Alkalinity Research Articles

Comparison of Thermophilic-Mesophilic and Mesophilic-Thermophilic Two-Phase High-Solid Sludge Anaerobic Digestion at Different Inoculation Proportions: Digestion Performance and Microbial Diversity.

This study investigated the performance of thermophilic-mesophilic (T-M) and mesophilic-thermophilic (M-T) two-phase sludge anaerobic digestion at different inoculation proportions after a change in digestion temperature. After temperature change, the pH, total ammonia nitrogen (TAN), free ammonia nitrogen (FAN), solubility chemical oxygen demand (SCOD), and total alkalinity (TA) levels of two-phase digesters were between thermophilic control digesters and mesophilic control digesters. However, the volatile fatty acid (VFA) levels of two-phase digesters were higher than those of thermophilic or mesophilic control digesters. The bacteria communities of M-T two-phase digesters were more diverse than those of T-M. After a change in digestion temperature, the bacterial community was dominated by Coprothermobacter. After a change of digestion temperature, the relative abundance (RA) of Methanobacterium, Methanosaeta, and Methanospirillum of M-T two-phase digesters was higher than that of T-M two-phase digesters. In comparison, the RA of Methanosarcina of T-M two-phase digesters was higher than that of M-T two-phase digesters. The ultimate methane yields of thermophilic control digesters were greater than those of mesophilic control digesters. Nevertheless, the ultimate methane yield levels of M-T two-phase digesters were greater than those of T-M two-phase digesters. The ultimate methane yields of all two-phase digesters presented an earlier increase and later decrease trend with the increasing inoculation proportion. Optimal methane production condition was achieved when 15% of sludge (T-M15) was inoculated under mesophilic-thermophilic conditions, which promoted 123.6% (based on mesophilic control) or 27.4% (based on thermophilic control). An optimal inoculation proportion (about 15%) balanced the number and activity of methanogens of high-solid sludge anaerobic digestion.

Mechanisms and drivers controlling spatio-temporal evolution of pCO2 and air-sea CO2 fluxes in the southern Java coastal upwelling system

Upwelling systems are known for their complex dynamic processes spanning a wide variety of spatio-temporal scales, due to strong coupling between the ocean and atmosphere. One such upwelling system is found at the eastern boundary of the Indian Ocean along the southern coast of Java during the southeast monsoon (SM). This study examines the mechanisms and drivers involved in the spatial and temporal evolutions of surface pCO2 in this upwelling system over seasonal to inter-annual timescales using a coupled, high-resolution regional model. A decomposition analysis was used to quantify the changes in pCO2 in response to changes in surface-temperature (T), surface-salinity (S), dissolved inorganic carbon (DIC), and total alkalinity (ALK). The upwelling of deeper, cooler waters decreases the surface pCO2 by 50 ± 1.48 μatm from June to September. However, the presence of DIC-rich waters at significantly shallower depths increases the surface pCO2 by 27 ± 0.9 μatm. The surface pCO2 increases by 5 ± 0.50 μatm due to changes in salinity, which exerts less control than T-driven changes. Biological changes increase the surface pCO2 by 17.54 ± 2.74 μatm. The maximum seasonal amplitudes of the variations in pCO2 caused by seawater solubility and biology are in counterbalance during the SM. Therefore, the upwelling-driven combined effect of physical mechanisms dominates the effect of biological mechanisms in reducing surface pCO2 under these conditions. During the SM, the southern coast of Java acts as a seasonal CO2 sink (−1.36 ± 6.48 g C m−2 year−1), although consideration of the mean flux over 2006–2017 shows that the region acts as a source of CO2 (1.31 ± 5.03 g C m−2 year−1). Furthermore, following a negative Indian Ocean Dipole (IOD) year, a strong sink of atmospheric CO2 is observed during the SM.

