Black Carbon and Kerogen in Soils and Sediments. 2. Their Roles in Equilibrium Sorption of Less-Polar Organic Pollutants

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• 作者：Baohua Xiao ; Zhiqiang Yu ; Weilin Huang ; Jianzhong Song ; and Ping'an Peng
• 刊名：Environmental Science & Technology
• 出版年：2004
• 出版时间：November 15, 2004
• 年：2004
• 卷：38
• 期：22
• 页码：5842 - 5852
• 全文大小：390K
• 年卷期：v.38,no.22(November 15, 2004)
• ISSN：1520-5851

文摘

The first paper of this series reported that soil/sedimentorganic matter (SOM) can be fractionated into fourfractions with a combined wet chemical procedure andthat kerogen and black carbon (BC) are major SOMcomponents in soil/sediment samples collected from theindustrialized suburban areas of Guangzhou, China. The goalof this study was to determine the sorptive propertiesfor the four SOM fractions for organic contaminants. Sorptionisotherms were measured with a batch technique usingphenanthrene and naphthalene as the sorbates and fouroriginal and four Soxhlet-extracted soil/sediment samples,15 isolated SOM fractions, and a char as the sorbents.The results showed that the sorption isotherms measuredfor all the sorbents were variously nonlinear. The isolatedhumic acid (HA) exhibited significantly nonlinear sorption,but its contribution to the overall isotherm nonlinearityand sorption capacity of the original soil was insignificantbecause of its low content in the tested soils andsediments. The particulate kerogen and black carbon (KB)fractions exhibited more nonlinear sorption with muchhigher organic carbon-normalized capacities for bothsorbates. They dominate the observed overall sorption bythe tested soils and sediments and are expected to bethe most important soil components affecting bioavailabilityand ultimate fate of hydrophobic organic contaminants(HOCs). The fact that the isolated KB fractions exhibitedmuch higher sorption capacities than when they wereassociated with soil/sediment matrixes suggested that alarge fraction of the particulate kerogen and BC was notaccessible to sorbing HOCs. Encapsulation within soilaggregates and surface coverage by inorganic and organiccoatings may have caused large variations in theaccessibility of fine kerogen and BC particles to HOCsand hence lowered the sorption capacity of the soil. Thisvariability posts an ultimate challenge for preciselypredicting HOC sorption by soils from the contents ofdifferent types of SOM.