Seasonal Variation of Acid Volatile Sulfide and Simultaneously Extracted Metals in Sediment Cores from the Pearl River Estuary

The simultaneously extracted metals/acid volatile sulfide (SEM/AVS) method is widely used to estimate the toxicity of metals in sediment. In this study, SEM and AVS concentrations were obtained by the cold-acid purge-and-trap technique during spring (April) and winter (December) at six sites in the Pearl River estuary. Total organic carbon, grain size distribution, and total metals were also measured in winter samples. AVS concentrations in spring sediments were slightly higher than those in winter sediments, except at site 2. AVS concentrations showed more distinct locational and temporal variation compared with SEM concentrations. Generally, AVS contents increased downcore, whereas SEM concentrations decreased slightly with depth. Higher SEM concentrations were observed in the west shoal (sites 2, 6, and 7) and site 4 (1.24 approximate to 4.28mol center dot g(-1)) compared with those at sites 1 and 3 (0.73 approximate to 2.14mol center dot g(-1)) in the middle shoal. Most SEM metals have a significant linear positive correlation with the total metals, especially for Cd, Zn, and Pb, which were easily extracted by 1M HCl compared with Cr and Ni. According to the toxicity threshold value of 1.7mol center dot g(-1) for the difference of SEM-AVS, a toxic effect is expected at sites 1, 2, and 4 in spring and at sites 4, 6, and 7 in winter, which also indicates a relatively obvious seasonal variation in heavy metal bioavailability. However, comparisons between the total heavy metal concentrations in winter sediments with the sediment quality guidelines of ERLs/ERMs and TELs/PELs showed that adverse biological effects may occasionally occur at sites 2, 4, 6, and 7. Therefore, SEM/AVS prediction in conjunction with sediment quality guidelines can give a more reliable evaluation of the bioavailability of heavy metal in sediments.Environmental SciencesSCI(E)EI0ARTICLEfrchen@gig.ac.cn4480-4962