Surface Water Quality in the South Section of the Grand Canal in China along An Urbanization Gradient.

Urbanization has imposed proverbial problems on urban environment. Waterbody is the most sensitive indicator for this kind of urban environmental problems. China has been considered as a "living laboratory in urbanization" since she rapidly achieved a considerable urbanization level in the past 30 years, usually taking over few centuries in the western countries. We chose the south section of the Grand Canal in China as the investigation object for evaluating urbanization effects on surface water quality. Surface water samples of the Grand Canal were collected in its urban sections of nine cities/towns as well as samples were collected in a farmland section as a control. The nine cities/towns represent a gradient of urbanization levels, from 8.6% to 93.2% of population urbanization rate and from 1.08 billion to 325.79 billion Yuan RMB of gross domestic product (GDP). Surface water quality, including nutrients, heavy metals, and common physiochemical properties, from sections under various urbanization levels indicated that no relationships were explored with population urbanization rate and the GDP structure. But, industry specificity of towns was related to concentrations of specific heavy metals. For instance, tannery resulted in significant chromium concentrations in surface water, and the thermometer and electricity-saving bulb manufactories caused detectable concentrations of mercury in surface water of the urban section of the Grand Canal. The principal component analysis (PCA) grouped the nine cities/towns into three clusters. The estuary cluster, two out of nine cities/towns, close to Yangtze River and Qianjiang River where surface water of the Grand Canal gets exchanged by rivers, had lower concentrations of nutrients and copper than others, separated by dissolved oxygen and pH. Secondary industrial cluster is another group characterized by high concentrations of heavy metals in surface water while tertiary industrial cluster is driven by nutrients and physiochemical properties of surface water in urban sections of the Grand Canal.