Bioavailability of polycyclic aromatic hydrocarbons in size fractions of field-contaminated sediment

Distributions of 15 polycyclic aromatic hydrocarbons (PAHs) in four different size fractions of field-contaminated sediment from Hangzhou section of the Jinghang Canal in China were investigated. Total PAH concentrations ranged from 644.8 to 5407.4 ng g^-1 dw and varied largely with particle sizes. The XAD-2 assisted desorption assay was used to assess its potential to determine the bioavailable fraction of PAHs in different size fractions of field-contaminated sediment. A parallel experiment on biodegradation of these PAHs by microorganisms indigenous to size fractions was also conducted. The 15 PAH concentrations in size fraction reached constant values after four weeks in the two processes. About 25% of total PAHs were non-bioavailable in all size fractions. Positive relationships were obtained between the initial or residual concentrations of PAHs with the TOC contents of size fractions. TOC content is the determining factor to the non-bioavailable fraction of PAHs and should be taken into consideration when establishing sediment quality guidelines.