Contamination of soil and groundwater by nitrate: a new methodologic approach to the identification of source through biomolecular analyses

Currently, there is not yet defined a microbiologically-based method for identifying sources of nitrate contamination. This work aims at identifying a standard methodology based on biomolecular analyses, which can reveal the origin of the contamination. In the DEMETRA DSS project, techniques and activities for monitoring agricultural soils and groundwater were developed for the identification of eventual correlations between the soil and the groundwater and for bringing up possible nitrate contamination from agricultural source. A specific method of sampling and analysis, both chemical and microbiological, of the two matrices has been fully defined, in order to discriminate whether any nitrate present in the water originates from an incorrect agricultural practice or comes from upstream areas. Starting from nitrate pollution prone areas and the characterization of the territory, 77 sites, located throughout the Apulian territory in six monitoring sub-areas, were identified and sampled for chemical analyses, relative to the nitrogen line, and biomolecular analyses. Specific REAL TIME-PCR protocols were developed and applied to water and soil samples, and the analysis focused on microorganisms involved in nitrification and denitrification activities. The application of real time techniques allowed the identification and quantification of specific bacterial species linked to the different matrices at the different sites, thus making it possible to determine the microbial activity linked to the nitrogen cycle