Partitioning characteristics of PAHs between sediment and water in a shallow lake

Abstract

tory conditions, suggesting that the measured pore water PAH concentrations were lower than those predicted. That is to say, not all the sediment PAHs can be available to partition rapidly into sediment pore waters. A variation in soot content is a possible reason. Furthermore, concentrations of PAHs on SPM were higher than those in sediments. The compositions of PAHs on SPM and in sediments were similar, indicating the importance of re-suspension process of sediments in the partitioning process of the shallow lake. Conclusions. The results indicated the equilibrium partitioning model could be used to predict PAHs distribution in various phases of a shallow lake in the stagnation period, but re-suspension processes should be considered to modify the relationship between log K oc s and log K ow s. Recommendations and Perspectives. Concentration, particle size and composition of resuspended particles could affect the relationship between log K oc s and log K ow s. Further work should be done under field conditions, especially where a steady thermodynamic equilibrium state could be assumed.Keywords: Aquatic ecosystems; China; freshwater lake; K ow ; PAHs; partitioning; polycyclic aromatic hydrocarbons; shallow lake; SPM; surface sediments; suspended particulate matter; Taihu Lake; water quality AbstractGoal, Scope and Background. Distribution of hydrophobic organic contaminants in abiotic compartments is essential for describing their transfer and fate in aquatic ecosystems. Taihu Lake is the third largest freshwater lake in China. Water quality of Taihu Lake has deteriorated greatly during the last decades and has threatened the water supply. The aim of the present study was to investigate the partitioning of polycyclic aromatic hydrocarbons (PAHs) among overlying water, suspended particulate matter (SPM), sediments, and pore water in Meiliang Bay, Taihu Lake and to provide useful information for the ecological engineering in this area. Materials and Methods. Overlying water and surface sediment were sampled from six sites in Meiliang Bay, Taihu Lake, China. Within 72 h of sampling, sediments were centrifuged to obtain the pore water. Overlying water samples were filtered to separate dissolved and SPM samples. After extraction, samples were purified following a clean-up procedure. PAH fraction was obtained by elution with a mixture of hexane: DCM (7:3, V/V) and analyzed by GC/MS. Results. PAHs concentrations in overlying water varied from 37.5 ng/L to 183.5 ng/L. Concentrations of PAHs in pore water were higher than those in overlying water. The total concentrations of 16 priority PAHs in sediments ranged from 2091.8 ng/ g-dw to 4094.4 ng/g-dw. PAHs concentrations on SPM were decreased with suspended solid concentrations (SSC). Total PAHs concentrations on SPM varied in the range of 3369.6 ng/g-dw to 7531.1 ng/g-dw. The partition coefficients between sediment and overlying water (log K oc ) for PAHs with log K ow <5 were positively correlated with their octanol-water partition coefficients (log K ow ) (n=39, r=0....

Impacts of particulate organic carbon and dissolved organic carbon on removal of polycyclic aromatic hydrocarbons, organochlorine pesticides, and nonylphenols in a wetland

“…Many studies also showed that K oc values of hydrophobic contaminants in suspended particulates or sediments were closely related to their K ow values (Qiao et al 2008;Karickhoff 1981;Chu and Chan 2000). It is widely acknowledged that K DOC is also closely related to K ow (Burkhard 2000).…”

“…Furthermore, one of the fundamental processes controlling the transport, transformation of organic contaminants, especially for hydrophobic organic compounds in aquatic environments is the partitioning and distribution between water, DOC, and POC (Qiao et al 2008;Servos and Muir 1989;Zhou and Rowland 1997). Contaminants can exist in freely dissolved, DOC-bound, POC-bound, sedimentassociated, and biota-associated forms in aquatic systems.…”

“…The change of DOC along the wetland corresponded well to the change of TSPs (Table 1). The concentrations of contaminants in filtered water (C dissolved ) were detected by solid-phase extraction method, which included freely dissolved (f free ) and DOC-bound (f DOC ) fractions (Qiao and Farrell 2002;Qiao et al 2008). Mean concentrations of PAHs, OCPs, and NPs in filtered water were summarized in Table 2.…”

Basal and benzo[a]pyrene-induced expression profile of phase I and II enzymes and ABC transporter mRNA in the early life stage of Chinese rare minnows (Gobiocypris rarus)

“…Water samples were collected within 20 min after dosing and analyzed to confirm BaP concentrations from each exposure container. The detailed protocol for sample extracting and BaP concentrations analysis in the exposure water were according to previous study from our laboratory (Qiao et al, 2008). BaP was not detected in any of the acetone treated group.…”

Screening for over 1000 organic micropollutants in surface water and sediments in the Liaohe River watershed

“…We also conducted a target analysis for PAHs in water and sediments of selected sampling sites using a traditional target analytical method described in Qiao et al (2008). The detailed results are listed in Tables S7 and S8.…”