Zinc Accumulation and Pollution Risk in Soils Under Different Land Use Types in Beijing
2006, 21 (1):
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.
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