Characterization of DOM from Soil in Unsaturated Zone and Its Implications on Arsenic Mobilization into Groundwater
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摘要: 为了解包气带土壤DOM组成特征, 探索其对砷向地下水中迁移的影响, 对江汉平原高砷区土壤DOM进行了三维荧光光谱分析.结果表明DOM主要为类腐殖质成分, 芳香性官能团的减少导致荧光强度随包气带深度增加而变小, 局部深度荧光信号不规则变化指示非均质土壤剖面上DOM组分或主导官能团的变化.平行因子分析表明, DOM组分可更细致地分解为4种组分, 与微生物源的还原、氧化醌类和陆生的腐殖质富里酸类等相似.砷很可能在DOM腐殖质成分络合作用下与之随水体一起向下迁移, 砷的迁移也可能与微生物源的醌类作用过程有关.三维荧光光谱分析准确、快速地刻画了包气带土壤DOM的组分类别及空间变化特征, 初步揭示了DOM影响砷迁移的可能作用方式, 为进一步的地下水砷污染机制的研究提供了重要的参考信息.Abstract: 3D fluorescent spectra analysis was conducted to understand the characteristics of dissolved organic matter (DOM) from soil of unsaturated zone and its potential influence on arsenic transport into groundwater. The results show that the humic-like component is the major constituent of DOM. The decrease in fluorescence intensity with depth is attributed to the reduction in aromatic functional groups. The irregular variation of the intensity in localized depth indicates the changes in DOM components or its major functional groups on soil section. Fluorescence information of DOM can be specifically decomposed by PARAFAC into four components, which are respectively similar to microbial reduced quinones, microbial oxidized quinones, terrestrial fulvic acid and so on. It is suggested that arsenic may be complexed by humic-DOMs and migrate with them into groundwater and the mobilization of arsenic also can be associated with the microbial quinones. Thus, 3D fluorescent spectra have been demonstrated to be a convenient and effective tool in DOM characterization and facilitate further study on effects on arsenic mobilization.
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图 1 土壤DOM荧光EEM光谱示意图(由上至下依次为S1-1、S2-1、S3-1)
Fig. 1. 3D fluorescent EEM diagram of soil DOM
图 2 EEM总荧光强度与土壤提取DOC浓度关系(以S1为例)
Fig. 2. Relationship of integrated fluorescence intensity with DOC concentration in soil DOM
图 3 平行因子模型鉴定的4种荧光组分激发、发射光谱特征
Fig. 3. Characteristics of excitation-emission spectra for four components identified by PARAFAC model
图 4 DOM组分与水溶态砷随深度的变化关系(左为S1，右为S2)
Fig. 4. Variation of DOM components and WEA with depth
表 1 采集的土壤样品描述
Table 1. Description of soil samples collected in field site
样品编号 经纬度 取样深度(cm) 土壤剖面岩性分层 DOC(mg/L) 砷含量(μg/kg) S1-1 E 113°40′38″
N 30°09′24″5 灰红色亚粘土，含较多杂质 24.2 27.8 S1-2 20 灰黄色亚粘土 21.5 6.90 S1-3 40 黄色粘土 18.4 0.00 S1-4 60 灰黄色粘土，少量铁锈 17.3 0.00 S1-5 80 黄色、黄褐色粘土 16.0 0.00 S2-1 E 113°39′10″
N 30°09′29″5 灰色亚砂土 22.0 28.1 S2-2 20 灰色、灰黄色亚砂土 19.6 38.9 S2-3 40 灰黄色亚砂土 36.2 26.9 S2-4 60 灰黄色亚粘土，黄色斑迹，疑为生物遗迹 18.5 30.9 S2-5 80 灰黄色亚粘土，少量黄色斑迹 18.2 2.50 S3-1 E 113°08′49″
N 30°19′25″5 灰色亚粘土，含根须 16.0 36.7 S3-2 20 灰色亚粘土，含白色贝壳 15.5 19.8 S3-3 40 灰色亚粘土 17.3 36.4 S3-4 60 灰黄色亚粘土 17.9 22.1 S3-5 80 灰黄色亚粘土 12.8 8.60 注：DOC即溶解性有机碳；砷含量最后换算成土壤含砷量；测试在生物地质与环境地质国家重点实验室完成. 
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表 2 土壤DOM的荧光峰位置及荧光强度
Table 2. The fluorescence peak position of soil DOM and its intensity (R.U.)
