中文摘要：

利用区域采样调查的方法,研究了长沙市郊3类不同种植年限菜地土壤有效态氮、磷和重金属的累积差异,并对其累积风险和可能来源作了初步分析.结果表明：随着种植年限的增加,长沙市郊菜地土壤硝态氮（NO3--N）、有效磷（Olsen-P）和重金属累积量均显著增加,蔬菜种植1～2年（宁乡县）、10～15年（长沙县）和30年（开福区）后土壤NO3--N平均含量分别达21.1、42.0和49.5mg·kg-1;Olsen-P平均含量分别达31.9、146.9和219.9mg·kg-1;重金属以Cd累积最明显,平均含量分别达0.33、0.52和1.40mg·kg-1.重金属按累积指数排序为：Cd〉〉Cu〉Pb〉Ni〉Zn.主成分分析和聚类分析表明,速效钾、pH、有机质、铵态氮等主要由自然因素决定,而Olsen-P和NO3--N等与重金属具有相似的累积特征,主要受人为施肥影响.长沙市郊菜地土壤环境和健康质量不容乐观,种植年限越长,氮、磷和重金属累积量越高,菜地土壤重金属与氮、磷来源相似,可能与菜地长期施肥活动有关.

英文摘要：

Soil samples were collected from three vegetable fields under different years of cultivation in Changsha suburbs of Hunan Province,South-central China to study the accumulation characteristics,risks,and sources of soil available nitrogen and phosphorus and heavy metals in the fields.With the increasing year of vegetable cultivation,the soil NO3--N,Olsen-P,and heavy metals contents in the fields increased significantly.The average contents of soil NO3--N,Olsen-P,and Cd in the vegetable fields having been cultivated for 1-2 years in Ningxiang County,10-15 years in Changsha County,and 30 years in Kaifu District were 21.1,31.9 and 0.33 mg·kg-1,42.0,146.9 and 0.52 mg·kg-1,and 49.5,219.9 and 1.40 mg·kg-1,respectively.The cumulative index（CI） of soil heavy metals generally followed the sequence of Cd Cu Pb Ni Zn.Principal component analysis and cluster analysis showed that compared with soil NH4OAc-extracted potassium,pH,organic matter and NH4＋-N,that were dominated by natural factors,the soil Olsen-P and NO3--N had the similar accumulation characteristics with the soil heavy metals,being mainly controlled by fertilization.It was considered that the soil environment and health quality of the vegetable fields in Changsha suburbs were not optimistic.The longer the cultivation year of vegetables,the more the soil NO3--N,Olsen-P,and heavy metals accumulated in the fields.The accumulation of these elements in the fields could be primarily due to the long-term fertilization.