Heavy metals are no longer uncommon in the Arctic. The sometimes massively increased concentrations, which have been detected in many places in the northern Polar region, can be attributed almost exclusively to human activities such as mining. In addition to these quantities, the thawing permafrost soil is another source of rising concentrations. In Alaska, scientists have now discovered that concentrations in many places are higher than the average concentration in other parts of the US. On the other hand, alarming data gaps for large parts of Alaska have emerged, making protection measures more difficult.
The US research group, led by lead author Clarice Perryman of the University of New Hampshire and the group leader, Assistant Professor Jessica Ernakovich of Towson University in Maryland, came to this conclusion after studying and comparing more than 1,000 soil samples from different regions of Alaska. The heavy metals studied during the work included arsenic, nickel, chromium, lead and mercury. Their concentrations were higher than the average values of soils in the United States, up to a factor of 10, according to the researchers. In addition, the results showed that the sites were concentrated in the southwest and south of Alaska, where mining activity is particularly high. But increased values were also found in other locations far from mining sites and populated areas.
However, this result of the study also showed one of three significant weaknesses, as the researchers write in their work: “We found a significant accumulation of sample sites in the southwestern part of Alaska in discontinuous and sporadic permafrost, while the continuous permafrost zone in northern Alaska and the more populous interior are much less studied.” This under-representation of data from central and northern Alaska also makes it particularly difficult to determine more precisely the impact of heavy metal concentrations on public health. Moreover, since heavy metals not only origin from human activities, but can also be released by natural processes such as erosion, a more detailed analysis of actual quantities and places of origin is hardly possible.
Perryman and the team also discovered further weaknesses in the fact that often analyses of the samples included only the top 10 centimeters of the thawed soil and had been performed at sites where the permafrost is discontinuous and sporadic. The continuous permafrost soils and deeper layers, which according to a few studies from other places have higher heavy metal values, are hardly examined in Alaska. But time is pressing to get better and more accurate results on heavy metals in the permafrost soils. This is because a further warming of the Arctic and its consequences will lead to further enrichment of the partial highly toxic substances such as mercury. A greater increase in tundra fires due to severe droughts also releases these substances in the environment. Alaska was hit by numerous such fires last summer. However, the amount of heavy metals released into the air has not been properly investigated. “Filling these data gaps will be necessary for understanding the potential for liberation of heavy metals from permafrost thaw into food and water resources that may present an unaccounted-for pathway of heavy metal exposure for communities in a warming Arctic,” the scientists conclude.
Source: Perryman et al. (2020)
Link to the study: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0233297
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