The use of factor analysis to distinguish the influence of parent material, mining and agriculture on groundwater composition in the Strumica valley, Macedonia

Determination of groundwater chemistry in the Strumica valley was essential given its widespread use for irrigation in the agricultural industry. 224 samples were collected form boreholes forming the dataset for the study. The groundwater chemical composition was examined for selected analytes: As, Sr, Mn, Ni, Cu, Zn, Mo, Ba, Pb, Na, Mg, Al, K, Ca, Ti, Li, Cr, Fe, U, CaCO3, Cl-, NO3-, NH4+, SO42- and PO43-. The source and internal correlations of the analytes were subjected to multivariate statistical analyses (factor analyses), which yielded 7 factors. Geochemical maps of these factors were generated using the kriging method. The groundwater chemistry was predominantly controlled by the geology with some anthropogenic influence due to agriculture and mining, affecting the concentrations and spatial distribution of arsenic, phosphates, sulphates, nitrates and some metals (copper, iron, chromium, lead, nickel, zinc). Mining of copper/gold (molybdenum) in the region of Ilovica increased the concentration of Al, Cu, Pb, Cr, NO3-, Ni, Zn, Na, K, Li and PO43- in groundwater, but only at a local level.