Metal accumulation in sediments and amphipods downstream of combined sewer overflows.

The aim of this study was to investigate the concentrations of the metals Ag, Cd, Cu, Mn, Mo, Pb, Pt and Zn in sediments and amphipods along a 100m transect downstream of three different combined sewer overflows (CSOs). Moreover, the study was implemented to better understand the biological availability of metals downstream of CSOs as well as to identify a potential risk of CSOs for benthic or pelagic biota. Samples were taken at downstream sampling sites, which were 1, 5, 10, 20, 50 and 100m away from the outlets of the CSOs. An upstream-located sampling site each was used as reference for the respective transect. Additionally, sediments in two retention zones, located between the CSOs and the receiving creeks were analyzed. All downstream located creek sediments showed a similar metal pattern. Metal concentrations were found to be highest within the first 20m of the creek sediments. Elevated metal concentrations were also detected in the sediments of the retention zones. Metal accumulation in the amphipods was different at all three locations, but highest levels were always found downstream of the sediment accumulation hot spots. This might indicate that the metals were remobilized and became available for the amphipods further downstream of the CSOs. Although the general contamination pattern with respect to each reference site was similar, the degree of contamination was different at each location as demonstrated by anthropogenic enrichment factors. The discharge frequency as well as anthropogenic influences from upper reaches appear to be the most important factors for high metal concentrations in the sediments. Accordingly, in one case high background concentrations in combination with the CSO lead to an exceedance of the predicted effect level of Zn for aquatic organisms. Therefore, sediment contamination should be included in risk assessment when constructing CSOs to protect aquatic life.

A versatile and low-cost open source pipetting robot for automation of toxicological and ecotoxicological bioassays.

In the past decades, bioassays and whole-organism bioassay have become important tools not only in compliance testing of industrial chemicals and plant protection products, but also in the monitoring of environmental quality. With few exceptions, such test systems are discontinuous. They require exposure of the biological test material in small units, such as multiwell plates, during prolonged incubation periods, and do not allow online read-outs. It is mostly due to these shortcomings that applications in continuous monitoring of, e.g., drinking or surface water quality are largely missing. We propose the use of pipetting robots that can be used to automatically exchange samples in multiwell plates with fresh samples in a semi-static manner, as a potential solution to overcome these limitations. In this study, we developed a simple and low-cost, versatile pipetting robot constructed partly using open-source hardware that has a small footprint and can be used for online monitoring of water quality by means of an automated whole-organism bioassay. We tested its precision in automated 2-fold dilution series and used it for exposure of zebrafish embryos (Danio rerio)-a common model species in ecotoxicology-to cadmium chloride and permethrin. We found that, compared to conventional static or semi-static exposure scenarios, effects of the two chemicals in zebrafish embryos generally occurred at lower concentrations, and analytically verified that the increased frequency of media exchange resulted in a greater availability of the chemical. In combination with advanced detection systems this custom-made pipetting robot has the potential to become a valuable tool in future monitoring strategies for drinking and surface water.

Nanoparticulate versus ionic silver: Behavior in the tank water, bioaccumulation, elimination and subcellular distribution in the freshwater mussel Dreissena polymorpha.

Zebra mussels (Dreissena polymorpha) were exposed to polyvinylpyrrolidone (PVP)-coated silver nanoparticles (AgNP; hydrodynamic diameter 80 nm; solid diameter 50 nm) to investigate the behavior of Ag in the tank water with respect to its uptake, bioaccumulation, elimination and subcellular distribution in the mussel soft tissue. Parallel experiments were performed with ionic Ag (AgNO3) to unravel possible differences between the metal forms. The recovery of the applied Ag concentration (500 µg/L) in the tank water was clearly affected by the metal source (AgNP < AgNO3) and water type (reconstituted water < tap water). Filtration (<0.45 µm) of water samples showed different effects on the quantified metal concentration depending on the water type and Ag form. Ag accumulation in the mussel soft tissue was neither influenced by the metal source nor by the water type. Ag concentrations in the mussel soft tissue did not decrease during 14 days of depuration. For both metal forms the Ag distribution within different subcellular fractions, i.e. metal-rich granules (MRG), cellular debris, organelles, heat-sensitive proteins (HSP) and metallothionein-like proteins (MTLP), revealed time-dependent changes which can be referred to intracellular Ag translocation processes. The results provide clear evidence for the uptake of Ag by the mussel soft tissue in nanoparticulate as well as in ionic form. Thus, zebra mussels could be used as effective accumulation indicators for environmental monitoring of both Ag forms.

