Review of drivers and threats to coastal groundwater quality in China

With rapid socio-economic development, China's coastal areas are among the fastest growing and most economically dynamic regions in the world. Under the influence of climate change and human activities, protecting the quality of coastal groundwater has emerged as one of the key environmental and resource management issues for these areas. This paper reviews (for the first time) groundwater quality data for the coastal basins of China, where over 600 million people live, focussing on key inorganic indicators/pollutants; groundwater salinity, nitrate, fluoride, and arsenic. These pollutants present major water quality issues and are also valuable as indicators of wider processes and influences impacting coastal groundwater quality - e.g. saltwater intrusion, agricultural pollution and release of geo-genic contaminants. We discuss the major drivers causing water quality problems in different regions and assess future trajectories and challenges for controlling changes in coastal groundwater quality in China. Multiple processes, including modern and palaeo seawater/brine migration, groundwater pumping for agricultural irrigation, pollution from agrochemical application, rapid development of aquaculture, urban growth, and water transfer projects, may all be responsible (to different degrees) for changes observed in coastal groundwater quality, and associated long-term health and ecological effects. We discuss implications for sustainable coastal aquifer management in China, arguing that groundwater monitoring and contamination control measures require urgent improvement. The evolution and treatment of coastal groundwater quality problems in China will serve as an important warning and example for other countries facing similar pressures, due to climate change, coastal development, and intensification of anthropogenic activity in coming decades.