Agro-Environmental Protection Institute, Ministry of Agriculture, Tianjin 300191, China; College of Agronomy & Resources and Environment, Tianjin Agricultural University, Tianjin, 300384, China.
Agro-Environmental Protection Institute, Ministry of Agriculture, Tianjin 300191, China.
Sci Total Environ. 2017 Feb 1;579:1282-1288. doi: 10.1016/j.scitotenv.2016.11.115. Epub 2016 Nov 29.
Heavy metals naturally occur in soil but their concentrations may be changed by seasonal rainfall under double-rice cropping system. The field trials at three sites, which represent low, medium and high cadmium (Cd) content in soil, revealed significant genotypic and environmental variations in grain Cd concentrations. Most cultivars in late rice at three sites produced grains with Cd content over the maximum permissible concentration (MPC) 0.20mgkg. However, grain Cd content in early rice was over MPC only at high Cd site. When planted at same site, late rice showed remarkably higher content of Cd as well as K, Mg, Fe and Mn than that in early rice in both grains and rachises. Content of Ni, Pb and Cr was generally in the safe range and it was determined by the interactions between genotypes and environmental factors. Element concentrations in rachises were about 2-10 times higher than those in grains, depending on element species, cultivars, locations and seasons. Low-Cd-accumulation cultivars generally displayed both lower Cd content in rachis and lower Cd transportation ratio from rachises to grains than those of high-Cd-accumulation cultivars. There was a significant and positive correlation between Cd and Mn concentrations in grains. The most important factor that causes great variation in Cd accumulation in rachises and grains between early and later rice is water contents and levels in paddy soils mainly caused by different rainfall amount. Inhibiting Cd accumulation in rachises and Cd transportation from rachises to grains could efficiently decrease Cd content in rice grains produced in contaminated soil.
重金属在土壤中自然存在，但在双季稻种植制度下，季节性降雨会改变它们的浓度。在三个代表土壤中镉（Cd）含量低、中、高的地点进行的田间试验表明，稻谷中 Cd 浓度存在显著的基因型和环境变异。三个地点的晚稻品种中，大多数品种的稻谷 Cd 含量超过最大允许浓度（MPC）0.20mgkg。然而，只有在 Cd 含量高的地点，早稻的稻谷 Cd 含量才超过 MPC。在同一地点种植时，晚稻的稻谷和稻穗中的 Cd 以及 K、Mg、Fe 和 Mn 的含量明显高于早稻。Ni、Pb 和 Cr 的含量一般在安全范围内，这取决于基因型和环境因素之间的相互作用。稻穗中的元素浓度大约是稻谷中的 2-10 倍，具体取决于元素种类、品种、地点和季节。低 Cd 积累品种的稻穗和稻谷中的 Cd 含量以及从稻穗向稻谷的 Cd 转运率通常低于高 Cd 积累品种。稻谷中 Cd 和 Mn 浓度之间存在显著的正相关关系。导致早稻和晚稻的稻穗和稻谷中 Cd 积累差异的最重要因素是水分含量和稻田土壤中的水平，这主要是由不同的降雨量引起的。抑制稻穗中 Cd 的积累和 Cd 从稻穗向稻谷的转运可以有效地降低受污染土壤中生产的稻谷中的 Cd 含量。
