Hydrochemistry and source apportionment of boron, sulfate, and nitrate in the Fen River, a typical loess covered area in the eastern Chinese Loess Plateau

Jun Xiao; Guorui Lv; Ningpan Chai; Jing Hu; Zhangdong Jin

doi:10.1016/j.envres.2021.112570

Hydrochemistry and source apportionment of boron, sulfate, and nitrate in the Fen River, a typical loess covered area in the eastern Chinese Loess Plateau

Environ Res. 2022 Apr 15:206:112570. doi: 10.1016/j.envres.2021.112570. Epub 2021 Dec 16.

Authors

Jun Xiao¹, Guorui Lv², Ningpan Chai³, Jing Hu³, Zhangdong Jin⁴

Affiliations

¹ SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences (IEECAS), Xi'an, 710061, China; Center for Excellence in Quaternary Science and Global Change, Chinese Academy of Sciences, No. 97 Yanxiang Road, Yanta Zone, Xi'an, 710061, Shaanxi, China. Electronic address: xiaojun@ieecas.cn.
² SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences (IEECAS), Xi'an, 710061, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
³ SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences (IEECAS), Xi'an, 710061, China.
⁴ SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences (IEECAS), Xi'an, 710061, China; Center for Excellence in Quaternary Science and Global Change, Chinese Academy of Sciences, No. 97 Yanxiang Road, Yanta Zone, Xi'an, 710061, Shaanxi, China.

PMID: 34922980
DOI: 10.1016/j.envres.2021.112570

Abstract

Fen River Basin (FRB) is water-deficient and strongly influenced by human activities in the eastern Chinese Loess Plateau. The spatio-temporal variation and controlling factors of hyrochemistry and quality, sources of high boron, sulfate, and nitrate of surface waters in FRB were unclear. Major ions, δ¹¹B, δ¹⁵N, and δ¹⁸O in surface waters in dry season and wet season of FRB were analyzed and correlation analysis (CA), principal component analysis (PCA), self-organizing map (SOM), forward model, and Bayesian isotope mixing model (MixSIAR) were used to solve above problems. Results showed that average riverine δ¹¹B, δ¹⁵N, and δ¹⁸O of FRB was 7.8‰, 11.2‰, and 1.3‰ (1SD), respectively. Dissolved solutes ranked midstream > downstream > upstream with water type of Na ⁺-Cl^-, Ca²⁺-Mg²⁺-Cl^-, and Ca²⁺-HCO₃^-, respectively. Low dissolved solutes were in forest areas while high values were in cropland and city areas. SOM analysis indicated that hydrochemistry was both influenced by natural (upstream) and pollutional input (midstream and downstream) and variation between dry season and wet season was minor. The abnormally high boron concentrations were mainly from silicate weathering (43%) and evaporites dissolution of loess (32%), urban and industrial input contributed 15% of riverine boron. High SO₄^2- (207 ± 267 mg/L, 1SD) was mainly from sulfates. δ¹⁵N and δ¹⁸O analysis indicated that nitrification was the primary N cycling process. Further, MixSIAR showed that NO₃^- was mainly from municipal sewage (∼67%) and the total contribution of chemical fertilizer and soil nitrogen was ∼30% with slightly higher values in upstream and wet season. Influenced by land-use types, evaporite dissolution, and anthropogenic input, water quality below midstream was worse and strict sewage reduction policies must be developed. This study highlights the significant influence of evaporite dissolution of loess and anthropogenic input (urban and industrial input for B and sewage for NO₃^-) on hydrochemistry and water quality.

Keywords: Fen river; Hydrochemistry; Loess weathering; Source identification; Spatial-temporal variation.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Bayes Theorem
Boron
China
Environmental Monitoring / methods
Humans
Nitrates* / analysis
Sulfates
Water Pollutants, Chemical* / analysis

Substances

Nitrates
Sulfates
Water Pollutants, Chemical
Boron