土壤硒与重金属元素的质量评价及农产品效应研究

Quality assessment of selenium and heavy metals in soil and their effects on agricultural products

关键词:  农业地质  富硒  耕地土壤  地球化学

Key words:  agricultural geology  selenium-rich  cultivated soil  geochemistry

摘要:

依托贵州省第一次全省耕地质量地球化学调查评价成果，根据收集的贵州某蔬菜产业园区地质、环境、地球化学等资料，以该园区572件表层耕地土壤及21件农产品为样本，评价该园区硒与重金属元素的地球化学质量等级及农产品效应。结果表明：园区富硒耕地土壤资源丰富，表层土壤硒（Se）元素平均含量为0.60 mg/kg，富硒特色耕地合计有33.15 km² ，占园区耕地面积的70.06%；同时，园区土壤重金属元素含量相对较低，仅镉（Cd）元素存在局部偏高情况。整体来说，以火烘组黑色黏土岩夹灰岩、泥灰岩及砂岩为成土母岩的园区内整体土壤性质较为优质，富硒的同时重金属元素以Ⅰ类级别为主。然而，针对园区部分农产品采样测试发现，采集的茄子和水稻样品存在部分重金属超标情况，且富硒比例较低，研究认为与园区内农作物品种和土壤酸碱度关系较大，后续园区作物种植应充分考虑土壤地球环境特征，遵循自然演化规律与生态系统原理，坚持科学发展观，种植适合的特色农作物，高效推动富硒特色健康、安全的农产品发展。

Abstract:

Background, aim, and scope Selenium is a vital nutrient with profound positive impacts on human health, and has been officially recognized as one of the essential trace nutrients for the human body by the World Health Organization (WHO); it exerts anti-cancer and antioxidant effects, and effectively enhances human immune function. Against the overarching backdrop of national food security, the targeted development of selenium-enriched agriculture in black rock series parent rock regions across China is urgently warranted. It is imperative to clarify the distribution and enrichment characteristics of selenium and heavy metal elements in regional soils, and implement targeted soil environment improvement measures, so as to upgrade cultivated land quality and lay a solid foundation for safeguarding national food security. The findings of this study are expected to promote the sustainable development of the regional ecological environment, support the development and optimization of selenium-enriched agricultural products, pave a characteristic and high-efficiency agricultural development path, and provide critical scientific support for the construction of local characteristic agricultural industrial bases and the cultivation of pillar industries that boost rural incomes. Materials and methods This study was conducted based on the results of the first round of geochemical survey and evaluation for cultivated land quality in Guizhou Province. Relying on the collected geological, environmental and geochemical data of a typical vegetable industrial park in Guizhou Province, a total of 572 surface cultivated soil samples and 21 agricultural product samples were collected from the park. A systematic assessment was carried out on the geochemical quality grades of selenium and heavy metal elements in the park’s soils, as well as the selenium enrichment and heavy metal safety effects of corresponding agricultural products. Results The results showed that the selenium-rich cultivated land in the park was rich in soil resources. The average selenium content in the surface soil was 0.60 mg/kg. The total selenium-rich characteristic cultivated land was 33.15 km² , accounting for 70.06% of the cultivated land area of the park. At the same time, the content of heavy metal elements in the soil of the park is relatively low, and only the cadmium element is locally high. On the whole, the overall soil properties in the park with the black clay rock of the Huohong Formation interbedded with limestone, marl and sandstone as the soil-forming parent rock are relatively high, and the heavy metal elements are mainly of Class I level while enriching selenium. Discussion Through sampling and testing of some agricultural products in the park, it was found that some heavy metals in the collected eggplant and rice samples exceeded the standard, and the selenium-rich ratio of the samples was low. The study believes that this phenomenon is closely related to the varieties of crops planted in the park and the soil pH. In the subsequent crop planting process of the park, full consideration should be given to the characteristics of the soil geochemical environment, following the laws of nature, adhering to the scientific concept of development, and planting suitable characteristic crops to effectively promote the development of selenium-rich characteristic, healthy and safe agricultural products. Conclusions (1) The content of selenium in the surface soil of the park is high. The geochemical comprehensive grade of soil environmental quality is mainly class Ⅰ, followed by class Ⅱ. Only the cadmium element is locally high, which is mainly affected by the distribution of soil parent rock. (2) Rice has a relatively strong ability to enrich elements in root soil, especially cadmium and selenium. However, eggplant has a stronger ability to enrich mercury and a weaker ability to enrich selenium. Different agricultural products have different absorption capacity of elements in soil. (3) Soil pH is one of the factors affecting the enrichment ability of crops to related elements in root soil. When the soil pH value is between 6 and 7, the enrichment ability is the strongest, especially cadmium and selenium. Recommendations and perspectives Based on the park’s soil-forming parent rock and soil pH characteristics, plant selenium-accumulating crops in the “high-selenium and low-cadmium areas” of Huohong Formation, promote low-cadmium varieties and avoid planting eggplants in carbonate rock “high-selenium and high-cadmium areas”. Reduce cadmium activity by applying lime or biochar, collaborate with research institutions to screen “high-selenium and low-heavy metal” varieties and establish a cultivation technology system. Supplement element absorption data of typical crops in Southwest China, build a “soil, irrigation water and agricultural products” monitoring network, label products with “parent rock+production area” information, and promote the transformation of geological resources into farmers’ income.