地块尺度城市土地质量地球化学调查方法:以雄安新区起步区为例

以土地质量地球化学调查评价成果服务于城市土地资源精准管护为目标，选择中国城镇化探路者的雄安新区起步区为研究对象，采用差异化分类布设样点，开展不同采样密度条件下地块尺度土壤元素空间插值精度、地块（图斑）插值精度和地球化学预测评价等级准确度的定量评估研究.结果表明：①采用差异化分类布设样点方法使平面上随机分布的区域地球化学量变值在每一个地块（图斑）都有明确的量值反映，能满足城市土地资源精准管护对单一地块（图斑）具有质量属性的基本需求；②研究区土壤元素指标空间变异性以轻中度为主；其中Hg、Pb、Cd、Cu、Zn、N、P和Se受人类生产活动影响，具有较高的空间变异性；③相同采样密度条件下，元素含量空间变异性越大，其空间插值精度和图斑插值精度越低；同一种元素插值精度受采样密度的影响，但采样密度的增大并不一定能够识别土壤元素含量的结构性连续组分；区内土壤环境本底清洁，重金属含量低于GB15618-2018标准，其插值评价等级和实测评价等级结果基本一致；养分指标N、P和K含量区间变化大，受人为扰动和空间变异性等因素影响，其预测等级和实测等级差异较大；④采用16点·km^-2的采样密度开展地块尺度城市土地质量地球化学调查评价可以满足研究区及类似地区城市土地资源精准管控的需求.

Geochemical Survey Method of Land Quality in Land Parcel Scale City: A Case Study of the Initial Area of the Xiong'an New District

In order to evaluate the land quality geochemical survey achievement in the service of the accurate management of urban land resources, the initial area of the Xiong''an New District as urbanization pathfinder in China is chosen as the research subject. The sample points were set by differential classification, and the spatial interpolation accuracy of the soil elements at a plot scale and a quantitative assessment of the consistency of the land plot (pattern spot) prediction evaluation were studied under the conditions of different sampling densities. The regional geochemical variation values randomly distributed on the plane can be reflected quantitatively by differential classification sampling, which can meet the basic demand of the quality attribute of a single plot (map spot) by the accurate management of urban land resources. The spatial variability of soil elements is mostly middle to moderate, and Cd, Cu, Pb, Hg, Se, N, P, and other elements of high spatial variability are affected by human industrial and agricultural production activities. Under the same sampling density, the larger the element variation coefficient, the worse the spatial interpolation accuracy. Although the interpolation accuracy of the same element index is affected by the sampling density, the increase in the sampling density could not identify the continuous component on the structure of the soil element content. The soil environment is clean, and the heavy metal content is lower than the GB15618-2018 standard. The interpolation results are basically consistent with the grading results of the measured values, while the contents of N, P, and K of the nutrient indices vary greatly, and the predicted and measured geochemical grades of the plots (map spot) differ substantially under the influence of factors such as human disturbance and spatial variability. The quantitative evaluation of the six different sampling densities indicates that the 16 points·km^-2 sampling density adopted in the geochemical survey and evaluation of urban land quality can satisfy the needs of an accurate control of urban land resources in the study area and similar areas. The research can provide key technologies to support and serve the accurate management of urban land resources for geochemical surveys and the evaluation of land quality in land parcel scale cities.