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Abstract: The long-time use of persistent organic pollutants (POPs) led to a world-wide contamination of environmental compartments. Although, bans of numerous POPs reduced the POP input to rivers. Floodplain soils are still highly contaminated, because they are sinks for these compounds, which restrict their agricultural use. Hence, the intention of this study was the determination of 29 relevant POPs in two soil depths (0–10cm and 10–20 cm) of a field experiment to get a survey on the small-scale spatial variability of the experimental site and to establish a baseline for phytoremediation experiments. The POP concentrations ranged from 0.1μgkg−1 to 160μgkg−1 and showed an increase of dieldrin, endrin, endosulfan I, endosulfan II, heptachlor, p,p′-DDE, o,p′-DDE and methoxychlor concentrations on average in the river Elbe floodplains between the years 1998 and 2007. However, there was a pronounced small-scale spatial variability of POP concentrations in vertical and horizontal direction. The latter was estimated by comparing the relative standard deviations (RSDs) of the POP concentrations in sample sets located at sites of increasing distance from <1m to >10000m. [Copyright &y& Elsevier]

Abstract: Relationships between soil organic matter (SOM) molecular composition, thermal stability and decomposability by soil enzymes and microbes are largely unknown. We incubated soils from unfertilized and NPK-fertilized neighboring field plots of a long-term rye (Secale cereale) monoculture experiment and investigated relationships between changes in the molecular-chemical composition of SOM, the CO2 flux and the activities of enzymes. Pyrolysis-field ionization mass spectrometry (Py-FIMS) showed larger ion intensities in the NPK-fertilized than in the unfertilized soil at start of the incubation, only small changes in composition and thermal stability in the unfertilized soil, and a preferential reduction in thermally stable components as well as general shifts towards lower pyrolysis temperature after three weeks of incubation in the NPK-treatment. We found evidence that thermally labile and stable proportions of various compound classes were differently susceptible to decomposition, depending on the fertilization history of the soil. Irrespective of fertilization treatment, peaks in xylanase activity after 7 days of incubation followed by decreasing values were reflected by the ratio of xylan (m/z 114) to xylose (m/z 132) marker signals in the Py-FI mass spectra. Thus, the study proved that (1) SOM composition was changed due to long-term rye cropping without and with NPK-fertilization, (2) the modified SOM composition affected the decomposability and microbial parameters under optimized conditions and (3) the thermal properties of individual compound classes derived from Py-FI mass spectra can be sensitive predictors of microbial decomposition. [Copyright &y& Elsevier]

Abstract: Fatty acids as major compounds of soil lipids may affect many soil properties, but the input and turnover rates in soil are largely unknown. The objective of this study was to identify and quantify fatty acids in soils as a result of input from primary sources such as plant residues, farmyard manure and soil organisms, and to evaluate the corresponding turnover- and stabilization processes. The concentrations of n-C10:0 to n-C34:0 fatty acids were determined in the Ap horizon of a Phaeozem with long-term cropping of rye and maize and the treatments ‘Unfertilized’ (‘U’) and fertilized with ‘Farmyard manure’ (‘FYM’). The most important primary sources of fatty acids such as rye and maize stubble and roots, soil micro- and mesofauna, and the applied FYM were also investigated. The quantification of fatty acids by gas chromatography/mass spectrometry (GC/MS) showed that long-term FYM application led to larger concentrations of n-alkyl fatty acids in the plots grown with rye (‘U’: 48.1μgg−1, ‘FYM’: 57.7μgg−1, **P≤0.01, n=3) and maize (‘U’: 17.0μgg−1, ‘FYM’: 23.4μgg−1, ***P≤0.001, n=3). The observed bimodal fatty acid distribution in soils from n-C10:0 to n-C21:0 and from n-C21:0 to n-C34:0 with a predominance at n-C16:0 and at n-C28:0 was apparently due to input from crop residues, soil organisms and FYM. The short-chain lengths may have originated from the investigated primary sources. The major contributors to the long-chain lengths, with a maximum at n-C28:0, were rye stubble and FYM. A change in mono-culture from rye to maize, 38 years prior to sampling, led to a decrease in fatty acid concentrations by factors of about 2.8 (‘U’) and 2.5 (‘FYM’). Therefore, rye-derived fatty acids and soil tillage had a larger impact on fatty acid pools than the input of primary organic matter. The changes in fatty acid distributions and pools under the consideration of the quantified input of primary organic matter led to the conclusion that the short-chained fatty acids were more rapidly decomposed than the long-chains. [Copyright &y& Elsevier]