{"id":118,"date":"2026-04-10T02:53:07","date_gmt":"2026-04-10T02:53:07","guid":{"rendered":"https:\/\/books.gw-project.org\/age-dating-young-groundwater\/chapter\/ch043-xhtml\/"},"modified":"2026-05-07T20:35:02","modified_gmt":"2026-05-07T20:35:02","slug":"5-7-summary","status":"publish","type":"chapter","link":"https:\/\/books.gw-project.org\/age-dating-young-groundwater\/chapter\/5-7-summary\/","title":{"raw":"5.7 Summary","rendered":"5.7 Summary"},"content":{"raw":"<div id=\"summary-2\" class=\"level1\">\r\n<div data-custom-style=\"First Paragraph\">\r\n\r\n[latex]{SF}_{6}[\/latex] is a relatively stable gas and the atmospheric concentration has been monotonically increasing since the mid\u20111950s. As a transient age\u2011dating tracer, [latex]{SF}_{6}[\/latex] benefits from nearly linear increase in the atmosphere of seven to eight\u00a0percent\u00a0per\u00a0year since about 1980. Its low solubility in water combined with ppt\u2011level concentration in the atmosphere result in low but measurable concentrations in young groundwater.\r\n\r\n<\/div>\r\n<div data-custom-style=\"Body Text\">\r\n\r\nFurther, measurement of [latex]{SF}_{6}[\/latex], while still somewhat specialized, is less complicated than with tracers such as [latex]_{}^{3}H[\/latex] and noble gases. The process of calculating a tracer age involves measuring an aqueous concentration, calculating the atmospheric (gas-phase) concentration that would be in equilibrium\u2014after correcting for excess air\u2014with the aqueous concentration, and comparing the atmospheric\u2011equivalent value with the history of [latex]{SF}_{6}[\/latex] in the atmosphere.\r\n\r\n<\/div>\r\n<div data-custom-style=\"Body Text\">\r\n\r\nThe primary limitation to [latex]{SF}_{6}[\/latex] dating is uncertainty that results from the amount of excess air in a sample, and from the existence of terrigenic [latex]{SF}_{6}[\/latex]. Despite these limitations, excellent agreement between [latex]{SF}_{6}[\/latex] ages and CFC ages (e.g., Busenberg &amp; Plummer, 2000) and [latex]_{}^{3}H[\/latex]\/[latex]_{}^{3}{He}[\/latex] ages (e.g., Solomon et al., 2015) have been reported. When samples contain less than about 2\u00a0ml\/kg of excess air and no terrigenic sources, age uncertainties of \u00b1\u00a05\u00a0years are typical for [latex]{SF}_{6}[\/latex] dating.\r\n\r\n<\/div>\r\n<div data-custom-style=\"Body Text\">\r\n\r\nWhile [latex]{SF}_{6}[\/latex] is a potent greenhouse gas and was included in the Kyoto Protocol, there is currently no indication that the rate of atmospheric growth is declining. From a groundwater\u2011dating point of view, higher atmospheric values are 1) easier to measure, and 2) tend to minimize complications due to terrigenic sources. As such, [latex]{SF}_{6}[\/latex] is likely to become an increasingly common dating method in the future.\r\n\r\n<\/div>\r\n<\/div>","rendered":"<div id=\"summary-2\" class=\"level1\">\n<div data-custom-style=\"First Paragraph\">\n<p>[latex]{SF}_{6}[\/latex] is a relatively stable gas and the atmospheric concentration has been monotonically increasing since the mid\u20111950s. As a transient age\u2011dating tracer, [latex]{SF}_{6}[\/latex] benefits from nearly linear increase in the atmosphere of seven to eight\u00a0percent\u00a0per\u00a0year since about 1980. Its low solubility in water combined with ppt\u2011level concentration in the atmosphere result in low but measurable concentrations in young groundwater.<\/p>\n<\/div>\n<div data-custom-style=\"Body Text\">\n<p>Further, measurement of [latex]{SF}_{6}[\/latex], while still somewhat specialized, is less complicated than with tracers such as [latex]_{}^{3}H[\/latex] and noble gases. The process of calculating a tracer age involves measuring an aqueous concentration, calculating the atmospheric (gas-phase) concentration that would be in equilibrium\u2014after correcting for excess air\u2014with the aqueous concentration, and comparing the atmospheric\u2011equivalent value with the history of [latex]{SF}_{6}[\/latex] in the atmosphere.<\/p>\n<\/div>\n<div data-custom-style=\"Body Text\">\n<p>The primary limitation to [latex]{SF}_{6}[\/latex] dating is uncertainty that results from the amount of excess air in a sample, and from the existence of terrigenic [latex]{SF}_{6}[\/latex]. Despite these limitations, excellent agreement between [latex]{SF}_{6}[\/latex] ages and CFC ages (e.g., Busenberg &amp; Plummer, 2000) and [latex]_{}^{3}H[\/latex]\/[latex]_{}^{3}{He}[\/latex] ages (e.g., Solomon et al., 2015) have been reported. When samples contain less than about 2\u00a0ml\/kg of excess air and no terrigenic sources, age uncertainties of \u00b1\u00a05\u00a0years are typical for [latex]{SF}_{6}[\/latex] dating.<\/p>\n<\/div>\n<div data-custom-style=\"Body Text\">\n<p>While [latex]{SF}_{6}[\/latex] is a potent greenhouse gas and was included in the Kyoto Protocol, there is currently no indication that the rate of atmospheric growth is declining. From a groundwater\u2011dating point of view, higher atmospheric values are 1) easier to measure, and 2) tend to minimize complications due to terrigenic sources. As such, [latex]{SF}_{6}[\/latex] is likely to become an increasingly common dating method in the future.<\/p>\n<\/div>\n<\/div>\n","protected":false},"author":7,"menu_order":28,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-118","chapter","type-chapter","status-publish","hentry"],"part":33,"_links":{"self":[{"href":"https:\/\/books.gw-project.org\/age-dating-young-groundwater\/wp-json\/pressbooks\/v2\/chapters\/118","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/books.gw-project.org\/age-dating-young-groundwater\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/books.gw-project.org\/age-dating-young-groundwater\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/books.gw-project.org\/age-dating-young-groundwater\/wp-json\/wp\/v2\/users\/7"}],"version-history":[{"count":1,"href":"https:\/\/books.gw-project.org\/age-dating-young-groundwater\/wp-json\/pressbooks\/v2\/chapters\/118\/revisions"}],"predecessor-version":[{"id":248,"href":"https:\/\/books.gw-project.org\/age-dating-young-groundwater\/wp-json\/pressbooks\/v2\/chapters\/118\/revisions\/248"}],"part":[{"href":"https:\/\/books.gw-project.org\/age-dating-young-groundwater\/wp-json\/pressbooks\/v2\/parts\/33"}],"metadata":[{"href":"https:\/\/books.gw-project.org\/age-dating-young-groundwater\/wp-json\/pressbooks\/v2\/chapters\/118\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/books.gw-project.org\/age-dating-young-groundwater\/wp-json\/wp\/v2\/media?parent=118"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/books.gw-project.org\/age-dating-young-groundwater\/wp-json\/pressbooks\/v2\/chapter-type?post=118"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/books.gw-project.org\/age-dating-young-groundwater\/wp-json\/wp\/v2\/contributor?post=118"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/books.gw-project.org\/age-dating-young-groundwater\/wp-json\/wp\/v2\/license?post=118"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}