Identification of Hydrobiogeochemical Processes Controlling Seasonal Variations in Arsenic Concentrations Within a Riverbank Aquifer at Jianghan Plain, China

Abstract

The arsenic concentration in groundwater varies significantly with time and space in groundwater‐surface water exchange zones. Various processes have been identified that control arsenic concentration distribution and mobility in laboratory systems. However, it is still challenging to identify important processes controlling arsenic concentration distribution at the field scale due to the complex coupling of hydrobiogeochemical processes. In this study, a reactive flow and transport model was used to identify dominant processes controlling arsenic distribution and seasonal variations in groundwater‐surface water exchange zones using Jianghan Plain, China, as an example. The results revealed the importance of river water and groundwater interactions on seasonal changes in arsenic concentration; however, the affected region is limited to within 50‐m distance to the river. The modeling results, unexpectedly, revealed the predominant importance of groundwater extraction to the seasonal variation in arsenic concentration. The groundwater extraction changed the groundwater flow pattern and induced vertical leakage of oxygen‐containing surface water into the aquifer, which triggered a series of biogeochemical reactions that changed groundwater redox conditions and promoted arsenic sorption, resulting in a rapid decrease in arsenic concentrations in groundwater. After groundwater extraction ceased, aquifer recovered to anoxic condition, promoting arsenic release from the sorbed phase, leading to a rapid rebounding in groundwater arsenic concentrations. Overall, this study provided a tool to identify coupled hydrobiogeochemical processes on arsenic spatiotemporal distribution and migration in groundwater.

Quantifying Geochemical Processes of Arsenic Mobility in Groundwater From an Inland Basin Using a Reactive Transport Model

“…Increased pumping has been suggested to lower As concentrations in deltaic aquifers (Stute et al, 2007). Furthermore, fresh O 2 -rich surface water/groundwater flushing can also depress dissolved As concentrations by increasing groundwater Eh and oxidizing dissolved Fe (II) (Huang et al, 2018). However, the introduction of labile organic matter into an aquifer via groundwater pumping has been observed to enhance As mobilization (C.F.…”

Seasonal variations in arsenic mobility and bacterial diversity: The case study of Huangshui Creek, Shimen Realgar Mine, Hunan Province, China

“…Changes in biogeochemical factors related to seasonal conditions can also affect arsenic speciation and mobility (Sarmiento et al, 2007;Stuckey et al, 2015;Huang et al, 2018). These factors include available nutrients, micro-plankton abundance (Hasegawa, 1996), seasonal water temperature (Howard et al, 1995) and physical variation, such as ice cover (Palmer et al, 2019) and rainfall (Sultan, 2006).…”

Conceptual Model of Arsenic Mobility in the Shallow Alluvial Aquifers Near Venice (Italy) Elucidated Through Machine Learning and Geochemical Modeling

“…Geogenic (i.e., naturally occurring) arsenic (As) contamination is a well‐known issue that affects unconsolidated and fractured aquifers worldwide (e.g., Choudhury et al, 2018; Desbarats et al, 2017; Erickson et al, 2018; Huang et al, 2018; Jakobsen et al, 2018; Pedretti et al, 2019), including Italian aquifers (e.g., Aiuppa et al, 2003; Carraro et al, 2013; Molinari et al, 2013; Rotiroti et al, 2014; Ungaro et al, 2008). Identifying a valid site‐specific conceptual model able to describe As mobility in groundwater is fundamental for many purposes related to As risk management.…”