基于农业区位论的北京市土壤-小麦系统中重金属Pb积累特征及其健康风险

Pb Accumulation and Its Health Risk in Soil-wheat System of Beijing City Based on Agricultural Location Theory

基于农业区位论,采集23组土壤-小麦匹配样品,探究北京市不同圈层土壤-小麦系统中Pb的全量、形态与生物有效性。结果表明:①频繁的交通活动与工业释放致使城区土壤呈现出Pb污染,而长期污水灌溉等农业活动导致了近郊平原局部土壤Pb污染。②土壤中Pb主要以残余态与有机结合态形式存在,其次是铁锰氧化态,而碳酸盐结合态与离子交换态非常少。Pb的活性从中心城区到近郊平原、远郊平原逐渐下降。③小麦植株中Pb含量与土壤中铁锰氧化态Pb含量呈正相关;④麦粒中Pb的富集系数仅约为0.004 4,但仍发现城区与近郊麦粒中部分Pb含量超标。

Based on Agricultural Location Theory, 23 groups of suited soil-wheat samples from were collected in different circles of Beijing City （central city, suburban plain and exurban plain）, and the accumulation, chemical forms and bioavailability of Pb in soil-wheat system were analyzed under different human activity in- tensities. The results showed that： ① Urban soil exhibited Pb contamination with its average concentration （35.59 mg/kg） above the limit, probably due to the emission of traffic activities and industrial processes. In ad- dition, long-term sewage irrigation and other agricultural activities led to local Pb contamination in the subur- ban agricultural soil. ② Pb was predominantly associated with residual and organic fractions, followed by Fe/ Mn oxide, and very small proportion of carbonate and exchangeable fractions. Furthermore, compared with the suburban agricultural soils, Pb in the urban agricultural soil showed higher mobility, whereas, the exurban agri- cultural soil presented the lowest mobility. ③ Pb contents in different parts of wheat plants were largely depen- dent on the Fe/Mn oxide fractions in the studied soil, ④ The average bioconcentration factor （the ratio of metal concentration in plant tissues and metal concentration in their rooted soil） of Pb in wheat seeds was 0.0044, on- ly contained 3.42% of Pb in roots. However, part Pb concentrations in wheat seeds in the urban and suburban agricultural soil were above standard limit, which might bring potential risk to human health in the urban and suburban sites.