RESUMEN
In recent years increasing attention has been given to the potential use of contaminated lands for biofuel production, because these degraded soils cannot be used for food production. To establish these crops in Mediterranean contaminated areas, where the soil quality is usually very poor, the addition of soil amendments might be necessary to improve soil productivity. In addition, the use of crops with low water demands, adapted to these particular conditions of climate and soil contamination, is a key requirement. We studied the development of Cynara cardunculus and Silybum mariamun crops (both suitable for the production of biomass for biofuel uses under a Mediterranean climate) in trace element contaminated soils under field conditions. To our knowledge, this is the first such work under these particular experimental conditions (soil contamination and field trial). Soil physical (hydraulic), chemical, and biochemical properties were monitored for one year in experimental plots, where we tested the effects of the addition of two different amendments (sugar lime and biosolid compost) on soil functioning and crop productivity. Seed germination and plant biomass production were low, although amendment addition improved both parameters. The chemical and biological indicators (enzyme activities, PLFA profiles, and soil respiration) tended to be slightly improved by the amendments, especially sugar lime. The hydraulic properties of the soil in the experimental area were very deficient, and the effect of the amendments was not enough to improve them; this was probably the main cause of the general low productivity of these rain-fed crops, as water infiltrated poorly through the root zone. To improve crop productivity under these soil conditions, certain aspects could be improved: higher doses of amendments should be applied and deeper tillage of the soil after amendment addition should be performed to facilitate water infiltration.
Asunto(s)
Contaminantes del Suelo , Oligoelementos , Biomasa , Productos Agrícolas , SueloRESUMEN
The long-term influence of a mine spill in soil was studied 12 years after the Aznalcóllar accident. Soils where the pyritic sludge was not removed, a fenced plot established for research purposes (2000 m(2)) and soils where the process of remediation was accomplished successfully were sampled and studied in detail. Soils were characterized at different depths, down to 100 cm depth, determining chemical parameters and total concentrations of major and trace elements. Moreover plants colonizing remediated (RE) and non remediated (NRE) soils were also analysed attending their potential risk for herbivores. Strong acidification was observed in the NRE soil except in surface (0-10 cm). The progressive colonization of natural vegetation, more than 90% of the fenced plot covered by plants, could facilitate this increased pH values in the top soil (pH 6). In the NRE soil, the successive oxidation and hydrolysis of sulphide in the deposited sludge on the surface after the accident resulted in a re-dissolution of the most mobile element (Cd, Cu and Zn) and a penetration to deeper layers. Trace element concentrations in plants growing in the NRE soil showed normal contents for higher plants and tolerable for livestock. Nitrogen and mineral nutrients were of the same order in both soils, and also normal for high plants and adequate for animal nutrition. Despite of the natural remediation of the NRE soil, results demonstrate that the remediation tasks carried out in all the area, the Guadiamar Green Corridor at present, were necessary to avoid the leaching of the most mobile elements and minimize the risk of contamination of groundwater sources, many of them close to the Doñana National Park.