Equilibration Times of Dissolved Inorganic Carbon During pH Transitions

Equilibration times of dissolved inorganic carbon (DIC) depend on conversion reactions between CO2(aq) and the dissociation products of carbonic acid [S = (H2CO3) + (HCO3−) + (CO32−)]. Here, we develop analytical equations and a numerical model to calculate chemical equilibration times of DIC during pH transitions in buffered and unbuffered solutions. We approximate the equilibration degree of the DIC reservoir by the smaller of the CO2(aq) and S pools at the new pH, since the smaller pool is always farther from equilibrium during the chemical evolution. Both the amount of DIC converted and the rate of conversion differ between a pH increase and decrease, leading to distinct equilibration times for these general cases. Alkalinity perturbations in unbuffered solutions initially drive pH overshoots (increase or decrease) relative to the new equilibrium pH. The increased rates of DIC conversion associated with the pH overshoot yield shorter equilibration times compared to buffered solutions. Salinity has opposing effects on buffered and unbuffered solutions, decreasing and increasing equilibration times, respectively.

Black pepper (Piper nigrum) fruit-based gold nanoparticles (BP-AuNPs): Synthesis, characterization, biological activities, and catalytic applications – A green approach

As compared to conventional techniques, currently nanotechnology has gained significant attention of scientists for the development of plant-based natural nanoparticles (NPs) due to their safety, effectiveness, and environment friendly nature. The current study was aimed for development, characterization (energy-dispersive X-ray, ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, and scanning electron microscopy), and evaluation of the biological efficiency of black pepper (BP; Piper nigrum) fruit-based gold NPs (BP-AuNPs) through different in vitro and in vivo assays. BP extract revealed maximum antibacterial and antifungal potential against Escherichia coli (24 mm) and Aspergillus flavus (47 mm), respectively. However, BP-AuNPs (200 µg·mL−1) inhibited the urease, xanthine oxidase, and carbonic acid-II activities with a percent inhibition of 83.11%, 91.28%, and 86.87%, respectively. Further, the anti-inflammatory effect of BP extract at the dose of 100 mg·kg−1 was 72.66%, whereas for BP-AuNPs it was noticed to be 91.93% at the dose of 10 mg·kg−1. Similarly, the extract of BP and prepared AuNPs demonstrated significant (p < 0.01) sedative effect at all tested doses. The BP-AuNPs catalytically reduced methyl orange dye. Results suggest that BP-AuNPs possess significant biological activities, and further studies must be conducted to identify the probable mechanism of action associated with these activities.

Stabilizing the Exotic Carbonic Acid by Bisulfate Ion

Carbonic acid is an important species in a variety of fields and has long been regarded to be non-existing in isolated state, as it is thermodynamically favorable to decompose into water and carbon dioxide. In this work, we systematically studied a novel ionic complex [H2CO3·HSO4]− using density functional theory calculations, molecular dynamics simulations, and topological analysis to investigate if the exotic H2CO3 molecule could be stabilized by bisulfate ion, which is a ubiquitous ion in various environments. We found that bisulfate ion could efficiently stabilize all the three conformers of H2CO3 and reduce the energy differences of isomers with H2CO3 in three different conformations compared to the isolated H2CO3 molecule. Calculated isomerization pathways and ab initio molecular dynamics simulations suggest that all the optimized isomers of the complex have good thermal stability and could exist at finite temperatures. We also explored the hydrogen bonding properties in this interesting complex and simulated their harmonic infrared spectra to aid future infrared spectroscopic experiments. This work could be potentially important to understand the fate of carbonic acid in certain complex environments, such as in environments where both sulfuric acid (or rather bisulfate ion) and carbonic acid (or rather carbonic dioxide and water) exist.

