Impact of different sterilisation techniques on sorption and NER formation of test chemicals in soil.

Standard OECD tests are used to generate data on biodegradation (OECD 307) and sorption (OECD 106) of test chemicals in soil. In such tests, data on abiotic degradation using sterile samples are utilised to investigate any losses due to abiotic processes. The data from sterile samples are also used to interpret results and findings of non-sterile samples, especially in the context of sorption and non-extractable residue (NER) formation. However, to ensure the comparability of the data obtained from sterile and non-sterile experiments, effects of sterilisation on the soil matrix should be minimal. The objective of this study was to investigate the efficiencies of different sterilisation techniques and the impact of the sterilisation on sorption and NER formation in soil. In this study, experiments in accordance with OECD 307 and OECD 106 guidelines were performed with two soils covering wide range of soil characteristics and treated with the three sterilisation techniques autoclaving, gamma(γ)-radiation and adding 1% (w/w) sodium azide. As a test item, 14C-labelled phenanthrene and bromoxynil was used for OECD 307 test, whereas non-labelled phenanthrene and atrazine was used for OECD 106. The sterilisation efficiencies were investigated using traditional viable plate count and molecular approaches (RNA extraction method). The results suggest that none of the tested techniques resulted in completely sterilised soil with autoclaving being the most efficient technique. Adding sodium azide led to most inefficient sterilisation and a significant increase (0.56 units) in soil pH. OECD 307 results showed differences in NER formation of the test chemicals, especially for soil poisoning and γ-radiation, which could be due to inefficient sterilisation and/or change in soil physico-chemical properties. OECD 106 results suggest that none of the sterilisation techniques considerably affected sorption behaviour of the test chemicals. Based on our results, we recommend autoclaving as most suitable sterilisation technique.

Plastic in the air?! - Spider webs as spatial and temporal mirror for microplastics including tire wear particles in urban air.

Studies concerning quantities of microplastics (MP) including tire wear particles (TWP) contamination in air samples are scarce. Spider webs have been suggested as a cheap and easily accessible biomonitor particularly for inorganic contaminates. Here, we emphasize the potential of spider webs to gain insights in the spatial and temporal trends of MP in urban air. The samples, collected in a mid-sized German city, were processed with Fentons reagent and measured using pyrolysis-gas chromatography-mass spectrometry for specific, polymer related indicator compounds. All samples contained TWP and other MP. The latter are detected and quantified as pyrolysis products of a polymer backbone. The results were expressed as clusters (prefix "C"). Determined polymer contaminations ranged from 11.4 µg/mg to 108 µg/mg spider web sample. The dominant polymer was C-PET (Ø 36.0% of total MP) derived most likely from textile fibers. Additionally, there was evidence for traffic-related contaminations. In particular car tire tread (Ø 40.8% of total MP) and ⁎C-PVC (Ø 12.0% of total MP) were found, with the latter presumably originating from paint used for road markings. Truck tire tread, C-PE, C-PP, C-PS, C-PMMA, and C-PC were also frequently found, but in much lower abundance (Ø <6.4% of total MP). Differences in contamination levels could be plausibly related to the sampling locations.