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This study examined to what degree bioaccumulated pesticides in transplanted zebra mussels can give an insight to pesticide bioavailability in the environment. In addition, it was investigated if pesticide body residues could be related to ecological responses (changes in macroinvertebrate community composition). For this at 17 locations, 14 pesticide concentrations and nine dissolved metals were measured in translocated zebra mussels and the results were related to the structure of the macroinvertebrate community. Critical body burdens in zebra mussel, above which the ecological status was always low, could be estimated for chlorpyrifos, terbuthylazine and dimethoate being respectively 8.0, 2.08 and 2.0 ng/g dry weight. With multivariate analysis, changes in the community structure of the macroinvertebrates were related to accumulated pesticides and dissolved metals. From this analysis, it was clear that the composition of the macroinvertebrate communities was not only affected by pesticides but also by metal pollution. Two different regions could be clearly separated, one dominated by metal pollution, and one where pesticide pollution was more important. The results of this study demonstrated that zebra mussel body burdens can be used to measure pesticide bioavailability and that pesticide body burdens might give insight in the ecological impacts of pesticide contamination. Given the interrelated impacts of pesticides and heavy metals, it is important to further validate all threshold values before they can be used by regulators., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The present study describes total mercury (THg) levels in surface water, sediment and biota from the Olifants River Basin (ORB) (South Africa) and investigates the trophic transfer of THg by means of trophic magnification factors (TMFs) in the subtropical ORB food web. Although levels in surface water, sediment and invertebrates were low, elevated levels of THg were measured in fish species of higher trophic levels (0.10-6.1 μg/g dw). This finding supports the biomagnificative character of mercury. THg concentrations in fish from the present study were find to be higher than most values reported in fish from other African aquatic ecosystems and comparable or lower compared to more industrialized regions. Fish length, trophic level, sediment THg levels and TOC in sediment were determining factors for THg levels in fish tissue. Concentrations were found to be higher in larger (and older) fish. Mercury has a high affinity for organic matter and will bind with the TOC in sediment, thus reducing the bioavailability of THg for aquatic biota which is reflected in the significant negative correlation between THg and TOC in sediment. A significant positive relationship between relative trophic level and THg concentrations was observed and also TMFs indicate biomagnification in the ORB food web. However, the trend of lower TMFs in tropical areas compared to temperate and arctic regions was not supported by the results. The consumption of fish from higher trophic levels at the average South African consumption rate is expected to pose a significant health risk., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

This study investigates the trophic transfer of persistent organic pollutants (POPs: PCBs, PBDEs, OCPs and PFASs) in the subtropical aquatic ecosystem of the Olifants River Basin (South Africa) by means of trophic magnification factors (TMFs). Relative trophic levels were determined by stable isotope analysis. POP levels in surface water, sediment and biota were low. Only ∑DDTs levels in fish muscle (1, indicating biomagnification of all detected POPs. Calculated TMFs for PCBs were comparable to TMF values reported from the tropical Congo River basin and lower than TMFs from temperate and arctic regions. For p,p'-DDT, a higher TMF value was observed for the subtropical Olifants River during the winter low flow season than for the tropical Congo river. TMFs of DDTs from the present study were unexpectedly higher than TMFs from temperate and arctic aquatic food webs. The fish species in the aquatic ecosystem of the Olifants River can be consumed with a low risk for POP contamination., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Inundation of formerly embanked areas in order to combine flood control and tidal marsh restoration will be applied increasingly. However, areas suitable for the implementation are often found to be contaminated. Re-inundation of metal contaminated soils can have consequences on total metal concentrations as well as metal mobility. In this study, metal mobility in a tidal marsh restoration project was evaluated based on the modified BCR sequential extraction method, concentrations of acid volatile sulfides (AVS) and simultaneously extracted metals (SEM) and metal concentrations in plants. The results obtained from the sequential extraction suggest an increase in metal mobility following inundation due to the reduction of Fe and Mn oxides and the subsequent release of associated metals. However, the differences in results between sequential extraction and [SEM-AVS] may indicate that redistribution of the metals to the mobile fraction can be caused by sample processing. High AVS concentrations in newly deposited sediments in the restored marsh may indicate that the formation of insoluble metal-sulfide complexes will reduce metal mobility on the longer term. Processes following inundation of metal contaminated land are complex and different conditions prevailing in other sites or estuaries can result in different behavior of the trace metals. More in situ research is needed to get a better insight in the risks involved., (Copyright © 2013 Elsevier B.V. All rights reserved.)

We investigated the accumulation of persistent organic pollutants in damselfly larvae (Ischnura elegans) in sixteen ponds in Flanders (Belgium), widely differing in the surrounding land use. Concentrations of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE) and hexachlorobenzene (HCB) were measured. From all targeted PBDE-congeners, only three congeners (IUPAC nos. 47, 99, 100) were above the limit of quantification (LOQ). The ∑PBDE concentrations ranged from LOQ (0.20 ngg(-1) ww) with values up to 3.30 ngg(-1) ww in the pond at Hamme. In fifteen ponds, the HCB concentrations were >LOQ (0.05 ngg(-1) ww) with values up to 0.24 ngg(-1) ww. For the available data in the literature a comparison with different species was done for some of the sampled ponds. The monitored ponds can be separated in three groups based on their contamination. The first group is characterised by a relative low POP content (∑PBDEs, ∑PCBs, HCB). Group 2 contained more HCB and p,p'-DDE than the overall mean while this was the case for PBDEs and PCBs in group 3. The vectors of both contaminated groups are situated nearly perpendicular which is suggesting a different pollution sources., (Copyright © 2012 Elsevier B.V. All rights reserved.)