Hydrochemical peculiarities and groundwater quality assessment of the Birimian and Tarkwaian aquifer systems in Bosome Freho District and Bekwai Municipality of the Ashanti Region, Ghana

The Birimian and Tarkwaian aquifer systems are the main sources of water supply for the Bosome Freho District and Bekwai Municipality inhabitants in the Ashanti region of Ghana. A hydrogeochemical assessment was carried out to ascertain the natural baseline chemistry of the groundwaters and the factors influencing groundwater chemistry in these two areas. A multivariate statistical tool consisting of principal component analysis (PCA) and hierarchical cluster analysis (HCA) together with hydrochemical graphical plots was applied on 64 groundwater samples. The Q–mode HCA results were used to explain the changes in groundwater chemistry along the flow paths where three spatial groundwater zones and water types were delineated. The first type consists of Ca–Mg–HCO3 freshwater (recharge zone), which transitions into Ca–Na–HCO3 or Na–Ca–HCO3 mixed waters (intermediate zone) and finally evolves to the third type of Na–Ca–Mg–HCO3–Cl water (discharge zone). The study also reveals that the natural process influencing water chemistry is groundwater–rock interaction from carbonate and silicate weathering/dissolution, aided by carbonic acid from precipitation and releases concentration of Na+, Ca2+, Mg2+, and HCO3− into the groundwaters significantly. The chloro-alkaline indices also reveal cation exchange as the principal natural factor that controls groundwater chemistry in the area. Inverse geochemical modelling shows the dissolution of primary minerals such as dolomite, plagioclase, halite, gypsum, and precipitation of calcite and chlorite along the groundwater flow path. Anthropogenic activities have little influence on groundwater chemistry. The quality of groundwater in the Bosome Freho District and Bekwai Municipality is suitable for irrigational use and drinking water consumption. The results obtained so far will contribute to research paucity in the study area and serve as a guide for decision-makers for improved water resources management.

Shallow Groundwater Quality Assessment and Its Suitability Analysis for Drinking and Irrigation Purposes

For shallow groundwater, hydrogeochemical processes and quality assessment must be addressed because shallow groundwater is freely available in many parts of the globe. Due to recent anthropogenic activities and environmental changes in Sakrand, Sindh, Pakistan, the groundwater is extremely vulnerable. To provide safe drinking and agricultural water, hydrogeochemical analysis is required. Ninety-five groundwater samples were analyzed using agricultural and drinking indices to determine the hydrogeochemical parameters using multivariate analysis such as Pearson correlations, principal component cluster analysis, as well as Piper diagrams and Gibbs plot for drinking and agricultural indices. An abundance of ions was observed through the statistical summary; however, cations and anions were recorded in the orders Na+ > Ca2+ > Mg2+ > K+ and HCO3− > Cl− > SO42− > NO3− > F−. The hydrogeochemical process used to quantify the major reactions occurring in the groundwater system showed rock dominance; the Piper diagrams evaluated the water type. A mixed pattern of calcium, magnesium, and chloride ions (Ca2+−Mg2+−Cl− type) was observed. Additionally, the ion exchange method showed an excess of bicarbonate ions due to carbonic acid weathering. The water quality index (WQI) resulted 32.6% of groundwater being unsuitable for human consumption; however, the United States Salinity Laboratory (USSL) diagram showed 60% of samples fall in the irrigable category and the Wilcox diagram depicted 5% of samples lying in the unsuitable region. Most of the water samples were suitable for drinking; only a few samples were unsafe for drinking purposes for children due to the high hazard index. High salinity meant some samples were unsuitable for irrigation.

A Method for Quantifying the Role of Carbonate Acid, Sulfuric Acid and Nitric Acid in Carbonate Weathering After Modifying the Effect of Evaporite in Qingjiang Karst Catchment

Qingjiang river is the second largest tributary of the Yangtze River in Hubei province, it’s also a typical karst catchment. Eighty-two important groundwater samples were collected during high and low water period of 2019. The results show that: (1) The major hydrochemistry types are Ca+Mg-HCO3 and Ca-HCO3, indicate that carbonate weathering is the main source of groundwater chemistry; (2) The results of inverse hydrochemical modeling show that there are two kinds of groundwater-carbonate rock interactions. One is co-dissolution of calcite and dolomite, the other is dedolomitization, and thereinto, dedolomitization is widespread in dolomite aquifers. Furthermore, gypsum has a tendency to dissolve in each aquifer, and the common ion effect of Ca2+ caused by gypsum dissolution promotes dedolomitization. The modeling results suggest that major elements have a good traceability effect on the material source of groundwater. (3) The chemical weathering of carbonate rock is mainly affected by carbonic acid, sulfuric acid and nitric acid. After modifying the impact of evaporite and atmospheric input, the calculations show that the contribution of carbonic acid involved in carbonate weathering is 70.9% (high water period) and 70.0% (low water period). Through statistics of karst springs discharge and contribution of acid involved in carbonate weathering, the two are in a positive relationship. The result can reflect the laws of sulfuric acid and nitric acid under the hydrodynamic condition in different seasons. Therefore, the carbonate weathering should be carefully evaluated in karst areas which have abundant groundwater and the role of groundwater in carbonate weathering is worthy of further study.

