Earth Science Frontiers ›› 2022, Vol. 29 ›› Issue (3): 88-98.DOI: 10.13745/j.esf.sf.2022.1.26

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Distribution characteristics and causes of arsenic in shallow groundwater in the Pearl River Delta during urbanization

LÜ Xiaoli1(), ZHENG Yuejun1, HAN Zhantao2,*(), LI Haijun3, YANG Mingnan4, ZHANG Ruolin1, LIU Dandan5,*()   

  1. 1. China Institute of Geo-Environmental Monitoring, Beijing 100081, China
    2. Technical Centre for Soil, Agriculture and Rural Ecology and Environment, Ministry of Ecology and Environment, Beijing 100012,China
    3. Hebei Investigation Institute of Hydrogeology and Engineering Geology, Shijiazhuang 050021, China
    4. Institute of Hydrogeology and Environmental Geology, Chinese Academy of Geological Sciences, Shijiazhuang 050061, China
    5. Center for Hydrogeology and Environmental Geology Survey,China Geological Survey, Baoding 071051, China
  • Received:2021-10-30 Revised:2022-01-24 Online:2022-05-25 Published:2022-04-28
  • Contact: HAN Zhantao,LIU Dandan


A high level of arsenic (As) in groundwater (ρ(As)>10 μg/L) is a potential threat to safe drinking water and the ecological environment. The sources of As in groundwater derived from coastal urbanized areas are complex, which mainly include various anthropogenic and geogenic sources. The rapidly urbanized Pearl River Delta was selected as the study area. The occurrence of and key driving factors for As enrichment in the shallow aquifers in areas with different urbanization levels in the Pearl River Delta were evaluated via mathematical statistics and principal component analysis. According to the results, the total dissolved As concentration in shallow groundwater ranged from below the detection limit to 420 μg·L-1 in the study area, with As(Ⅲ) as the main form. ρ(As) was found to be generally higher in porous aquifers than in fractured or karst aquifers. The proportion of As in the groundwater of urbanized areas was more than five times that of non-urbanized areas. Among the 1567 groups of groundwater samples collected from the study area, 89 high As groups, or 5.7% of total, had high level of As (ρ(As) >10 μg·L-1). Among them, 82 groups were from shallow porous aquifers, 4 groups from fissure aquifers, and 3 groups from karst aquifers, accounting for 7.8%, 0.8%, and 9.7% of total, respectively. Compared with historical hydrochemical data collected from 2005 to 2008, the average ρ(As) in shallow high As groundwater of newly added construction areas increased by 30% in 10 years. The chemical type of high As groundwater mainly included HCO3-Ca and Cl-Na types, characterized by high pH, low redox potential (Eh), low NO 3 - concentration, and positive correlation between ρ(As) and concentrations of NH 4 +, Fe, and Mn or oxygen consumption. Under microbial degradation and mineralization of organic matter, reductive dissolution of As-bearing iron (oxygen) hydroxide in the Quaternary basement muddy sedimentary strata in the Delta plain was identified as the cause of As mobilization. The leaking and infiltration of As-containing industrial wastewater produced during the urbanization process were also important sources of As in groundwater in Shunde District, southern Foshan City. Due to the dual effects of the original sedimentary environment and human input, the neutral to weakly alkaline, closed to semi-closed reducing environment that is rich in organic matter formed in the Delta plain, was the main cause of the occurrence of high As in groundwater.

Key words: urbanization, arsenic in groundwater, distribution characteristics, driving factors, ionic ratios, Pearl River Delta

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