New publication in Water Research on reproducible model freshwater particulate matter analogues


Aquatic fate models and risk assessment require information on contaminants' affinity for riverine suspended particulate matter (SPM). Particulate contaminants, such as engineered nanomaterials, incidental nanoparticles, micro- or nanoplastics, can not be assessed employing classical partition or sorption coefficients, since the underlying assumption of chemical equilibrium is only valid for dissolved contaminants. Particle interactions with SPM are governed by physicochemical forces between the respective surfaces. To allow reproducible testing, a suitable standard SPM material is required. We developed a procedure to generate SPM analogue flocs from components selected to represent the most abundant and crucial constituents of natural riverine SPM, and the process-relevant SPM surface characteristics regarding interactions with particulate contaminants. Illite, hematite, quartz and tryptophan, combined at environmentally realistic mass-ratios, were associated to complex flocs. Flocculation was reproducible regarding floc size and fractal dimension, and multiple tests on floc resilience towards physical impacts (agitation, sedimentation-storage-resuspension, dilution) and hydrochemical changes (pH, electrolytes, dissolved organic matter concentration) confirmed their robustness. These reproducible, ready-to-use SPM analogue flocs will strongly support future research on emerging particulate contaminants.