Dissolved metal assessment in surface seawater: A spatial-seasonal evaluation in the Zhejiang coastal waters, the East China Sea.

The spatial-seasonal distributions and variations, correlations with environmental variables and the pollution degrees of dissolved metals in the Zhejiang coastal seawater were investigated. The concentrations of six dissolved metals (i.e. Cu, Pb, Zn, Cd, As and Hg) were in the ranges of 0.10-6.40 (1.6 ± 0.8), 0.16-3.60 (1.2 ± 0.7), 2.50-24.0 (8.5 ± 4.8), 0.011-0.180 (0.07 ± 0.03), 0.85-4.20 (2.1 ± 0.8) and 0.001-0.110 (0.06 ± 0.02) μg/L, throughout the four seasons, respectively. Significant differences in all the dissolved metals were found among seasons, whereas no significant differences were found among stations. The average concentrations of metals were in the following order: Zn > As>Cu > Pb > Cd > Hg. Single metal contamination factor was in the following order: Pb > Hg > Zn > Cu > As>Cd. The pollution level of dissolved metals in the Zhejiang coastal waters (ZCW) was low. Most of the dissolved metals were correlated to temperature, indicating seasonal differences. The redundancy analysis (RDA) indicated that depth, temperature, nitrate and phosphate could best explain the variance pattern of dissolved metals in the ZCW.