free of pollution. A Sediment Quality Triad (SQT) assessment of
shallow subtidal marine sediments within the two adjacent northern Tasmanian estuaries
was conducted to assess sediment quality in terns of potential to elicit adverse biological
effects. The SQT provides a weight-of-evidence approach integrating toxicological and
chemical analysis with benthic community structure to determine likely impacts of
contaminants. Generic effects-based sediment quality guideline (SQG) values were also
used to facilitate evaluation of sediment quality by identification of potential contaminants
or mixtures of contaminants, likely to cause adverse biological effects. Chemical analysis
involved assessment of total trace metals and organics concentrations within sediments.
Assessment of toxicity involved the adaptation of a suite of first tier screening bioassays,
currently used for testing toxicity of marine water: Micro lox®, sea urchin larval
development inhibition and algal growth inhibition tests. Benthic macroinvertebrate
community structure was evaluated using univariate, distributional and multivariate
analysis of assemblages: species diversity indices, hierachical cluster analysis and nonmetric
multi-dimensional scaling ordination.
Differential SQT analysis indicated strong evidence of contaminant-induced stress, and
possible environmental degradation in the Tamar River estuary at Deceitful Cove.
Additionally, contaminant-induced stress was not restricted to a geographically isolated
area adjacent to the industrial estate. Multi-dimensional scaling ordination and univariate
analyses identified significant differences between the patterns of distribution and
abundance of benthic fauna from contaminated and non-contaminated estuaries. There was
a significant correlation between patterns of assemblages and concentrations of trace
metals.
The overall findings from the SQT and multivariate analyses strongly suggest that a
combination of metal contaminants are directly related to elevated pore water toxicity and
alteration in macroinvertebrate community structure. The liquid phase Microtox® and algal
growth bioassays are suitable for testing pore water toxicity of Tasmanian coastal marine
sediments. However, difficulty in interpreting Microtox® solid phase test results limits the
use of this assay for routine testing. Additionally, research on extending the spawning
period of the sea urchin Heliocidaris tuberculata is necessary before this species can be
used for routine bioassay work.
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Pesticides emitted into the environment may contribute to complex mixtures including the parent molecules, degradates in association with other pollutants. It is of paramount importance to implement suitable monitoring procedures to assess the fate of pesticides, their transfer to groundwater and the effects of water quality on aquatic and terrestrial organisms. The alluvial domain of the Ariege River (about 538 km2) is an unconfined aquifer, the thin thickness of vadose zone making it vulnerable to contamination. The aquifer is in direct hydraulic connection with rivers Ariege and Hers Vif and feeds them during much of the year. As a result, the quality of surface water is highly influenced by groundwater quality. Due to intensive agriculture in this area, related to corn cultivation in particular, groundwater quality is affected by pesticides and some of their metabolites. Monthly monitoring of water quality at 16 water points in the plain was initiated in March 2009 and is still on-going. It includes some 50 organic molecules, major ions such as nitrate and other nonconservative parameters (pH, temperature, redox potential). A strong spatial variability of the contamination was demonstrated, with predominance of degradation products over parent molecules in some locations, and also showed a strong temporal variability. Besides aiming at a better understanding of the pesticides' fate, our study also addresses the effects of altered water quality on various aquatic organisms. Laboratory ecotoxicological tests calibrated with realistic environmental concentrations found in the aquifer and accounting for proportion of the different molecules were performed. In parallel, investigations of in situ exposures were better controlled. Spatial and temporal distribution of the microbial diversity in groundwater is followed to evaluate its relevance as bioindicators. Macro-organisms restricted to groundwater (hypogean organisms such as isopods or amphipods) are investigated in situ at the scale of species, populations and communities while acute and chronic toxicities are determined in laboratory. First results on amphibians, also studied, showed that the contamination of surface water affects populations (richness) in the environment while in most cases no toxicity has been demonstrated in Xenopus larvae. To our knowledge this project may be the first investigation of the effects of pesticides on these three types of organisms using both lab and aquifer studies.
Alluvial plain
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Abstract Recent research trends in sediment quality assessment have demonstrated the need for an integrated approach which combines chemical characterisation with biological effects evaluation, both in the laboratory (toxicity bioassays) and in situ (macrobenthic community structure investigations). The Sediment Quality Triad organises these three aspects of sediment quality assessment in a single approach, where each component is complementary to the others. Considering the lack of previous studies, this preliminary work aimed to verify the potential of an integrated approach in a complex ecosystem, the Venetian lagoon. Five sampling stations along a presumed quality gradient were chosen. The chemical analyses of heavy metals and organic pollutants have been compared with the results of the toxicity bioassays (Microtox ® solid phase, saline extracts and pore water, and sea urchin Paracentrotus lividus sperm cell bioassay performed with saline extracts) and with the characterisation of the infaunal community structure. The results of this first application pointed out the complementarity of the three approaches and the ability of the integrated approach in discriminating different levels of environmental stress. Nevertheless, deeper investigations both on the response of the macrobenthic community to natural variability and on the environmental toxicity of several sulphur compounds (i.e. elemental sulphur) will be necessary.
