title: New insight into the correlations between land use and water quality in a coastal watershed of China: Does point source pollution weaken it?
abstract: Uncovering the associations between land use and river water quality is useful for managing land-based pollution in the catchment-coast continuum. However, it is not clear how land use affects water quality in the context of simultaneous point source (PS) pollution. In this study, we develop a self-organizing map (SOM)-based approach to explore the relationship between land use and water quality in the Minjiang River Watershed, Southeast China. Water samples from 139 headwater sub-watersheds were associated with six land use categories, namely, Woodland, Agriculture, Orchard, Built-up, Unused land and Water. Sampling sites are delineated into six clusters based on six water quality parameters: ammonium-N, nitrate-N, total nitrogen, soluble reactive phosphate, total phosphate and potassium permanganate index. Local relationships between land use and water quality among four clusters that have sufficient sample sizes are further identified. There is no significant land use-water quality correlation in one of the four clusters (including 37 sub-watersheds). And the greater the PS pollution is, the less significant the land use-water quality correlations are in clusters. The results demonstrate how PS pollution weakens the land use-water quality correlation. Our method can help to determine whether non-point source or PS pollution exerts greater influence on the quality of the water coming from watershed.
authors.affiliation: Coastal and Ocean Management Institute, Xiamen University, Xiamen 361102, China; Fujian Provincial Key Laboratory of Coastal Ecology and Environmental Studies, Xiamen University, Xiamen 361102, China.
authors.forename: Pei
authors.initials: P
authors.lastname: Zhou
authors.affiliation: Coastal and Ocean Management Institute, Xiamen University, Xiamen 361102, China; Fujian Provincial Key Laboratory of Coastal Ecology and Environmental Studies, Xiamen University, Xiamen 361102, China. Electronic address: jlhuang@xmu.edu.cn.
authors.forename: Jinliang
authors.initials: J
authors.lastname: Huang
authors.affiliation: Graduate School of Geography, Clark University, Worcester, MA 01610, USA.
authors.forename: Robert Gilmore
authors.initials: RG
authors.lastname: Pontius
authors.affiliation: Coastal and Ocean Management Institute, Xiamen University, Xiamen 361102, China; Fujian Provincial Key Laboratory of Coastal Ecology and Environmental Studies, Xiamen University, Xiamen 361102, China.
authors.forename: Huasheng
authors.initials: H
authors.lastname: Hong
mesh_terms: D000383:Agriculture / Q000706:statistics & numerical data; D000641:Ammonia / Q000032:analysis; D002681:China; D004784:Environmental Monitoring; D009566:Nitrates / Q000032:analysis; D009584:Nitrogen / Q000032:analysis; D010710:Phosphates / Q000032:analysis; D045483:Rivers; D014507:Urbanization / Q000639:trends; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014877:Water Pollution, Chemical / Q000706:statistics & numerical data; D060753:Water Quality
chemical_list: D009566:Nitrates; D010710:Phosphates; D014874:Water Pollutants, Chemical; D000641:Ammonia; D009584:Nitrogen
keywords: Land use; Point source pollution; Self-organizing map; Spatial variation; Water quality