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Kuwait, being one of the leading oil producers in the world, is enriched with CO2 in the atmosphere, despite the frequent dust storms. Rainwater dissolves the atmospheric CO2 that acts as a carbon sink. The different sources for the contribution of CO2 in an arid region like Kuwait were determined by collecting 50 rainwater samples from November 2018 to December 2019. Total CO2, dissolved inorganic carbon (DIC) and pCO2 calculated from the analytical values of rainwater chemistry were distributed spatially to identify the specific areas enriched with CO2. Shuaiba, an industrial region, observed acidic pH (5.69) that led to the highest pCO2 (388ppmV) while Ishbiliya, the residential area, had alkaline pH with the highest DIC and total CO2 as 1147.9 µmole/L and 50.4 mg/L, respectively. The carbonate dust and major neutralizing ions were inferred to govern the DIC and the total CO2 in rainwater. Comparing the rainwater values to that of the groundwater and the seawater reflects similar pCO2 values, but the seawater has very high DIC. The biotic respiration and phytoplankton community influence pCO2 at the ocean-atmospheric interface. This phenomenon alters the transfer of CO2 to the atmospheric sink, thereby CO2 concentration in the rain showers. The statistical analysis of the rainwater chemistry data for samples from both residential and industrial regions predominantly indicated the influence of natural than anthropogenic sources. Samples of the study area and those from different parts of the world were represented in a bivariate plot using Total CO2 and (HCO3−/Ca2+ + Mg2+) variables. It was inferred from the graph that the samples of GCC region fall in a definite range. [ABSTRACT FROM AUTHOR]

Research on the ionic chemistry of rivers and weathering types provides the basis for elucidating the dynamics of river chemistry and exploring carbon cycling in river systems. There is a lack of water chemistry study in the river systems in the Tibet Plateau, especially in the streams/rivers flowing from and through glaciers and permafrost. Samples in the rivers flowing through different land covers (lakes, glaciers, permafrost, grasslands, peatlands) were collected in different months (April, June, August and October) in 2016, covering various hydrological regimes. The temporal and spatial dynamic variations of major ions and the underlying causes were explored. The results revealed that in the headwater region Ca2+ and HCO3− were the dominant ions, derived primarily from the dissolution of carbonatites and evaporates. However, the concentrations of ions from different land covers were vastly different.The high concentrations of Na+ and K+ in the lakes sample were mainly affected by evaporation and precipitation. The acid deposition caused by atmospheric pollutants resulted in high concentration of SO42− in glacial and permafrost streams. K+ concentration was high in the grassland region with frequent agricultural activities such as the planting and fertilization of highland barleys that applied nitrogen and potassium fertilizers. Although Total Dissolved Load (TDS) was higher for the lakes and streams/rivers from glaciers and permafrost, and its average (287.28 ± 40 mg/L) over the headwater region was lower than that in the middle and lower reaches of the Yellow River because of low temperature. The current study provided the basis of and reference for the overall water chemistry characteristics and carbon cycling processes of the entire Yellow River. [ABSTRACT FROM AUTHOR]

One of the most important questions in the science of global carbon cycle is how to balance the atmospheric CO2 budget. However, there is a large terrestrial carbon sink is missing. The locations, magnitudes, variations, and mechanisms responsible for this terrestrial missing carbon sink are uncertain and the focus of much continuing debate. In order to provide a basis for the assessment of carbonate weathering-related carbon sink, this study investigated the spatial and temporal variations of dissolved inorganic carbon (DIC) and particulate organic carbon (POC), and used stable carbon isotopes and hydrochemical data to quantitatively estimate the proportion of DIC transformation to POC and analyze the potential influence of the transformation of DIC into OC on the carbon isotope composition in the Lijiang River (typical karst surface water), Southwest China. The results showed that DIC concentrations are high in winter and low in summer and increase from upstream to downstream. POC concentrations are high in summer and low in spring. δ13CPOC and δ13CDIC are negatively correlated in the Lijiang River. The δ13CDIC values are high in spring and low in summer, compared with the estimated δ13CDIC(cal.); the observed δ13CDIC values have a maximum positive shift in spring and similar in the summer; the δ13CPOC values decrease from upstream to downstream, and are high in summer and low in spring. These observations indicate that the isotopic compositions of both DIC and POC are significantly affected by aquatic photosynthesis that transforms DIC into OC. In-river primary production contribute 12–54% of POC, and the contributions of carbonate rock-sourced DIC to the riverine POC range from 7 to 30%, which suggests an important sink of atmospheric CO2 in river systems and should be taken into account in global carbon cycle. [ABSTRACT FROM AUTHOR]

