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1. Laboratory experiments testing pH, alkalinity and particle impacts on Mn removal

   https://doi.org/10.6073/pasta/84fc50f3798a1b758e04570a98caaf55  

   Ming, Cissy L; Schreiber, Madeline E (June 2023, Environmental Data Initiative)

   Laboratory experiments were conducted to investigate impacts of pH, alkalinity, and presence of particles on Mn removal in freshwater. The dataset includes monitoring data from: 1) a 14-day experiment in Mn(II) solutions in nanopure water, 2) a 24-hour experiment in Mn(II) solutions in nanopure water, and 3) a 10-day experiment in water from two drinking water reservoirs. The 14-day pH and alkalinity laboratory experiment was conducted starting October 30, 2022 and included sample collection and pH monitoring on day 0, 1, 4, 7, 10, and 14. The 24-hour pH and alkalinity laboratory experiment was conducted starting February 20, 2023 and included sample collection and pH monitoring at 0, 1, 2, 6, 12, and 24 hours. The reservoir water laboratory experiment was conducted starting March 22, 2023 and included sample collection and pH monitoring on day 0, 1, 4, 7, and 10. This experiment tested Mn removal in water collected from the lower water column of Falling Creek Reservoir (FCR) and Carvins Cove Reservoir (CCR), located in Vinton, Virginia, USA and Roanoke, Virginia, USA respectively. Both reservoirs are owned and operated by the Western Virginia Water Authority and are managed as drinking-water sources for the city of Roanoke, VA, USA. 

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2. Southern Ocean Calcification Controls the Global Distribution of Alkalinity

   https://doi.org/10.1029/2020GB006727  

   Krumhardt, K. M.; Long, M. C.; Lindsay, K.; Levy, M. N. (December 2020, Global Biogeochemical Cycles)

   null (Ed.)
3. Global inorganic nitrate production mechanisms: comparison of a global model with nitrate isotope observations

   https://doi.org/10.5194/acp-20-3859-2020  

   Alexander, Becky; Sherwen, Tomás; Holmes, Christopher D.; Fisher, Jenny A.; Chen, Qianjie; Evans, Mat J.; Kasibhatla, Prasad (January 2020, Atmospheric Chemistry and Physics)

   null (Ed.)

   Abstract. The formation of inorganic nitrate is the main sink for nitrogenoxides (NOx = NO + NO2). Due to the importance of NOx forthe formation of tropospheric oxidants such as the hydroxyl radical (OH) andozone, understanding the mechanisms and rates of nitrate formation isparamount for our ability to predict the atmospheric lifetimes of mostreduced trace gases in the atmosphere. The oxygen isotopic composition ofnitrate (Δ17O(nitrate)) is determined by the relativeimportance of NOx sinks and thus can provide an observationalconstraint for NOx chemistry. Until recently, the ability to utilizeΔ17O(nitrate) observations for this purpose was hindered by ourlack of knowledge about the oxygen isotopic composition of ozone (Δ17O(O3)). Recent and spatially widespread observations of Δ17O(O3) motivate an updated comparison of modeled andobserved Δ17O(nitrate) and a reassessment of modeled nitrateformation pathways. Model updates based on recent laboratory studies ofheterogeneous reactions render dinitrogen pentoxide (N2O5)hydrolysis as important as NO2 + OH (both 41 %) for globalinorganic nitrate production near the surface (below 1 km altitude). Allother nitrate production mechanisms individually represent less than 6 %of global nitrate production near the surface but can be dominant locally.Updated reaction rates for aerosol uptake of NO2 result in significantreduction of nitrate and nitrous acid (HONO) formed through this pathway inthe model and render NO2 hydrolysis a negligible pathway for nitrateformation globally. Although photolysis of aerosol nitrate may haveimplications for NOx, HONO, and oxidant abundances, it does notsignificantly impact the relative importance of nitrate formation pathways.Modeled Δ17O(nitrate) (28.6±4.5 ‰)compares well with the average of a global compilation of observations (27.6±5.0 ‰) when assuming Δ17O(O3) = 26 ‰, giving confidence in the model'srepresentation of the relative importance of ozone versus HOx (= OH + HO2 + RO2) in NOx cycling and nitrate formation on theglobal scale. 

