Impacts of Anthropogenic Changes on the Mun River Water: Insight from Spatio-Distributions and Relationship of C and N Species in Northeast Thailand

et al. 2019

Water

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The nutrient contents of Mun River water in northeast Thailand during the dry season were measured to investigate the effect of human activities on dissolved load species. Dissolved organic carbon (DOC) values varied from 2.5 to 17.1 mg/L, averaging 9.0 mg/L; dissolved inorganic nitrogen (DIN) ranged between 0.12 and 0.11 mg/L; Cl− values ranged from 1.7 to 668.6 mg/L, with an average value of 84.8 mg/L; dissolved silicon (DSi) varied from 1.7 to 9.9 mg/L; and SO42− values averaged 8.9 mg/L. DOC, Cl−, and SO42− contents decreased with the flow direction. The high concentrations of DOC, K+, Cl−, and SO42− in the upper reaches were closely related to anthropogenic inputs, specifically industrial sewage. The covariation demonstrated that these dissolved loads may have the same sources. In other regions, Cl− contents were derived from weathering products. DIN contents maintained the same level on the river, and few sampling sites with high concentrations of DIN were influenced by point source pollution. The extremely low P concentrations limited algal growth, and the DSi showed no clear relationship with N and K, indicating that DSi in the Mun River was controlled by the weathering input rather than biological effects. The exact reverse spatial distributions of DOC between the wet and dry seasons (which increased with the flow direction in the wet season) were due to different precipitation rates, and the rare rainfall in the dry season had difficulty flushing the soil and transporting soil organic matter into the rivers. The local government should control sewage discharge and optimize farming methods.

Section: The Impact Of Precipitation and Soil Erosionsupporting

confidence: 91%

Section: Land-use Type and Precipitation Distributionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Distributive Characteristics of Riverine Nutrients in the Mun River, Northeast Thailand: Implications for Anthropogenic Inputs

et al. 2019

Water

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“…The study area and sample sites were described in detail by the authors of references [22,23]. Briefly, the Mun River lies in the northeast of Thailand between latitudes 14° N to 16° N and longitudes 101°30′ E to 105°30′ E (Figure 1a), the total area is 71,060 square kilometers.…”

Section: Methodsmentioning

confidence: 99%

Hydrochemistry and Dissolved Inorganic Carbon (DIC) Cycling in a Tropical Agricultural River, Mun River Basin, Northeast Thailand

Song

et al. 2019

IJERPH

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Dissolved inorganic carbon isotope composition (δ13CDIC), together with major ion concentrations were measured in the Mun River and its tributaries in March 2018 to constrain the origins and cycling of dissolved inorganic carbon. In the surface water samples, the DIC content ranged from 185 to 5897 μmol/L (average of 1376 μmol/L), and the δ13CDIC of surface water ranged from −19.6‰ to −2.7‰. In spite of the high variability in DIC concentrations and partial pressure of carbon dioxide (pCO2), the δ13CDIC values of the groundwater were relatively consistent, with a mean value of −16.9 ± 1.4‰ (n = 9). Spatial changes occurred in the direction and magnitude of CO2 flux through water-air interface (FCO2). In the dry season, fluxes varied from −6 to 1826 mmol/(m2·d) with an average of 240 mmol/(m2·d). In addition to the dominant control on hydrochemistry and dissolved inorganic carbon isotope composition by the rock weathering, the impacts from anthropogenic activities were also observed in the Mun River, especially higher DIC concentration of waste water from urban activities. These human disturbances may affect the accurate estimate contributions of carbon dioxide from tropical rivers to the atmospheric carbon budgets.

“…River water is the important component of hydrosphere and draws great attention in geological and environmental research, for it constitutes the lateral channels transporting the territorial matters towards the ocean [1,2]. The riverine dissolved loads transported along river waters are derived from both natural processes and anthropogenic perturbations [3,4,5,6], among which the chemical weathering is considered as the dominant source [1,7,8]. Thus, estimating the contributions of the different minerals during chemical weathering to the riverine solutes can help researchers to better understand the chemical composition of river water and regular patterns of matter cycling [9,10].…”

Section: Introductionmentioning

confidence: 99%

Distribution, Sources and Water Quality Evaluation of the Riverine Solutes: A Case Study in the Lancangjiang River Basin, Tibetan Plateau

Zeng

et al. 2019

IJERPH

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To examine the chemical composition, potential sources of solutes, and water quality of Lancangjiang River, the concentrations of major ions (Ca2+, Mg2+, Na+, K+, HCO3−, SO42−, Cl− and NO3−) in 45 river water samples collected in July and August 2019 were determined. Ca2+ and HCO3− are the predominant ions in river water. The extremely low K+ and NO3− concentrations and the sparse population suggest that the anthropogenic inputs are limited. The Pearson correlation coefficients and the elemental ratios Ca2+/Na+ versus Mg2+/Na+, Ca2+/Na versus HCO3−/Na+, [Ca2+ + Mg2+]/[HCO3−] versus [SO42−]/[HCO3−] reveal the mixing processes of different sources; the chemical composition of the river water is controlled by the mixture of carbonate weathering, evaporite weathering and silicate weathering inputs. To quantify the contributions of atmospheric input and rock dissolution, the forward method is employed in this study, which is based on the mass balance equation. The calculation results suggest the carbonate weathering inputs and gypsum dissolution make up the majority of the riverine cations, while silicate weathering and halite dissolution constitutes a relatively small proportion, the contributions of the atmospheric input are limited. The fast dissolution rate of evaporite and carbonate minerals and their lithologic distributions should be the key factor. To evaluate the water quality for drinking and irrigation purposes, the drinking water quality guidelines and the calculated parameters were employed, including sodium adsorption ratio (SAR), soluble sodium percentage (Na%,) and residual sodium carbonate (RSC). The assessments indicate that the river waters in the middle-lower reaches are generally suitable for irrigation and drinking purpose, and will not lead to health and soil problems, such as soil compaction and salinization. While in the upper reaches, the dissolution of carbonate and gypsum minerals transport abundant ions into river water and the river waters are not appropriate to use directly. This result highlights that the water quality status can also be affected by natural weathering processes in the area without anthropogenic inputs, where the long-time monitoring of water quality is also necessary.