Groundwater potential risk of agricultural activity in Vercelli Plain, North Italy

As the increasing population and food consumption, more and more agriculture and natural resources are needed to keep the pace with the demands. To meet this gap, land expansion and land intensification are required, which consequently lead to problems like climate change, biodiversity loss and degradation of land soil and water bodies. Therefore, the principal challenge of agriculture expansion in the following decades, will be achieving an appropriate equilibrium between sufficient food and fiber production for the growing global population and meanwhile minimizing environmental cost. Agrochemicals can harm human health, as can pathogens, including antibiotic-resistant pathogens associated with certain animal test. Therefore, it is extremely urgent to develop a relative precise and cost effective method to evaluate the influence of agriculture activity on groundwater quality in regional areas. Thanks to the development of geographic information systems (GIS), which is ideally suited to the mapping and analyzing groundwater vulnerability factors over regions. The whole thesis deals with the relation between agrochemical application and potential risk of aquifer that beneath agricultural land use. In the first chapter, DRASTIC model and SINTACS model were used to determine the intrinsic vulnerability of the groundwater and the model output results were compared. Both of the two models showed that most of the Vercelli plain’s groundwater is at high to very high risk in terms of pollution potential. Moreover, the results of this chapter reveal that the pesticide contamination in groundwater is much serious than nitrate in the rice paddy field, which is the main agricultural land in the study area. In chapter 2, the water balance in the rice paddy was calculated on the base of measured data on a field scale in 6 treatments. Different agriculture treatments and irrigation management are the main factors influencing the infiltration rate. It was also found that the infiltration rate could be a negative value, assuming that the interaction between the flooded water of rice paddy and shallow aquifer could influence the infiltration rate. Based on the study of water balance in rice field, the fate a transport of agrochemical can be simulated. RICEWQ model and the developed N mass balance model both considered little about the risk of groundwater by agrochemicals, although the detected agrochemicals concentrations in groundwater were used to verify the simulation result. The water type of the shallow alluvial aquifer in Vercelli Plain mainly belonged to Mg-Ca-HCO3. Seeing the trend over time, no obvious upward or downward trend of pesticide concentration was observed in shallow aquifers. The change of agrochemicals concentration in groundwater coincided with the change of the groundwater table. Related to the relative low health risk based on reported toxicity study, the harm to human health is slight. However, the study only considers the exposure routs from groundwater, the routes through air and soil have not been estimated here.