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4. Inorganic Carbon-Limited Freshwater Algal Growth at High pH: Revisited with Focus on Alkalinity

   https://doi.org/10.13031/ja.15411  

   Watson, Mary Katherine; Flanagan, Elizabeth; Drapcho, Caye M. (January 2023, Journal of the ASABE)

   Highlights Non-carbonate components of BG11 media impact TIC calculation on average 4.00 mg/L at high pH. BG11 media non-carbonate alkalinity (NCA) varies with pH: NCA (meq/L) = 0.0393×e^0.2075×pH+ (2.086×10^-9)e^1.860×pH.Monod kinetic constants with CO₂, HCO₃^-, and CO₃^2-as inorganic carbon sources are improved from a previous report.Kinetic constants continue to be the only known reports considering multiple inorganic carbon sources.Algal stoichiometric reactions are developed that account for variation in cell content and carbon source. Abstract.Due to increasing atmospheric CO2, algal growth systems at high pH are of interest to support enhanced diffusion and carbon capture. Given the interactions between algal growth, pH, and alkalinity, data from Watson and Drapcho (2016) were re-examined to determine the impact of the non-carbonate constituents in BG11 media on estimates of Monod kinetic parameters, biomass yield, and cell stoichiometry. Based on a computational method, non-carbonate alkalinity (NCA) in BG11 media varies with pH according to: NCA (meq/L) = 0.0393×e0.2075×pH + (2.086×10-9)e1.860×pH (R2 = 0.999) over the pH range of 10.3 – 11.5. Updated maximum specific growth rates were determined to be 0.060, 0.057, and 0.051 hr-1 for CO2, HCO3, and CO3, respectively. Generalizable stoichiometric algal growth equations that consider variable nutrient ratios and multiple inorganic carbon species were developed. Improved kinetic and stoichiometric parameters will serve as the foundation for a dynamic mathematical model to support the design of high pH algal carbon capture systems. Keywords: Algae, Alkalinity, Carbon Abatement, Carbon Capture, Kinetics, Stoichiometry, Total Inorganic Carbon. 

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5. Hunting for Extremophiles: A Systematic Screening of Freshwater Microalgae for Tolerance to High-pH and High-Alkalinity Cultivation

   https://doi.org/10.1021/acssuschemeng.5c09906  

   Thomas, Patrick K; Gerlach, Robin; Narwani, Anita (March 2026, ACS Sustainable Chemistry & Engineering)

   ABSTRACT: Microalgae hold the potential to supply sustainable food, fuel, plastics, and chemicals at commercial scales. Cultivating microalgae at extreme pH (>10) and high alkalinity provides multiple benefits, including (1) reducing the risk of contamination by undesired organisms and (2) enabling direct air capture of CO2, which expands the land area suitable for algae farming compared to using CO2 point sources alone. However, we currently have a limited understanding of which algal taxa can grow under these conditions. Therefore, we conducted a high-throughput screening of 49 freshwater microalgae strains, comprising 40 species, for their ability to grow in moderate (pH 8.5, 25 mM alkalinity), high (pH 10, 75 mM alkalinity), and extreme (pH 10, 150 mM alkalinity) cultivation environments. Our results show that moderate alkalinity tends to significantly increase algae growth (including potentially harmful strains). However, higher levels inhibited all but a small subset of green algae and cyanobacteria. Effects of salinity and alkalinity differed, indicating that they are broadly decoupled. Our results identify new industrially relevant alkaline-tolerant strains, show that algae isolated from “normal” ecosystems can be extremophilic, and suggest that future bioprospecting efforts for alkaline-tolerant algae adapted to local climatic conditions could yield additional productivity gains for the algae industry. 

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