Distribution of heavy metals and minerals in the various size fractions of soil from Copșa Mică, România
G. Damian, C. Lanzerstorfer, F. Damian, G. Iepore - Distribution of heavy metals and minerals in the various size fractions of soil from Copșa Mică, România - WATER, AIR AND SOIL POLLUTION, Vol. 229, No. 1, 2018, pp. 1-14
The Copşa Mică area is one of the most polluted anthropic sites in Romania. After the end of the industrial activity there it became one of the critical areas on the Romanian territory. Heavy metal content exceeds the alert threshold for sensitive ecosystems, approaching the intervention threshold, and for lead the maximum values exceed the intervention threshold for less sensitive ecosystems. Because higher heavy metal concentrations occur in finer fractions, this research focuses on the size fraction <500μm. A two kilogram soil sample was sieved on the 500µm sieve and was air classified into size fractions down to the low micrometer range. The size fraction’s composition was investigated by ICP-OES, IC, XRD and FTIR spectrometry. Approximately 80% and 62% of the material was smaller than 2mm and <500µm, respectively. The predominant size fraction had a mass median diameter of approximately 75μm. The smallest size fraction with a mass median diameter of 2.2μm had a share of 3.6% and contained the highest amount of heavy metals. The concentrations of Pb, Zn. Cd, Cu, Sb and As exceeded the standards. The respective concentrations were 26,900mg/kg, 27,600mg/kg, 415mg/kg, 2,130mg/kg, 466mg/kg and 915mg/kg. In the coarser size fractions 5, 4, 3 the predominant minerals were quartz and alkaline feldspar, while in the finer size fractions 1, 2 the clay minerals and total carbon were predominant. The good correlation between heavy metals and TC suggests that these metals are likely to be strongly retained by black carbon in the top soil and can be an indicator of the level of heavy metal pollution. Illites and montmorillonites in the fine fraction composition retain heavy metals due to the high levels of cation exchange capacity. Black carbon accumulated in soil acts as a heavy metal adsorbent due to its porosity and high specific surface area.