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Within the context of the Water Framework Directive, the need to identify new monitoring tools in support of the traditional chemical monitoring process is emerging. Chemical characterization by itself does not provide specific biological information about potential hazards to organisms, in particular when facing cocktails of contaminants. Therefore, ecotoxicity tests can represent a useful tool supporting the chemical information. In the present work, the value of ecotoxicity tests as an effect-based tool for monitoring freshwater and sediment quality of the south-western basin of Lake Como (Northern Italy) was evaluated, assessing the potential risk of pollutants. Results obtained from D. magna toxicity tests showed a temporal variation of toxic response in relation to the variability of organic micropollutant load characteristics of urban rivers. Sediment ecotoxicity test data showed the spatial variability of the sediments’ contamination within the lake, confirmed by chemical analysis of two classes of pollutants (dichlorodiphenyltrichloroethane (DDT) and polychlorobiphenyls (PCB)). The observed effects on organisms in laboratory tests caused by a mixture of almost unknown chemicals underline the importance of integrating effect-based tools into monitoring efforts.
Ecotoxicity
Water Framework Directive
Environmental Monitoring
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In this study, nutrients, trace metals and priority pesticide compounds were investigated for the first time in water and sediment samples in streams of the Evrotas River basin (S.E. Greece) from 2006 to 2008. The most important sources of contamination were from the entry of pesticides and nutrients into surface waters and sediments as a result of the intensive agricultural activity as well as from the uncontrolled disposal of olive mill and citrus processing wastewaters. Aquatic risk assessment revealed that all insecticides detected showed high risk, suggesting adverse effects on the stream biota. Among the metals analyzed, Cr, Ni and Ba presented the highest concentrations in sediments, however, due to natural geological processes. Multivariate statistical techniques applied for data compression, exploration and interpretation proved to be useful tools for identifying the most critical pollutants affecting the surface water quality. The findings of this study suggest that the inclusion of streams with small catchment areas into WFD monitoring and assessment programs is essential, especially those of the Mediterranean region.
Biota
Mediterranean Basin
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The Water Framework Directive (WFD) regulates freshwater and coastal water quality assessment in Europe. Chemical and ecological water quality status is based on measurements of chemical pollutants in water and biota together with other indicators such as temperature, nutrients, species compositions (phytoplankton, microalgae, benthos and fish) and hydromorphological conditions. However, in the current strategy a link between the chemical and the ecological status is missing. In the present WFD, no microbiological indicators are foreseen for integrating the different anthropogenic pressures, including mixtures of chemicals, nutrients and temperature changes, to provide a holistic view of the freshwater ecosystem water quality. The main aim of this work was to evaluate if natural microbial populations can be valuable indicators of multiple stressors (e.g. chemical pollutants, temperature, nutrients etc.) to guide preventive and remediation actions by water authorities. A preliminary survey was conducted to identify four sites reflecting a contamination gradient from the source to the mouth of a river suitable to the objectives of the European Marie Curie project, MicroCoKit. The River Tiber (Italy) was selected as a pilot case study to investigate the correlation between bacteria taxa and the chemical status of the river. The main physicochemical parameters, inorganic elements, organic pollutants and natural microbial community composition were assessed at four selected sites corresponding to pristine, agricultural, industrial and urban areas for three consecutive years. The overall chemical results indicated a correspondence between different groups of contaminants and the main contamination sources at the selected sampling points. Phylogenetic analysis of the microbial community analyzed by Fluorescence In Situ Hybridization method (FISH) revealed differences among the four sampling sites which could reflect an adaptive bacterial response to the different anthropogenic pressures.
Water Framework Directive
Biota
Benthos
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The aim of study was to integrate chemical analyses and toxicity bioassays in order to assess the environmental risk connected with the presence of trace elements in the sediments. This study examined the ecological significance of trace elements in bottom sediments by applying a set of complementary sediment quality assessment methods sediment quality guidelines (SQGs) (mean probable effect concentration quotient (PECQ)), potential ecological risk index (PERI), contamination degree (C d) and two bioassays: the bacterial luminescence inhibition test with Vibrio fischeri on sediment elutriates and the direct contact test with the ostracod crustacean Heterocypris incongruens. The samples were collected from 50 stations of Rybnik reservoir. The reservoir is a region with enormous concentration of industry, mainly hard coal mining, electric power industry, and transportation. Despite the high diversity in metal concentration in the sediments, the spatial distribution of trace elements in the sediments was very similar. Moreover, the strong positive correlations between individual pairs of trace elements indicate that they may derive from a similar source and move together. According to mean PECQs, 68 % of the samples were potentially non-toxic and 32 % of the samples were potentially toxic. PERI values suggested that 70 % of the sediment sampling sites exhibited low ecological risk from metal pollution while 24 % of the samples had severe and serious risk. Based on our combined evaluation, we believe that Cd and Cu in the sediment samples frequently caused adverse biological effects. Higher toxic responses were observed in the Microtox test than in the Ostracodtoxkit test. All the sediment samples were found toxic to V. fischeri, and 96 % of the samples had effect percentages >50 %. For H. incongruens, 12 % of the sediments were not toxic and 44 % had effect percentages >50 %. In order to perform a complex assessment of the environmental impact of metal pollution, both chemical and ecotoxicological analysis should be carried out.
Ecotoxicity
Trace metal
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The physics, chemistry and biology of even simple sediment systems (e.g., sand habitats along a semi-exposed coast) are complex. In part, this complexity is due to the natural spatio-temporal variability in most measures. The authors investigated porewater chemistry, microphytobenthic biomass and meiofaunal abundance in a sandy habitat along the coast of Western Australia and in 2,000 liter mesocosms that contained transplanted patches of this habitat. One aim was to document the response how systems in the mesocosms responded, but another key outcome was to determine spatio-temporal variation at local scales in the field and among mesocosms. The results of these investigations have implications for the interpretation of estimates of toxicity arising from laboratory-based sediment toxicity tests. In particular, the importance of toxicity estimates to environmental managers relies on a comparison to background levels of variation.
Mesocosm
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