School of Environment and Resources, Shanxi University, Taiyuan, 030006, China.
State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing, 100875, China.
Chemosphere. 2019 Jul;227:124-132. doi: 10.1016/j.chemosphere.2019.04.042. Epub 2019 Apr 8.
Elevated chromium (Cr) level is challenging agricultural production and affecting soil biochemical process. This study evaluated the effect of amendments including surface-modified biochars (HBC: acid washing, Fe(III)-HBC: ferric iron loading, nZVI-HBC: nanoscale zero-valent iron loading) and activated carbon on hexavalent chromium (Cr(VI)) removal in soil and on N cycling enzyme activities, transformation of soil inorganic nitrogen, and growth of maize under Cr stress. The results showed that amendments increased Cr(VI) removal by 72.9%-96.34% at three levels of spiked Cr(VI) (low: 125 mg kg, moderate: 250 mg kg, high: 500 mg kg). Under low Cr stress, amendments generally significantly decreased urease and nitrite reductase activities but increased nitrate reductase activity (p < 0.05). The NH-N content had a significant positive correlation with urease activity (p < 0.01), while both NO-N and NO-N were absent correlations with N cycling enzyme studied. Amendments decreased NH-N/NO-N ratio under low Cr stress but increased it under moderate Cr stress, although the difference was not significant. Under high Cr stress, only Fe(III)-HBC significantly increased NH-N/NO-N ratio (p < 0.05). The decrease and increase of NH-N/NO-N ratios indicate the enhancement of nitrification and denitrification, respectively. The increase in Cr(VI) removal by amendments contributed to the increase in the migration of NO-N from roots to shoots. Amendments (except for nZVI-HBC in soil under low Cr stress) increased maize height by 20%-59%. Under low Cr stress, however, nZVI-HBC significantly decreased maize height by 65% (p < 0.05), indicating the toxic effect of nZVI on maize growth overwhelmed low Cr stress.
铬（Cr）含量升高对农业生产造成挑战，并影响土壤生化过程。本研究评估了包括表面改性生物炭（HBC：酸洗，Fe(III)-HBC：三价铁负载，nZVI-HBC：纳米零价铁负载）和活性炭在内的改良剂对土壤中六价铬（Cr(VI)）去除以及氮循环酶活性、土壤无机氮转化和铬胁迫下玉米生长的影响。结果表明，在三种添加 Cr(VI)水平（低：125mgkg、中：250mgkg、高：500mgkg）下，改良剂可将 Cr(VI)去除率提高 72.9%-96.34%。在低 Cr 胁迫下，改良剂通常显著降低脲酶和亚硝酸盐还原酶活性，但提高硝酸盐还原酶活性（p<0.05）。NH-N 含量与脲酶活性呈显著正相关（p<0.01），而 NO-N 和 NO-N 与研究的氮循环酶均无相关性。在低 Cr 胁迫下，改良剂降低了 NH-N/NO-N 比值，但在中 Cr 胁迫下增加了该比值，尽管差异不显著。在高 Cr 胁迫下，只有 Fe(III)-HBC 显著增加了 NH-N/NO-N 比值（p<0.05）。NH-N/NO-N 比值的降低和增加分别表明硝化和反硝化作用的增强。改良剂增加 Cr(VI)去除率有助于增加从根部向地上部迁移的 NO-N。除低 Cr 胁迫下的 nZVI-HBC 外，改良剂使玉米株高增加 20%-59%。然而，在低 Cr 胁迫下，nZVI-HBC 使玉米株高显著降低 65%（p<0.05），表明 nZVI 对玉米生长的毒性效应超过了低 Cr 胁迫。
