桂中典型碳酸盐岩区水稻及根系土硒含量特征

硒对人体的健康具有重要意义。水稻作为中国南方的主要粮食作物,研究水稻籽实与根系土硒含量特征及其影响因素,可为富硒水稻种植、富硒产业开发、提升土地利用价值提供科学依据。本文以桂中典型碳酸盐岩地区为研究区,通过采集、测试400套水稻籽实及对应的根系土样品,研究讨论其含硒水平及影响因素。结果表明:(1)水稻根系土硒含量为0.11～3.82 mg/kg,平均值为0.61 mg/kg,明显高于全国其他省份表层土壤硒含量值。(2)根系土中Cd、Cr、Hg、S元素含量高于全国土壤背景值,Cd、Cr、Hg富集现象显示了广西典型碳酸盐岩区土壤重金属高背景属性,碳酸盐岩区Se与Cd等重金属元素次生富集特征近似。(3)根系土中硒含量主要受成土母质岩系控制,土壤中Se高含量主要与石炭系、泥盆系、二叠系、三叠系地层碳酸盐岩、硅质岩的分布密切相关。此外,与土壤有机质呈明显正相关,土壤中的有机质能对硒起吸附固定作用,使得硒在土壤表层富集。(4)研究区水稻籽实硒最小值为0.015 mg/kg,最大值为0.532 mg/kg,平均值为0.08 mg/kg,富硒率高达81.5%。水稻籽实硒含量除了与根系土硒含量有关外,还与土壤中的有机质、S、pH呈显著负相关性。

Characteristics of Selenium Contents in Rice and Rhizosphere Soil in a Typical Carbonate Region of Central Guangxi

Selenium is one of the essential trace elements which are of great importance to human health. Rice is a major grain crop in south China. A thorough understanding of selenium contents in the rice and rhizosphere soil system can provide the scientific basis for the cultivation of selenium-rich rice, the development of selenium-rich industry and improving the utilization value of lands. This study chose a typical carbonate area in central Guangxi as the research area and collected 800 samples of rice seed and rhizosphere soil to study the selenium levels and the possible influencing factors. The results showed that:(1)The rhizosphere soils were generally acidic, and their selenium contents ranged from 0.11 to 3.82 mg/kg with an average of 0.61 mg/kg, which was significantly higher than those of other regions of China. (2) Cd, Cr, Hg and S elements in rhizosphere soils were relatively enriched compared with the soil background value of China, consistent with their high background contents in carbonate rock regions of Guangxi, while high contents of Se and Cd in in rhizosphere soils might be resulted from their secondary enrichments. (3) The minimum, the maximum and the average Se contents in rice seeds were 0.015mg/kg, 0.532 mg/kg and 0.08 mg/kg, respectively, the enrichment rate of Se in rice seeds was as high as 81.5%. (4) The selenium content in rhizosphere soils was controlled mainly by the parent material of the soils and related closely to the widely distributed carbonate and siliceous rocks of Carboniferous, Devonian, Permian and Triassic in the study area. In addition, significant positive correlations were found between heavy metals and soil organic matter contents. The soil organic matter can adsorb and fix Se to enrich Se in the surface soil. The selenium contents in rice seeds were controlled by the selenium contents of rhizosphere soils and correlated negatively with soil organic matter content, S content and pH of the rhizosphere soils.