Wetlands contain a large proportion of the world’s carbon, of which dissolved inorganic carbon (DIC) is one of the important fractions in wetland carbon cycle. We collected groundwater, river water, and wetland water from the Caohai catchment to investigate the isotope composition of DIC and inorganic carbon cycling. The main sources of groundwater DIC were carbonate dissolution and soil CO2. Groundwater was the main source of riverine DIC, but the δ13CDIC value in river water showed a more positive excursion than groundwater because of phytoplankton photosynthesis and CO2 evasion. Seasonal variations in DIC concentrations and the δ13CDIC indicate the influence of local rainfall events in the high-flow season and the longer residence time of water in the low-flow season. There was marked seasonal variation in the pCO2 and δ13CDIC in wetland water. During the high-flow season, the pCO2 in the emergent plant zone was higher than that of the atmosphere because of respiration of roots and sediments. Because of photosynthesis, the pCO2 in the submerged plant zone was lower than that of the atmosphere. Furthermore, in this zone, the δ13CDIC ranged from −15.13 to −6.68 ‰ (mean value of −10.79 ‰), and may have been influenced by chemically enhanced fractionation and photosynthesis. In the low-flow season, the pCO2 was mostly higher than atmospheric pCO2 because of organic matter decomposition in sediments. Additionally, during this season, the δ13CDIC ranged from −6.23 to −0.06 ‰ (mean value of −2.52 ‰), and may have been influenced by CO2 evasion, CO2 reduction to methane, and phytoplankton photosynthesis. [ABSTRACT FROM AUTHOR]

To elucidate the type and extent of anthropogenic DIC (dissolved inorganic carbon), carbon isotopic composition of DIC and dissolved ion concentration were determined in three streams (Gap, Yudeung and Daejeon) draining populated Daejeon metropolitan area, South Korea. Seasonal variations in water chemistry and carbon isotopic composition of DIC (δC) reflected changing contribution from two main DIC sources, i.e., soil weathering and sewages. DIC input from the soil weathering was characterized by δC values ranging from −16.7 to −16.0 ‰ and higher during Jun-Nov. The sewage-derived DIC became dominant during Dec-May with δC values ranging from −11.4 to −7.4 ‰. Si and Cl served as indicators of DIC inputs from soil weathering and sewages, respectively. The higher δC values of sewages in the study area indicated that detergents (δC of −12.0 to −6.5 ‰) carried by the urban sewages were the main anthropogenic DIC component. The extent of anthropogenic DIC relative to soil-derived DIC in stream waters increased when the precipitation was low and discharge decreased. The results of this study provide a method to quantify anthropogenic DIC, which can help manage water quality in urban stream waters. [ABSTRACT FROM AUTHOR]

Ureolysis mediated increase of culture medium pH, dissolved inorganic carbon (DIC) by Bacillus pasteurii and subsequent utilization of the cell-free broth on calcification mediated carbon (CO) capture was investigated. In an ureolytic process with an initial biomass of 80 mg/l, about 55 % of the original urea (100 mM) in the nutrient broth-NaCl medium was hydrolyzed over 24 h; this increased DIC to 1,145 mg/l and pH to 9.1. The gas phase CO capture experiment, which used the culture medium supernatant in a closed system (liquid phase to headspace volume ratio of 1:3) containing 28.45 % v/v headspace CO (g), was triggered by injecting 50 mM CaCl. The calcification process decreased both the headspace CO and the liquid phase DIC to 18.48 % v/v and 942 mg/l, respectively, through precipitation of total 27.41 mM CaCO. Although only 21.8 % of the DIC input from ureolysis was actually captured as solid carbonate, solubility trapping (as soluble carbonate in DIC) effectively regulated CO release into the atmosphere. [ABSTRACT FROM AUTHOR]

