Groundwater quality affected by the pyrite ash waste and fertilizers in Valea Calugareasca, Romania

The aim of the study was to assess the groundwater quality in a rural area affected by
the abandoned pyrite ash waste dumps. The abundance of major ions in groundwater depends
largely on the nature of the rocks, climatic conditions, and mobility. To evaluate geochemical
processes, 30 groundwater samples collected from Valea Calugareasca, Prahova County, Romania,
were analyzed for the major anions (NO3− , SO42− , Cl− , HCO3− , and F− ) and cations (Ca2+, Mg2+,
Na+, and K+), which are naturally highly variable due to climatic and geographical location conditions.
Ca2+, Na+, Mg2+, and K+ varied between 118 and 275 mg/L, 32 and 160 mg/L, 12.2 and 78.4 mg/L,
and 0.21 and 4.48 mg/L, respectively. NO3− levels exceeding the World Health Organization (WHO)
limit of 50 mg/L were identified in 17% of the groundwater samples, mainly as result of fertilizers
applied to agricultural activities. The hydrogeochemical study identified dolomite dissolution and
halite precipitation as natural sources of ions as well as the presence of pyrite as a source of SO42−
ions in 60% of the samples. The sulfate content varied between 125 and 262 mg/L. Bicarbonate and
chloride concentrations varied between 202 and 530 mg/L and 21 and 212 mg/L. The saturation
index indicates the contribution of Ca2+ ions in the groundwater samples came from some processes
of dissolving rocks such as aragonites (values between 1.27 and 2.69) and calcites (values between
1.43 and 2.82). Negative halite values indicated that salt accumulation results from precipitation
processes. Only 10% of the analyzed groundwater samples were suitable for human consumption, the
samples being situated on the hill, far away from the pyrite ash waste dumps and agricultural land.