土壤硒富集空间分布特征及影响因素研究

以揭阳市土壤为对象,系统采集了表层土壤样(0～20 cm)1 330个和深层土壤样(150～200 cm)331个,并利用相关性分析、回归分析、方差分析及GIS空间分析技术等方法对土壤硒的含量分布、富集特征及影响因素进行了系统的分析。结果表明,揭阳市表层土壤Se含量处于0.02～2.01 mg/kg之间,几何平均值为0.48 mg/kg,是中国土壤Se平均含量的1.66倍。揭阳市土壤总体呈足硒及富硒特征,不存在硒过剩,极少区域土壤呈硒缺乏特征,表层与深层土壤表现基本一致,富硒土壤主要分布于普宁市、惠来县及北部边缘。表层土壤中Se富集面积达到52.03%,但在空间上分布零散,这可能与母质、土壤类型等因素有关。强富集区域集中分布于花岗岩与粉砂岩为母质的土壤区,而大部分由第四纪冲积物形成的土壤无富集。方差分析表明:不同母质、土壤类型及土地利用方式对土壤Se的含量及富集水平均造成不同程度的影响,其中影响揭阳市表层土壤Se含量的主要因素为成土母质。除此之外,土壤理化性质及海拔也是影响揭阳市表层土壤Se富集的重要因素。回归分析表明表层土壤Se与pH值呈极显著的负相关,并且分别与有机碳、Fe_2O_3及Al_2O_3呈极显著线性正相关。

Enrichment spatial distribution characteristics of soil selenium and its influencing factors

Abstract: Selenium (Se), a trace element in the soil, is mainly ingested by the human body from the soil-plant system through food chain. Meanwhile, Se in the soil is subjected to geological, geographical environmental factors and soil properties. Therefore, it is essential to study contents and distributions of Se in the soil for developing Se-enriched agricultural products and protecting human health. Jieyang City is one of distinctive agriculture areas of Guangdong Province, China, and the status of soil Se has an important impact on the development of local distinctive agriculture. Based on the above reasons, a total of 1 330 topsoil samples (0-20 cm) and 331 deep soil samples (150-200 cm) were collected systematically from Jieyang City to discuss the distribution, enrichment characteristics and influencing factors (including parent materials, soil types, land using types, soil physicochemical properties and elevation) of soil Se. Results showed that contents of Se in topsoil ranged from 0.02 to 2.01 mg/kg with a geometric mean value of 0.48 mg/kg that was 1.66 times larger than the average Se contents of soil in China. The topsoils of Jieyang City were in the category of Se sufficiency and Se abundance on the whole. According to the spatial distribution derived by the Kriging interpolation, soils of Se abundance were mainly distributed in Puning, Huilai and northern edge of Jieyang City. The Se enrichment area in the topsoil reached 52.03% of Jieyang City, but the spatial distribution was scattered, which may be related to factors such as parent materials and soil types. Strong Se enrichment soils were mainly distributed in the areas of granite and siltstone, while most of the soil which came from quaternary alluvial deposits was not enriched. Analysis of variance showed that different parent materials, soil types and land use patterns had different effects on soil Se contents and enrichment. The main factor affecting Se contents in surface soil of Jieyang City was soil parent materials. The soils which derived from mudstone and tuff were more likely to enrich Se. Among different land use types, farmland had great influences on soil Se content due to long-term agricultural activities. Among different soil types, yellow soil and latosolic red soil were easy to enrich Se due to their high contents of organic matter. Although soil Se content differed among different land use types, it was not obvious that soil Se was affected by human activities in Jieyang City. In addition, the physicochemical properties of soil and altitude were also important factors of leading to Se enrichment in the topsoil of Jieyang City. Regression analysis showed that there was a significantly negative correlation between Se and pH (P < 0.01), and Se was significantly positively correlated with TOC (P < 0.01), Fe2O3 (P < 0.01) and Al2O3 (P < 0.01) in the topsoil. Spearman correlation analysis showed that the Se content in the topsoil of Jieyang City had a significantly positive correlation with elevation (P < 0.01). The higher elevation, the soil Se was more easily enriched. Thus, in the development process of distinctive agriculture in Jieyang City, it is recommended to rationally use Se-enriched soils, plant Se-enriched crops, and promote the development of local distinctive agriculture in accordance with the principle of adapting to local conditions.