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The calibration of soil organic C (SOC) and hot water-extractable C (HWE-C) from visible and near-infrared soil reflectance spectra is hindered by the complex spectral interaction of soil chromophores that usually varies from one soil or soil type to another. The exploitation of spectral variables from spectroradiometer data is further affected by multicollinearity and noise. In this study, a set of soil samples (Fluvisols, Podzols, Cambisols and Chernozems; n = 48) representing a wide range of properties was analysed. Spectral readings with a fibre-optics visible to near-infrared instrument were used to estimate SOC and HWE-C contents by partial least squares regression (PLS). In addition to full-spectrum PLS, spectral feature selection techniques were applied with PLS (uninformative variable elimination, UVE-PLS, and a genetic algorithm, GA-PLS). On the basis of normalized spectra (mean centring + vector normalization), the order of prediction accuracy was GA-PLS ≫ UVE-PLS > PLS for SOC; for HWE-C, it was GA-PLS > UVE-PLS, PLS. With GA-PLS, acceptable cross-validated (cv) prediction accuracies were obtained for the complete dataset (SOC, , RPDcv = 2.42; HWE-Ccv, , RPDcv = 2.13). Splitting the soil data into two groups with different basic properties (Podzols compared with Fluvisols/Cambisols; n = 21 and n = 23, respectively) improved SOC predictions with GA-PLS distinctly (Podzols, , RPDcv = 3.14; Fluvisols/Cambisols, , RPDcv = 3.64). This demonstrates the importance of using stratified models for successful quantitative approaches after an initial rough screening. GA selection frequencies suggest that the spectral region over 1900 nm, and in particular the hydroxyl band at 2200 nm are of great importance for the spectral prediction of both SOC and HWE-C. [ABSTRACT FROM AUTHOR]

Background: The increasing production of nanoplastics and the fragmentation of microplastics into smaller particles suggest a plausible yet unclear hazard in the natural environment, such as soil. We investigated the short-term effects (28 days) of polystyrene nanoparticles (PS-NPs) on the activity and biomass of soil microbiota, and the functional diversity of soil enzymes at environmental relevant low levels in an incubation experiment.Results: Our results showed a significant decrease in microbial biomass in treatments of 100 and 1000 ng PS-NP g−1 DM throughout the incubation period. Dehydrogenase activity and activities of enzymes involved in N-(leucine-aminopeptidase), P-(alkaline-phosphatase), and C-(β-glucosidase and cellobiohydrolase) cycles in the soil were significantly reduced at day 28 suggesting a broad and detrimental impact of PS-NPs on soil microbiota and enzymes. Leucine-aminopeptidase and alkaline-phosphatase activities tended to decrease consistently, while β-glucosidase and cellobiohydrolase activities increased at high concentrations (e.g., PS-NP-1000) in the beginning of the incubation period, e.g., at day 1. On the other hand, basal respiration and metabolic quotient increased with increasing PS-NP application rate throughout the incubation period possibly due to increased cell death that caused substrate-induced respiration (cryptic growth).Conclusions: We herewith demonstrated for the first time the potential antimicrobial activity of PS-NPs in soil, and this may serve as an important resource in environmental risk assessment of PS-NPs in the soil environment. [ABSTRACT FROM AUTHOR]

The objective of the present work was to study the short-term stimulation of microbial and enzyme activity in mine soils by application of organic waste materials in lysimeter and mesocosm studies. The minesoils derived from tertiary and quaternary deposits were amelioratedwith brown coal filter ash (tertiary deposits) and lime (quaternary deposits). At the beginning of recultivation the soils were treated with varying amounts of sewage sludge, coal sludge, composted sewage sludge and compost to a depth of 30 cm. In the first 2 years after application of organic waste materials we found a very low level of microbial properties especially in the sandy materials from quaternary deposits but a significant increase in microbial respiration, substrateinduced respiration and enzyme activities like invertase and alkaline phosphatase with increasing application rates of sewage sludge, compost and sewage sludge mixed with coal sludge. This can be explained by an increase in organic matter and nutrient content of the soils and an improvement of soil physical properties such as water and nutrient retention capacity. Additionally it can be assumed, that constituents of the coal admixtures of tertiary deposits can be mineralised orconverted by the soil microorganisms. In the tertiary materials ameliorated with brown coal ash the highest amounts of microbial and enzyme activities were measured after application of nitrogen-rich sewagesludge or very high amounts of mature compost mainly consisting of green waste. Compared with sewage sludge the stimulating effects of composted sewage sludge were quite lower because of organic matter fragmentation and a reduced energy and nutrient supply to soil microorganisms. [ABSTRACT FROM AUTHOR]