中文摘要：

以西藏拉萨国家农业科技园区温室连续种植12年的温室土壤为研究对象,随机选取9座设施园区,对比园区种植前后各项土壤数据,比较pH、有机质、大量和微量元素以及重金属的变化。结果表明：随着日光温室土壤种植年限的增加,土壤的pH明显下降（P〈0.05）,有酸化的趋势,而土壤有机质在种植前后并没有发生显著变化;其中全磷、速效磷和全钾含量随着种植年限的增加而增加;但全氮含量随着种植时间的增加而呈下降趋势,速效钾含量变化并不明显;铁（Fe）含量随着种植年限的增加而呈下降趋势,而镁（Mg）含量呈上升趋势,锌含量变化不明显;重金属元素铅（Pb）、砷（As）、汞（Hg）、镉（Cd）含量符合国家环境保护总局发布的温室蔬菜产地环境质量评价标准,均未超标。其中Pb、As和Hg的环境质量等级均评价为一级,为清洁;总镉的环境质量等级为二级,为尚清洁,说明该园区温室土壤的重金属含量是符合国家标准,土壤耕层没有受到重金属的污染。

英文摘要：

In order to know the changes of pH,organic matter,trace elements and heavy metals in greenhouse soil after continuous cultivating in the Lhasa National Park of Agricultural Science and Technology,which has been running for 12 years.The soil samples from nine greenhouse were selected to conduct experiments.The results showed that the soil pH decreased significantly（P〈0.05）,and the soil organic matter was not changed significantly.The content of total phosphorus,available phosphorus and total potassium increased with the increase of planting years.However,the total nitrogen decreased and the change of available potassium was not change significantly.The content of Fe decreased and Mg content increased,significantly with the increase of planting years but Zn content was not change.The content of As,Hg,Cd,Pb were not exceeded,which in accordance with the standards of greenhouse vegetable production environmental quality evaluation issued by the National Environmental Protection Administration.The environmental quality grade of Pb,Hg and As as were evaluated for grade one and clean;total cadmium environmental quality grade for grade two,was still clean,indicating that soil heavy metal content was in line with national standards in Greenhouse,topsoil did not receive the heavy metal pollution..