城市受污染疏浚底泥特性与作绿地用土的可行性分析

受污染河道疏浚底泥消纳是上海市环境治理中面临的问题之一。中、轻度污染的疏浚底泥用作绿地用土是具有资源化价值的底泥消纳适用途径,为分析此途径的可行性。选择上海市典型中度污染河道底泥作了植物生长相关理化性质和重金属污染特性(总量、浸出液浓度、分级提取比例分布)分析,并据此讨论了此类(中、轻度污染)疏浚底泥的绿地利用可行性,分析结果表明,中度污染河道疏浚底泥的植物相关特性为：速效植物养分含量高,但阳离子交换容量低;总溶解盐含量高,但苏打盐和氯化钠含量低：重金属总量和浸出液重金属浓度低于国家农用污泥污染物控制标准和危险废物鉴别标准——浸出毒性鉴别限值,但Pb和Cd的可交换态比例较高(24％和62％)。底泥综合理化性质的分析结果：中度以下污染程度的上海市河道疏浚污泥具有作绿地用土必须的植物相容性,可用作绿地用土：但底泥的保肥能力较差,作绿地用土初期宜种植速生、需肥量大的植物,以控制植物养分流失;对于重金属、尤其是可交换态比例高的重金属溶出造成的环境影响,宜采用底泥施用量控制等手段对其不利影响进行防治。

Characteristics of Urban Polluted Dredged Materials and Feasibility Study of its Beneficial Use as Greening Vegetative Soil

The outlet of contaminated urban dredged materi- als is one of environmental issues which Shanghai is confronted with. Beneficial use of the light and medium-contaminated materials as greening vegetative soil is a promising alternative. In order to analyze the feasibility of this kind of beneficial use method, it was experimented and analyzed on the relative physico-chemical properties about plant culture and pollution characteristics caused by heavy metals (the parameters including total content, concentration in the leachate and geochemical speciation) and discussed about the feasibility of beneficial use as greening vegetative soil. Analysis on the properties of dredged materials indicated that medium-contaminated dredged materials possessed high nutrients content easily utilized by vegetables with low cation-exchanging capacity, high total soluble salt with low sodium carbonate and sodium chloride. The total content of heavy metals and heavy metals concentration in the leachate were less than the limited values in the "Control Standards for Pollutants in Sludges for Agricultural Use" (GB4284-84) and "Identification Standard for Hazardous Wastes-- Identification for Extraction Procedure Toxicity" (GB5085.3-1996), however, the contents of Pb and Cd in exchangeable status were high (24% and 62% respectively). The analysis result about comprehensive physico-chemical characteristics of dredged materials was that medium-or ligh-contaminated urban dredged materials in Shanghai has vegetative consistency and could be beneficially used as green vegetative soil. However it was poor in fertilizer-containing ability, so quickly-growing and fertilizer-consuming vegetables should be planted in the initial stages when beneficially used, so as to constrain the loss in vegetative nutrients. The unfavorable environmental effects caused by the extraction of heavy metals, especially those high in exchangeable status, should be prevented with measures such as load control of empolyed dredged materials.