施用海泡石对铅、镉在土壤-水稻系统中迁移与再分配的影响

Effect of Sepiolite Application on the Migration and Redistribution of Pb and Cd in Soil Rice System in Soil with Pb and Cd Combined Contamination

以浙江省绍兴市某铅(Pb)、镉(Cd)复合重污染地区土壤(全Pb含量为2 028.22 mg·kg^(-1),全Cd含量为2.36 mg·kg^(-1))及具有低Pb、Cd积累特性的浙江省典型晚粳稻品种嘉33为对象,通过土培盆栽试验,研究了海泡石的施用对铅、镉复合污染土壤中有效态Pb、Cd的含量以及水稻植株对Pb、Cd的吸收和分配关系的影响.结果表明:供试土壤中有效态Pb、Cd的含量与添加的海泡石量呈显著负相关,其相关系数分别为-0.940、-0.952,均达到显著水平(P<0.01).随着海泡石添加量的增加,水稻根、茎、叶和精米中Pb、Cd的含量有不同程度地降低,水稻根、茎、叶及精米对Pb、Cd的富集系数显著下降,同时茎对根系吸收的Pb、Cd以及精米对茎中Pb、Cd的转运系数也显著下降.当海泡石的添加量为9.00 g·kg^(-1)土时,嘉33精米中的Pb、Cd含量分别为(0.14±0.02)mg·kg^(-1)、(0.03±0.01)mg·kg^(-1),均低于国家的限量指标(GB 2762-2012);相比于对照组而言,水稻根、茎、叶及精米对Pb的富集系数分别下降了8.83%、29.96%、49.20%、79.41%,对Cd的富集系数分别下降了23.08%、63.22%、44.00%、82.35%;另外,茎对根吸收的Pb、Cd的转运系数分别下降了23.18%、52.19%,精米对茎转运的Pb、Cd的转运系数分别下降了70.83%、52.00%,意味着在铅、镉复合重污染土壤上,海泡石同时对重金属Pb、Cd在土壤-水稻系统的迁移与再分配具有较好的阻控作用,合理施用海泡石与低重金属积累品种相结合可以实现污染浓度相对较高的重金属Pb、Cd复合污染土壤的农业安全利用.

In order to research the coordination relation between sepiolite application and the contents of available lead（Pb） and cadmium（Cd） in soil or rice absorption and redistribution of Pb and Cd, a pot experiment was conducted by selecting the soil sampled from a area polluted by Pb and Cd combination in Shaoxing City of Zhejiang Province and atypical late Japonica Rice Varieties in Zhejiang Province（Jia 33） with lower accumulation for Pb, Cd. The results showed that：the contents of available Pb and Cd in soil were significantly negatively correlated with the concentration of sepiolite added, the correlation coefficients of contents of available Pb and Cd with the concentration of sepiolite added were -0.940 respectively and -0.952, which reached the significant level（P〈0.01）.The contents of Pb and Cd in rice roots, stems, leaves and polished rice had different reducing rates with the increase of the concentration of sepiolite. In addition, with the increase of the concentration of sepiolite added, the enrichment coefficients of Pb and Cd in rice roots, stems, leaves and polished rice decreased dramatically. At the same time, Pb and Cd absorbed by roots transferred to the stems decreasingly, Pb and Cd absorbed by stems transferred to the polished rice decreasingly. When the addition of Sepiolite was 9.00 g·kg-1 soil, the contents of Pb and Cd in polished rice of Jia 33 were（0.14±0.02） mg·kg-1 and（0.03±0.01） mg·kg-1 respectively, which were all lower than the national limit index（GB 2762-2012）. Compared with the control group, the enrichment coefficients of Pb in roots, stems and leaves and polished rice decreased by 8.83%, 29.96%, 49.20%, 79.41% respectively, and the enrichment coefficients of Cd decreased by 23.08%, 63.22%, 44.00%, 82.35% respectively. In addition, the transportation coefficients of Pb and Cd absorbed by roots transfer to the stems were decreased by 23.18% and 52.19% respectively and the transportation coefficients of stem rice translocation of Pb and Cd absorbed by stems transfer to the polished rice were decreased by 70.83%, 52.00%, respectively. This result means the sepiolite had a good resistance control in the migration and redistribution of Pb and Cd in soil rice system on the soil polluted by lead and cadmium, indicating the combination of rational application of sepiolite and rice varieties with lower accumulation for heavy metals can achieve safe agricultural utilization of the soil with combined contamination by a relatively higher concentration of Pb and Cd.