Appraisal of heavy metal pollution in alluvial aquifers. Study case on the protected area of Ronișoara Forest, Romania

Abstract

• Waters from protected area are rich in As, Ca and heavy metals (Pb, Al, Mn, Fe, Se). • Generally, the WQI scores indicate excellent, medium, and low quality. • HEI and HPI scores indicate three levels of pollution. • Na, Ca, Mg, Co, Cd are mainly transfer from mud to the alluvial aquifers. • This research is a reference for aquifers protection in a protected area. This study was carried out in a protected area (Ronișoara Forest) in Romania. A combined approach of quality assessment of alluvial aquifers is employed, by determining the chemistry and applying two pollution indices based on heavy metals concentrations (HPI- Heavy metal Pollution Index and HEI- Heavy metal Evaluation Index), a quality assessment index based on specific physico-chemical indicators (WQI- the Water Quality Index) and different plots (Durov, Schoeller and TIS-Total Ion Salinity). The study revealed that waters are rich in manganese, calcium, sodium, sulphate, ammonium, manganese, iron, total dissolved solids, dominated by bicarbonates. The chemicals’ sources are related to the water–rock interactions and to mine exploitation activities. Correlations were observed between the electrical conductivity and sulphate, total dissolved solids and sulphate, and total hardness and electrical conductivity. The results based on the levels of heavy metals pollution indicate that the studied water samples are characterized by low, medium and high pollution levels, with values ranging between 0.40 and 234. The WQI scores vary from 8.6 to 54, generally indicating excellent and medium quality, and low quality for two samples. This research, one of the first in the area, can serve as a reference for the protection of natural water resources and for the contamination control of alluvial aquifers in the protected area of Ronișoara Forest.