大气臭氧胁迫对稻季土壤Cd生物有效性的影响

为明确大气O_3浓度升高对稻季土壤Cd生物有效性的影响,利用开顶式气室(OTCs)设置正常大气和臭氧浓度升高(比周围大气高40 nmol·mol-1)处理,土壤设置外源加入0、5、50 mg·kg~(-1)Cd处理,研究水稻生长期间不同深度土壤Cd含量的动态变化以及成熟期植株生物量和体内Cd含量的变化情况。在水稻分蘖期、拔节期、抽穗期和成熟期分别采集耕层0~5、5~10、10~15 cm深度土样,同时利用BCR连续提取法和DTPA提取法评价盆栽水稻土壤Cd生物有效性。结果表明,臭氧熏蒸显著降低了无污染土壤处理水稻籽粒生物量,降幅达2.92%,但却有增加植株各器官Cd含量的趋势,中度和重度污染土壤处理水稻的籽粒Cd含量较对照分别增加了20.20%和6.67%,差异不显著;臭氧熏蒸加剧了水稻生长对残渣态Cd的活化,营养生长时期更加明显,臭氧熏蒸不利于水稻的生长,在Cd污染土壤上会加剧Cd对作物的毒害,可能增加其通过生物富集进入食物链的风险。

Atmospheric ozone stress improving biological availability of Cd in soil during the rice season

The objective of this study was to determine the changes in the bioavailability of Cd in soil exposed to elevated atmospheric O₃ during the rice season. Open-top chambers(OTCs) were used to set up normal atmospheric conditions and an elevated atmospheric O₃ condition(elevated 40 nmol·mol^-1 more than normal atmospheric conditions). We added 0 mg·kg^-1,5 mg·kg^-1, and 50 mg·kg^-1 extrinsic Cd to soil to study the dynamic changes of Cd in the soil while the rice was growing. The changes in plant biomass and Cd content in different plant organs at the maturity period were recorded. Soil samples were collected at 0~5 cm, 5~10 cm, and 10~15 cm depths of topsoil at tillering, jointing, heading, and maturity stages. The bioavailability of soil Cd was evaluated by the Community Bureau of Reference(BCR) sequential extraction and the DTPA extraction. The results showed that ozone fumigation significantly reduced the grain yield of rice in the treatment of non-polluted soil, with a decrease of 2.92%. However, Cd content tended to increase in plant organs from contaminated soil-20.20%(moderately polluted soil) and 6.67%(heavily polluted soil), respectively. Ozone fumigation aggravated the activation of residual Cd in rice growth, and the vegetative growth period. Ozone fumigation demonstrated a negative effect on the growth of rice, while the presence of Cd pollution did more harm to the crops, which may increase the risk of Cd biological enrichment into the food chain.