The effect of total alkalinity on growth performance and calcification in juvenile Pacific abalone Haliotis discus hannai

A 45-day trial was conducted to study the effect of seawater total alkalinity (TA) level up- and downregulation on the growth performance and calcification of Haliotis discus hannai Ino, while seawater pH was maintained at pHNBS = 8.1. Although seawater was not acidified, the results showed that TA downregulation caused a significant reduction (P < 0.05) in the somatic tissue growth of juvenile abalone, while TA upregulation significantly increased growth performance (P < 0.05). Similar to the impacts of pH reduction, TA downregulation also induces a decline in CO2 buffering capacity, which may be the reason why somatic tissue growth was reduced, as lowered CO2 buffering capacity was reported to shift the acid-base balancing of abalone. Parts of the periostracum layer weremissing and exposed the inner shell layers of the individuals from the TA-downregulated group. Scanning electron microscopy (SEM) results showed calcium carbonate densely deposited onto the inner shell in the control and TA-upregulated groups, while sparsely deposited calcium carbonate was observed in the TA-downregulated group. The C: N ratio in the shell of individuals from the TA-downregulated group was significantly lower than that of the other two groups, indicating that less inorganic carbon was added to the shell. As a result, abalone grew lighter and thinner shells in TA-downregulated seawater. Although seawater was not acidified, TA downregulation also caused a reduction in the calcium carbonate saturation state (Ω), which induced the erosion of the surface shell and the interruption of calcium carbonate generation. In conclusion, although seawater pH remained at ambient levels, the lowered CO2 buffering capacity and Ω induced by seawater TA downregulation also showed a detrimental effect on the growth and calcification of Pacific abalone. The impact of ocean acidification on the growth of abalone should not be assessed using only seawater pH and/or pCO2 but rather taking into account all of carbonate chemistry, particularly the CO2 buffering capacity. Abalone cultivation is suggested to be carried out in seawater with a higher level of CO2 buffering capacity and Ω, which can be achieved through integrated culture with seaweed or increasing the seawater TA level.

Growth performance of Thai Pangus (Pangasianodon hypophthalmus) using different synthetic amino acids in plant protein based formulated diets

An experiment was carried out for a period of 120 days to evaluate three formulated diets among of which T1 was formulated based on animal protein, T2 was partially replaced animal protein with plant protein and adding amino acid whereas the T3 was formulated with fully plant protein with adding amino acid to assess the growth performance of Thai Pangus, Pangasionodon hypophthalmus. Each treatment had three replicates using 9 (nine) mini experimental ponds. The stocking density was 120 fish/decimal. Initially, the fish were fed twice daily at a rate of 5% of their body weight, which was progressively reduced to 2% by the end of the experiment. During the experimental period, the water quality parameters observed (temperature 26.0°C-31.5°C, pH 7.50-8.44, DO 4.30-5.94 mgL-1, ammonia-nitrogen 0.01 to 0.03 mgL-1, and total alkalinity 155-185 mgL-1) were found to be optimal and stable. The mean weight gains (WG) of Thai Pangus were 421.6±4.71 g, 407.34±1.97 g and 345.89±4.44 g for T1, T2 and T3, respectively and significantly (p&lt;0.05) highest WG was obtained in T1 and T2 followed by T3. The specific growth rate (SGR) was found highest in T2 (2.70±0.03) followed by T1 (2.53±0.06) and T3 (2.16±0.04), respectively. The highest feed conversion ratio (FCR) was found in T1 (1.62) whereas lowest FCR obtained from T2 (1.52±0.01) followed by T3 (1.55). The protein efficiency ratio (PER) values were ranged between 2.03 and 2.13 and highest was found in T2 (2.13±0.05). The highest production was attained from T1 (13557.50±51.60 kg ha-1) followed by T2 (13227.71±50.72 kg ha-1) and T3 (11450.60±49.87 kg ha-1), respectively. The findings of this study revealed that, the partial replacement of animal protein with plant protein adding limited amino acid (lysine and methionine) exhibited the best performance on the basis of nutritive value and growth performance.

Spatiotemporal variability in pH and carbonate parameters on the Canadian Atlantic continental shelf between 2014 and 2022