The Wujiang River is an important tributary to the Changjiang River that has been intensively impounded for hydropower exploitation. To understand the potential impact of reservoir construction on the riverine inorganic carbon transport, seasonal longitudinal sampling was conducted in four reservoirs Hongjiadu (HJD), Dongfeng (DF), Suofengying (SFY) and Wujiangdu (WJD) along the Wujiang River from April 2006 to January 2007. Results indicated that damming the river induced an obvious discontinuity of water chemistry in the warmer seasons. δC of dissolved inorganic carbon (DIC) ranged from −3 to −11.4 ‰, likely as the results of photosynthesis, respiration and carbonate weathering. During periods of thermal stratification, the addition of CO from respiration to hypolimnion and the deep water release for hydropower generation led to higher pCO downstream, as well as C depletion in DIC and undersaturated to calcite. An estimate of DIC budget indicated that only DF reservoir was the sink for DIC while reservoirs HJD, SFY and WJD were the sources for DIC. However, when the retained water was taken into account, for the reason of water storage occurring mainly in HJD and DF, all reservoirs became the sources for DIC with exporting rates of 26.68, 7.97, 6.22 and 11.80 % for HJD, DF, SFY and WJD, respectively. [ABSTRACT FROM AUTHOR]

Baseline monitoring at the proposed enhanced gas recovery site in Altmark (Germany) was carried out in combination with theoretical and laboratory investigations to describe and predict the principles of expected stable carbon isotope and dissolved inorganic carbon (DIC) trends during CO injection in reservoirs. This provides fundamental data for site-specific characterisation for monitoring purposes. Baseline δC values at the Altmark site ranged between −1.8 and −11.5 ‰ and DIC values were about 2 mmol L. These baseline values form the basis for a theoretical study on the influences of the ambient reservoir conditions on the state of geochemical and isotope equilibrium of the reservoir fluids. Transferring this theoretical study to the Altmark site enables predictions on geochemical trends during potential injection. Assuming that CO would be injected at the Altmark site to pCO = 100 bar and with a δC of −30 ‰, at isotopic and geochemical equilibrium, δC values would approach this end-member, and DIC concentrations of 1,000 mmol L would be expected. Laboratory experiments were conducted at low pCO levels (4-35 bars) to mimic the approach of a CO plume at a monitoring well. These results support field investigations from other sites: that δC is a sensitive tool for monitoring CO migration in the subsurface and simultaneously allows quantification of geochemical trapping of CO. [ABSTRACT FROM AUTHOR]

The forest ecosystem in the Maolan karst forest, southwest China is the only concentrated, intact, and relatively stable karst forest ecosystem which has survived in the area at the same latitude in the world, and is a valuable karst forest plant resource as well. Groundwater samples from Maolan karst forest were collected from wells and springs during summer; and concentrations of major ions and dissolved inorganic carbon (DIC) isotopic compositions were measured. The pH values range from 7.2 to 8.3 results from the dissolution of carbonate, HCO3 − is the dominant species of DIC in groundwater. Calcium and HCO3 −, followed by Mg2+ and SO4 2− dominate the chemical composition of major ions in the groundwaters. Groundwater samples have δ13C values in the range from −8.1‰ to −16.6‰, which are lower than that of the other karst city groundwaters in the southwest China. Combining δ13CDIC ratios with measurements of HCO3 − and pH clearly distinguishes the principal processes underlying the geochemical evolution of groundwater in Carboniferous carbonate aquifers, where processes can be both degradation of organic matters in the soil and the carbonate dissolution. [ABSTRACT FROM AUTHOR]