Riverine Hydrochemical Characteristics of a Typical Karst Urban Watershed: Major Ion Compositions, Sources, Assessment, and Historical Evolution

Abstract

Urban watersheds suffer from great pressure concerning poor water carrying capacity in the karst area with a fragile ecology system and urbanization disturbance. The hydrochemistry of karst urban rivers plays a vital role in the maintenance of water ecology. This study determined the sources of major ions (Na + , K + , Mg 2+ , Ca 2+ , F − , Cl − , NO 3 − , SO 4 2− , and HCO 3 − ) in the Nanming urban watershed. The ion concentrations were dominated by the HCO 3 − -Ca 2+ •Mg 2+ type and complied with the compoment characteristics of major ions in karst rivers with the order of Ca 2+ (mean: 83.1 mg/L) > Mg 2+ (mean: 17.6 mg/L) > Na 2+ (mean: 15.2 mg/L) > K + (mean: 6.7 mg/ L) and HCO 3 − (mean: 252.7 mg/L) > SO 4 2− (mean: 101.5 mg/L) > Cl − (mean: 17.8 mg/L) > NO 3 − (mean: 17.7 mg/L). The chemical composition of the Nanming River was possibly affected by carbonate weathering (Ca 2+ , Mg 2+ , and HCO 3 − ) and anthropogenic inputs (SO 4 2− , NO 3 − , Cl − , Na + , and K + ) through methods of principal component analysis (PCA) and ion ratios. The irrigation water quality and health risk were evaluated by the calculation of sodium adsorption ratio (SAR), soluble sodium percentage (Na%), residual sodium carbonate (RSC), and hazard quotient (HQ) and the comparison of corresponding guidelines. The results showed that the Nanming River was marginally suitable for agricultural irrigation but dangerous for direct drinking intake, and the noncarcinogenic health risk of riverine ions should also be of concern. The control of urban wastewater discharge should be paid more attention to improve the water quality in such an urban watershed.

Water Chemical Characteristics and Water Quality Evaluation of the River under the Ecological Water Replenishment: A Case Study in the Yongding River Basin in North China

“…Although the YDR was obviously affected by anthropogenic activities, the contribution of natural weathering was critical, especially in the upstream areas. The ratios of Ca 2+ /Na + versus Mg 2+ /Na + and Ca 2+ /Na + versus HCO 3 – /Na + can serve as indicators of mixing lithologies. , These ratios in river waters are inherited from their mineral sources. The silicate end-members used in this study were Ca 2+ /Na + = 0.35 ± 0.15, Mg 2+ /Na + = 0.24 ± 0.15, and HCO 3 – /Na + = 2 ± 0.5, while the carbonate end-members were Ca 2+ /Na + ratios closed to 50, Mg 2+ /Na + ratios close to 10, and HCO 3 – /Na + closed to 50 .…”

“…In general, the excess solute in river water affected human health through skin absorption, drinking water, and the food chain . At present, NO 3 – and F – have been widely used for the evaluation of non-carcinogenic health hazards. − To calculate the HQ index of NO 3 – and F – , the United States Environmental Protection Agency (USEPA) is employed, and details are as follows normalA normalD normalD normali normaln normalg normale normals normalt normali normalo normaln = normalC × normalI normalR × normalE normalF × normalE normalD / ( B W × A Y ) normalH normalQ = normalA normalD normalD / normalR normalf normalD where ADD ingestion is the ingestion intake per day; C is the NO 3 – concentration (mg/L); IR is the daily ingestion rate (0.7 and 1.5 L/d for children and adults, respectively); EF is the frequency of exposure (d/y); ED is the exposure duration (12–25 years); BW is the body weight (16 and 56 kg for children and adults, respectively); and AT is the average time (4380 and 10,950 days for children and adults, respectively). All the data mentioned above are from previous studies .…”

Biogeochemical Processes of Dissolved Nitrogen in the Backwater Zone of a Tributary in Three Gorges Reservoir, China: Implications from the Hydrologic Processes and Isotopic Tracing

“…Probably due to the mixing processes between mainstream of TGR and XBZ, most samples were more close to the river water line of TGR (TRWL, δ 2 H = 8.413 × δ 18 O + 15.782) 36 than GMWL and LMWL. The intense evaporation of river water can also enrich the heavy isotopes in river water and affected the biogeochemical processes of nutrients, 27,53,54 accompanied by a significant decrease in the d-excess value and less than the average value of the GMWL (d-excess = 10‰). 51 Although the d-excess tended to decrease with the increase of δ 18 O in the study area (Figure 4b), the d-excess values of all samples were higher than 10‰, suggesting that the river water experienced slight evaporation.…”

Heavy Metal Contamination Status of Water, Agricultural Soil, and Plant in the Semiarid Region of Kandahar, Afghanistan

“…In urban and sub-urban areas, wastewater is one of the main reasons for deteriorating water quality. , Poor-quality irrigation might indeed be the main reason why Afghan agricultural products were rejected from global markets due to the high HM concentrations. , Moreover, it has been reported that children of refugees and immigrants who have recently migrated from Afghanistan to other countries have high blood Pb levels. , It is possible that those affected individuals have been exposed via intake of HM-containing plant edible portions since this is one of the most common pathways for these metals to accumulate in the human body. , In addition, the farmers and other residents of the region are not aware of the harmful effects of HM accumulation in agricultural products originating from irrigation sources.…”

“…11 In urban and sub-urban areas, wastewater is one of the main reasons for deteriorating water quality. 16,17 Poor-quality irrigation might indeed be the main reason why Afghan agricultural products were rejected from global markets due to the high HM concentrations. 18,19 Moreover, it has been reported that children of refugees and immigrants who have recently migrated from Afghanistan to other countries have high blood Pb levels.…”