Editing Permafrost (section)

=== Release of toxic pollutants ===
[[File:Langer 2023 thawed pollution.png|thumb|Graphical representation of leaks from various toxic hazards caused by the thaw of formerly stable permafrost.<ref name="Langer2023" />]]
For much of the 20th century, it was believed that permafrost would "indefinitely" preserve anything buried there, and this made deep permafrost areas popular locations for hazardous waste disposal. In places like Canada's [[Prudhoe Bay]] oil field, procedures were developed documenting the "appropriate" way to inject waste beneath the permafrost. This means that as of 2023, there are ~4500 industrial facilities in the Arctic permafrost areas which either actively process or store hazardous chemicals. Additionally, there are between 13,000 and 20,000 sites which have been heavily contaminated, 70% of them in Russia, and their pollution is currently trapped in the permafrost.{{citation needed|date=August 2024}}

About a fifth of both the industrial and the polluted sites (1000 and 2200–4800) are expected to start thawing in the future even if the warming does not increase from its 2020 levels. Only about 3% more sites would start thawing between now and 2050 under the climate change scenario consistent with the [[Paris Agreement]] goals, [[Representative Concentration Pathway|RCP2.6]], but by 2100, about 1100 more industrial facilities and 3500 to 5200 contaminated sites are expected to start thawing even then. Under the very high emission scenario RCP8.5, 46% of industrial and contaminated sites would start thawing by 2050, and virtually all of them would be affected by the thaw by 2100.<ref name="Langer2023">{{Cite journal |last1=Langer |first1=Morit |last2=Schneider von Deimling |first2=Thomas |last3=Westermann |first3=Sebastian |last4=Rolph |first4=Rebecca |last5=Rutte |first5=Ralph |last6=Antonova |first6=Sofia |last7=Rachold |first7=Volker |last8=Schultz |first8=Michael |last9=Oehme |first9=Alexander |last10=Grosse |first10=Guido |date=28 March 2023 |title=Thawing permafrost poses environmental threat to thousands of sites with legacy industrial contamination |journal=Nature Communications |volume=14 |issue=1 |page=1721 |doi=10.1038/s41467-023-37276-4 |pmid=36977724 |pmc=10050325 |bibcode=2023NatCo..14.1721L }}</ref>

[[Organochlorine]]s and other [[persistent organic pollutant]]s are of a particular concern, due to their potential to repeatedly reach local communities after their re-release through [[biomagnification]] in fish. At worst, future generations born in the Arctic would enter life with weakened [[immune system]]s due to pollutants accumulating across generations.<ref name="Miner2021">{{Cite journal |last1=Miner |first1=Kimberley R. |last2=D'Andrilli |first2=Juliana |last3=Mackelprang |first3=Rachel |last4=Edwards |first4=Arwyn |last5=Malaska |first5=Michael J. |last6=Waldrop |first6=Mark P. |last7=Miller |first7=Charles E. |date=30 September 2021 |title=Emergent biogeochemical risks from Arctic permafrost degradation |journal=Nature Climate Change |volume=11 |issue=1 |pages=809–819 |doi=10.1038/s41558-021-01162-y |bibcode=2021NatCC..11..809M |s2cid=238234156 }}</ref>
[[File:Langer 2023 alaska distributions.png|thumb|left|Distribution of toxic substances currently located at various permafrost sites in Alaska, by sector. The number of fish skeletons represents the toxicity of each substance.<ref name="Langer2023" />]]
A notable example of pollution risks associated with permafrost was the [[2020 Norilsk oil spill]], caused by the collapse of [[diesel fuel]] storage tank at Norilsk-Taimyr Energy's [[thermal power plant]] No. 3. It spilled 6,000 tonnes of fuel into the land and 15,000 into the water, polluting [[Ambarnaya]], [[Daldykan]] and many smaller rivers on [[Taimyr Peninsula]], even reaching lake [[Pyasino]], which is a crucial water source in the area. [[State of emergency]] at the federal level was declared.<ref name=TASS>{{cite news |title=Diesel fuel spill in Norilsk in Russia's Arctic contained |url=https://tass.com/emergencies/1164423 |access-date=7 June 2020 |work=[[TASS]] |date=5 June 2020 |location=Moscow, Russia}}</ref><ref name="Seddon2020">{{Cite news |url=https://www.ft.com/content/fa9c20a0-2dad-4992-9686-0ec98b44faa8 |archive-url=https://ghostarchive.org/archive/20221210/https://www.ft.com/content/fa9c20a0-2dad-4992-9686-0ec98b44faa8 |archive-date=10 December 2022 |url-access=subscription |title=Siberia fuel spill threatens Moscow's Arctic ambitions |author=Max Seddon |work=[[Financial Times]] |date=4 June 2020}}</ref> The event has been described as the second-largest oil spill in modern Russian history.<ref name=nyt>{{citation |url=https://www.nytimes.com/2020/06/04/world/europe/russia-oil-spill-arctic.html |title=Russia Declares Emergency After Arctic Oil Spill |last=Nechepurenko |first=Ivan |work=[[New York Times]] |date=5 June 2020}}</ref><ref>{{cite news |last1=Antonova |first1=Maria |title=Russia Says Melting Permafrost Is Behind The Massive Arctic Fuel Spill |url=https://www.sciencealert.com/russia-claims-melting-permafrost-is-behind-the-massive-arctic-fuel-spill |access-date=19 July 2020 |agency=Science Daily |date=5 June 2020}}</ref>

Another issue associated with permafrost thaw is the release of natural [[mercury (element)|mercury]] deposits. An estimated 800,000 tons of mercury are frozen in the permafrost soil. According to observations, around 70% of it is simply taken up by vegetation after the thaw.<ref name="Miner2021" /> However, if the warming continues under RCP8.5, then permafrost emissions of mercury into the [[atmosphere]] would match the current global emissions from all human activities by 2200. Mercury-rich soils also pose a much greater threat to humans and the environment if they thaw near rivers. Under RCP8.5, enough mercury will enter the [[Yukon River]] basin by 2050 to make its fish unsafe to eat under the [[EPA]] guidelines. By 2100, mercury concentrations in the river will double. Contrastingly, even if mitigation is limited to RCP4.5 scenario, mercury levels will increase by about 14% by 2100, and will not breach the EPA guidelines even by 2300.<ref name="Schaefer2020">{{Cite journal |last1=Schaefer |first1=Kevin |last2=Elshorbany |first2=Yasin |last3=Jafarov |first3=Elchin |last4=Schuster |first4=Paul F. |last5=Striegl |first5=Robert G. |last6=Wickland |first6=Kimberly P. |last7=Sunderland  |first7=Elsie M. |date=16 September 2020 |title=Potential impacts of mercury released from thawing permafrost |journal=Nature Communications |volume=11 |issue=1 |page=4650 |doi=10.1038/s41467-020-18398-5 |pmid=32938932 |pmc=7494925 |bibcode=2020NatCo..11.4650S }}</ref>