Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation, China Agricultural University, Beijing, 100193, China.
College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China.
Environ Sci Pollut Res Int. 2017 Oct;24(28):22679-22687. doi: 10.1007/s11356-017-9797-4. Epub 2017 Aug 16.
There are an increasing number of studies, which have shown the potential importance of abiotic denitrification in nitrogen biogeochemistry through pure chemical coupling between nitrate/nitrite reduction and Fe(II) oxidation. However, there is little direct evidence showing the environmental significance of abiotic nitrate (NO) reduction in acidic soils. We assessed the magnitude and gaseous product stoichiometry of abiotic nitrate reduction in acidic forest soils based on sterilized anoxic soil incubations at different soil pHs and nitrate loadings. The results showed that 24.9, 53.4, and 88.7% of added nitrate (70 mg N kg) were lost during 15 days incubation at pHs 3.9, 4.8, and 5.6, respectively. Nitrous oxide (NO) was found as the dominant gaseous product of abiotic nitrate reduction, accounting for 5.0, 28.9, and 47.9% of nitrate losses at three pH levels, respectively. Minor but clear NO accumulations were observed for all nitrate-amended treatments, with the maxima at intermediate pH 4.8. The percentage of NO increased significantly with soil pH decline, leading to a negative correlation between NO/NO ratio and soil pH. Though saturations were found under excessive nitrogen loading (i.e., 140 mg N kg), we still pose that abiotic nitrate reduction may represent a potentially important pathway for nitrate loss from acidic forest soils receiving nitrogen deposition. Our results here highlight the importance of abiotic nitrate reduction in the soil nitrogen cycle, with special relevance to nitrate removal and nitrogenous trace gas (NO and NO) emissions from acidic soils.
越来越多的研究表明，通过硝酸盐/亚硝酸盐还原与 Fe(II)氧化之间的纯化学偶联，非生物脱氮在氮生物地球化学中具有潜在的重要性。然而，几乎没有直接证据表明酸性土壤中非生物硝酸盐（NO）还原的环境意义。我们基于不同 pH 值和硝酸盐负荷的无菌缺氧土壤培养，评估了酸性森林土壤中非生物硝酸盐还原的幅度和气态产物化学计量。结果表明，在 pH 值分别为 3.9、4.8 和 5.6 的条件下，15 天的培养过程中，分别有 24.9%、53.4%和 88.7%的添加硝酸盐（70 mg N kg）损失。发现氧化亚氮（NO）是非生物硝酸盐还原的主要气态产物，分别占三个 pH 值水平下硝酸盐损失的 5.0%、28.9%和 47.9%。所有添加硝酸盐的处理均观察到少量但明显的 NO 积累，最大值出现在中间 pH 值 4.8。NO 的百分比随着土壤 pH 值的降低而显著增加，导致 NO/NO 比与土壤 pH 值呈负相关。尽管在过量氮负荷下（即 140 mg N kg）发现了饱和度，但我们仍然认为非生物硝酸盐还原可能代表酸性森林土壤接受氮沉降时硝酸盐损失的一个潜在重要途径。我们的研究结果强调了非生物硝酸盐还原在土壤氮循环中的重要性，特别是对酸性土壤中硝酸盐去除和含氮痕量气体（NO 和 NO）排放的重要性。
