Herbicide and nutrient monitoring in surface waters and groundwater of a paddy district in northern Italy.

Italy is the leading rice producer in Europe and the second in the Mediterranean basin (after Egypt), with most of the production concentrated in a large paddy area between the Lombardy and Piedmont regions (northern Italy). In this area, irrigation of rice was traditionally carried out by wet seeding and continuous flooding; in the last fifteen years, this technique has been gradually replaced by dry seeding followed by a delayed flooding (DFL) or by an alternation of flooding and dry periods (FTI), which are economically more advantageous. This study presents the results of an extensive monitoring campaign designed and carried out in 2021 in a representative paddy district of the Lomellina area (Pavia, northern Italy) to assess the impact of the actual rice cropping strategies on surface water and groundwater quality, with particular attention to two widely used herbicides (MCPA and clomazone) and to nutrient losses (e.g., N, P, K). Results show that MCPA and clomazone concentrations detected in surface water and groundwater are always below the RAC (Regulatory Acceptable Concentration) values. As to nutrients, they do not show significant trends along the season in surface water and groundwater: this may be due to the fact that nutrient sources are many. Concerning the concentrations, nitrates may pose a problem for the area, especially for groundwater. However, further studies would be needed to understand to which extent rice cropping can be considered the major source of contamination for water resources.