Evaluation of Heavy Metal Pollution Index (HPI) and Metal Index (MI) of the groundwater in the Mesta River Basin, SW Bulgaria

Abstract

Ground waters may undergo a process of contamination in various ways, but the presence and amount of heavy metals in them can be indicative of their purity and usage. Apart from that, the heavy metals are among the most widely spread pollutants in nature, and their presence in groundwater indicates the existence of natural or anthropogenic sources of contamination. Ground waters polluted with heavy metals can also be very toxic and harmful to human health, and very damaging to the environment as well. In this article, the concentrations of eight toxic heavy metals (Fe, Mn, Cu, Al, Ni, Pb, Zn, Cr) were analyzed in the ground waters of the Mesta River Basin. A number of data for the concentrations of those heavy metals were used in order to calculate the following two indices describing groundwater purity: the Heavy Metal Pollution Index (HPI), and the Metal Index (MI). Both indices describe the overall quality of groundwater in direct relationship to the sum total of heavy metal concentrations. On one hand, minimal concentrations of heavy metals are necessary for the faultless functioning of organisms and indispensable to various biochemical processes, but on the other hand, in high concentrations, they might lead to dysfunctions in the cells of healthy organisms, and problems within their enzyme system. And these effects are entirely dependent upon the nature of the heavy metals involved. The research carried out so far shows that, according to HPI, about 65% of the shallow ground waters in the Mesta River Basin can be classified as being of excellent quality. The values obtained for the HPI are in the range of 3 to 64 (id est under the critical value of 100), or the groundwater is not contaminated with heavy metals. The MI varies within the range of 0.3 to 2.6, and therefore the groundwater from the zones with active water exchange can be characterized as being of slight to medium poor quality (41%), and the groundwater within Class II (or classified as pure with values of MI between 0.3 and 1.0) comprise approximately 59% of the overall catchment area.

Spatial and temporal variations of groundwater contribution to streamflow in the Mesta River Basin

“…A detailed analysis of the hydrogeological conditions in the Mesta River Basin for groundwater resources assessment is found in the Master Plans (2000). In recent years, hydrogeological descriptions of the study area have been made in view of the formation of the chemical composition of shallow groundwater (Vasileva and Toteva, 2019;Vasileva, 2020;Vasileva and Sholev, 2021;Mihaylova et al, 2022Mihaylova et al, , 2023. The hydrogeological conditions in the border areas of Bulgaria and Greece, along with assessment of the probability of transboundary transfer of groundwater, are presented in Spasov et al (2017).…”

Geological factors for the formation of the chemical composition of groundwater in the catchment area of the Mesta river

“…Този район е избран като пилотен във връзка с работата по Националната научна програма "Опазване на околната среда и намаляване на риска от неблагоприятни явления и природни бедствия". Досега съществуват данни за регионалните закономерности на изменение на показатели, характеризиращи химичния състав на подземните води в България (Stanchev, 1961(Stanchev, , 1962Kehaiov, 1967Kehaiov, , 1968Kehaiov, , 1978Kehaiov, , 1982Kehaiov, , 1984Antonov, Danchev, 1980;Kehaiov et al, 2002;Benderev et al, 2018Benderev et al, , 2019Vasileva, 2020a), включително и водосбора на р. Места, както и някои изследвания, насочени само към конкретния район (Vasileva, Toteva, 2019;Vasileva, 2020b;Mihaylova et al, 2022;Vasileva, Sholev, 2021). Интерес представляват и някои разработки, свързани с качествата на водите на р. Места (Georgieva et al, 2018, Yotova et al, 2021.…”

Geological and tectonic preconditions for hydraulic heterogeneity of the rocks in the area of the Gotse Delchev valley

“…Groundwater formed in different reservoirs is characterized by different chemical composition. Studies of heavy metal pollution in the Mesta River valley were done by defining of Heavy Metal Pollution Index (HPI), and the Metal Index (MI) (Vasileva, Toteva, 2019;Vasileva, 2020;Vasileva, Sholev, 2021).…”