Abstract. The Atlantic Zone Monitoring Program (AZMP) was established by Fisheries and Oceans Canada (DFO) in 1998 with the aim of monitoring physical and biological ocean conditions in Atlantic Canada in support of fisheries management. Since 2014, at least two of the carbonate parameters (pH; total alkalinity, TA; and dissolved inorganic carbon, DIC) have also been systematically measured as part of the AZMP, enabling the calculation of derived parameters (e.g., carbonate saturation states, Ω, and partial pressure of CO2, pCO2). The present study gives an overview of the spatiotemporal variability in these parameters between 2014 and 2022. Results show that the variability in the carbonate system reflects changes in both physical (e.g., temperature and salinity) and biological (e.g., plankton photosynthesis and respiration) parameters. For example, most of the region undergoes a seasonal warming and freshening. While the former will tend to increase Ω, the latter will decrease both TA and Ω. Spring and summer plankton blooms decrease DIC near the surface and then remineralize and increase DIC at depth in the fall. The lowest pCO2 values (down to ∼ 200 µatm) are located in the cold coastal Labrador Current, whereas the highest values (&gt;1500 µatm) are found in the fresh waters of the Gulf of St. Lawrence and the St. Lawrence Estuary. The latter is also host to the lowest pH values of the zone (7.48 in the fall of 2022). Finally, most of the bottom waters of the Gulf of St. Lawrence (&gt;90 %) are undersaturated with respect to aragonite (Ωarg&lt;1). In addition to providing a baseline of carbonate parameters for the Atlantic Zone as a whole, this comprehensive overview is a necessary and useful contribution for the modelling community and for more in-depth studies. The full dataset of measured and derived parameters is available from the Federated Research Data Repository: https://doi.org/10.20383/102.0673 (Cyr et al., 2022a).

Carbon dioxide uptake in a eutrophic stratified reservoir: Freshwater carbon sequestration potential

Carbon capture and storage due to photosynthesis activities has been proposed as a carbon sink to mitigate climate change. To enhance such mitigation, previous studies have shown that freshwater lakes should be included in the carbon sink, since they may capture as much carbon as coastal areas. In eutrophic freshwater lakes, there is uncertainty about whether the equilibrium equation can estimate the partial pressure of carbon dioxide (pCO2), owing to the presence of photosynthesis due to phytoplankton, and pH measurement error in freshwater fluid. Thus, this study investigated the applicability of the equilibrium equation and revealed the need to modify it. The modified equilibrium equation was successfully applied to reproduce pCO2 based on total alkalinity and pH through field observations. In addition, pCO2 at the water surface was lower than the atmospheric partial pressure of carbon dioxide due to photosynthesis by phytoplankton during strong stratification. The stratification effect on low pCO2 was verified by using the Net Ecosystem Production (NEP) model, and a submerged freshwater plants such as Potamogeton malaianus were found to have high potential for dissolved inorganic carbon (DIC) sequestration in a freshwater lake. These results should provide a starting point toward more sophisticated methods to investigate the effect of freshwater carbon on DIC uptake in freshwater stratified eutrophic lakes.

Coupling between chromophoric dissolved organic matter and dissolved inorganic carbon in Indian estuaries

This study investigates the coupling between Chromophoric Dissolved Organic Matter (CDOM) and Dissolved Inorganic Carbon (DIC) in eighteen Indian estuaries across salinity gradient of the east and west coasts during the monsoon season, characterized by significant river discharge. The hypothesis that humic acids (HA) and fulvic acids (FA), prominent in estuarine CDOM, closely correspond to the ‘organic alkalinity’ (Aorg) component of total alkalinity is examined. In most estuaries, specifically those along the northeast coast (NE) and southwest coast (SW), a significant linear relationship exists between DIC, CDOM abundance, and pH level. Notably, minor estuaries along the southeast coast (SE) and northwest coast (NW) exhibit elevated DIC levels beyond what this relationship predicts. These estuaries also reveal heightened ammonium levels, increased δ15N values, and decreased δ13C values, indicative of anthropogenic influence. CDOM properties, such as spectral slope (S300–500) and spectral slope ratio (SR, S275–295:S350–400), align with these findings, with SE and NW estuaries displaying higher values. On average, CDOM contributes 110.5 μM (6.8 %) to DIC in NE, 390.7 μM (11 %) in SE, 24.4 μM (4.8 %) in SW, and 122.2 μM (4 %) in NW estuaries. The relationship between total alkalinity minus DIC (TA-DIC) and pH25 suggests that CDOM, mediated by HA/FA, buffers the inorganic carbon system in estuaries. This buffering capacity weakens at elevated DIC levels, and this condition is marked by anomalous SR values compared to the baseline salinity-SR linear regression. This Study suggests that estuarine CDOM could largely represent “organic alkalinity” and could help monitor acidification in estuaries.

