深港西部通道填海区淤泥重金属化学形态分析

SPECIATION OF HEAVY METALS IN MUD IN COASTAL RECLAMATION AREAS IN THE SHENZHEN-HONGKONG WESTERN CORRIDOR

以深港西部通道填海区淤泥为研究对象,研究了重金属的化学形态特征,分析了填海工程活动带来的填海区地下水物理化学条件变化对重金属各个形态的影响。结果表明:除残留态外,填海区重金属存在形态主要为铁锰结合态、碳酸盐结合态和硫化物及有机结合态,其中,Pb和Ni以铁锰氧化物结合态和碳酸盐结合态为主,Cu以碳酸盐结合态和有机结合态为主,Zn以有机结合态和铁锰氧化物结合态为主,而Cd则以碳酸盐结合态为主。各金属在深港西部通道填海区淤泥的潜在迁移能力序列如下:Pb(39.68%)>Cu(31.59%)>Zn(20.49%)>Cd(12.80%)>Ni(10.98%)。

Large-scale coastal reclamation has been carried out along the coastal areas near Shenzhen, China to build the Shenzhen-Hong Kong western corridor by dumping fall materials over the marine mud at the sea bottom. Changes in the burial conditions of mud and the physical and chemical properties of pore water in the mud may induce the release of some heavy metals in the mud. To understand why some of the heavy metals can be released from the mud more easily than others, a sequential extraction method was used to study the operationally determined chemical forms of five heavy metals （Cu, Ni, Pb, Zn and Cd ） in the mud samples. Heavy metals can be presented in five chemical forms： exchangeable, carbonate, Fe Mn oxide, organic and residual. Ni and Pb were mainly associated with the Fe-Mn oxide fraction and carbonate fraction, Zn was mainly associated with organic fraction and Fe-Mn oxide fraction, while Cu and Cd were associated with organic fraction and carbonate fraction, respectively. If the residual fraction can be considered as an inert phase of the metal that earmot be mobilized, it is the other four forms of heavy metal that cause noticeable changes in the concentrationsof heavy metals in mud. On the basis of the speeiation of heavy metals, the mobility of metals follows theorder： Pb（39.68%） 〉 Cu（31.59%） 〉 Zn（20.49%） 〉 Ni（12.80%） 〉 Cd （10.98%）.