There is a consensus within the scientific community that sediments act as a long-term sink for a variety of organic and inorganic pollutants, which, however, can re-enter the water column upon resuspension of deposited material under certain hydraulic conditions such as flood events. Within the implementation of the European Water Framework Directive, it is important to understand the potential short- and long-term impact of suspended particulate matter (SPM)-associated contaminants on aquatic organisms as well as the related uptake mechanisms for a sound risk assessment. To elucidate the effects of sediment-bound organic pollutants, such as polycyclic aromatic hydrocarbons (PAHs), rainbow trout (Oncorhynchus mykiss) were exposed to three resuspended natural sediments with different contamination levels. Physicochemical parameters including dissolved oxygen concentration, pH and temperature, total PAH concentration in sediments and SPM as well as different biomarkers of exposure in fish (7-ethoxyresorufin Odeethylase activity, biliary PAH metabolites, micronuclei, and lipid peroxidation) were measured following seven days of exposure within an annular flume, a device to assess erosion and deposition processes of cohesive sediment. Concentrations of PAHs in SPM remained constant and represented the different contamination levels in the unsuspended sediments. Significant differences in bile metabolite concentrations as well as in 7-ethoxyresorufin Odeethylase induction compared to control experiments (untreated animals and animals that were exposed in the annular flume without sediment) were observed for all exposure scenarios. The ratio between 1-hydroxypyrene in bile from fish exposed to the three different contamination levels was 1.0:3.6:10.7 and correlated well with (1) the ratio of pyrene concentrations in corresponding sediments which was 1.0:3.1:12.7 and (2) with the ratio of particle-bound pyrene in SPM which was 1.0:2.7:11.7. In contrast, hepatic lipid peroxidation and micronuclei formation represented the different contamination levels less conclusive. The results of this study clearly demonstrate that firmly bound PAH from aged sediments can become bioaccessible upon resuspension under flood-like conditions and are readily absorbed by aquatic organisms such as rainbow trout. Associated short-term effects were clearly documented and possible adverse long-term impacts due to genotoxicity are likely to follow.

The stock of the European eel (Anguilla anguilla L.) continues to decline and has reached a new minimum in 2011. Poor health status of the spawners due to organic contaminants is one of the possible causes for this dramatic situation. Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants, which are rapidly metabolized in vertebrates. EROD (ethoxyresorufin-O-deethylase) and GST (glutathione-S-transferase) are two enzymes involved in PAH detoxification in fish. In this study, PAH metabolites as well as EROD and GST activity in a large, comprising dataset of more than 260 migratory and pre-migratory eels from five large German river basin districts were used to describe PAH exposure and its metabolism as possible indicators for the habitat quality for eels. Eel from the river Elbe appear to be moderately contaminated with PAH. Highest mean values of PAH metabolites were analysed in fish from the river Rhine. However, the results suggest that contaminants such as PAH are metabolized in the fish and may have contributed to EROD activity in eels caught from the Elbe estuary to 600 km upstream. Since the eel’s onset of cessation of feeding is closely linked to maturation and migration, we propose bile pigments as new indicators contributing to identify the proportion of migratory eel, which is crucial information for eel management plans. We showed that PAH metabolites normalized to bile pigments as well as EROD could be used to describe the habitat quality and might be suitable parameters in search for suitable stocking habitats.

Bac Lieu is a coastal province the Mekong River Delta (MRD), Vietnam. Aside from salinity intrusion from the sea, the province is strongly affected by acidic pollution as 58% of the area (250,000 ha) is overlaid with acid sulphate soil (ASS). Previous studies showed that the eminent sea level rise (SLR) would influence the hydrology and salinity of the canal networks in the province. This study, using the previously validated hydraulic and water quality model VRSAP-ACIDITY (Vietnam River Systems And Plains, coupled with ACIDITY Module), aimed at quantifying impacts of different SLR scenarios (SLR = 17, 30, 50, or 75 cm) on acidic pollution in the province. Under the present sea level, widespread acidic pollution (pH < 5) of surface water occurred at the start of the rainy season, due to leaching of acidity from canal embankments and fields in ASS. The acceleration of SLR reduced the area of acidic polluted water. The lessening in acidic pollution was attributed to (1) SLR that raised the water level in the Mekong River, increasing the amount of fresh water flowing into the study area; and (2) the amount of water drained out of the study area increased, bringing with its acidity. It concluded that SLR has a positive effect on acidic pollution in the ASS coastal area.