Halophyte Elymus dahuricus colonization regulates microbial community succession by mediating saline-alkaline and biogenic organic matter in bauxite residue

Alkalinity regulation and nutrient accumulation are critical factors in the construction of plant and microbial communities and soil formation in bauxite residue, and are extremely important for sustainable vegetation restoration in bauxite residue disposal areas. However, the establishment and succession of microbial communities driven by plant colonization-mediated improvements in the physicochemical properties of bauxite residues remain poorly understood. Thus, in this study, we determined the saline-alkali properties and dissolved organic matter (DOM) components under plant growth conditions and explored the microbial community diversity and structure using Illumina high-throughput sequencing. The planting of Elymus dahuricus (E. dahuricus) in the bauxite residue resulted in a significant decrease in total alkalinity (TA), exchangeable Na, and electrical conductivity (EC) as well as the release of more tryptophan-like protein compounds and low-molecular-weight humic substances associated with biological activities into the bauxite residue substrate. Taxonomical analysis revealed an initial-stage bacterial and fungal community dominated by alkaline-tolerant Actinobacteriota, Firmicutes, and Ascomycota, and an increase in the relative abundances of the phyla Bacteroidota, Cyanobacteria, Chloroflexi, and Gemmatimonadota. The biological activities of phylum Actinobacteriota, Bacteroidota, and Gemmatimonadota were significantly associated with protein-like and UVA-like humic substances. As eutrophic bacteria, Proteobacteria participate in the transformation of humic substances and can not only utilize small molecules of organic matter and convert them into humic substances but also promote the gradual conversion of humic acids into simple molecular compounds. Our results suggest that plant roots secrete organic matter and microbial metabolites as the main biogenic organic matter that participates in the establishment and succession of the microbial community in bauxite residues. Root length affects bacterial and fungal diversity by mediating the production of protein-like substances.

Assessment of water quality of the Bhima River for drinking purpose by water quality index

The objective of this study is to determine various water characteristics of the Bhima River and its suitability for drinking, followed by a water quality index evaluation. For continuous monitoring, samples were taken at eight locations between October 2020 and September 2021. The physicochemical parameters, such as pH, electrical conductivity (EC), total dissolved solids (TDS), dissolved oxygen (DO), total alkalinity (TA), total hardness (TH), chloride (Cl-), sulphate (SO42-), phosphate (PO43-), and nitrate (NO3-) were measured. The measured values of these parameters were compared with Indian standards. Due to anthropogenic activities, values of parameters EC, TH, and TA at all the stations exceeded their BIS limits (The Bureau of Indian Standards). It was found that the river's total water quality index ranged from 45.23 to 75.43, indicating that the water quality varies from good to very poor. Correlation reveals that EC and TDS show remarkable similarities and a strong correlation was existed between total hardness and total alkalinity indicating anthropogenic activities. Therefore, it is important to assess physiochemical concentration of the river water before using it for drinking.

Microbial assessment of foaming dynamics in full-scale WWTP anaerobic digesters

Research on foaming processes in wastewater treatment plants (WWTPs) anaerobic digesters is increasing since it is a common phenomenon that can seriously affect digesters performance and treatment cost. This paper presents data from a full-scale experience of foam monitoring and antifoam reagents dosing as well as microbial community structure. The association of foaming episodes with microbial population structure and operational parameters has improved understanding of foaming episodes and their causes. During this long-term study (273 days), two foaming episodes occurred in the anaerobic digesters under study. Microbial community analysis showed that the first foaming episode is correlated with the proliferation of ST-12K33 (midas_s_22), which could be related to variations in the hydraulic retention time, a decrease in inflow solids concentration, and a decrease in digesters total alkalinity. The second foaming episode coincide with a clear migration of Ca. Microthrix parvicella from the activated sludge (bulking episodes) to the anaerobic digesters and its capacity to metabolize substrate under anaerobic conditions. Laboratory experiments showed that an increase in anaerobic digestion temperature and sludge pre-treatments have a positive impact on foam biodegradability and, therefore, they could be used as foam mitigation strategies. Finally, a techno-economic analysis showed that foaming episodes had an over cost of about 250 € d−1 and dropped the WWTP energy self-sufficiency from 67 to 63 %.

