北京市不同土地利用方式下土壤锌的积累及其污染风险

通过对北京市菜地、稻田、果园、绿化地、麦地、自然土壤以及公园等7种土地利用方式共630个土壤样品的调查分析,探讨了不同土地利用方式对土壤锌积累的影响。结果发现,不同土地利用方式下锌含量存在较大差异,在7种土地利用方式中,土壤锌的平均含量从高到低依次为:公园>果园>稻田>绿化地>菜地>自然土壤>麦地。占样点大多数的麦地和自然土壤的锌含量与背景值没有显著差别,而公园、果园、稻田和菜地土壤锌含量则显著高于背景值。与土壤锌含量基线值相比,公园、果园、菜地土壤超标率分别为25.8%、23.8%、9.7%,其它利用方式的土壤超标率并不严重。石景山、昌平、朝阳、丰台4个区是超标样点集中分布的地区。金属冶炼、交通以及垃圾填埋可能是导致土壤锌含量增加的重要因素。

Zinc Accumulation and Pollution Risk in Soils Under Different Land Use Types in Beijing

Zinc is an essential element for animals and plants,and is of widely concern in agricul-tural sciences and environmental sciences,but the point to be concerned by the two fields aboves not always the same.Zn is commonly considered as a beneficial element by agricultural scientists who pay more attention to its positive effects on plant,while environmental scientists always take Zn as one of the heavy metals and give more attention to its negative effects on environment.According to a report by FAO in 1967,it's very common for Zn deficiency for the soil in the world,such as most of the countries in Europe,and a majority of states in USA.According to the data of the Second National Soil Survey of China,the area of Zn deficiency soil reached to 0.49×108ha,accounting for 51.1% of the total cultivated land. Beijing,capital of China,is located between 116°20′E and 39°56′N and surrounded by mountains on the west,the north and the northeast.Lying in the northern part of North China Plain,Beijing covers a total area of 16 808km₂.Of which 10 418km₂ are mountainous areas,or 62% of the total area of Beijing,while plain area covers 6 390km₂,or 38% of the city's total. Information on the environmental effects of different land uses is lacking,especially in Beijing.Such information is important for the understanding of the sustainable development and regional agricultural planing.To identify the effects of land use on the accumulation of Zn in the soils,630 samples were obtained from 7 land-use types of Beijing,including park,vegetable field,paddy field,orchard,greenbelt,cornfield and natural soil,and their zinc was determined with Flame Atomic Absorption Spectrometry(FAAS).It was found that there was a rather large difference of the accumulation of soil Zn under different land use types.Compared with background concentration(GM=57.5mg·kg-1) of zinc in soil of Beijing,the accumulation of Zn in the park soils(GM=83.3mg·kg-1),orchard(GM=70.0mg·kg-1),paddy fields(GM=68.6mg·kg-1),greenbelt(GM=66.3mg·kg-1) and vegetable fields(GM=63.6mg·kg-1) was significant,while that of cornfields(GM=56.9mg·kg-1) and natural soils(GM=59.7mg·kg-1),accounted for the majority of the total samples,were not significantly different from background concentration.Using the Zn baseline concentration,product of geometrical mean(GM) and square of geometrical standard deviation(GSD),of soil in Beijing(97.2 mg·kg-1) as background,the ratios of soil samples exceeding the set standard in park,orchard,vegetable field,cornfield,and greenbelt were 25.8%,23.8%,9.7%,2.6% and 7.7%,respectively,while the overall ratio for the study was 6.4%.According to this investigation,some anthropogenic factors such as metal smelt,traffic,application of zinc-contained fertilizers and pesticides,sewage irrigation,and incineration of waste and landfill of waste,played quite important roles in the accumulation of soil sample Zn.According to the geometrical mean of Zn in the soil,the order of the 7 land-use types,from the highest to the lowest in Zn concentra-tion,was park soil>orchard>paddy fields>greenbelt>vegetable fields>natural soils>cornfields. In general,from the viewpoint of agricultural production and human health,there is a zinc deficiency on the whole in soils of Beijing,and zinc pollution is not obvious.