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| Influence of humic acid and cadmium on the transport of clay colloids in saturated porous media |
| Received:January 10, 2018 |
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| KeyWord:clay colloids;Cd2+;HA;saturated quartz sand;co-transport |
| Author Name | Affiliation | E-mail | | TANG Zhang | Key Lab of Eco-restoration of Regional Contaminated Environment Ministry of Education, Shenyang University, Shenyang 110044, China | | | YANG Xin-yao | Key Lab of Eco-restoration of Regional Contaminated Environment Ministry of Education, Shenyang University, Shenyang 110044, China | yangxinyao@hotmail.com | | YAN Xin-yu | Key Lab of Eco-restoration of Regional Contaminated Environment Ministry of Education, Shenyang University, Shenyang 110044, China | | | ZHANG Hai-yan | Hydrogeology and Engineering Geology Exploration Institute of Heilongjiang Province, Haerbin 150030, China | | | YANG Yue-suo | Key Lab of Eco-restoration of Regional Contaminated Environment Ministry of Education, Shenyang University, Shenyang 110044, China
Key Laboratory of Groundwater Environment and Resources, Ministry of Education, Jilin University, Changchun 130021, China | |
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| Abstract: |
| With the aim to explore the impact of humic acid(HA) and cadmium ion(Cd2+) on the transport of clay colloids in saturated porous media, co-transport column experiments were performed using montmorillonite and kaolinite colloids as surrogates. Results showed that the deposition rate of kaolinite colloids was the highest in the absence of HA and Cd2+(3.72 min-1), lower in the presence of only Cd2+ (2.82 min-1), even lower in the presence of both HA and Cd2+(2.01 min-1), and the lowest in the presence of only HA(0.46 min-1). The similar trend in changing deposition rate in response to the variability of Cd2+ and/or HA was also observed for montmorillonite colloids, i.e., the rate was 1.02 min-1 in the absence of HA and Cd2+, 0.97 min-1 in the presence of only Cd2+, 0.85 min-1 in the presence of both HA and Cd2+, and 0.30 min-1 in the presence of only HA. These results demonstrated the consistent role of HA and Cd2+ in the mobility of both clay colloids; HA and Cd2+ both promoted the transport of the two clay colloids. The effect of HA was stronger than that of Cd2+. Moreover, an antagonistic interaction between humic acid and cadmium ions occurred, rendering the combined effect of the two lower than that of only HA. Based on the particle size and zeta potential measurement of the clay colloids, we speculated that HA and Cd2+ promoted the colloid mobility via different mechanisms:HA achieved this by modifying the surface electrical properties of the clay colloids, while Cd2+ achieved this by inducing particle aggregation. These findings improve current knowledge on the translocation and concentration distribution of natural soil colloids in the environment. |
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