On programming of polyvinylidene fluoride–limestone composite for four-dimensional printing applications in heritage structures

Heritage structures are under the effect of chemical, physical and biological weathering, and out of these common effects, chemical weathering has a significant impact (as it results in nifty formation and causes fractures in heritage structures). Chemical weathering may include carbonation, oxidation, hydration, hydrolysis, and acidification. Most heritage structures are made up of limestone, which is more susceptible to carbonation. According to the reported literature, commercial practices for the maintenance and repair of these heritage structures use epoxy-based solutions, which may not be best suited as per the various regulations imposed by different government/public authorities. But so far little has been reported on the use of innovative, programmable thermoplastic composites for the maintenance and repair of such structures. This study highlights the effect of chemical treatment (as a stimulus) using a one-way programming of three-dimensional-printed thermoplastic composite-based (polyvinylidene fluoride–6% limestone) functional prototype as a solution for the maintenance and repair of heritage structures (grade III). For one-way programming, three-dimensional-printed substrate is exposed to dimethylformamide, and the changes in morphological and surface properties are noticed. After this, carbonation cycle (with carbonic acid) is performed and the changes in morphological and surface properties are compared to ascertain the stimulus effect for one-way programming (of polyvinylidene fluoride–6% limestone composite). The results of the study outline that the prepared composite may be programmed by controlling the exposure of dimethylformamide and carbonic acid (as a stimulus). Further best settings for preparing feedstock filament (for three-dimensional printing of functional prototypes in case of a selected heritage structure) are 200 °C screw temperature, 0.35 N m torque and an applied load of 8 kg in terms of better mechanical properties and shore D hardness.

Investigating the effect of carbon dioxide on the acidity of the Ocean

There is a significant effect of carbon dioxide on the acidification of the ocean. This research focuses on the acidification of the ocean and its effect on the animal life in the ocean. Also, it focuses on the effect of carbon dioxide concentration in the atmosphere on the ocean acidification. The data are collected from the research institutions and laboratories, such as National Snow and Ice Data Center (NSIDC), Japan, National Oceanic and Atmospheric Administration (NOAA), USA, Mauna Loa Observatory in Hawaii, and other sources of research about acidification of ocean. The results show that the acidity increases with increasing the amount of carbon dioxide in the atmosphere. This is because ocean absorbs nearly 50% of carbon dioxide from the atmosphere. Carbonate ions (CO32-) will be used in forming carbonic acid, which will increase the acidity of the water. Increasing the acidity of water will affect building of the animal Skeleton. It is recommended to reduce the amount of carbon dioxide in the atmosphere; therefore the acidity will be decreased in the ocean.

Investigating Increased CO2 concentration on the pH of various plant species

The concept of bioremediation is quickly becoming the norm in the resolution of environmental issues. The steady increase in carbon dioxide levels, as documented by NASA, inspired scientists to engineer plants to absorb excess carbon dioxide from the atmosphere. Here, we have explored the consequences of the uptake of excess carbon dioxide by select plants. Carbon dioxide dissolves in water to produce carbonic acid, which dissociates to yield H+ ions. We hypothesized that increased carbon dioxide absorption results in decrease in pH of plant sap. Three plants (Byophyllum pinnatum, Romaine Lettuce and Nevada Lettuce), exposed to increased carbon dioxide concentrations (15%), demonstrated a consistent increase in pH towards alkalinity compared to control plants. Based on the outcome being opposite of what we have hypothesized, our results suggest Byophyllum pinnatum, Romaine lettuce and Nevada lettuce, all have a unique homeostatic system to prevent over-absorption of carbon dioxide in a carbon dioxide-rich environment.