采用盆栽试验,利用开顶式气室(Open Top Chamber,OTC)研究了5个籼稻品种在高、低铜镉复合污染土壤上,CO_2浓度升高对水稻生长及吸收Cu、Cd和矿质元素Fe、Zn、Ca、Mn的影响,并对稻米中Cd的安全性进行了评价,了解Cd污染对人类健康的潜在风险。结果表明:CO_2浓度升高,显著降低了低复合污染土壤上稻米的生物量,而显著增加了高复合污染土壤上的稻米生物量。CO_2浓度升高降低了低污染土壤上稻米Cu含量,降低幅度为4.75%-24.49%,增加了高污染土壤上稻米Cu含量,增加幅度为6.60%-40.37%;而稻米Cu的总吸收量在低、高复合污染土壤上均是降低的。低、高复合污染土壤上,CO_2浓度升高显著降低了三香优974稻米的Cd含量和吸收量;增加了其他4个品种稻米Cd含量和吸收量。CO_2浓度升高对不同品种稻米中Fe、Zn、Ca、Mn含量影响存在显著差异。CO_2浓度正常、升高条件下,两种污染土壤上金优463稻米中Cd含量超过食品卫生标准(Cd≤0.2 mg/kg),三香优974在正常CO_2浓度条件下其稻米Cd含量超过食品卫生标准。在低、高复合污染土壤上,金优463和三香优974稻米中Cd的THQ值均大于1,说明对人体暴露接触的潜在风险比较严重。CO_2浓度升高显著降低了三香优974稻米中Cd对人体暴露接触的潜在风险,而对其他4个水稻品种稻米Cd的THQ值影响不明显。
英文摘要:
CO_2 concentrations are presently elevated and are expected to continue increasing in the future,resulting in global warming and climate change.Heavy metal pollution is also a serious issue,particularly in copper mining areas.While there have been results published on each of these issues individually,these have been limited to single factors.Consequently,there have been limited data on the comprehensive combined effects of climate change and heavy metal pollution (for example,combined copper and cadmium pollution in soils).This study aimed to investigate the effects of elevated CO_2 levels on the uptake of Cu and Cd in rice varieties grown in soil contaminated with both of these pollutants.The study also considered concentrations of four mineral elements(Fe,Zn,Ca,and Mn),together with potential hazards of Cd contamination in rice to human health.A pot experiment was conducted in an open top chamber at two CO_2 concentration levels,i.e.,normal level of ambient concentration(380mumol/mol) and an elevated concentration level(760mumol/mol).Five different varieties of rice were selected for purposes of this experiment.The results showed a reduction in dry biomass production of rice grown in soil subject to low-level contamination from multiple pollutants;conversely,dry biomass production was enhanced under conditions of elevated CO_2 in soils with high-level contamination from multiple pollutants.Cu concentrations of the five indica rice grains decreased by 4.75%-24.49%in low-level multi-contaminated soils but incr2 eased by 6.6%-40.37%in high-level multi-contaminated soils with elevated CO_2 concentrations.Total Cu uptake in rice decreased at both contamination levels under elevated CO_2 concentrations.Similarly,Cd concentrations and total Cd uptake of the San Xian-you(974)grain declined significantly at both levels of contamination,with decreases in Cd content of 43.44%, 57.95%,and 47.01%,60.56%,respectively.While Cd concentrations and total Cd uptake of the four rice varieties all increased,the range of increase was between 25.42%-103.07% and 12.62%-20.05%,respectively.The total uptake of Cd and Cu of the four rice varieties was higher in high-level multi-contaminated soils under elevated and ambient CO_2 treatments,when compared to soils subject to a low level of contamination.There were significantly different effects on concentrations of Fe,Zn,Ca,and Mn in the five indica rice varieties of elevated CO_2 concentrations.Zn concentrations of the San Xian-you(974)grain increased significantly in both low-level and highlevel multi-contaminated soils with elevated CO_2 concentrations.Similarly,Mn concentrations of San Xiang-you(974)and Jinyou-463 increased significantly at both contamination levels under elevated CO_2 conditions.Cd concentrations in the Jinyou-463 grain exceeded food hygienic standards(Cd<0.2 mg/kg)under both elevated and ambient CO_2 treatments,at both levels of contamination.Cd concentrations of Sanxiangyou-974 also exceeded food hygienic standards under ambient CO_2 levels.At both contamination levels,the target hazard quotient(THQ)for Cd of Jinyou-463 and Sanxiangyou(974)exceeded 1,indicating that the consumption of both rice varieties would lead to high potential human health risks.