香港土壤中的重金属含量及其污染现状

A STUDY ON HEAVY METAL POLLUTION IN SOILS IN HONG KONG

通过详细的土壤调查分析，探讨了香港表层土壤（０～５ｃｍ）中重金属的含量及其污染现状。５８个代表性样品的分析结果表明，香港土壤的Ａｓ、Ｃｄ、Ｃｕ、Ｐｂ和Ｚｎ分别为１３、１、１７、５７和５５ｍｇ／ｋｇ；用ＮａＨＣＯ３／ＤＴＰＡ浸提的有效态Ｃｄ、Ｃｕ、Ｐｂ和Ｚｎ分别为０．１、０．０３、０．７和１．１ｍｇ／ｋｇ。从土壤种类来看，除Ｐｂ元素之外，一般果园土壤的重金属平均含量最高，菜园土壤次之，城市土壤和乡村土壤更次之，林业土壤中的含量最低；但从Ｐｂ平均含量来看，果园和城市土壤较高，而在菜园土壤、乡村土壤和林业土壤中的平均含量相差不大。从土地利用的分区来看，在商业区、工业区、农业区和林业区４种功能区中，通常是工业区的重金属污染相对较严重，而林业区的土壤污染相对较轻。汽油燃烧和农业化学物质的投入，是香港土壤中Ｐｂ污染的重要来源。

Heavy metal contents in top soils in Hong Kong and their pollution levels were studied in the presented paper using soil survey. Averages of total As, Cd, Cu, Pb and Zn contents in the 58 selected soils were 13, 1, 17, 57 and 55 mg/kg soil, respectively. Average contents of NaHCO 3/DTPA——extractable Cd, Cu, Pb and Zn in the soils were 0.1, 0.03, 0.7 and 1.1 mg/kg soil, respectively. In general, the maximum average contents of heavy metal except for Pb were found in vegetable soil type, the medium ones were found in urban soil type and rural soil type, and the minimum ones were in forest soil type. However, the fruit soil type and urban soil type had the highest Pb contents. The average Pb contents in vegetable soil type, rural soil type and forest soil type were lower. Among the 4 function areas (i.e. agricultural, commercial, forest and industrial areas) in the city, more serious pollution by heavy metals were usually observed in industrial areas while minimum pollution was found in forest areas. Oil gas combustion was the major source of Pb pollution in the soils. Repeated applications of agrochemicals were an important input of As, Cu and Zn in the agricultural soils.