High-Arsenic Groundwater in Paleochannels of the Lower Yellow River, China: Distribution and Genesis Mechanisms

Abstract

High–arsenic (As) groundwater poses a serious threat to human health. The upper and middle reaches of the Yellow River are well–known areas for the enrichment of high–arsenic groundwater. However, little is known about the distribution characteristics and formation mechanism of high-As groundwater in the lower reach of the Yellow River. There were 203 groundwater samples collected in different groundwater systems of the lower Yellow River for the exploration of its hydrogeochemical characteristics. Results showed that more than 20% of the samples have arsenic concentrations exceeding 10 μg/L. The high-As groundwater was mainly distributed in Late Pleistocene–Holocene aquifers, and the As concentrations in the paleochannels systems (C2 and C4) were significantly higher than that of the paleointerfluve system (C3) and modern Yellow River affected system (C5). The high-As groundwater is characterized by high Fe2+ and NH4+ and low Eh and NO3−, indicating that reductive dissolution of the As–bearing iron oxides is probably the main cause of As release. The arsenic concentrations strikingly showed an increasing tendency as the HCO3− proportion increases, suggesting that HCO3− competitive adsorption may facilitate As mobilization, too. In addition, a Gibbs diagram showed that the evaporation of groundwater could be another significant hydrogeochemical processes, except for the water–rock interaction in the study area. Different sources of aquifer medium and sedimentary structure may be the main reasons for the significant zonation of the As spatial distribution in the lower Yellow River.

Using Radar and Optical Satellite Images to Delineate Paleodrainages in Desert Regions: A Case of Saudi Arabia

“…In many regions, paleochannels have been considered as a solution to address freshwater scarcity problems in arid zone such as in the Eastern Sahara (Egypt and Libya) and New South Wales, (Australia). Hence, the signi cance of paleochannels in groundwater storage has been mentioned in several studies (Wray, 2009;Owen and Dahlin, 2010;Samadder et al, 2011;Paillou et al, 2012;Ghoneim et al, 2012;Zhi et al, 2021); while, the role of paleochannels in seeping saltwater into the coastal aquifers was mentioned (Mulligan et al, 2007;Rizk et al, 2007), and this might interpret the presence of Sabkhas in several localities at range from the coastline the Arabian Peninsula such as in those in Dammam Region.…”

Microbial Community Structure of Arsenic-Bearing Groundwater Environment in the Riverbank Filtration Zone

“…The formation of arsenic-bearing groundwater is the result of a series of water-rock interactions, hydrogeochemistry and geological microorganisms. The release mechanisms are mainly as follows: desorption, reductive dissolution of arsenic-bearing minerals, oxidation of arsenic-bearing minerals and the direct reduction of arsenic [17][18][19][20][21][22]. There are mainly two forms of arsenic in nature, inorganic arsenic and organic arsenic, and its main valence states are As 3+ and As 5+ .…”