title: Cotransport of bismerthiazol and montmorillonite colloids in saturated porous media.
abstract: While bismerthiazol [N,N'-methylene-bis-(2-amino-5-mercapto-1,3,4-thiadiazole)] is one of the most widely used bactericides, the transport of bismerthiazol in subsurface environments is unclear to date. Moreover, natural colloids are ubiquitous in the subsurface environments. The cotransport of bismerthiazol and natural colloids has not been investigated. This study conducted laboratory column experiments to examine the transport of bismerthiazol in saturated sand porous media both in the absence and presence of montmorillonite colloids. Results show that a fraction of bismerthiazol was retained in sand and the retention was higher at pH7 than at pH 4 and 10. The retention did not change with ionic strength. The retention was attributed to the complex of bismerthiazol with metals/metal oxides on sand surfaces through ligand exchange. The transport of bismerthiazol was enhanced with montmorillonite colloids copresent in the solutions and, concurrently, the transport of montmorillonite colloids was facilitated by the bismerthiazol. The transport of montmorillonite colloids was enhanced likely because the bismerthiazol and the colloids competed for the attachment/adsorption sites on collector surfaces and the presence of bismerthiazol changed the Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energies between colloids and collectors. The transport of bismerthiazol was inhibited if montmorillonite colloids were pre-deposited in sand because bismerthiazol could adsorb onto the colloid surfaces. The adsorbed bismerthiazol could be co-remobilized with the colloids from primary minima by decreasing ionic strength. Whereas colloid-facilitated transport of pesticides has been emphasized, our study implies that transport of colloids could also be facilitated by the presence of pesticides.
authors: Department of Soil and Water Sciences, China Agricultural University, Beijing 100193, China.
authors: Chongyang
authors: C
authors: Shen
authors: Department of Soil and Water Sciences, China Agricultural University, Beijing 100193, China.
authors: Hong
authors: H
authors: Wang
authors: Department of Plant and Soil Sciences, University of Delaware, Newark, DE 19716, United States.
authors: Volha
authors: V
authors: Lazouskaya
authors: Department of Soil and Water Sciences, China Agricultural University, Beijing 100193, China.
authors: Yichun
authors: Y
authors: Du
authors: Department of Soil and Water Sciences, China Agricultural University, Beijing 100193, China.
authors: Weilan
authors: W
authors: Lu
authors: Department of Applied Chemistry, China Agricultural University, Beijing 100193, China.
authors: Junxue
authors: J
authors: Wu
authors: Department of Applied Chemistry, China Agricultural University, Beijing 100193, China. Electronic address: hongyan@cau.edu.cn.
authors: Hongyan
authors: H
authors: Zhang
authors: Department of Soil and Water Sciences, China Agricultural University, Beijing 100193, China. Electronic address: yfhuang@cau.edu.cn.
authors: Yuanfang
authors: Y
authors: Huang
mesh_terms: D000327:Adsorption; D001546:Bentonite / Q000032:analysis / Q000737:chemistry; D003102:Colloids / Q000737:chemistry*; D060587:Groundwater / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D062070:Hydrology / Q000379:methods*; D008670:Metals / Q000737:chemistry; D009994:Osmolar Concentration; D010087:Oxides; D010575:Pesticides / Q000737:chemistry; D016062:Porosity; D012822:Silicon Dioxide; D012996:Solutions; D013438:Sulfhydryl Compounds / Q000032:analysis / Q000737:chemistry; D013830:Thiadiazoles; D013844:Thiazoles / Q000032:analysis / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000737:chemistry
chemical_list: D003102:Colloids; D008670:Metals; D010087:Oxides; D010575:Pesticides; D012996:Solutions; D013438:Sulfhydryl Compounds; D013830:Thiadiazoles; D013844:Thiazoles; D014874:Water Pollutants, Chemical; C000608952:bismerthiazol; D001546:Bentonite; D012822:Silicon Dioxide
keywords: Bismerthiazol; Montmorillonite colloids; Porous media; Sand; Transport