The partitioning behavior of persistent toxicant organic contaminants in eutrophic sediments: Coefficients and effects of fluorescent organic matter and particle size

Abstract

In the shallow lakes, the partitioning of organic contaminants into the water phase from the solid phase might pose a potential hazard to both benthic and planktonic organisms, which would further damage aquatic ecosystems. This study determined the concentrations of polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs), and phthalate esters (PAEs) in both the sediment and the pore water from Lake Chaohu and calculated the sediment - pore water partition coefficient (K) and the organic carbon normalized sediment - pore water partition coefficient (K), and explored the effects of particle size, organic matter content, and parallel factor fluorescent organic matter (PARAFAC-FOM) on K. The results showed that log K values of PAHs (2.61-3.94) and OCPs (1.75-3.05) were significantly lower than that of PAEs (4.13-5.05) (p < 0.05). The chemicals were ranked by log K as follows: PAEs (6.05-6.94) > PAHs (4.61-5.86) > OCPs (3.62-4.97). A modified MCI model can predict K values in a range of log 1.5 at a higher frequency, especially for PAEs. The significantly positive correlation between K and the octanol - water partition coefficient (K) were observed for PAHs and OCPs. However, significant correlation was found for PAEs only when excluding PAEs with lower K. Sediments with smaller particle sizes (clay and silt) and their organic matter would affect distributions of PAHs and OCPs between the sediment and the pore water. Protein-like fluorescent organic matter (C2) was associated with the K of PAEs. Furthermore, the partitioning of PARAFAC-FOM between the sediment and the pore water could potentially affect the distribution of organic pollutants. The partitioning mechanism of PAEs between the sediment and the pore water might be different from that of PAHs and OCPs, as indicated by their associations with influencing factors and K.

Distribution Dynamics of Phthalate Esters in Surface Water and Sediment of the Middle-Lower Hanjiang River, China

“…Sediment accumulates PAEs in the process of water adsorption. When different PAE monomers coexist, there may be competition in the adsorption process, and when the environmental redox conditions change, it will also lead to the release of PAEs in the sediment [ 38 , 39 ]. This study shows that the order of PAE concentration is sediment > water ( Table A2 and Table A5 ), which indicates that sediment is an important reservoir of PAEs.…”