Analysis and modelling of profiles to understand fractionation processes for contaminations with polychlorinated biphenyls observed in fish.

Polychlorinated biphenyls (PCB) both continue to spread into the environment and to bioaccumulate from primary urban and industrial sources as well as from secondary sources such as soils and the oceans. Fractions of congeners in PCB mixtures, i.e. PCB profiles, can be used as fingerprints to trace contamination pathways from sources to sinks because PCB mixtures fractionate during transport due to congener specific phase changes and degradation. Using a statistical analysis of a total of 8584 PCB profiles with seven congeners (CB28, CB52, CB101, CB118, CB138, CB153, CB180) for contaminated fish from two international datasets as well as a modelling of profiles, two major fractionation processes related to distinct contamination pathways were identified: (1) A relative enrichment of lighter congeners (CB28, CB52, CB101) in seawater fish due to a predominantly atmospheric transport, whereas freshwater and some coastal fish had higher fractions of heavier congeners (CB138, CB153) because those were mainly contaminated by particle-sorbed PCB from surface runoff. (2) A temperature driven fractionation tended to affect congeners with a medium molecular weight (CB118) as well as the heaviest congeners (CB180), a fractionation process which was conceptually associated with transport of PCB from secondary sources. Specifically, medium chlorinated PCB is sufficiently volatile and persistent for a preferred transport into cooler waters. In warmer climates, only the highest chlorinated congeners are persistent enough to ultimately accumulate in fish. Our analysis and modelling provide a starting point for the development of systems to trace - better than before - sources of PCB contaminations observed in fish.

Sorption and dialysis experiments to assess the binding of phenolic xenobiotics to dissolved organic matter in soil.

The binding of two phenolic compounds, nonylphenol (NP) and bisphenol A (BPA), and the herbicide metabolite hydroxydesethyl terbuthylazine (HDT) to dissolved organic matter (DOM) as well as its impact on the environmental fate of the compounds in soil have been investigated. In sorption studies with an acidic silty loam soil and a neutral loam soil, no impact of added DOM on adsorption and desorption coefficients was observed. Adsorption coefficients normalized to soil organic carbon (Koc) of the compounds on the loamy silt soil spanned three orders of magnitude: 90, 890, and 9,140 L/kg for HDT, BPA, and NP, respectively. Significantly lower Koc values for HDT on the neutral loam soil as compared to the acidic loamy silt soil indicated additional polar interactions between the latter and the basic herbicide metabolite. In dialysis experiments with fulvic acid from silty loam soil (FA) and peat humic acid (HA), a formation of analyte-DOM associates was observed only for HA. The degree of association was characterized by distribution coefficients normalized to the dissolved organic carbon concentration (KDOC). Values for NP (8,970 L/kg) and BPA (860 L/kg) corresponded with the respective soil sorption coefficients, suggesting similar binding mechanisms in both cases.

Comparative assessment of plant protection products: how many cases will regulatory authorities have to answer?

BACKGROUND: The substitution principle has been included in the EU pesticides legislation as a new element. Comparative assessments will have to be conducted for all uses of plant protection products (PPPs) that contain active substances with certain hazardous properties, the so-called candidates for substitution (CFS). This study investigated the resulting workload in terms of the number of cases for comparative assessments that regulatory authorities may have to face. The analysis was carried out for Germany as an example. MAIN TEXT: In Germany, the requirement for comparative assessments may affect up to 25% of all PPPs and around 50% of all uses of PPPs. In absolute terms, these are around 350 candidate products with 1,850 different uses. Alternative products without CFS may be available for around 40% of these uses. On average, a candidate product is authorised for around 18 different uses. For 11 of these uses, no alternatives are authorised. For the remaining seven uses, slightly more than seven alternatives are available on average. Multiplication of these factors gives an indicative figure of around 18,500 possible pairwise comparisons of candidate products with alternative products for every common use. CONCLUSIONS: The high number of expectable cases poses a formidable challenge for the efficient conduct of the new task of comparative assessments by competent Member States authorities. To this end, new data handling systems, assessment procedures, and decision rules need to be established.