The influence of pulsed redox conditions on soil phosphorus

The effects of eleven pulsed reduction-oxidation cycles (20 and 2 days respectively) on soil phosphorus (P) dynamics are compared for 12 soils having contrasting properties and overfertilised with respect to P. Incubation conditions simulated transient waterlogging of the soil profile and involved repeated sampling and analysis of both the solution and solid phase P forms. An initial increase in P concentration occurred upto and including the fourth full cycle was followed by a sharp decline in concentration for all but one soil. Accompanying changes in the main extractable forms of P, which appeared to be cumulative, could be summarised as a general decline in the organic P fraction and an overall increase in amorphous associated inorganic forms of P. The fact that up to 60% of the total soil P was demonstrated to change its sensitivity for a particular extractant suggests that these operationally defined P forms can experience substantial transformations. There was also a suggestion that certain changes in P forms may not be reversible. While the laboratory conditions represent an extreme situation changes in timing and frequency of intense precipitation events, as predicted in many climate change scenarios, may increase the risk of episodic soil waterlogging. The potential onset of reducing conditions even for periods of less than twenty days will influence soil P dynamics and short-term bioavailable P. Various mechanisms are involved but the robustness of sequential extraction procedures and general soil test methods (e.g. Olsen) for quantifying and reliably distinguishing specific soil P forms/associations are questioned

Metal availability and bio-accessibility in water-logged soils: in vitro experiments

Presentado al congreso European Geosciences Union. General Assembly, 2010. 2-7 mayo en Viena, Austria.Reducing conditions of submerged soils were simulated in vitro by keeping various soil samples for various times of reaction (between 1 and 15 days) in sealed flasks and N2 atmosphere under an aqueous solution, 0.01 M CaCl2 containing 1 g/l glucose. Surface samples of soils from urban green areas of Ljubljana (LJU), Torino (TOR) and Sevilla, were chosen. In the latter case, two samples of the same soil were included, before (SE-0) and after (SE-8) receiving a composted biosolid (two yearly doses of 80000 kg/ha) obtained from sewage sludge, often used as amendment by the Parks & Gardens Service of the local Government. A fifth soil (QUE) was chosen from the area affected by an accident where 2 million m3 of metal-rich mine tailings were spilled over the Guadiamar river (SW Spain) and its riparian areas. This highly polluted soil was included for comparison. Values of Eh, pH and several metal concentrations were determined in the solution after each time, and metal availability and bio-accessibility were estimated in the soils after treatment. The metals studied were Fe, Mn and some of those called ‘urban’ metals, namely Cu, Pb and Zn.Peer reviewe

Il suolo dentro e intorno alle città

Quando una città occupa un suolo tutto cambia: cambia il funzionamento, cambiano le funzioni del suolo. Il ruolo principale diventa quello di sorreggere gli edifici e le infrastrutture e, in questo, il suolo riesce solitamente bene. Così bene che ci si comincia a chiedere se l’espansione urbana non sia dannosa in termini ecologici cioè se non sottragga una parte troppo rilevante alle altre funzioni del suolo. Il problema del consumo di suolo si delinea dunque come un danno ecologico complessivo, una perdita quasi irrimediabile di servizi ecosistemici. Naturalmente la lotta al consumo di suolo deve essere condotta anche con strumenti normativi ed economici che incentivino ristrutturazioni e ricostruzioni, disincentivando l’utilizzo di terreni liberi

Metal release under anaerobic conditions of urban soils of four European cities

Urban soil contamination may represent an environmental threat in view of their proximity to humans. The ecological homogenization of urban areas has been postulated, and as the sources of pollution are the same in most European cities, it is possible that soil contamination is another factor of convergence. The current climate change with consequent increase of extreme rain events may affect the mobility of potentially toxic elements (PTE) thus increasing the risks. If the soil is submerged, Eh decreases and causes the solubilization of Fe and Mn oxides, which are important carriers of PTE. We compared the release of Cu, Pb, and Zn from 48 soils of four cities (namely Glasgow, Ljubljana, Sevilla, and Torino) when submerged for up to 30 days. A decrease of the redox potential was observed in all soils after a few days and an increase of Mn and then Fe in solution. Cu, Pb, and Zn were consequently released to the solution according to the general soil contamination. Despite the marked differences in soil properties, the reaction to anaerobiosis appeared to be similar in all samples indicating that waterlogging of urban soil contaminated with PTE may pose a serious environmental risk and substantiating the hypothesis of ecological convergence

Heavy metal load and effects on biochemical properties in urban soils of a medium-sized city, Ancona, Italy

none6noUrban soils are often mixed with extraneous materials and show a high spatial variability that determine great differences from their agricultural or natural counterparts. The soils of 18 localities of a medium-sized city (Ancona, Italy) were analysed for their main physicochemical and biological properties, and for chromium (Cr), copper (Cu), cobalt (Co), lead (Pb), nickel (Ni), zinc (Zn), and mercury (Hg) total content, distribution among particle-size fractions, and extractability. Because of the absence of thresholds defining a hot spot for heavy metal pollution in urban soils, we defined a “threshold of attention” (ToA) for each heavy metal aiming to bring out hot spot soils where it is more impellent to intervene to mitigate or avoid potential environmental concerns. In several city locations, the soil displayed sub-alkaline pH, large contents of clay-size particles, and higher TOC, total N, and available P with respect to the surrounding rural areas, joined with high contents of total heavy metals, but low availability. The C biomass, basal respiration, qCO2, and enzyme activities were compared to that detected in the near rural soils, and results suggested that heavy metals content has not substantially compromised the soil ecological services. We conclude that ToA can be considered as a valuable tool to highlight soil hot spots especially for cities with a long material history and, for a proper risk assessment in urban soils, we suggest considering the content of available heavy metals (rather than the total content) and soil functions.openSerrani D.; Ajmone-Marsan F.; Corti G.; Cocco S.; Cardelli V.; Adamo P.Serrani, D.; Ajmone-Marsan, F.; Corti, G.; Cocco, S.; Cardelli, V.; Adamo, P