A direct solid sampling analysis method for the detection of silver nanoparticles in biological matrices.

Engineered silver nanoparticles (AgNPs) are implemented in food contact materials due to their powerful antimicrobial properties and so may enter the human food chain. Hence, it is desirable to develop easy, sensitive and fast analytical screening methods for the determination of AgNPs in complex biological matrices. This study describes such a method using solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry (GFAAS). A recently reported novel evaluation strategy uses the atomization delay of the respective GFAAS signal as significant indicator for AgNPs and thereby allows discrimination of AgNPs from ionic silver (Ag(+)) in the samples without elaborate sample pre-treatment. This approach was further developed and applied to a variety of biological samples. Its suitability was approved by investigation of eight different food samples (parsley, apple, pepper, cheese, onion, pasta, maize meal and wheat flour) spiked with ionic silver or AgNPs. Furthermore, the migration of AgNPs from silver-impregnated polypropylene food storage boxes to fresh pepper was observed and a mussel sample obtained from a laboratory exposure study with silver was investigated. The differences in the atomization delays (Δt(ad)) between silver ions and 20-nm AgNPs vary in a range from -2.01 ± 1.38 s for maize meal to +2.06 ± 1.08 s for mussel tissue. However, the differences were significant in all investigated matrices and so indicative of the presence/absence of AgNPs. Moreover, investigation of model matrices (cellulose, gelatine and water) gives the first indication of matrix-dependent trends. Reproducibility and homogeneity tests confirm the applicability of the method.

Distribution of platinum and other traffic related metals in sediments and clams (Corbicula sp.).

Platinum is part of traffic-emitted metals since the introduction of automotive catalyst converters. Still, automobile emissions are one of the major sources for metals in European river systems. However, field data on Pt is scarce and there is a lack of knowledge concerning the distribution and biological availability of Pt. Therefore, the distribution of traffic related metals (Cd, Cr, Cu, Ni, Pb, Pt, and Zn) was analyzed in sediment samples and in the Asian clam Corbicula sp. Samples were taken from three transects following road runoff inlets. Pt was introduced into the river by road runoff. The highest Pt concentrations in sediments were analyzed in the silt/clay fraction (45 ng/g), while the highest total Pt burden was obtained for the sand fraction, that makes up more than 60% of the sediment. Metal concentrations were related to the area of the drained street section as well as to their distance from the discharge point, and to grain size distribution within the sediment. Pt and other traffic related metals were accumulated by clams. Due to the feeding behavior of the freshwater mussel Corbicula sp. Pt concentrations in the soft tissue remain relatively low (max Pt concentration: 1.3 ng/g freeze dried soft tissue) and acute lethal or toxic effects therefore appear to be unlikely. Nonetheless, chronic exposure effects still have to be examined.

Progress in ecotoxicology, environmental chemistry and ecology.

This Editorial introduces a series of papers on 'Progress in ecotoxicology, environmental chemistry and ecology' and was initiated in the context of the Joint SETAC GLB/GDCh Annual Meeting 2013 at the University of Duisburg-Essen. According to the title of the conference 'Ecotoxicology in an urban context' (Ökotoxikologie im urbanen Raum), a couple of conference contributions dealing with the occurrence and availability of pollutants relevant for organisms in urban environments will be published as papers in this series. Additional contributions with a focus on current developments in any field of ecotoxicology, environmental chemistry or ecology or which specifically address the importance of multiple stressors are welcome. We cordially invite all colleagues who feel they can contribute to the topic to submit a manuscript to ESEU with reference to this series.