【摘要】 文章以浙江省平湖市为典型三角洲平原区,开展了多种尺度、不同采样方法的对比试验。结果表明,田块内土壤元素分布较为均匀,小范围内元素的空间分异性较小,而田块之间土壤元素含量差异性明显增加;Hg,Cd等典型污染元素空间分异性较强,而人为污染扰动较弱的元素的空间分布较为均一;不同采样方法取得的区域性资料,其统计值接近,空间分布模式也相似,但有些元素仍有较明显差异。因此,中大比例尺地球化学调查时,应根据调查研究的目标任务,充分考虑地块分布、土壤类型和土地利用方式,选择合理的采样点。土壤样品可采取多坑点采集、多子样组合的方式,以保证样品的代表性,同时减少分析测试工作量。更多还原

【Abstract】 Sampling strategy and its rationality is the key factor controlling data quality of a geochemical survey. Spatial distribution pattern and variability of soil property and elements are the theoretic basis to make sampling layout. However, soil sample density and sampling technique should consider not only sample representative but also its cost and maneuverability in the field.The study area, Pinghu of Zhejiang Province, lies in the Yangtze River delta plain. As soil property and element concentration exist in a multi-scale distribution pattern and variability, this study was designed with different sampling density, covering areas from several square kilometers to 64km 2 by several sampling techniques. A few soil geochemical indicators including As, B, Cd, Cu, Hg, Mo, N, organic carbon, Pb, pH, and Zn were determined by the analytical center at IGGE. By comparing statistical parameters of element concentration and their spatial distribution pattern, middle and large-scale soil geochemical survey methods were recommended.It showed that the variation of soil element concentration between sampling sites is quite little in the same farm plot. But element concentration varies greatly between farm plots in a quite small area such as within 1km 2. It is also clear that the variation of typical contamination elements is greater than those non-contamination or subtle-polluted elements both inner one farm plot and between different farm plots. The variation between farm plots is apparently related to land formation and different cultivation and fertilization level though hundred and thousand of years. As the area of each farm plot is small, particularly in southern China, it was suggested that farm plots should be chosen as analytical sample unit when carrying on 1 ∶5 000 and 1 ∶10 000 scale geochemical survey. To assure sample representative three to five sampling pits should be selected to collected soils, and then get a composite sample for analysis.Considering the great variation of soil element concentration between farm plots, it was suggested that sampling sites should be carefully selected within analytical sample units of 0.25km 2 or 1km 2 dependent on soil type and land use when doing 1 ∶50 000 scale geochemical survey. It should also consider geochemical survey target to select suitable sampling sites so that the data achieved can be used for special expected study. It was also recommended that soil samples should be collected at several pits and are composed of several sub-samples. For example, a composite analytical sample for 1km 2 unit can be achieved by more than five sub-samples, each of which is composed of 2～3 sampling pits. Another way is that 1km 2 unit can be divided into 4 sub-units of 0.25km 2 and sub-samples were collected within them.The test results of three different sampling methods showed that average contents of soil elements don’t have great difference, and their spatial distribution patterns are also very similar for most elements. But there are some differences for typical contamination elements such as Cd and Zn particularly for the third sampling method. It presented that although the third sampling method can obtain a representative sample for one farm plot it seems un-available to indicate the geochemical characteristics of the survey unit as a whole. So other two methods are more adaptable to soil geochemical mapping.更多还原