样点编号 峰A 峰C IA/IC Ex/Em(nm) 峰强IA(R.U.) Ex/Em(nm) 峰强IC(R.U.) S1-1 270/443 1.14 330/437.5 0.81 1.41 S1-2 260/415.5 0.42 320/421 0.35 1.20 S1-3 240/413.5 0.32 310/420 0.30 1.07 S1-4 230/407.5 0.37 350/410 0.28 1.34 S1-5 260/427 0.20 340/416 0.17 1.16 S2-1 270/448.5 0.92 330/443.5 0.95 0.98 S2-2 270/446 0.84 310/432.5 0.82 1.01 S2-3 260/444 0.60 320/425 0.51 1.17 S2-4 260/446 0.72 320/426.5 0.54 1.33 S2-5 240/443 0.26 330/419.5 0.20 1.30 S3-1 240/444.5 0.39 370/436 0.52 0.75 S3-2 240/441.5 0.44 370/439 0.55 0.81 S3-3 270/444.5 0.44 330/413.5 0.50 0.88 S3-4 230/396 0.66 390/426.5 0.26 2.58 S3-5 230/402.5 0.50 390/408.5 0.25 1.99 注：Ex表示激发波长；Em表示发射波长；R.U.表示以350 nm激发光下荧光强度的拉曼积分作归一化处理，单位以Raman(R.U.)表示；IA/IC表示峰A和峰C强度比.
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表 3 平行因子分析鉴定的荧光组分及特征
Table 3. The peak position of identified DOM components and its characterization
组分 Ex./Em.Max(nm) 以前报道的相似组分(nm) 性质和可能来源 参考文献 C1 270(370)/458.5 SQ2: 270(375)/462 (1)还原醌类；微生物来源 Cory and McKnight (2005) C4: 250(360)/440 (2)陆源/原位富里酸 Stedmon and Markager (2005) C2 320/410 C2: 315/418;P1: 310/414 (1)陆源腐殖质 Murphy et al.(2008) Component 5:325/428 (2)陆地或人为腐殖质，农业活动 Stedmon and Markager (2005) C3 < 250(300)/383 Q3: < 250(300)/388 氧化醌类；微生物来源 Cory and McKnight (2005) C4 370/439.5 ‘C’peak: 320-360/420-460 陆源腐殖质 Coble(1996) 注：Ex./Em.Max表示荧光强度最大处的激发/发射波长对，基于平行因子分析.
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[1] Chen, R.F., Bada, J.L., 1994. The fluorescence of dissolved organic matter in porewaters of marine sediments. Marine Chemistry, 45(1-2): 31-42. doi: 10.1016/0304-4203(94)90089-2 [2] Coble, P.G., 1996. Characterization of marine and terrestrial DOM in seawater using excitation-emission matrix spectroscopy. Marine Chemistry, 51(4): 325-346. doi: 10.1016/0304-4203(95)00062-3 [3] Cory, R.M., McKnight, D.M., 2005. Fluorescence spectroscopy reveals ubiquitous presence of oxidized and reduced quinones in dissolved organic matter. Environmental Science & Technology, 39(21): 8142-8149. doi: 10.1021/es0506962 [4] Fu, P.Q., Liu, C.Q., Wu, F.C., et al., 2004. Three-dimensional excitation emission matrix fluorescence spectroscopic characterization of dissolved organic matter in sediment pore water in Lake Erhai. Quaternary Sciences, 24(6): 695-700 (in Chinese with English abstract). http://www.ingentaconnect.com/content/jccs/jccs/2012/00000037/00000008/art00027 [5] Fu, P.Q., Liu, C.Q., Wu, F.C., et al., 2005. Three-dimensional exeitation emission matrix fluorescence spectroscopic characterization of dissolved organic matter. Spectroscopy and Spectral Analysis, 25(12): 2024-2028 (in Chinese with English abstract). http://www.ingentaconnect.com/content/jccs/jccs/2012/00000037/00000008/art00027 [6] Gu, B.H., Schmitt, J., Chen, Z.H., et al., 1994. Adsorption and desorption of natural organic matter on iron oxide: mechanisms and models. Environmental Science & Technology, 28(1): 38-46. doi: 10.1021/es00050a007 [7] Han, Y.C., Guo, W.D., 2009. The fluorescence excitation emission matrix spectroscopy of chromophoric dissolved organic matter in the Jiulong River estuary. Acta Scientiae Circumstantiae, 29(3): 641-647 (in Chinese with English abstract). http://www.oalib.com/paper/1591859 [8] Lapworth, D.J., Gooddy, D.C., Butcher, A.S., et al., 2008. Tracing groundwater flow and sources of organic carbon in sandstone aquifers using fluorescence properties of dissolved organic matter (DOM). Applied Geochemistry, 23(12): 3384-3390. doi: 