粤北某矿区周边镉锌污染稻田土壤田间植物修复研究

摘要

粤北地区多金属矿开采导致的矿区周边农田土壤重金属污染问题突出,探索适合当地条件的土壤污染修复技术与模式对逐步改善土壤环境质量,保障农产品安全和人体健康具有重要意义.为考察植物技术措施对粤北矿区周边重金属污染农田土壤的修复和安全利用的可行性,选择粤北某矿区周边重金属镉锌中度污染稻田,通过田间试验开展了超富集植物伴矿景天(Sedum plumbizincicola)、富集植物杨桃(Averrhoa carambola)、农作物玉米(Zea mays)低积累品种单种及套种对污染土壤植物修复和安全利用效果研究.结果表明,单种模式下,伴矿景天田间生长217 d后,其地上部生物量可达2.82 t·hm-2,地上部Cd和Zn平均质量分数分别为119 mg·kg-1和7716 mg·kg-1,对Cd的修复效率可达11.1%;杨桃田间生长约600 d后,其根、茎和叶生物量分别可达15.4、15.5和7.81 t·hm-2,Cd质量分数分别为8.21、14.1和15.4 mg·kg-1,Zn质量分数分别为199、294和642 mg·kg-1,其对Cd的总体修复效率可达15.9%.伴矿景天和杨桃套种模式下,两者种植密度均较单种时降低一半,两种修复植物套种处理对Cd修复效率可达到13.5%.试验稻田改种低积累品种玉米,无论玉米单种或同伴矿景天套种其籽粒中Cd质量分数均可达到食品安全国家标准限量要求.利用伴矿景天和杨桃对粤北受镉中度污染稻田土壤进行修复以及通过种植低积累品种玉米实现污染土壤安全利用具有较强的可行性.%There is substantial trace metal pollution of agricultural land around a mining area in Northern Guangdong Province due to mining of the ores of multiple metals. It is very important to improve soil quality and to ensure the safety of agricultural products and human health by exploring remediation technology and a model of soil pollution suitable for the local conditions. Therefore, a field experiment was carried out to evaluate the phytoremediation or safe utilization of Cd and Zn polluted paddy soil in the mining area in Northern Guangdong using intercropping with Sedum plumbizincicola,Averrhoa carambola and Zea mays or sole cropping of the three crop species.After 217 days of monocropping the aboveground biomass of Sedum plumbizincicola was 2.82 t·hm-2,with average contents of Cd and Zn of 119 mg·kg-1and 7 716 mg·kg-1, respectively, and the remediation efficiencies of Cd was up to 11.1%.After about 600 days of growth the root,stem and leaf biomass values of Averrhoa carambola were up to 15.4,15.5 and 7.81 t·hm-2, the contents of Cd were 8.21, 14.1 and 15.4 mg·kg-1, and the contents of Zn were 199, 294 and 642 mg·kg-1. Based on whole plants of Averrhoa carambola, Cd remediation efficiencies was 15.9%. The intercropping planting density was half that of the monocrop.The remediation efficiency of Cd for two-species intercropping reached 13.5%.When Zea mays was grown in the paddy soil the grain Cd content reached the upper limit of the national food safety standards in both monocropping and intercropped with Sedum plumbizincicola.The results indicate that it is feasible to use Sedum plumbizincicola and Averrhoa carambola to remediate paddy soils moderately polluted with cadmium in Northern Guangdong Province or to achieve safe utilization of the contaminated soil by planting Zea mays varieties with low Cd accumulation.