城市土壤磷赋存形态特征及其环境风险识别

Urban soil is an essential component of urban ecosystem, concerning urban environment quality and human health. Previous studies demonstrated that urban soils had significant phosphorus (P) accumulation due to anthropogenic impact, posing a serious threat to the aquatic ecosystem in urban and suburban areas. To date, the environmental consequences of P accumulation in urban soils were not well established. And there are still some aspects needing improvement, including P accumulation form in urban soils and the identification for its environmental risk. To advance the knowledge of the environmental chemical behavior of P accumulation in urban soils, the proposed research will employ soil P fractionation method and X-ray absorption near-edge structure (XANES) technique to characterize P accumulation form in urban soils. Thereafter, the spatio-temporal variation of P in urban soils will be investigated by geostatistics analysis from land use type and urbanization age perspectives, to benefit P environment assessment. Finally, the environmental risk of P accumulation in urban soils will be identified by using P sorption characteristics and “change-points” of the urban soils, determined by chemical analysis, combined with the P spatio-temporal variation. This study will demonstrate the form and spatio-temporal variation of P in urban soils, and quantitatively identify the potential environmental risk for P accumulation. The results of this research will provide scientific guide for environment monitoring and land use management, and advance the study of the impact of urbanization on the ecosystems.

城市土壤是城市生态系统的重要组成部分，关系到城市生态环境质量和人类健康。人类活动改变了城市土壤磷的循环过程，造成了显著的磷富集现象，已对城市及周边水体生态系统构成严重威胁。从研究现状来看，目前对城市土壤磷富集的环境风险未给予足够重视，在磷的赋存形态及风险识别方面仍有待进一步完善。本项目拟采用土壤磷分组结合XANES谱技术研究城市土壤磷的赋存形态，进一步揭示城市土壤累积磷的环境化学行为；在此基础上，借助地统计学方法，从土地利用方式与城市化时间角度，分析城市土壤磷的时空变异；最后采用土壤化学方法，分析土壤磷的吸附特性并获取磷环境敏感临界值，结合磷时空变化特征评估预警城市土壤磷富集的环境风险。通过本项目的开展能揭示城市土壤磷的赋存特征及其富集的时空变化规律，实现对城市土壤磷累积环境风险的定量评估，为城市环境监测及土地资源管理提供科学依据，也可为进一步开展城市化生态环境效应研究提供基础知识。

人类活动改变了城市土壤磷的循环过程，造成了显著的磷富集现象，已对城市及周边水体生态系统构成严重威胁。目前对城市土壤磷富集的环境风险未给予足够重视，在磷的赋存形态及风险识别方面仍有待进一步完善。本项目在南昌市区典型公园绿地科学布设并采集了土壤样品，同时在郊区森林和水稻田中采集了部分样品作为对比。采用Hedley磷分组方法研究了城市土壤磷的赋存形态，采用多点等温吸附手段研究了城市土壤磷的吸附特性。同时，测定了影响磷固持的相关土壤性质。结果表明：与南昌郊区土壤相比，城市土壤中主要的磷组分为NaOH-Pi、NaOH-Po、残渣磷。但是，城市土壤具有较高的PH2O、PKCl和PHCl；进一步分析表明，影响城市土壤磷组分变化的主要因素是土壤pH与钙镁含量；表层土壤（0–5cm）磷吸附能力显著低于亚表层（5–15cm），原因可能是表层土壤中无定型铝含量较低而土壤有机碳含量较高，从而限制了土壤磷的吸附能力。逐步多元回归分析也表明，无定型铝与土壤有机碳含量是影响城市土壤磷吸附能力的关键因素；土壤交换态钙镁的含量显著影响了土壤磷的吸附饱和度。总之，成土母质决定了城市土壤的磷吸附能力，而人类活动增加了土壤钙镁含量，进而降低了土壤对磷的吸附能力并提高了土壤磷的移动性。