Suspended Particulate Matter—A Source or Sink for Chemical Mixtures of Organic Micropollutants in a Small River under Baseflow Conditions?

Abstract

Suspended particulate matter (SPM) plays an important role in the fate of organic micropollutants in rivers during rain events, when sediments are remobilized and turbid runoff components enter the rivers. Under baseflow conditions, the SPM concentration is low and the contribution of SPM-bound contaminants to the overall risk of organic contaminants in rivers is assumed to be negligible. To challenge this assumption, we explored if SPM may act as a source or sink for all or specific groups of organic chemicals in a small river. The concentrations of over 600 contaminants and the mixture effects stemming from all chemicals in in vitro bioassays were measured for river water, SPM, and the surface sediment after solid-phase extraction or exhaustive solvent extraction. The bioavailable fractions of chemicals and mixture effects were estimated after passive equilibrium sampling of enriched SPM slurries and sediments in the lab. Dissolved compounds dominated the total chemical burden in the water column (water plus SPM) of the river, whereas SPM-bound chemicals contributed up to 46% of the effect burden even if the SPM concentration in rivers was merely 1 mg/L. The equilibrium between water and SPM was still not reached under low-flow conditions with SPM as a source of water contamination. The ratios of SPM-associated to sediment-associated neutral and hydrophobic chemicals as well as the ratios of the mixture effects expressed as bioanalytical equivalent concentrations were close to 1, suggesting that the surface sediment can be used as a proxy for SPM under baseflow conditions when the sampling of a large amount of water to obtain sufficient SPM cannot be realized.

Trace organic contaminants within solid matrices along an anthropized watercourse: Organo-mineral controls on their spatial distribution

“…Conversely, SPM samples were devoid of coarse particles (even if grainsize analyses were not performed on these samples) and more organic than sediment samples, and were therefore less heterogeneous along the water course. Some authors assume that the level of SPM contamination may be, in certain conditions, in equilibrium with that of the dissolved phase (Niu et al, 2021), which means that the solid/water partition coefficient (i.e. Kd) can be used in order to link aqueous and solid contamination.…”

“…TrOCs, which are rather hydrophilic, are mostly studied in the dissolved phase, even if their occurrences in solid matrices as sediments (Kerrigan et al, 2018;Thiebault et al, 2021a) and suspended particulate matter (SPM) are increasingly investigated (Ledieu et al, 2021;Niu et al, 2021). The distribution of contaminants between solid and dissolved phases differs according to the properties of both the solid phase and the TrOC (Kodešová et al, 2015;Nunes et al, 2019).…”

Exploring the partitioning of hydrophobic organic compounds between water, suspended particulate matter and diverse fish species in a German river ecosystem

“…In this context, an alternative, robust and cost-efficient monitoring approach free of ethical concerns is needed as a proxy to offer a less biased and more generic and robust estimation of the internal exposure of fish. Passive sampling devices (PSDs) applied in the different abiotic compartments surrounding the fish, such as sediment [14][15][16], SPM [17,18], and water [19], have shown potential for this purpose, when the concentrations in the passive sampling polymer are translated into equilibrium partitioning concentrations in model lipids, C Lip⇆Medium . In general, PSDs can simulate the uptake of HOCs via bioconcentration into the lipid phase of low TL organisms [20].…”

Mutagenicity of the Danube River: The contribution of liquid phase and particulate suspended matter

“…Different mutagenic compounds can be present in the water and, depending on their hydrophobicity, they can stay in the liquid phase (LP) or can be adsorbed to the suspended particulate matter (SPM; Vincent‐Hubert et al, 2012). Important mutagenic contaminants such as polycyclic aromatic hydrocarbons (PAH) were found adsorbed to SPM (Niu et al, 2021). Therefore, to evaluate the mutagenicity of water extracts it is important to consider both phases (LP and SPM) and to use strains with specific sensitivities to allow the detection of different classes of compounds.…”

“…Vincent -Hubert et al, 2012). Important mutagenic contaminants such as polycyclic aromatic hydrocarbons (PAH) were found adsorbed to SPM (Niu et al, 2021). Therefore, to evaluate the mutagenicity of water extracts it is important to consider both phases (LP and SPM)…”