A case study of complex pollution characteristics associated with suspended particulate matter and heavy metals

Suspended particulate matter (SPM) plays a pivotal role in the transport and separation of heavy metals (HMs) in river systems and has a significant impact on water quality and ecosystem integrity. This study examined the seasonal dynamics of total suspended solids (TSS), SPM particle size distribution, and the separation of HMs (Cd, Pb, Cr, Zn, Cu, Mn, Fe) between dissolved and particulate phases in the Styr River (Ukraine) throughout 2024. Analytical methods included gravimetric analysis, inductively coupled plasma optical emission spectrometry (ICP-OES), and laser-based particle sizing. The TSS concentrations and median floc size (D50) were substantially elevated during the warm season, enhancing sorption of metals onto SPM, especially for Fe, Cd, Pb, and Mn (K_d > 3). In contrast, Zn, Cu, and Cr exhibited stronger preferences for the dissolved phase. Pearson correlation analysis revealed strong associations between TSS and particulate-bound metals during warmer periods. Seasonal variations in hydrological and biological parameters significantly influence the physicochemical behavior of SPM and the separation of HMs. This is important for assessing the contamination of surface water with both dissolved and particulate phases of HMs.