[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"detail-sidebar-cat-0-en-105":3,"doc-seo-289652-105":59,"doc-detail-289652-en":130},{"code":4,"msg":5,"data":6},0,"success",[7,13,18,23,28,33,38,43,48,51,55],{"id":8,"doc_module":4,"doc_module_name":9,"category_name":10,"show_sort_weight":11,"slug":12},1,"Document","Story & Novel",90,"story-novel",{"id":14,"doc_module":4,"doc_module_name":9,"category_name":15,"show_sort_weight":16,"slug":17},2,"Literature",80,"literature",{"id":19,"doc_module":4,"doc_module_name":9,"category_name":20,"show_sort_weight":21,"slug":22},4,"Exam",70,"exam",{"id":24,"doc_module":4,"doc_module_name":9,"category_name":25,"show_sort_weight":26,"slug":27},5,"Comic",60,"comic",{"id":29,"doc_module":4,"doc_module_name":9,"category_name":30,"show_sort_weight":31,"slug":32},6,"Technology",50,"technology",{"id":34,"doc_module":4,"doc_module_name":9,"category_name":35,"show_sort_weight":36,"slug":37},7,"Healthcare",40,"healthcare",{"id":39,"doc_module":4,"doc_module_name":9,"category_name":40,"show_sort_weight":41,"slug":42},8,"Research & Report",30,"research-report",{"id":44,"doc_module":4,"doc_module_name":9,"category_name":45,"show_sort_weight":46,"slug":47},9,"Religion & Spirituality",20,"religion-spirituality",{"id":46,"doc_module":4,"doc_module_name":9,"category_name":49,"show_sort_weight":46,"slug":50},"World Cup","world-cup",{"id":52,"doc_module":4,"doc_module_name":9,"category_name":53,"show_sort_weight":52,"slug":54},10,"Lifestyle","lifestyle",{"id":56,"doc_module":4,"doc_module_name":9,"category_name":57,"show_sort_weight":24,"slug":58},19,"General","general",{"code":4,"msg":60,"data":61},"ok",{"site_id":62,"language":63,"slug":64,"title":65,"keywords":66,"description":67,"schema_data":68,"social_meta":123,"head_meta":125,"extra_data":127,"updated_unix":129},105,"en","phreeqc-and-phreeqci-frequently-asked-questions","PHREEQC and PhreeqcI - Frequently Asked Questions","","Frequently Asked Questions for PHREEQC and PhreeqcI addresses stability constants for seawater and how log K values relate to ionic strength corrections. It explains the roles of activities, activity coefficients, Debye-Huckel/Davies activity models, and the use of conditional constants for seawater. Additional questions clarify the definitions of Total CO2 versus Total Carbon, especially the contribution of dissolved inorganic carbon, methane, and complexes. The FAQ also discusses challenges in modeling high ionic strength saline Arctic spring waters, comparing PHREEQC, Pitzer-based approaches, and alternative freezing/evaporation modeling codes.",{"@graph":69,"@context":122},[70,84,105],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":30,"@type":76,"position":81},"https://docshare.wps.com/document/technology/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/phreeqc-and-phreeqci-frequently-asked-questions/289652/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":99,"encodingFormat":97,"isAccessibleForFree":100,"interactionStatistic":101},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/phreeqc-and-phreeqci-frequently-asked-questions/289652.png","ImageObject",300,407,{"name":92,"@type":93},"Quinn Holloway","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-10-08","2026-09-17",true,{"@type":102,"interactionType":103,"userInteractionCount":81},"InteractionCounter",{"@type":104},"ViewAction",{"@type":106,"mainEntity":107},"FAQPage",[108,114,118],{"name":109,"@type":110,"acceptedAnswer":111},"How does PHREEQC handle stability constants (log K) when ionic strength changes in seawater?","Question",{"text":112,"@type":113},"PHREEQC uses mass-action equations written in terms of activities, so ionic strength corrections are applied through activity coefficients rather than directly modifying log K values. Debye-Huckel (anion-specific b*I) or Davies forms are used to compute these activity coefficients.","Answer",{"name":115,"@type":110,"acceptedAnswer":116},"What is the difference between Total CO2 and Total Carbon in PHREEQC output?",{"text":117,"@type":113},"Total CO2 (dissolved inorganic carbon) sums CO2, HCO3-, CO3-2, and related ion pairs/complexes. Total Carbon equals DIC plus methane, so they differ when methane is entered or produced in reaction calculations.",{"name":119,"@type":110,"acceptedAnswer":120},"Why can modeling high-ionic-strength saline spring waters be difficult, and what modeling approaches are suggested?",{"text":121,"@type":113},"High ionic strength can restrict the use of contemporary geochemical models such as WATEQ and PHREEQ, motivating use of specialized codes like FREZCHEM2 for freezing/evaporation. The discussion also contrasts ion-association (PHREEQC) with Pitzer specific interaction approaches (e.g., PHRQPITZ) and notes limitations such as missing carbonate species in some models.","https://schema.org",{"og:url":83,"og:type":124,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":126,"canonical":83},"index,follow",{"doc_id":128,"site_id":62},289652,1791459510,{"code":4,"msg":5,"data":131},{"doc_id":128,"user_id":132,"nickname":92,"user_avatar":133,"doc_module":4,"category_id":29,"category_name":30,"doc_title":65,"doc_description":67,"doc_content":134,"file_id":135,"file_url":136,"file_type":137,"file_size":138,"view_count":81,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":139,"language":140,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":141,"faqs":142,"seo_title":143,"seo_description":67,"update_tm":144,"read_time":145},2336474466712,"https://ap-avatar.wpscdn.com/davatar_a8503ba1806abce46bf441b54a3ca4cd","Frequently Asked Questions for PHREEQC and PhreeqcI  \n1. STABILITY CONSTANTS FOR SEAWATER: We focus our investigations in marine environments and we are concerned about the database file PHREEQC.DAT with respect to seawater instead of fresh-or groundwater. There is the dependence of log K data from ionic strength (or salinity) and it isnot exactly clear which circumstances the listed dataset represents, but surely no marine environment.  \nThe program seems not to correct log K data by itself, if the ionic strength increases by adding, i.e., Na and Cl. Do such corrections have to be added manually to the database file by changing the log Kfor the corresponding reaction? Are there any database files with log K coherent data for seawater available?  \nThe log K's in phreeqc.dat are for infinite dilution, consistent with thermodynamics and the free energies of formation of the species. The log K is assumed to apply at all ionic strengths because the mass-action equations are written in terms of activities. All ionic strength corrections go into the activity coefficients ofthe aqueous species. Either a Debye-Huckel expression with anion-specific b-dot ionic-strength term (b*I) or the Davies Debye-Huckel expression (which depends only on the charge of the species) is used to calculate activity coefficients.  \nIf you use conditional constants for seawater, the mass action equations are written with molalities rather than activities and all ionic strength corrections go into the log K. Effectively, PHREEQC automatically uses  \nlog K(conditional) = log K(thermodynmaic) *  \ngamma(reactants)/gamma(products)  \nwhere gamma(reactants) is a product of activity coefficients calculated from the ionic strength of the solution for the reactant side of the balanced reaction, each activtiy coefficient raised to the power denoted by the stoichiometric  \ncoefficient. Gamma(products) is similar for the product side.  \nThe activity coefficient parameters of the major ions are derived predominantly from sodium and chloride mean-activity-coefficient data. They should work best in sodium chloride solutions like seawater, but \"best\" is probably not as  \ngood as some of the conditional constants for seawater. The Davies equation is used for activity coefficients of ion complexes.  \nIf you want to use conditional constants, it would be necessary to redefine the log K's to the conditional constants and force activity coefficients to 1.0 (by defining a very large \"a\" term and a 0 \"b\" term in the Debye-Huckel expression for each ion. For example:  \nNa+ + SO4-2 = NaSO4-  \nlog_k 0.700 \\#redefine with conditional constant  \n-gamma 1e6 0.0  \nI do not have a file that is set up with conditional constants for seawater. If you know the constants from other sources, it should not be hard to set up the database file.  \n2. TOTAL CO2 and TOTAL CARBON: I'm wondering why, in the \"Description of Solution\" section of my output, Total Carbon and Total CO2 are both given. For all of my simulations, their concentrations are the same. How are these parameters calculated, and are their any situations where they would be different?  \nTotal CO2 can also be called \"dissolved inorganic carbon\" and it is the sum of all the CO2, HCO3-, and CO3-2 species plus their ion pairs and other complexes. Total carbon includes DIC plus methane, so Total CO2 and Total Carbon differ only if you either enter methane in a solution composition or generate methane in a reaction calculation,  \n3. HIGH IONIC STRENGTH and REDOX REACTIONS: Iam currently looking at the geochemistry of two groups of saline perennial spring discharge in the Canadian High Arctic. The springs discharge at a constant temperature around +6.5 C and precipitate calcite along with smaller amounts of undetermined iron-and sulfur-based minerals. Sulfate-reducing bacteria are believed to exist in the springs, associated with a notable presence of H2S at the outlets. The pH of the waters rise with increasing distance from the spring outl","cbCaiiidWAkYx8r4","https://ap.wps.com/l/cbCaiiidWAkYx8r4","pdf",500040,61,"English","# Stability Constants for Seawater\n## Total CO2 and Total Carbon\n## High Ionic Strength and Redox Reactions","[{\"question\":\"How does PHREEQC handle stability constants (log K) when ionic strength changes in seawater?\",\"answer\":\"PHREEQC uses mass-action equations written in terms of activities, so ionic strength corrections are applied through activity coefficients rather than directly modifying log K values. Debye-Huckel (anion-specific b*I) or Davies forms are used to compute these activity coefficients.\"},{\"question\":\"What is the difference between Total CO2 and Total Carbon in PHREEQC output?\",\"answer\":\"Total CO2 (dissolved inorganic carbon) sums CO2, HCO3-, CO3-2, and related ion pairs/complexes. Total Carbon equals DIC plus methane, so they differ when methane is entered or produced in reaction calculations.\"},{\"question\":\"Why can modeling high-ionic-strength saline spring waters be difficult, and what modeling approaches are suggested?\",\"answer\":\"High ionic strength can restrict the use of contemporary geochemical models such as WATEQ and PHREEQ, motivating use of specialized codes like FREZCHEM2 for freezing/evaporation. The discussion also contrasts ion-association (PHREEQC) with Pitzer specific interaction approaches (e.g., PHRQPITZ) and notes limitations such as missing carbonate species in some models.\"}]","PHREEQC and PhreeqcI - Frequently Asked Questions | PDF",1789636168,154]