Acid-volatile sulfide(AVS), simultaneously extracted metals(SEM)in intertidal sediments of Donghai Island, Zhanjiang and their toxic effect on the organism

The contents and distributions of acid-volatile sulfide(AVS) and simultaneously extracted metals(SEM)(Cr Cu, Zn, Cd, Pb) were studied in the surface sediments collected from the tidal flat of Donghai Island, Zhanjiang. The results indicated that at most stations, the AVS concentration was lower in summer with the average of 0.449 μmol/g than in winter with the average of 1.816 μmol/g. The AVS contents were higher in the southern and northern areas and lower in the western and eastern areas. The average contents of ∑SEM were between 0.56 μmol/g and 4.60 μmol/g in summer and between 0.65μmol/g and 2.21 μmol/g in winter. The concentration change of single metal was ZnCrPbCuCd at most stations. The content percentages of ∑ SEM were below 1 % for Cd and over 70 % for Zn. SEMZnwas the key pattern to control the distribution of ∑SEM due to its high percentage of concentration. Based on the assessment methods of( ∑SEM/AVS) and(∑SEM-AVS) and the thresholds for the metal toxicity to the benthic organism, most value of(∑SEM-AVS) in the tidal flat of Donghai Island was between 0 and 5. The most toxicity region was in Tongminghai area located in the west tidal zone of Donghai Island, and the most toxicity metal was zinc in summer in Tongminghai area.