Biogeochemical Mechanisms of HCO3–Ca Water and NO3− Pollution in a Typical Piedmont Agricultural Area: Insights from Nitrification and Carbonate Weathering
Abstract
1. Introduction
2. Materials and Methods
2.1. Site Information and Sampling Campaign
2.2. Hydrochemical, Isotopic and Microbial Analysis
2.3. Data Analysis
3. Results
3.1. Overall Riverine Hydrochemistry
3.2. Isotopic Parameters
3.3. Microbial Communities
4. Discussion
4.1. Environmental Factors
4.1.1. Evaporation and Recharge Processes
4.1.2. Topography and Channel Structure
4.2. Mineral Dissolution Dominated by Carbonate Rocks
4.2.1. Hydrochemical Indicators
4.2.2. Saturation Index
4.2.3. Forward Model
4.3. Agricultural NH4+ Emissions
4.4. Biogeochemical Mechanisms
5. Conclusions
Supplementary Materials
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
References
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Parameters | Unit | A-RW (n = 13) | U-RW (n = 7) | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Mean | Min. | Max. | SD | CV | Mean | Min. | Max. | SD | CV | ||
pH | / | 8.48 | 7.75 | 8.75 | 0.28 | 0.03 | 8.86 | 8.46 | 9.18 | 0.25 | 0.03 |
DO | mg/L | 10.1 | 8.40 | 13.7 | 1.45 | 0.14 | 10.6 | 3.79 | 15.0 | 4.26 | 0.40 |
T | °C | 15.0 | 12.1 | 18.4 | 2.20 | 0.15 | 20.0 | 18.0 | 22.2 | 1.37 | 0.07 |
ORP | mV | −76.4 | −92.7 | −33.7 | 16.0 | 0.21 | −100 | −123 | −75.2 | 17.4 | 0.17 |
TDS | mg/L | 415 | 346 | 546 | 58.9 | 0.14 | 267 | 230 | 296 | 22.8 | 0.09 |
K+ | mg/L | 3.33 | 0.37 | 5.07 | 1.38 | 0.41 | 5.86 | 4.30 | 7.72 | 1.22 | 0.21 |
Na+ | mg/L | 30.9 | 24.3 | 40.1 | 4.81 | 0.16 | 33.2 | 30.1 | 37.0 | 2.87 | 0.09 |
Ca2+ | mg/L | 90.9 | 80.6 | 112 | 8.63 | 0.09 | 36.5 | 25.9 | 50.0 | 7.30 | 0.20 |
Mg2+ | mg/L | 20.6 | 13.6 | 33.5 | 6.93 | 0.34 | 17.0 | 15.3 | 18.4 | 1.21 | 0.07 |
Cl− | mg/L | 34.0 | 19.9 | 43.4 | 8.18 | 0.24 | 43.2 | 39.3 | 49.7 | 3.32 | 0.08 |
SO42− | mg/L | 57.1 | 32.7 | 87.3 | 16.6 | 0.29 | 49.6 | 39.7 | 62.1 | 9.06 | 0.18 |
HCO3− | mg/L | 285 | 223 | 411 | 63.6 | 0.22 | 160 | 134 | 176 | 14.2 | 0.09 |
NO3− | mg/L | 35.6 | 3.08 | 52.8 | 12.5 | 0.35 | 1.12 | 0.52 | 2.86 | 1.16 | 1.03 |
NO2− | mg/L | / | BDL | BDL | / | / | 1.38 | 1.03 | 1.69 | 0.35 | 0.26 |
NH4+ | mg/L | / | BDL | 0.16 | / | / | 0.35 | 0.24 | 0.48 | 0.07 | 0.21 |
F− | mg/L | / | BDL | 0.03 | / | / | / | BDL | BDL | / | / |
δ2H-H2O | ‰ | −73.2 | −80.0 | −63.0 | 5.18 | 0.07 | −53.3 | −66.0 | −43.0 | 7.89 | 0.15 |
δ18O-H2O | ‰ | −9.90 | −10.8 | −8.20 | 0.84 | 0.08 | −6.66 | −8.70 | −4.50 | 1.41 | 0.21 |
d-excess | ‰ | 6.05 | 2.60 | 7.80 | 1.74 | 0.29 | −0.03 | −7.00 | 3.60 | 3.62 | / |
δ13C-DIC | ‰ | −10.6 | −12.0 | −8.60 | 1.14 | 0.11 | −5.01 | −7.12 | −3.88 | 1.08 | 0.22 |
Regions | NH4+-Containing Pollutants | References |
---|---|---|
Comarca Lagunera, Mexico | Manure from concentrated animal-feeding operations (~48%), urban sewage (~43%), soil organic nitrogen (~4%), NH4+-synthetic fertilizers (~3%) and atmospheric deposition (~1%). | [45] |
Huixian karst wetland, China | Atmospheric nitrogen deposition (3.44%), synthetic NH4+ fertilizer (36.6%), soil organic nitrogen (28.0%), domestic sewage and manure (15.1%). | [25] |
Hohhot Basin’s Piedmont, China | Manure (20.5%), soil nitrogen (63.8%) and ammonia fertilizer (28.8%). | [40] |
Nyando tropical river basin, Kenya | Ammonium in fertilizer/rain (10%), soil nitrogen (18–41%), manure and sewage (46–70%). | [56] |
Bukit Merah Reservoir, Malaysia | Atmospheric deposition (23–29%), soil nitrogen (25–26%), manure and sewage (25–33%), | [57] |
Sardinia, Italy | NH4+ fertilizers (2.13%), soil organic nitrogen (0.55%), sewage and manure (58.5%). | [58] |
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Xu, L.; Xin, B.; Liu, W.; Liu, H.; Yang, G.; Hao, G. Biogeochemical Mechanisms of HCO3–Ca Water and NO3− Pollution in a Typical Piedmont Agricultural Area: Insights from Nitrification and Carbonate Weathering. Toxics 2025, 13, 394. https://doi.org/10.3390/toxics13050394
Xu L, Xin B, Liu W, Liu H, Yang G, Hao G. Biogeochemical Mechanisms of HCO3–Ca Water and NO3− Pollution in a Typical Piedmont Agricultural Area: Insights from Nitrification and Carbonate Weathering. Toxics. 2025; 13(5):394. https://doi.org/10.3390/toxics13050394
Chicago/Turabian StyleXu, Li, Bo Xin, Wei Liu, Haoyang Liu, Guoli Yang, and Guizhen Hao. 2025. "Biogeochemical Mechanisms of HCO3–Ca Water and NO3− Pollution in a Typical Piedmont Agricultural Area: Insights from Nitrification and Carbonate Weathering" Toxics 13, no. 5: 394. https://doi.org/10.3390/toxics13050394
APA StyleXu, L., Xin, B., Liu, W., Liu, H., Yang, G., & Hao, G. (2025). Biogeochemical Mechanisms of HCO3–Ca Water and NO3− Pollution in a Typical Piedmont Agricultural Area: Insights from Nitrification and Carbonate Weathering. Toxics, 13(5), 394. https://doi.org/10.3390/toxics13050394