The benthic-pelagic coupling affects the surface water carbonate system above groundwater-charged coastal sediments

Submarine groundwater discharge (SGD) can be a significant source of dissolved nutrients, inorganic and organic carbon, and trace metals in the ocean and therefore can be a driver for the benthic-pelagic coupling. However, the influence of hypoxic or anoxic SGD on the carbonate system of coastal seawater is still poorly understood. In the present study, the production of dissolved inorganic carbon (DIC) and alkalinity (AT) in coastal sediments has been investigated under the impact of oxygen-deficient SGD and was estimated based on the offset between the measured data and the conservative mixing of the end members. Production of ATand DIC was primarily caused by denitrification and sulphate reduction. The ATand DIC concentrations in SGD decreased by approximately 32% and 37% mainly due to mixing with seawater counterbalanced by reoxidation and CO2release into the atmosphere. Total SGD-ATand SGD-DIC fluxes ranged from 0.1 to 0.2mol m-2d-1and from 0.2 to 0.3mol m-2d-1, respectively. These fluxes are probably the reason why the seawater in the Bay of Puck is enriched in ATand DIC compared to the open waters of the Baltic Sea. Additionally, SGD had low pH and was undersaturated with respect to the forms of the aragonite and calcite minerals of CaCO3. The seawater of the Bay of Puck also turned out to be undersaturated in summer (Inner Bay) and fall (Outer Bay). We hypoth​e​size that SGD can potentially contribute to ocean acidification and affect the functioning of the calcifying invertebrates.

Fungi increases kelp (Ecklonia radiata) remineralisation and dissolved organic carbon, alkalinity, and dimethylsulfoniopropionate (DMSP) production

Fungi are key players in terrestrial organic matter (OM) degradation, but little is known about their role in marine environments. Here we compared the degradation of kelp (Ecklonia radiata) in mesocosms with and without fungicides over 45 days. The aim was to improve our understanding of the vital role of fungal OM degradation and remineralisation and its relevance to marine biogeochemical cycles (e.g., carbon, nitrogen, sulfur, or volatile sulfur). In the presence of fungi, 68 % of the kelp detritus degraded over 45 days, resulting in the production of 0.6 mol of dissolved organic carbon (DOC), 0.16 mol of dissolved inorganic carbon (DIC), 0.23 mol of total alkalinity (TA), and 0.076 mol of CO2, which was subsequently emitted to the atmosphere. Conversely, when fungi were inhibited, the bacterial community diversity was reduced, and only 25 % of the kelp detritus degraded over 45 days. The application of fungicides resulted in the generation of an excess amount of 1.5 mol of DOC, but we observed only 0.02 mol of DIC, and 0.04 mol of TA per one mole of kelp detritus, accompanied by a CO2 emission of 0.081 mol. In contrast, without fungi, remineralisation of kelp detritus to DIC, TA, dimethyl sulfide (DMS), dimethylsulfoniopropionate (DMSP) and methanethiol (MeSH) was significantly reduced. Fungal kelp remineralisation led to a remarkable 100,000 % increase in DMSP production. The observed substantial changes in sediment chemistry when fungi are inhibited highlight the important biogeochemical role of fungal remineralisation, which likely plays a crucial role in defining coastal biogeochemical cycling, blue carbon sequestration, and thus climate regulation.

Carbonate Chemistry and the Potential for Acidification in Georgia Coastal Marshes and the South Atlantic Bight, USA

In coastal regions and marginal bodies of water, the increase in partial pressure of carbon dioxide (pCO2) in many instances is greater than that of the open ocean due to terrestrial (river, estuarine, and wetland) influences, decreasing buffering capacity and/or increasing water temperatures. Coastal oceans receive freshwater from rivers and groundwater as well as terrestrial-derived organic matter, both of which have a direct influence on coastal carbonate chemistry. The objective of this research is to determine if coastal marshes in Georgia, USA, may be “hot-spots” for acidification due to enhanced inorganic carbon sources and if there is terrestrial influence on offshore acidification in the South Atlantic Bight (SAB). The results of this study show that dissolved inorganic carbon (DIC) and total alkalinity (TA) are elevated in the marshes compared to predictions from conservative mixing of the freshwater and oceanic end-members, with accompanying pH around 7.2 to 7.6 within the marshes and aragonite saturation states (ΩAr) <1. In the marshes, there is a strong relationship between the terrestrial/estuarine-derived organic and inorganic carbon and acidification. Comparisons of pH, TA, and DIC to terrestrial organic material markers, however, show that there is little influence of terrestrial-derived organic matter on shelf acidification during this period in 2014. In addition, ΩAr increases rapidly offshore, especially in drier months (July). River stream flow during 2014 was anomalously low compared to climatological means; therefore, offshore influences from terrestrial carbon could also be decreased. The SAB shelf may not be strongly influenced by terrestrial inputs to acidification during drier than normal periods; conversely, shelf waters that are well-buffered against acidification may not play a significant role in mitigating acidification within the Georgia marshes.

