A review of the distribution of particulate trace elements in urban terrestrial environments and its application to considerations of risk

We review the evolution, state of the art and future lines of research on the sources, transport pathways, and sinks of particulate trace elements in urban terrestrial environments to include the atmosphere, soils, and street and indoor dusts. Such studies reveal reductions in the emissions of some elements of historical concern such as Pb, with interest consequently focusing on other toxic trace elements such as As, Cd, Hg, Zn, and Cu. While establishment of levels of these elements is important in assessing the potential impacts of human society on the urban environment, it is also necessary to apply this knowledge in conjunction with information on the toxicity of those trace elements and the degree of exposure of human receptors to an assessment of whether such contamination represents a real risk to the city’s inhabitants and therefore how this risk can be addressed

Soil enzymatic response to addition of municipal solid-waste compost.

International audienceModifications of soil microbiological activity by the addition of municipal solid-waste compost were studied in laboratory incubations. Three composts were compared, one lumbricompost and two classical composts with different maturation times. Organic C mineralization and nine enzyme activities (dehydrogenase, peroxidase, cellulase, beta-glucosidase, beta-galactosidase, N-acetyl-beta-glucosaminidase, protease, amidase, and urease) were determined in the composts and the amended soil. Initial enzyme activities varied in the soil according to the sampling date (winter or summer) and were greater in the composts than in the soil, except for urease. Generally, the youngest compost exhibited greater activity than the oldest one. In the amended soil, the composts did not increase enzyme activity in an additive way. Dehydrogenase, the only strictly endocellular enzyme, was the only one for which the activity in the amended soil increased significantly in proportion to the addition of compost. During the incubations, C mineralization and dehydrogenase activity were significantly correlated, indicating that dehydrogenase was a reliable indicator of global microbial activity. Peroxidase activity in the soil remained constant, but increased in the composts and amended soil. Addition of the oldest compost had no effect on the activity of the C cycle enzymes, but the youngest compost increased creased soil activity at the higher application rate. Enzymes of the N cycle were stimulated by all compost amendments, but the increase was only transient for amidase and urease. Lumbricomposting had no marked effect on compost enzyme activity, either before or during the incubation

Effect of organic amendment on soil fertility and plant nutrients in a post-fire Mediterranean ecosystem

International audienceBackgrounds and aims In Mediterranean frequentlyburnt areas, the decrease of soil fertility leads to regressivevegetation dynamics. Organic amendments couldhelp to accelerate post-fire ecosystem resilience, byimproving soil properties and plant nutrition. This studywas conducted to assess the potential of a compostedbiosolid to restore an early post-fire shrubland.Methods About 50Mg.ha−1 of fresh co-composted sewagesludge and green wastes were surface applied7 months after fire on a silty-clayey soil. We monitoredover a 2-year period organic matter and nutrient transfersto soil, nutrient responses of dominant plant species,and ecosystem contamination by potentially toxic traceelements.Results Over the experimental survey, compost rapidlyand durably improved soil P2O5,MgO and K2O content,and temporarily increased N-(NO3− + NO2−) content.Plant nutrition was improved more or less durably dependingspecies. The most positive compost effect wason plant and soil phosphorus content. Plant nutrientstorage was not improved 2 years after amendment,suggesting luxury consumption. No contamination bytrace elements was detected in soil and plant.Conclusions The use of compost after fire could helpfor rapidly restoring soil fertility and improving plantnutrition. The increase of soil nutrient pools afteramendment emphazised the diversity of plant nutritionaltraits. Eutrophication risk could occur from high compostand soil P2O5 content