Temporal variability of nitrate concentration in a schist aquifer and transfer to surface waters

摘要: Nitrate concentrations monitored for 2.5 a in the stream water and groundwater of small catchment, 86.5% which is devoted to intensive agriculture, show temporal variations with maximum during winter (as much as 200 mg l−1 100 water) minimum at end summer/beginning autumn. Variations were also observed shallow after rainfall. The processes involved explain these variations, determined mainly from NO3− Cl−, SO42−, piezometric streamflow data, are: (a) variability relative contributions by upward fluxes deeper which, demonstrated previously, denitrified result reaction pyrite. (b) Denitrification summer organic matter acting electron donor. (c) Dilution rain water. both depend on amount precipitation, an increased contribution deep dry periods. concentration several metres below table are related preferential rapid movement NO3−-polluted through fractures large fissures, has been estimated 1 m day−1. pollution because interaction pyrite, increases net chemical weathering rate values exceeding world average.