不同气氛热解生物炭可溶性有机碳的光谱特征

Spectral characteristics of dissolved organic carbon from biochar pyrolysis in different atmospheres

为探明不同气氛热解生物炭可溶性有机碳(BDOC)的性质特征,在不同热解气氛(CO_(2)、N_(2)和空气限制)和热解温度(300~750℃)下制备了一系列小麦秸秆生物炭,通过提取其BDOC并结合紫外-可见光谱和荧光光谱-平行因子分析方法对BDOC性质进行分析.热解温度为300℃时,CO_(2)和N_(2)热解生物炭释放的DOC含量高(CO_(2):10.55mg/g,N_(2):10.17mg/g);而热解温度为450~750℃时,空气限制热解生物炭释放的DOC含量高(0.31~2.88mg/g).生物炭释放DOC含量与生物炭的挥发性物质含量、H/C和(O+N)/C呈正相关关系.空气限制热解BDOC具有更低的分子量,更高的芳香性(SUVA254范围:7.66~16.86),腐殖化程度(HIX范围:10.77~52.21)和类腐殖酸物质含量,而CO_(2)和N_(2)热解BDOC含有更多的类蛋白物质.此外,CO_(2)和N_(2)气氛热解BDOC光谱特征的温度变异性大于空气限制热解.

In order to explore the spectrum characteristics of biochar-derived dissolved organic carbon(BDOC)from different pyrolysis atmospheres,a series of biochar were prepared from wheat straws,with the combination of different pyrolysis atmospheres(CO_(2),N_(2),or air-limitation)and temperatures(300~750℃).BDOC was then extracted and characterized with ultraviolet-visible spectroscopy and fluorescence parallel factor analysis.We found that The DOC released from biochar was enhanced under the CO_(2)(10.55mg/g)and N_(2)(10.17mg/g)pyrolysis at 300℃and also under the air-limited pyrolysis at 450~750℃,resulting in a release of DOC ranging from 0.31~2.88mg/g.The concentration of DOC released from biochar was positively correlated with biochar parameters such as volatile matter content,H/C,and(O+N)/C ratios.In general,air-limitation pyrolysis facilitated the occurrence of BDOC associated with lower molecular weights,or higher aromaticity(SUV254:7.66~16.86)and humification degree(HIX:10.77~52.21),or humic acid-like substance;while the contents of proteinoids were higher in the BDOC from CO_(2) and N_(2) pyrolysis.In addition,the spectral characteristics of BDOC were more sensitive to temperature variation under the CO_(2) and N_(2) atmospheres than under air-limited pyrolysis.