南方稻田土壤有效态镉提取方法研究

摘要

土壤有效态镉是评估土壤镉污染风险和指导镉污染土壤修复的重要指标,但适用于我国南方稻田土壤的有效态镉提取方法尚未明确.为此,采集典型南方稻田土壤与早晚稻"一对二"样品90组,采用0.1 mol/L CaCl2(T1)、0.01 mol/L CaCl2(T2)、DTPA(T3)、NH4OAc(T4)、TCLP(T5)、HCl(T6)、MehlichⅢ(T7)、NaNO3(T8)、MehlichⅠ(T9)9种方法,分析了其提取能力及提取态镉与稻米镉含量的相关关系.与土壤全镉相比,9种方法分别能够提取土壤全镉的4.7％～74.4％,而提取态镉与稻米镉含量呈现更好的相关性;其中T1的提取能力适中(提取率为41.9％),其提取态镉含量与早稻、晚稻以及早晚稻米镉含量均达到极显著相关(P<0.01),相关系数(r)分别为0.618、0.338和0.363,且与大多数供试水稻品种稻米镉含量的相关性也达到显著水平(P<0.05),相关系数(r)为0.376～0.793.研究表明,0.1 mol/L CaCl2法可推荐为我国南方稻田土壤有效态镉的提取方法.%Soil available Cd plays a key role in soil Cd pollution risk assessment and Cd-contaminated soil remediation. However, there was limited research on the suitable single extraction method for evaluating the Cd bioavailability from paddy soils to rice in south China. Therefore, 90 groups of 'one-to-two' soil and rice (both early rice and late rice) samples were collected and 9 single extraction methods were assessed. The extraction methods were 0.1 mol/L CaCl2 (T1), 0.01 mol/L CaCl2 (T2), DTPA (T3), NH4OAc (T4), TCLP (T5), HCl (T6), Mehlich Ⅲ (T7), NaNO3 (T8) and Mehlich Ⅰ (T9). The extraction capacity and relationship between extractable Cd and Cd contents in rice were analyzed. The results indicated that the 4.7％ to 74.4％ of the total Cd in soils could be extracted by different extractants. The correlation relationships between extracted Cd in soils and Cd contents in rice were better than that between soil total Cd and rice Cd contents. Among the 9 tested extractants, T1 has an intermediate extraction capacity (41.9％). In T1 treatment, significant correlations were detected between extractable Cd in soils and Cd in early rice, late rice and both early rice and late rice with r of 0.618, 0.338 and 0.363, respectively (P<0.01). Moreover, significant correlations were discovered between extractable Cd of T1 treatment in soils and rice Cd contents of major rice varieties (r=0.376 to 0.793). In conclusion, the phytoavailability of Cd in paddy soils could be well described by extractable Cd from method T1 and it could be recommended as the extraction method of soil available Cd in south China.