麥田土壤重金屬超標及其誘發的小麥安全生產問題是當前我國的重要農業環境問題。近日，中國農科院環發所楊建軍研究員課題組在Science of The Total Environment上發表了題為 “Mercury fractionation, bioavailability, and the major factors predicting its transfer and accumulation in soil–wheat systems”的研究論文。該研究基於全國不同類型土壤探究了小麥在汞超標土壤的吸收累積特徵，系統揭示了土壤汞生物有效性及其主控因子，並利用多元迴歸構建小麥汞吸收累積的預測模型，為土壤汞有效性預測及麥田汞安全閾值構建提供了重要理論依據。

doi：10.1016/j.scitotenv.2022.157432

Shoot Hg content positively correlated to soil total/available Hg, and Amo-Mn.

Hg uptake and accumulation was affected by exchangeable/organically bound Hg.

Soil pH role was determinant in Hg mobility and soil-shoot bioaccumulation.

Acidic soils tend to bear a lower grain yield compared to alkaline soils.

Soil mercury (Hg) and its bioaccumulation in food crops have attracted widespread concerns globally due to its harmful effects on biota. However, soil mercury fractionation, bioavailability, and the major factors predicting its transfer and accumulation in soil–wheat-systems have not been thoroughly explored. Twenty-one (21) soil samples collected throughout China with a wide spectrum of physico-chemical characteristics were contaminated with HgCl2 and winter wheat (Triticum aestivum L.) was grown on the soils in a greenhouse pot-culture experiment for 180 days. A four-step sequential extraction was used segregating soil Hg into water-soluble (F1, 0.21 %), exchangeable (F2, 0.07 %), organically bound (F3, 16.40 %), and residual fractions (F4, 83.32 %). Step-wise multiple linear regression (SMLR) and path analysis (PA) were used to develop a prediction model and identify the major controlling factors of soil-wheat Hg transference. The SMLR results revealed that wheat Hg in leaves, husk, and grain was positively correlated with soil total and available Hg, and crystalline manganese (Cryst-Mn), while negatively correlated with soil pH, amorphous manganese (Amor-Mn) and crystalline aluminium (Cryst-Al). Bioconcentration factor (BCF) values were significantly higher in acidic soils (highest 0.05), with phytotoxic effects in some soils, as compared to alkaline soils (lowest 0.006). Furthermore, wheat grain Hg was significantly correlated with total (R2 = 0.25), water-soluble (R2 = 0.54) and NH4Ac-extractable Hg (R2 = 0.43) while also had a good correlation with soil pH (R2 = 0.20). In conclusion, the soil total and available Hg (water-soluble + exchangeable fraction), pH, organic matter, and Amor-Mn are the most important soil variables that support Hg uptake in the wheat plants, which benefit managing Hg-enriched agricultural soils for safe wheat production.

本研究發現不同土壤中汞在小麥的吸收累積量與土壤pH密切相關，總體而言，酸性土壤中小麥體內汞的吸收累積量偏高，而鹼性土壤中小麥體內汞的吸收累積量偏低（圖1）；該研究結果與小麥的BCF變化特徵相一致，酸性土壤中小麥汞的BCF值顯著高於鹼性土壤（圖2）。路徑分析和相關性分析等表明控制土壤-小麥系統中Hg運移轉化的主要因素包括土壤醋酸銨提取態有效態汞含量、水溶態汞含量以及晶體錳含量、pH、有機質等（圖3）。多元迴歸分析發現高精度預測土壤-小麥體系中汞的有效性涉及多種環境因子，表明其遷移轉化過程複雜，相關機制有必要進一步探究。

Fig. 1. Hg concentration (in milligrams per kilogram) in the different parts of the wheat (a) Hg concentration in grain (b) Hg concentration in husk and (c) Hg concentration in leaf.

Fig. 2. BCF of the wheat in the 21 investigated soils under different Hg treatments; (CK), low Hg (spiking level 1) and high Hg (spiking level 2).

Fig. 3. Path diagram for the relationship between soil properties, including soil total and available Hg and wheat grain Hg contents.

通訊作者：楊建軍研究員

中國農科院農業環境與可持續發展研究所

現任國家小麥產業體系華北重金屬汙染防治崗位科學家，入選中國農業科學院“農科英才”；國家萬人領軍人才——曾希柏研究員領銜的“退化及汙染農田修復”創新團隊骨幹成員；主要研究方向：土壤-植物系統重金屬汙染控制及修復機理、土壤-作物系統養分週轉機制、同步輻射/核磁共振技術在環境土壤學的新應用；擔任國際Agronomy雜誌編委，中國土壤學會土壤環境專業委員會委員；主持承擔國家重點研發計劃課題、國家自然基金面上項目、國家自然科學基金大科學裝置聯合基金項目等，在ES&T等雜誌上發表SCI論文60餘篇，申請國家發明專利8項（授權3項）。

校對和審核：張陽 王農