A coupled field study of subsurface fracture flow and colloid transport

Zhang, Wei, Tang, Xiang-Yu, Weisbrod, Noam, Zhao, P and Reid, Brian ORCID: https://orcid.org/0000-0002-9613-979X (2015) A coupled field study of subsurface fracture flow and colloid transport. Journal of Hydrology, 524. pp. 476-488. ISSN 0022-1694

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Field studies of subsurface transport of colloids, which may act as carriers of contaminants, are still rare. This is particularly true for heterogeneous and fractured matrices. To address this knowledge gap, a 30-m long monitoring trench was constructed at the lower end of sloping farmland in central Sichuan, southwest China. During the summer of 2013, high resolution dynamic and temporal fracture flow discharging from the interface between fractured mudrock and impermeable sandstone was obtained at intervals of 5 min (for fast rising stages), 30–60 min (for slow falling stages) or 15 min (at all other times). This discharge was analyzed to elucidate fracture flow and colloid transport in response to rainfall events. Colloid concentrations were observed to increase quickly once rainfall started (15–90 min) and reached peak values of up to 188 mg/L. Interestingly, maximum colloid concentration occurred prior to the arrival of flow discharge peak (i.e. maximum colloid concentration was observed before saturation of the soil layer). Rainfall intensity (rather than its duration) was noted to be the main factor controlling colloid response and transport. Dissolved organic carbon concentration and d18O dynamics in combination with soil water potential were used to apportion water sources of fracture flow at different stages. These approaches suggested the main source of the colloids discharged to be associated with the flushing of colloids from the soil mesopores and macropores. Beyond the scientific interest of colloid mobilization and transport at the field scale, these results have important implications for a region of about 160,000 km2 in southwest China that featured similar hydrogeologic settings as the experimental site. In this agriculture dominated area, application of pesticides and fertilizers to farmland is prevalent. These results highlight the need to avoid such applications immediately before rainfall events in order to reduce rapid migration to groundwater via fracture flow in either dissolved form or in association with colloids.

Item Type: Article
Uncontrolled Keywords: colloid transport,fracture flow,colloid response,natural rainfall
Faculty \ School: Faculty of Science > School of Environmental Sciences
UEA Research Groups: Faculty of Science > Research Centres > Centre for Ecology, Evolution and Conservation
Faculty of Science > Research Groups > Environmental Biology
Faculty of Science > Research Groups > Resources, Sustainability and Governance (former - to 2018)
Faculty of Science > Research Groups > Geosciences
Faculty of Science > Research Groups > Geosciences and Natural Hazards (former - to 2017)
Depositing User: Pure Connector
Date Deposited: 01 Apr 2015 12:30
Last Modified: 21 Oct 2022 00:48
URI: https://ueaeprints.uea.ac.uk/id/eprint/53011
DOI: 10.1016/j.jhydrol.2015.03.001

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