Submarine Groundwater Discharge Strengthens Acidification in the Coastal Semi‐Closed Bays

AbstractCoastal ocean acidification is a worldwide problem associated with anthropogenic activity and climate change. In this study, a close relationship between submarine groundwater discharge (SGD) and coastal ocean acidification in Hong Kong's coastal waters is discovered. We for the first time evaluated the direct influence of SGD on seawater pH decline. Results show that SGD can contribute to up to 48% of seawater pH variation among terrestrial water input, air‐sea CO2 exchange, photosynthesis/respiration, and bay‐open water exchange in semi‐closed bays through direct input of carbonate species. Local air‐sea CO2 exchange has negligible influences on the seawater pH. In the semi‐closed bay areas, SGD and aerobic respiration are major contributors to seawater pH variation but in areas with open space, the exchange process with open waters is more important. In addition to the direct input of carbonate species (total alkalinity and dissolved inorganic carbon), SGD also influences the seawater pH via considerable nutrient loadings. The findings highlight the importance of the investigation and management of groundwater to alleviate the fast coastal ocean acidification.

Declines in the Mekong’s Megadiverse Larval Fish Assemblages: Implications for Sustainable Development

Migratory fishes of the Mekong Basin are facing challenges from human-induced stressors. Quantifying the patterns of fish’s early life stages provides important information on spawning seasons, spawning and nursery habitats, reproductive strategies, migration and dispersal patterns, and stock status. However, the ecology of the Mekong larval fishes, including patterns and drivers of larval fish dispersal, is not well understood. Here, we investigate the temporal variability of drifting larval and juvenile fish assemblages in the Cambodian Mekong River and identify their environmental drivers using long-term (10 year) daily fish larval/juvenile data collections. We found that, in the Mekong main channel, the larval and juvenile assemblages were dominated by longitudinal migrants from the families Cyprinidae and Pangasiidae. Peak abundance and richness were found to occur in July and August, respectively. We detected a significant decline in larval and juvenile abundance and richness over the study period. Cross-wavelet analysis revealed that water levels always lead larval abundance, but lag richness. In addition, cross-correlation analysis observed that peak abundance and richness occurred eight weeks and one week, respectively, before the peak water level. We also discovered that species abundance and richness had a strongly positive relationship with maximum water levels. Variation in fish larval and juvenile abundance and richness was also related to total phosphorus, nitrate, alkalinity, and conductivity. Maximum water levels and the key water quality parameters (e.g., phosphorus, nitrate, alkalinity, and conductivity) significantly influence larval and juvenile fish abundance and richness patterns. Therefore, safeguarding natural seasonal flows, especially maximum flows associated with the peak flood pulse, as well as maintaining good water quality, are key to the reproductive success of many migratory fishes and effective dispersal of offspring to the lower floodplain for nursing, rearing, and growth. Clean and unregulated rivers support productive and diverse fisheries.

