Photooxidation of pyrogenic organic matter reduces its reactive, labile C pool and the apparent soil oxidative microbial enzyme response
Photooxidation of pyrogenic organic matter reduces its reactive, labile C pool and the apparent soil oxidative microbial enzyme response
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DOI：
10.1016/j.geoderma.2017.01.011
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发表时间：
2017-05
期刊：
影响因子：
6.1
通讯作者：
Ruzhen Wang;Christy D. Gibson;T. Berry;Yong Jiang;J. Bird;T. Filley
中科院分区：
文献类型：
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作者：
Ruzhen Wang;Christy D. Gibson;T. Berry;Yong Jiang;J. Bird;T. Filley
环境中各种非生物和生物氧化和吸附/解吸过程改变了热解有机物质(PYOM)的表面化学。在添加到土壤或沉积物中之前或在大气中携带时，将PYOM暴露在高能光下可能会引起显著的表面光氧化，即光化学风化，从而改变其环境反应性。我们报道了一项为期30天的土壤培养实验，测试了在450℃下热解产生的富含13C的黄松PYOM的光化学风化对PYOM和土壤有机碳(SOC)矿化的影响。测量了光化学风化(即经紫外线处理的PYOM或PYOMUV)和未暴露在高能光下(即PYOMW作为暗对照)的PYOM C矿化。在30d的研究中，PyOMUV表现出3.7倍的C矿化速率，这是由于前6天可获得的/不稳定的C的大量早期矿化所驱动的。相比之下，在实验的后期(11-30天)，PyOMUV的C矿化速率更快。总体而言，PyOMUV的净C矿化量比未经处理的PyOMW低13%，其中可到达的PyOMUV-C和PyOMW-C的MRT分别为25.7±26.8和1.7±0.2d。与未改良的对照土壤相比，这两种形式的PYOM促进了自然SOC矿化的类似净减少(即负启动)约50%。与未改良的土壤相比，添加任何一种PYOM都能使土壤中可提取的木质素、酚和取代脂肪酸的浓度略有下降。在30d时，土壤酚氧化酶和过氧化物酶活性在添加任何一种形式的PYOM时都高于未添加PYOMUV的对照土壤，但其活性低于PYOMW。我们的结果表明，PYOM光化学风化可以使PYOM的短期反应性和土壤微生物活性发生重要变化，这可能通过最终降低NSC和PYOM-C的周转速率而对土壤系统产生重要影响。
The surface chemistry of pyrogenic organic matter (PyOM) is altered by a variety of abiotic and biotic oxidative and sorption/desorption processes in the environment. Exposure of PyOM to high energy light prior to addition to soil or sediment, or while entrained in the atmosphere, may induce significant surface photooxidation, i.e., photochemical weathering, altering its environmental reactivity. We report on a 30-day soil incubation experiment testing the effects of the photochemical weathering of a13C-enriched ponderosa pine PyOM, produced by pyrolysis at 450 °C, on PyOM and soil organic carbon (SOC) mineralization. PyOM C mineralization was measured for both the photochemically weathered (i.e. UV treated PyOM or PyOMUV) and PyOM not exposed to high-energy light (i.e. PyOMW serving as a dark control). PyOMW exhibited a 3.7 times faster C mineralization rate across the 30-d study, which was driven by a large early mineralization of accessible/labile C during the first 6 d. In contrast, PyOMUV had faster C mineralization rates in the later part of the experiment (days 11–30). Overall, PyOMUV had a 13% lower net C mineralization than the untreated PyOMW where the MRT of accessible PyOMUV-C and PyOMW-C was calculated at 25.7 ± 6.8 d and 1.7 ± 0.2 d, respectively. Both forms of PyOM promoted a similar net reduction in native SOC mineralization (i.e., negative priming) of approximately 50% relative to the unamended, control soil. Addition of either PyOM form resulted in an equivalent minor decrease in the concentration of extractable soil lignin phenols and substituted fatty acids chemistry with respect to the unamended soil. At 30 d, soil phenol oxidase and peroxidase enzyme activities were higher with additions of either form of PyOM compared with the unamended control soils with PyOMUV exhibiting lower activities than PyOMW. Our results indicate that PyOM photochemical weathering can impart important changes to short-term PyOM reactivity and soil microbial activity, which could have important implications for soil systems by ultimately lowering turnover rates for both NSC and PyOM-C.