叶面调理剂对复合污染农田小麦籽粒Cd、As和Pb累积的阻控效应

针对麦田土壤镉（Cd）、砷（As）和铅（Pb）复合污染问题，采用田间小区试验，于拔节期、孕穗期和灌浆初期对小麦进行叶面单独和混合喷施Zn（0.2% ZnSO₄）、Mg（0.4% MgSO₄）和Mn（0.2% MnSO₄）处理，以期探究叶面调理剂对小麦籽粒Cd、As和Pb累积的阻控效应，最终筛选出适用于北方重金属复合污染区有效阻控小麦籽粒中Cd、As和Pb累积的叶面调理剂.结果表明，与对照相比，叶面喷施Zn+Mg+Mn复配溶液能够显著降低小麦籽粒中Cd、As和Pb含量，降幅分别为18.96%、23.87%和51.31%，TF_{籽粒/秸秆}分别降低了14.62%、27.73%和47.70%，该叶面调理剂能够通过抑制Cd、As和Pb从小麦茎叶到籽粒的转运进而降低其在籽粒的累积；研究还发现，对照的籽粒中Cd和As主要分布在中心胚乳（34.08%~37.08%），而Pb主要分布在果皮和种皮（27.78%）.喷施Zn+Mg+Mn复配溶液可显著降低Cd和As在糊粉层含量，分别比CK降低81.10%和82.24%，而Pb除果皮和种皮、中心胚乳外，各层次Pb含量均显著降低（降幅为42.85%~91.15%），各层次面粉只有糊粉层（P2）重金属含量与Zn含量呈显著负相关.综上所述，对于北方石灰性土壤Cd、As和Pb中度复合污染农田，于小麦拔节期、孕穗期和灌浆初期各喷施一次Zn+Mg+Mn复配的叶面调理剂，可有效阻控Cd、As和Pb在小麦籽粒尤其是糊粉层的累积.在此基础上，可通过去除麦麸来进一步降低重金属尤其是Cd的污染，保证小麦安全生产和粮食安全.

Blocking Effects of Foliar Conditioners on Cadmium, Arsenic, and Lead Accumulation in Wheat Grain in Compound-contaminated Farmland

Heavy metal contamination of soil has become a hot issue of social concern due to its impact on the safety of agricultural products in recent years. Wheat is one of the most dominant staple food crops worldwide and has become a major source of toxic metals in human diets. Foliar application was considered to be a more efficient and economical method of heavy metal remediation. Field experiments were carried out in Cd-, As-, and Pb-contaminated farmland soils. The effects of foliar conditioners on the accumulation of Cd, As, and Pb in wheat grains were investigated after being sprayed with Zn (0.2% ZnSO₄), Mg (0.4% MgSO₄), and Mn (0.2% MnSO₄) separately and in combination. Thus, the effective foliar conditioners were selected to block the accumulation of Cd, As, and Pb in wheat grains grown in combined heavy metal-contaminated farmland in north China. The results showed that, compared with that in the control, the Cd, As, and Pb contents in wheat grains of the Zn+Mg+Mn foliar treatment were significantly decreased by 18.96%, 23.87%, and 51.31%, respectively, and TF_grain/straw decreased by 14.62%, 27.73%, and 47.70%, respectively. Thus, spraying the compound foliar conditioner of Zn+Mg+Mn could effectively reduce heavy metal accumulation in wheat grains through inhibition translocation of those metals from stem leaves to grain. In addition, the results indicated that Cd and As were mainly distributed at the central endosperm (34.08%-37.08%), whereas Pb was primarily distributed at the pericarp and seed coat (27.78%) of the wheat grain. Compared with that in the control, spraying the compound foliar conditioner of Zn+Mg+Mn extremely decreased Cd and As accumulation in the aleurone layer of the wheat grain by 81.10% and 82.24%, respectively. Except for the pericarp, seed coat, and central endosperm layers, the Pb content in each grain layer was dramatically decreased by 42.85% to 91.15%. There was only a significant negative correlation between heavy metal content and Zn content in the aleurone layer (P2) of wheat flour. In summary, the accumulation of Cd, As, and Pb in wheat grains, especially in the aleurone layer, could be effectively reduced by foliar conditioner application at the jointing, booting, and early filling stages of wheat, separately. Furthermore, besides the foliar treatment, removing wheat bran to reduce Cd contamination in wheat grains is highly recommended to ensure the safe production of wheat.