For decades, the explosive RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) has been used for military and industrial applications. Residues of RDX pollute soils in large areas globally and the persistence and high soil mobility of these residues can lead to leaching into groundwater. Dendroremediation, i.e. the long-term use of trees to clean up polluted soils, is gaining acceptance as a green and sustainable strategy. Although the coniferous tree species Norway spruce and Scots pine cover large areas of military land in Central Europe, the potential of any coniferous tree for dendroremediation of RDX is still unknown. In this study, uptake experiments with a 14C-labelled RDX solution (30 mg L−1) revealed that RDX was predominantly retained in the roots of 6-year-old coniferous trees. Only 23 % (pine) to 34 % (spruce) of RDX equivalents (RDXeq) taken up by the roots were translocated to aboveground tree compartments. This finding contrasts with the high aerial accumulation of RDXeq (up to 95 %) in the mass balances of all other plant species. Belowground retention of RDXeq is relatively stable in fine root fractions, since water leaching from tissue homogenates was less than 5 %. However, remobilisation from milled coarse roots and tree stubs reached up to 53 %. Leaching from homogenised aerial tree material was found to reach 64 % for needles, 58 % for stems and twigs and 40 % for spring sprouts. Leaching of RDX by precipitation increases the risk for undesired re-entry into the soil. However, it also opens the opportunity for microbial mineralisation in the litter layer or in the rhizosphere of coniferous forests and offers a chance for repeated uptake of RDX by the tree roots.

Defoliation is an indicator for forest health in response to several stressors including air pollutants, and one of the most important parameters monitored in the International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests). The study aims to estimate crown defoliation in 2030, under three climate and one nitrogen deposition scenarios, based on evaluation of the most important factors (meteorological, nitrogen deposition and chemical soil parameters) affecting defoliation of twelve European tree species. The combination of favourable climate and nitrogen fertilization in the more adaptive species induces a generalized decrease of defoliation. On the other hand, severe climate change and drought are main causes of increase in defoliation in Quercus ilex and Fagus sylvatica, especially in Mediterranean area. Our results provide information on regional distribution of future defoliation, an important knowledge for identifying policies to counteract negative impacts of climate change and air pollution

Defoliation is one of the most important parameters monitored in the International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests). Defoliation is an indicator for forest health and vitality. Conventional statistical analysis shows weak or not significant correlations between tree crown defoliation and climatic conditions or air pollution parameters, because of its high variability. The study aims to evaluate the most important factors among climatic, pollutants (Nox and NHy) and stand parameters affecting crown defoliation of the main European tree species (Fagus sylvatica, Picea abies, Quercus ilex, Pinus sylvestris and Quercus petraea) through application of a new and powerful statistical classifier, the random forests analysis (RFA). RFA highlighted that tree crown defoliation was mainly related to age in P. abies, to geographic location in F. sylvatica and to air pollution predictors in Q. ilex, while it was similarly linked to meteorological and air pollution predictors in P. sylvestris and Q. petraea. In this study, RFA has proven to be, for the first time, a useful tool to discern the most important predictors affecting tree crown defoliation, and consequently, it can be used for an appropriate forest management.

Land use specific deposition velocities of atmospheric trace gases and aerosols—particularly of reactive nitrogen compounds—are a fundamental input variable for a variety of deposition models. Although the concept is known to have shortcomings—especially with regard to bi-directional exchange—the often limited availability of concentration data and meteorological input variables make it a valuable simplification for regional modeling of deposition fluxes. In order to meet the demand for an up-to-date overview of recent publications on measurements and modeling studies, we compiled a database of ammonia (NH3) deposition velocities published from 2004 to 2013. Observations from a total of 42 individual studies were averaged using an objective weighing scheme and classified into seven land use categories. Weighted average and median deposition velocities are 2.2 and 2.1 cm s-1 for coniferous forests, 1.5 and 1.2 cm s-1 for mixed forests, 1.1 and 0.9 cm s-1 for deciduous forests, 0.9 and 0.7 cm s-1 for semi-natural sites, 0.7 and 0.8 cm s-1 for urban sites, 0.7 and 0.6 cm s-1 for water surfaces, and 1.0 and 0.4 cm s-1 for agricultural sites, respectively. Thus, values presented in this compilation were considerably lower than those found in former studies (e.g., VDI 2006). Reasons for the mismatch were likely due to different land use classification, different averaging methods, choices of measurement locations, and improvements in measurement and in modeling techniques. Both data and code used for processing are made available as supplementary material to this article.

Grey seals as top-predators bioaccumulate contaminants and can be considered as sentinels of ecosystem health. Pups are weaned after a short nursing period, characterised by an enormous lipid transfer and exposure to contaminants. This study established molecular biomarkers of the xenobiotic metabolism and immune system to help assess health and immune status. mRNA transcription of AHR, ARNT, PPAR~a and cytokine IL-2 and heat-shock-protein HSP70 was measured in blood of grey seal pups and adults in rehabilitation and permanent care using RT-qPCR and compared to rehabilitating harbour seal pups and haematology values. In pups highest levels at admission in xenobiotic biomarker, HSP70 and cytokine transcription may show contaminant exposure via lactation, stress during abandonment and dehydration. The significant decrease may be linked to diet, health improvement and adaptation. Adults showed higher levels and more variation in biomarker transcription and clear species-specific differences between harbour and grey seal pups were found.