10.1016/j.apgeochem.2008.07.011 [9] Leenheer, J.A., Croué, J.P., 2003. Characterizing aquatic dissolved organic matter. Environmental Science & Technology, 37(1): 18-26. doi: 10.1021/es032333c [10] Mladenov, N., Zheng, Y., Miller, M.P., et al., 2010. Dissolved organic matter sources and consequences for iron and arsenic mobilization in Bangladesh aquifers. Environmental Science & Technology, 44(1): 123-128. doi: 10.1021/es901472g [11] Murphy, K.R., Stedmon, C.A., Waite, T.D., et al., 2008. Distinguishing between terrestrial and autochthonous organic matter sources in marine environments using fluorescence spectroscopy. Marine Chemistry, 108(1-2): 40-58. doi: 10.1016/j.marchem.2007.10.003 [12] Reedy, R.C., Scanlon, B.R., Nicot, J.P., et al., 2007. Unsaturated zone arsenic distribution and implications for groundwater contamination. Environmental Science & Technology, 41(20): 6914-6919. doi: 10.1021/es070281b [13] Senesi, N., 1990. Molecular and quantitative aspects of the chemistry of fulvic acid and its interactions with metal ions and organic chemicals: Part Ⅱ. The fluorescence spectroscopy approach. Analytica Chimica Acta, 232: 77-106. doi: 10.1016/S0003-2670(00)81226-X [14] Sierra, M.M.D., Giovanela, M., Panlanti, E., et al., 2005. Fluorescence fingerprint of fulvic and humic acids from varied origins as viewed by single-scan and excitation/emission matrix techniques. Chemosphere, 58(6): 715-733. doi: 10.1016/j.chemosphere.2004.09.038 [15] Stedmon, C.A., Bro, R., 2008. Characterizing dissolved organic matter fluorescence with parallel factor analysis: a tutorial. Limnology and Oceanography: Methods, 6: 572-579. doi: 10.4319/lom.2008.6.572 [16] Stedmon, C.A., Markager, S., 2005. Resolving the variability in dissolved organic matter fluorescence in a temperate estuary and its catchment using PARAFAC analysis. Limnology and Oceanography, 50(2): 686-697. doi: 10.4319/lo.2005.50.2.0686 [17] Stedmon, C.A., Markager, S., Bro, R., 2003. Tracing dissolved organic matter in aquatic environments using a new approach to fluorescence spectroscopy. Marine Chemistry, 82(3-4): 239-254. doi: 10.1016/S0304-4203(03)00072-0 [18] The Ministry of Water Resources of the People's Republic of China, 2009. SL 327.1-2005, Water quality-determination of arsenic-atomic fluorescence spectrometric method. China WaterPower Press, Beijing (in Chinese). [19] Wang, S.L., Mulligan, C.N., 2006. Effect of natural organic matter on arsenic release from soils and sediments into groundwater. Environmental Geochemistry and Health, 28(3): 197-214. doi: 10.1007/s10653-005-9032-y [20] Zhang, J.S., Tao, S., Cao, J., 2000. Soil sample preservation and pretreatment for water soluble organic carbon determination. Chinese Journal of Soil Science, 31(4): 174-176 (in Chinese with English abstract). http://www.cnki.com.cn/Article/CJFDTotal-TRTB200004009.htm [21] 傅平青, 刘丛强, 吴丰昌, 2005. 溶解有机质的三维荧光光谱特征研究. 光谱学与光谱分析, 25(12): 2024-2028. doi: 10.3321/j.issn:1000-0593.2005.12.031 [22] 傅平青, 刘丛强, 吴丰昌, 等, 2004. 洱海沉积物孔隙水中溶解有机质的三维荧光光谱特征. 第四纪研究, 24(6): 695-700. doi: 10.3321/j.issn:1001-7410.2004.06.012 [23] 韩宇超, 郭卫东, 2009. 九龙江河口有色溶解有机物的三维荧光光谱特征. 环境科学学报29(3): 641-647. https://www.cnki.com.cn/Article/CJFDTOTAL-HJXX200903026.htm [24] 张甲珅, 陶澍, 曹军, 2000. 土壤中水溶性有机碳测定中的样品保存与前处理方法. 土壤通报, 31(4): 174-176. https://www.cnki.com.cn/Article/CJFDTOTAL-TRTB200004009.htm [25] 中华人民共和国水利部. SL327.1-2005, 水质-砷的测定-原子荧光光度法. 北京: 中国水利水电出版社, 2005. -
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