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

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。

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

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 intensities.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 addition,long-term sewage irrigation and other agricultural activities led to local Pb contamination in the suburban 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 agricultural soil presented the lowest mobility.③ Pb contents in different parts of wheat plants were largely dependent 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,only 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.