Interplay of legacy irrigation and nitrogen fertilizer inputs to spatial variability of arsenic and uranium within the deep vadose zone

Arindam Malakar; Chittaranjan Ray; Matteo D'Alessio; Jordan Shields; Craig Adams; Marty Stange; Karrie A Weber; Daniel D Snow

doi:10.1016/j.scitotenv.2023.165299

Interplay of legacy irrigation and nitrogen fertilizer inputs to spatial variability of arsenic and uranium within the deep vadose zone

Sci Total Environ. 2023 Nov 1:897:165299. doi: 10.1016/j.scitotenv.2023.165299. Epub 2023 Jul 6.

Authors

Arindam Malakar¹, Chittaranjan Ray², Matteo D'Alessio³, Jordan Shields⁴, Craig Adams⁴, Marty Stange⁵, Karrie A Weber⁶, Daniel D Snow⁷

Affiliations

¹ Nebraska Water Center, part of the Robert B. Daugherty Water for Food Global Institute and School of Natural Resources, University of Nebraska, Lincoln, NE 68583-0844, USA. Electronic address: [email protected].
² Nebraska Water Center, part of the Robert B. Daugherty Water for Food Global Institute, 2021 Transformation Drive, University of Nebraska, Lincoln, NE 68588-6204, USA.
³ Nebraska Water Center, part of the Robert B. Daugherty Water for Food Global Institute, University of Nebraska, Lincoln, NE 68583-0915, USA.
⁴ Nebraska Water Center, part of the Robert B. Daugherty Water for Food Global Institute and School of Natural Resources, University of Nebraska, Lincoln, NE 68583-0844, USA.
⁵ Hastings Utilities, 1228 N. Denver Avenue, Hastings, NE 68901, USA.
⁶ Nebraska Water Center, part of the Robert B. Daugherty Water for Food Global Institute, 2021 Transformation Drive, University of Nebraska, Lincoln, NE 68588-6204, USA; School of Biological Sciences, University of Nebraska, Lincoln, Lincoln, NE, USA; Earth and Atmospheric Sciences, University of Nebraska, Lincoln, Lincoln, NE 68588, USA.
⁷ Nebraska Water Center, part of the Robert B. Daugherty Water for Food Global Institute and School of Natural Resources, University of Nebraska, Lincoln, NE 68583-0844, USA. Electronic address: [email protected].

PMID: 37419358
DOI: 10.1016/j.scitotenv.2023.165299

Abstract

The vadose zone is a reservoir for geogenic and anthropogenic contaminants. Nitrogen and water infiltration can affect biogeochemical processes in this zone, ultimately affecting groundwater quality. In this large-scale field study, we evaluated the input and occurrence of water and nitrogen species in the vadose zone of a public water supply wellhead protection (WHP) area (defined by a 50-year travel time to groundwater for public supply wells) and potential transport of nitrate, ammonium, arsenic, and uranium. Thirty-two deep cores were collected and grouped by irrigation practices: pivot (n = 20), gravity (n = 4) irrigated using groundwater, and non-irrigated (n = 8) sites. Beneath pivot-irrigated sites, sediment nitrate concentrations were significantly (p < 0.05) lower, while ammonium concentrations were significantly (p < 0.05) higher than under gravity sites. The spatial distribution of sediment arsenic and uranium was evaluated against estimated nitrogen and water loading beneath cropland. Irrigation practices were randomly distributed throughout the WHP area and presented a contrasting pattern of sediment arsenic and uranium occurrence. Sediment arsenic correlated with iron (r = 0.32, p < 0.05), uranium negatively correlated to sediment nitrate (r = -0.23, p < 0.05), and ammonium (r = -0.19 p < 0.05). This study reveals that irrigation water and nitrogen influx influence vadose zone geochemistry and mobilization of geogenic contaminants affecting groundwater quality beneath intensive agricultural systems.

Keywords: Ammonium; Arsenic; Irrigation; Nitrate; Unsaturated/vadose zone; Uranium.