The impact of ICE‐6G ice sheet topography in the oceanic carbonate system

AbstractDuring the Last Glacial Maximum (approximately 21 ka BP) the presence of large ice sheets over the Northern Hemisphere (NH) caused significant changes in the ocean–atmosphere interaction. Remarkable changes are noticed in NH both topography and atmospheric CO2 levels. This paper investigates the impact of the most recent paleotopography (ICE6G) in the Earth's climate and the oceanic carbonate system, based on a series of experiments conducted with the oceanic‐atmosphere‐vegetation‐ice‐carbon model, UVic ESCM. Results indicate enhanced cooling in northern North America in the ICE6G compared to the ICE4G simulation due to the lapse rate effect. The decrease of −24°C in the surface temperature in the ICE6G relative to the present day (PD) led to a modification of the atmospheric circulation in the Atlantic and North Pacific regions. Positive and negative anomalies vary widely for the E–P (evaporation–precipitation) flux pattern, but colder and drier atmosphere leads to a reduction in precipitation in the ICE6G experiment. Changes in wind stress between ICE6G and PD induce low temperatures in the Northern Hemisphere. These features are related changes of Ekman's transport and evaporative cooling resulting in positive anomalies of SST. Thus, changes in sea surface temperature and salinity (SST, SSS), and E–P flux led to modifications in the oceanic carbonate system, resulting in an overall increase of total alkalinity and a reduction in the concentrations of total carbon dioxide (TCO2) in the ICE6G with respect to the PD values. This is a consequence of the low concentration of glacial CO2 and increment in concentrations. The total alkalinity (TA) and TCO2 do not show a similar response to the SST and SSS, in the sense that larger departures from the PD are found in the Pacific equatorial region, which are affected by changes in water dilution as a result of precipitation and evaporation processes.

Evaluation of Koga irrigation water in Mecha district, Amhara Region, as an example of irrigation water quality in Northwestern Ethiopia

Irrigation water quality impacts plant growth, crop production, and public health. Thus, understanding the trends in irrigation water quality is important to manage public health, and optimize crop production. The Koga region in Ethiopia is a developing area where crops are an important food source for a growing population, and irrigation is critical to supply additional food crops and secure food insecurity issues. This study measures physiochemical and biological parameters to assess the suitability of Koga irrigation water for crops intended for human consumption. In March 2022, irrigation water samples were collected and analyzed for physicochemical and biological qualities. Kelley’s ratio, magnesium danger, and sodium absorption ratio were calculated from the data obtained. Results showed that the turbidity (174.33–259.00 NTU), total suspended solids (80.33–175.00 mg/L), total alkalinity (143.33–195.33 mg/L), total hardness (150.67–224.6 mg/L), SO42−(43.96–73.00 mg/L), PO43−(56.27–87.43 mg/L), and BOD5 (63.23–95.40 mg/L) levels surpassed the recommended limit of FAO(35 NTU,50 mg/L,100 mg/L,100–150 mg/L,20 mg/L,3 mg/L and 30 mg/L, respectively). BOD5 levels of the tested water samples exceeded the permissible limit set by the EU (10 mg/L). The coliform and fecal coliform levels in all sampled waters were higher than the zero/100 mL limits of the EU and WHO set for irrigation water. The studied water samples were found to be unsuitable for the cultivation of crops and vegetables since TA, PO4−3, and NO3− levels exceeded the tolerance limit of the crops and vegetables cultivated in the site, while the coliform and BOD5 levels surpassed their tolerable limits. Consequently, it is not recommended to eat crops and vegetables without first properly preparing them. The results showed improper ratio of Mg2+:Ca2+ and Na+:Ca+2, and a magnesium hazard was foreseen. This study showed that the turbidity, total suspended solids, total alkalinity, total hardness, SO42−, PO43−, BOD5, and the coliform levels of the studied irrigation water samples of the Koga irrigation project were not found within the safe limits of FAO, WHO, EU, and irrigation water quality limits of different nations, even though additional samples evaluating seasonal fluctuations are needed to fully assess the water quality.

Environmental Challenges of Groundwater Contamination: An Assessment of Boreholes Water Quality in Ovom, Yenibebel and Yenaka Axis of Attisa Clan, Yenagoa, Bayelsa State

