Transfer of Metal(loid)s in a Small Vineyard Catchment: Contribution of Dissolved and Particulate Fractions in River for Contrasted Hydrological Conditions

The use of inorganic pesticides in viticulture leads to the accumulation of metal(loid)s in soils which can be transferred to the hydro-systems (groundwater and surface water) via several processes. This study reports on the occurrence and behavior of metal(loid)s (Li, Al, Cr, Ni, Cu, Zn, As, Sr, and Ba), with a particular focus on Cu, Zn, and As, in a small stream draining a vineyard catchment. Base flow and flood events were monitored in order to assess the spatiotemporal variability of metal(loid) concentrations and to evaluate the contribution of the particulate fraction to the transfer of metal(loid)s according to the hydrological conditions. Results show that very different patterns of metal(loid)s were observed in the Morcille River according to the hydrological conditions. In base flow conditions, Cu and As were mainly transported in dissolved phase, which contributed to more than 70 and 80%, respectively, of the total load during this period. On the contrary, during base flow, Zn was mainly transported as associated to particles (90%). During the two storm events monitored, the particulate fraction was dominant, as its represented around 74-80%, 97%, and 50-70% of the total Cu, Zn, and As load in the river, respectively. Thus, despite a weaker affinity for particles during floods (decrease of particulate content during floods), metal(loid)s were mainly brought as particles, given that high amounts of suspended particulate matter (up to 2031 mg/L) were mobilized. Finally, comprehensive fluxes estimations confirmed that floods were responsible for more than 90% of the total Cu, Zn and 75% for As load transiting in the Morcille River in August within a very short period of time (less than 17%).