College of Resource and Environmental Engineering, Guizhou University, Guiyang, 550025, China; College of Environmental Science and Engineering, Central South University of Forestry and Technology, Changsha, 410004, China.
College of Environmental Science and Engineering, Central South University of Forestry and Technology, Changsha, 410004, China; Hunan Engineering Laboratory for Control of Rice Quality and Safety, Changsha, 410004, China.
Environ Pollut. 2020 Sep;264:114681. doi: 10.1016/j.envpol.2020.114681. Epub 2020 Apr 28.
Rapeseed (Brassica napus L.) is a winter oil crop and biodiesel resource that has been widely cultivated in the southern part of China. Applying rapeseed residue (RSD) to summer rice fields is a common agricultural practice under rice-rapeseed double cropping systems. However, in Cd-contaminated paddy fields, the influence mechanisms of this agricultural practice on the migration and distribution of Cd fractions in soil are not clear. Therefore, a field experiment was carried out to analyse the changes in soil pH, organic matter (OM), microbial biomass carbon (MBC) and nitrogen (MBN), enzyme activity (urease (UA), acid phosphatase (ACP), and dehydrogenase (DH)), Cd distribution fractions, and Cd concentration in rice tissues after RSD application. The results showed that RSD treatment significantly increased the soil OM and MBC concentrations and UA, ACP, and DH activities, decreased the soil acetic acid-extractable fraction of Cd (ACI-Cd), and increased the reducible fraction of Cd (Red-Cd). The formation of stable organic complexes and chelates upon application of RSD is a result of the high affinity of Cd for soil OM. The activities of soil ACP, DH and MBC can well reflect Cd ecotoxicity in soil, particularly the DH activity. In addition, RSD application was helpful in inducing iron plaque formation. The "barrier" effect of iron plaque resulted in reduced Cd accumulation in different tissues of rice. The health risk of rice consumption also decreased as a result of RSD application; it decreased by 0.89-30.0% and 24.1-51.7% in the two tested fields. Overall, the application of RSD was increased soil OM, microbial biomass, and enzyme activity, and these changes was instrumental in reduce the risk of cadmium pollution in rice fields.
油菜（Brassica napus L.）是一种冬季油料作物和生物柴油资源，在中国南方广泛种植。在稻-油双季种植制度下，将油菜残体（RSD）应用于夏季稻田是一种常见的农业实践。然而，在镉污染的稻田中，这种农业实践对土壤中镉形态的迁移和分布的影响机制尚不清楚。因此，进行了田间试验，以分析 RSD 施用后土壤 pH 值、有机质（OM）、微生物生物量碳（MBC）和氮（MBN）、酶活性（脲酶（UA）、酸性磷酸酶（ACP）和脱氢酶（DH））、Cd 分布形态以及水稻组织中 Cd 浓度的变化。结果表明，RSD 处理显著增加了土壤 OM 和 MBC 浓度以及 UA、ACP 和 DH 活性，降低了土壤醋酸提取态 Cd（ACI-Cd），增加了可还原态 Cd（Red-Cd）。RSD 施用后形成稳定的有机络合物和螯合物，是因为 Cd 与土壤 OM 具有高亲和力。土壤 ACP、DH 和 MBC 的活性可以很好地反映土壤中 Cd 的生态毒性，尤其是 DH 活性。此外，RSD 施用有助于诱导铁膜的形成。铁膜的“屏障”效应导致水稻不同组织中 Cd 积累减少。RSD 施用也降低了水稻食用的健康风险，在两个试验田分别降低了 0.89-30.0%和 24.1-51.7%。总体而言，RSD 的施用增加了土壤 OM、微生物生物量和酶活性，这些变化有助于降低稻田镉污染的风险。