Groundwater and surface water pollution are among the prominent environmental challenges facing humanity globally in this 21 st century. Groundwater is vulnerable to natural and anthropogenic pollution. In this study, groundwater collected from selected boreholes in Ovom, Yenibebel and Yenaka communities in Attisa Clan within Yenagoa metropolis were assessed for their physicochemical and heavy metals qualities, using standard analytical procedures of the World Health Organisation guidelines. The aim of the study was to determine the suitability of the boreholes water for human consumption with view to protecting public health and wellbeing. The physical parameters measured include; Electrical conductivity (EC), total dissolved solid (TDS), total suspended solid (TSS) and total hardness (TH). Chemical parameters analysed include; total alkalinity (TA), pH, Dissolved oxygen (DO), Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD), Chloride (Cl), Fluoride (F), Nitrate (NO 3 ), Phosphate (PO 4 ), Sulphate (SO 4 ). Heavy metals analysed include; Calcium (Ca), Magnesium (Mg). Iron (Fe), Copper (Cu) Chromium (Cr), Cadmium (Cd) and Lead (Pb). The results of the analysis of the water quality parameters are presented in Table 3.1. The results indicate that the physical parameters measurements were lower than the limits set in the Nigeria standard quality for drinking water (NSDQW) and the world Health Organisation (WHO) standard, in all the sampling points. However HPI evaluation revealed that water samples collected from Ovom and Yenibebel are unsafe for human consumption due to high Cadmium concentration above the recommended level of (0.003mg/l).while the boreholes water from Yenaka are safe for human consumption. It is recommended that quality of boreholes water In Yenagoa should be monitored regularly in order to protect public health.

Impacts of Basal Melting of the Totten Ice Shelf and Biological Productivity on Marine Biogeochemical Components in Sabrina Coast, East Antarctica

AbstractTo clarify the impacts of basal melting of the Antarctic ice sheet and biological productivity on biogeochemical processes in Antarctic coastal waters, concentrations of dissolved inorganic carbon (DIC), total alkalinity (TA), inorganic nutrients, chlorophyll a, and stable oxygen isotopic ratios (δ18O) were measured from the offshore slope to the ice front of the Totten Ice Shelf (TIS) during the spring/summer of 2018, 2019, and 2020. Modified Circumpolar Deep Water (mCDW) intruded onto the continental shelf off the TIS and flowed along bathymetric troughs into the TIS cavity, where it formed a buoyant mixture with glacial meltwater from the ice shelf base. Physical oceanographic processes mostly determined the distributions of DIC, TA, and nutrient concentrations. However, photosynthesis and dilution by meltwater from sea ice and the ice shelf base decreased DIC, TA, and nutrient concentrations in surface water near the ice front. These causes also reduced the partial pressure of CO2 (pCO2) in surface water by more than 100 μatm with respect to mCDW in austral summer of 2018 and 2020, and the surface water became a strong CO2 sink for the atmosphere. Phytoplankton photosynthesis changed DIC and TA in a molar ratio of 106:16. Thus, pCO2 decreased mostly as a result of photosynthesis while dilution by glacial and sea ice meltwater had a small effect. The nutrient consumption ratio suggested that photosynthesis was stimulated by iron in the water column, supplied to the surface layer via buoyancy‐driven upwelling and basal ice shelf meltwater in addition to sea ice meltwater.

Spatio-temporal assessment of water quality of a tropical decaying river in India for drinking purposes and human health risk characterization.

River water pollution and water-related health problems are common issues across the world. The present study aims to examine the Jalangi River's water quality to assess its suitability for drinking purposes and associated human health risks. The 34 water samples were collected from the source to the mouth of Jalangi River in 2022 to depict the spatial dynamics while another 119 water samples (2012-2022) were collected from a secondary source to portray the seasonal dynamics. Results indicate better water quality in the lower reach of the river in the monsoon and post-monsoon seasons. Principal component analysis reveals that K+, NO3-, and total alkalinity (TA) play a dominant role in controlling the water quality of the study region, while, CaCO3, Ca2+, and EC in the pre-monsoon, EC, TDS, Na+, and TA in the monsoon, and EC, TDS and TA in the post-monsoon controlled the water quality. The results of ANOVA reveal that BOD, Ca2+, and CaCO3 concentrations in water have significant spatial dynamics, whereas pH, BOD, DO, Cl-, SO42-, Na+, Mg2+, Ca2+, CaCO3, TDS, TA, and EC have seasonal dynamics (p < 0.05). The water quality index depicts that the Jalangi River's water quality ranged from 6.23 to 140.83, i.e., excellent to unsuitable for drinking purposes. Human health risk analysis shows that 32.35% of water samples have non-carcinogenic health risks for all three groups of people, i.e., adults, children, and infants while only 5.88% of water samples have carcinogenic health risks for adults and children. The gradual decay of the Jalangi River coupled with the disposal of urban and agricultural effluents induces river pollution that calls for substantial attention from the various stakeholders to restore the water quality.