Arsenic in the Pearl River Delta and its related waterbody, South China: occurrence and sources, a review

The Pearl River Delta (PRD) is a densely populated special economic zone in South China where rapid development since the late 1990s coincided with an increase of many environmental problems in recent years. One of these concerns is the high concentration of arsenic (As; up to 300 mu g/L in groundwater) that has been documented in the PRD. Likewise, in surface water and soils, As levels are comparatively higher than in other places in China. Arsenic is discharged from various geogenic sources and anthropogenic activities along the river courses before it drains into the Pearl River Estuary. In general, relatively low As concentrations in the river are due to the limited input from weathering of parent rocks. In contrast, where mining is an important industry, As levels in the surroundings are higher, exceeding the national and international standards for drinking water and soil. The presence of sulfide ores and mining operations, such as extraction of heavy metals and disposal of mine tailings, are most likely responsible for the sharp increase of As above background levels in several tributaries draining into the Pearl River. Besides, in the middle and lower reaches of the tributaries, other anthropogenic sources, e.g., industrial effluents and domestic sewage discharge play an important role in increasing As levels. Finally, rice cultivated in the contaminated areas accumulates As and poses a health risk to the local people in the watershed.