黏土矿物混合生物炭包膜尿素的制备及其氮素污染减排潜力

为促进氮肥高效利用，实现氮素污染减排，选用膨润土和生物炭作为包膜材料，结合硝化抑制剂制备包膜尿素。设置包膜尿素淋溶模拟试验收集淋溶液，结合静态箱法收集N₂O，通过分析NH₄⁺-N，NO₃^--N淋失量和N₂O排放通量对包膜尿素氮素污染减排潜力进行了评估。结果表明:（1）膨润混合土生物炭包膜尿素（F₄）NH₄⁺-N淋溶损失率最低，较纯化肥尿素（F₁）NH₄⁺-N淋溶损失率降低19.76%。（2）硝化抑制剂型膨润土生物炭包膜尿素（F₅）NO₃^--N淋失率最低，较F₁降低16.74%。（3）F₅同时具有最优的N₂O减排效果，N₂O排放量较F₁降低77.8%。F₅氮素减排效果最优，其减排机制在于一方面硝化抑制剂可以从化学过程控制硝化和反硝化进程，延缓尿素酰胺态氮的水解和铵态氮的硝化，在降低NO₃^--N淋失的同时可以实现N₂O减排。另一方面F₅的包膜材料膨润土和生物炭可以通过吸附作用将更多的NH₄⁺-N富集在土壤表层，从而显著降低NH₄⁺-N淋失。综上所述，硝化抑制剂型膨润土生物炭包膜尿素氮素污染减排潜力最优，可使NH₄⁺-N，NO₃^--N和N₂O分别减排15.24%，16.74%和77.8%。

Clay Mineral and Biochar Mixture Coated Urea Preparation and Its Nitrogen Pollution Reduction Potential

In order to promote high efficient utilization of fertilizer and reduce nitrogen pollutant emission, we used bentonite and biochar as coating materials and combined nitrification inhibitor to prepare coated urea. The coated urea leaching simulation experiments were conducted to collect leaching solution, and static box method were also used to collect N₂O. Nitrogen reduction potential of coated urea was evaluated by analyzing NH₄⁺-N, NO₃^--N leaching amount and N₂O emission flux. The results showed that:(1) bentonite and biochar coated urea (F₄) has the lowest NH₄⁺-N leaching loss rate, the NH₄⁺-N leaching amount of the coated urea decreased by 19.99% compared with chemical urea (F₁); (2) nitrification inhibitor combined, bentonite and biochar coated urea (F₅) demonstrated minimum NO₃^--N leaching loss rate, the leaching loss rate of NO₃^--N decreased by 16.74% compared with F₁; (3) F₅ also showed the minimum N₂O emissions flux, N₂O emission decreased by 77.8% compared with F₁. Therefore, F₅ has the effect of optimal nitrogen pollution reduction. The reason is that nitrification inhibitor can control nitrification and denitrification process through chemical process which can delay the hydrolysis of amide nitrogen and the nitrification of ammonium nitrogen, thus to minimize N₂O emission significantly and reduce NO₃^--N leaching loss as well. In addition, the coating materials of bentonite and biochar in F₅ have high adsorption on NH₄⁺-N, which can concentrate more NH₄⁺-N in the top soil, thus reduce NH₄⁺-N leaching. In summary, urea combined with nitrification inhibitor and coated by bentonite and biochar has the best potential for nitrogen pollutant reduction, which can reduce NH₄⁺-N, NO₃^--N and N₂O by 15.24%, 16.74% and77.8%, respectively.