| Coastal area is a system with complex dynamic changes of the environment, the influence of human activity, which led to a lot of pollutants into coastal environment. Heavy metals have important influence on marine environment. Recently, with the rapid development of economy, especially for transportation, oil processing and aquaculture, causing Zhanjiang Bay increasing the environmental problems. Hence, this research is very important for Zhanjiang bay.By the field investigation and laboratory measurement, we researched the content distribution characteristic of suspended solids and the corresponding heavy metals, the concentration of heavy metals in different phase in Zhanjiang bay, a typical semi-closed bay. Main results for this study are as follows:1. The concentration of suspended solids ranged from 1.6mg/L to 28.2mg/L in 2014, with the average of 8.9mg/L. Compared with historical results, the content of suspended solids had obvious declined in Zhanjiang Bay. Compared with other domestic bay, the concentration of suspended solids was at lower levels in Zhanjiang bay. In the temporal distribution, the content of suspended solids in winter was significantly higher than in summer. The concentration of suspended solids during spring tide is higher than during neap period. The concentration of suspended solids in winter was higher during flow than during ebb, whereas it is reversed in summer. As for the space distribution of the content of suspengded solids, because of tide, wind and water environment factors, the highest value focused on the south of Zhanjiang bay and the content of suspended solids in bottom seawaters suspended was greater than that in surface water. A negative correlation was showed between suspended solids content and water temperature, while the content of suspended solids was positive correlative to p H, salinity, DO, COD and turbidity, respectively.2. Particulate organic matter(POM) content in suspended solids is varying between 0.07mg/mg and 0.73mg/mg, with an annual average of 0.30mg/mg. No significant difference was found in the percentage of POM content between in winter and in summer although the percent of POM was significantly between spring tide and neap tide. Moreover, there was insignificant difference in the percentage of POM content between ebb tide and low tide. Mediam diameter of suspended solids ranged from 1.6 μm to 19.4 μm, with an annual average of 62.5 μm, and the highest content was in the mouth of Zhanjiang bay and its adjacent waters. Particulate organic matter(POM) from suspended solids showed a significant positive correlation with the content of suspended solids(r=0.7792).3. The annual average content of heavy metals in suspended solids at Zhanjiang bay to Cu(65.33mg/kg), Zn(178.18mg/kg), Pb(49.97 mg/kg), Cr(175.28mg/kg) and Cd(2.32mg/kg). The concentration of heavy metals to Pb, Cr and Cd was higher in winter than in summer with time. However, heavy metals content was lower to Cu extracted from in winter than in summer. Similarly, the content of heavy metals to Cu in rising tide was also lower than ebb. The content of Zn had no notable changes with time. In addition to the concentration of Cu in rising tide was higher than ebb in spring tide, the rest time were lower from tide than ebb. The levels of heavy metals in suspended solids were not in proportion. The content of Cu、Zn、Pb、Cr、Cd did not change obviously with space. The negative correlation between all metals and suspended solids showed the impact of sediment re-suspension on heavy metals in suspended solids.4. The results showed that Cu, Zn, Cd in water existed as dissolved state, while Pb was mainly in particulate. Cr was more equilibrium distribution between dissolved state and particulate.5. The value of partition coefficient in both solid phase and liquid phase were more than 3, showed that the suspended solids had the strong accumulation ability to heavy metals. Otherwise, the results showed that the suspended solids had stronger enrichment ability than surface sediment. The highest ratio of different heavy metals in suspended solids was for Cd, followed by Zn, Pb, Cr, Cu. |
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