What can grasshoppers reveal about metal pollution? A study of nickel smelter in Slovakia

Abstract

Three-year biomonitoring compared the accumulation of 51 elements in grasshoppers (Euchorthippus declivus) from the vicinity of a former nickel smelter dump and two control sites. It was a positive finding that some major elements in the dump (Ni, Cr and Co, max. content 4.4, 9.4 and 0.24 mu g/g dry body weight, respectively) decreased by 50-80 % in grasshoppers between 2021 and 2023. The concentrations of PM 10 and PM 2.5 also declined over time, potentially reflecting a reduction in the abovementioned elements. Although some minor elements (Pb, Sn, Cd, As, U, Th, and rare earth elements) did not exhibit a time-dependent decline, their concentrations remained significantly lower compared to other industrially impacted regions worldwide. Among herbs, the highest accumulation of elements was typically found in Convolvulus arvensis (Ni, Cr, Se, U, Th, Re) and/or in Setaria viridis (Cd, W, Sn, As). Correlation analyses revealed a positive relationship between elemental concentrations in herbs and grasshopper bodies, particularly in C. arvensis, suggesting its potential as an effective bioindicator of elemental pollution. The bioaccumulation factor (BAF, ratio of elemental content in grasshoppers to that in herbs) varied depending on plant species and locality: grasshoppers revealed indication (BAF similar to 1, Fe, Ni, Co, and Mo), accumulation (BAF >1, Cu, Cd, Dy, U, Er, Yb) and exclusion (BAF <1, Cr, Mg, Rb, Sn, Re) values. Hierarchical cluster (HCA) and principal component analyses (PCA) confirmed a clear separation of the dump from the control sites based on the specific profile of the elements.