Review of decisive factors for controlling generation and environmental effect of dissolved organic matter from (micro)plastics.

Plastic-derived dissolved organic matter (DOM) is extensively generated in parallel with the increase of plastic waste, and its potential environmental risks are attracting increasing attention. This review first summarizes the unique compositions, structures and features of plastic-derived DOM. Then, the crucial factors controlling DOM generation from plastics are identified. Additionally, the important role of plastic-derived DOM in biogeochemical processes such as the photodegradation of other pollutants and carbon sources for microorganisms is specifically discussed. Through correlation analyses on data extracted from previous publications, illumination is identified as the most dominant factor over other factors (e.g. temperature, physical abrasion and oxygen) for affecting the generation of plastic-derived DOM. In addition, the generation potentials of DOM among various plastic types are revealed, with the orders following PS > PU > PP > PA > PE > PET > PC > EVA > PMMA > PVC, whose differences are mainly related to the associated functional groups (CH and CO) and unsaturated bonds (-CH=CH and CO). Moreover, the threshold concentration of plastic-derived DOM on pollutant transformation is determined as 20 mg C/L, where plastic-derived DOM exhibits the enhancing effect when exceeding the threshold value. This review contributes to a deeper understanding of plastic-derived DOM, thereby providing more accurate basis for risk assessment and pollution control strategies for plastic waste in natural ecosystems.