应用梯度扩散薄膜技术评价天然富硒土壤中硒的生物有效性

吴超; 孙彬彬; 陈海杰; 成晓梦; 贺灵; 曾道明

doi:10.15898/j.cnki.11-2131/td.202109290134

应用梯度扩散薄膜技术评价天然富硒土壤中硒的生物有效性

Assessment of Selenium Bioavailability in Natural Selenium-rich Soil Based on Diffusive Gradients in Thin Films

摘要

摘要: 有效硒是评价土壤中硒对植物供给能力的重要指标，中国目前尚无测定土壤有效硒的统一方法。化学提取法、土壤溶液法常用于测定土壤有效硒含量，但存在缺乏普遍适用提取剂类型、目标态提取不完全和对非目标态溶解等问题。梯度扩散薄膜（DGT）技术是一种基于解离、扩散动力学的有效态测定方法，已有学者将其应用于土壤有效硒的测定并取得良好效果，但是否适用于天然富硒土壤中硒生物有效性评价尚不明确。为探明梯度扩散薄膜技术评价天然富硒土壤中硒生物有效性的可行性，本文以浙江省上墅乡和汾口镇分布的天然富硒土壤为研究对象，实验应用化学提取法、土壤溶液法和DGT技术包括Fe-oxide（水铁矿型）DGT、Zr-oxide（水合氢氧化锆型）DGT评价土壤中硒的生物有效性。结果表明：①Fe-oxide DGT测得的有效硒平均含量为0.17±0.076μg/L，Zr-oxide DGT测得的有效硒平均含量为0.20±0.13μg/L。两种类型DGT测得有效硒含量差异不大，但由于Zr-oxide DGT对Se⁴⁺具有专性吸附特征，导致Zr-oxide DGT无法有效反映植物体内硒含量水平。对于检测土壤硒生物有效量，Fe-oxide DGT要优于Zr-oxide DGT；②植物体内硒含量C_plant-Se与三种方法测定的有效硒含量均呈显著正相关，但C_plant-Se与Fe-oxide DGT测定的有效硒含量相关系数（r=0.705）大于其他两种方法；③基于DGT技术计算得出的R值（土壤颗粒向土壤溶液补充硒的能力）和K_d值（土壤固相与液相之间的分配系数）表明上墅研究区相较于汾口研究区土壤中硒具有更强的迁移性，但其土壤固相向土壤溶液补充硒离子的速率小于汾口研究区。综上认为，对于评价天然富硒土壤中硒生物有效性而言，DGT方法优于化学提取法和土壤溶液法，在测试性能和反映土壤动力学过程信息方面更具优势。

Abstract:
BACKGROUNDAvailable selenium is an important index to evaluate the supply capacity of selenium from the soil to plants. Unfortunately, there is no general method for the determination of available selenium in soil in China. Chemical extraction and soil solution methods are commonly used to evaluate bioavailability of selenium. Furthermore, there are problems such as the lack of universally applicable extractant types, incomplete extraction of target states, and dissolution of non-target states. The diffusive gradient in thin-films (DGT) technique is a method based on dissociation and diffusion kinetics which has been successfully used to assess the bioavailability of selenium. However, it is not clear whether the DGT technique can be used in natural selenium-rich soil.
OBJECTIVESTo investigate the feasibility of the DGT technique to evaluate the bioavailability of selenium in natural selenium-rich soil.
METHODSNatural selenium-rich soils from Shangshu and Fenkou in Zhejiang Province were chosen as the research objects. Fe-oxide DGT, Zr-oxide DGT, chemical extraction, and soil solution methods were used to evaluate selenium bioavailability.
RESULTS(1) The average of available selenium measured by Fe-oxide DGT was 0.17±0.076μg/L, whereas the average of available selenium measured by Zr-oxide DGT was 0.20±0.13μg/L. Zr-oxide DGT cannot be used effectively to reflect the content of selenium in plants due to the specific adsorption characteristics to Se⁴⁺. Fe-oxide DGT was suitable for the bioavailability evaluation of selenium in soil rather than Zr-oxide DGT. (2) There was a significant positive correlation between the selenium content in plants (C_plant-Se) and the available selenium content determined by the three methods. The correlation between available Se by Fe-oxide DGT and Se concentration in plants (r=0.705) was greater than the chemical extraction method and soil solution method. (3) The K_d value and R value calculated from DGT and soil solution methods indicated that the soil of the Shangshu area had stronger selenium mobility than the Fenkou area, but the rate of Se supply from the soil solid phase to the soil solution was less than the Fenkou area.
CONCLUSIONSDGT is more suitable for evaluating selenium bioavailability compared with chemical extraction and soil solution methods because it has more advantages in testing performance and reflecting the information of soil dynamics process.

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