A simple methodology for the evaluation of groundwater pollution risks.

Groundwater represents a very significant source of fresh water for irrigation and drinking purposes and therefore preserving the availability and quality of this resource is extremely important. A first assessment of the amount of pollutants that can be exported to groundwater via soil drainage can be made by a) measuring the amount of contaminants present in the soil solution at the bottom of the soil after a prolonged simulated rainfall event, and b) estimating the amount of drainage water passing the soil bottom during a period of time long enough to include sufficient instances of both, wet and dry episodes inherent to the local climate. Drainage water was estimated by means of a simple infiltration model ("bucket model") which computes on a daily basis the inputs and outputs of soil water through rainfall and evapotranspiration generated by a stochastic model of the local climate along a period of 50-100 years. The methodology was applied in the Guadiamar valley after the toxic spill of a pyrite mine in Aznalcóllar (Spain). The results show that Zn is the dominant contaminant at the site with a 1.2 g m(-2)year(-1) contribution to groundwater. The presence of a gravel rich horizon below 50 cm depth reveals an increase in drainage and the threat to groundwater.

Guidelines for improving organic carbon recovery by the wet oxidation method.

The study of soil degradation processes as well as the monitoring of environmental quality often yields large sample batches in which organic carbon is the key property to be determined. A description is given for a rapid method to analyse organic carbon by wet oxidation; the reaction is carried out with 3ml K(2)Cr(2)O(7) and 6ml H(2)SO(4) in small vials, and Cr(3+) resulting from organic C oxidation is determined by spectrophotometry. No special equipment is needed and handling is reduced to a minimum, enabling over 100 samples per day to be analysed. There is one important detail in the operation protocol: the vials are placed inside an insulator block during oxidation. Heat insulation retards the cooling of vials, which results in a high organic C recovery (over 0.90). The improved method is feasible, simple, and easy to perform. Reproducibility was lower than 10% and recoveries from certified reference materials were about 90%. The simplified method is recommended for widespread organic C content sampling.