Spatial and temporal variations in riverine mercury in the Mackenzie River Basin, Canada, from community-based water quality monitoring data

Sammanfattning

Arctic rivers deliver similar to 40 t yr(-1) of mercury (Hg) to the Arctic Ocean, similar to 6% of which is from the Mackenzie River Basin (MRB), a region warming at similar to 3 times the mean hemispheric rate. How this will affect Hg transfer to ecosystems of the Beaufort Sea is a worrying issue. To help address this question, we analyzed >500 measurements of Hg and other water properties from 22 rivers collected in 2012-2018 by communities of the MRB. This new dataset provides a more comprehensive view of riverine Hg variations across the basin than was previously available. We find that rivers issued from mountains in the western MRB contribute the largest share of Hg in the Mackenzie River, 60-95 % of it being carried as fine suspended solids and probably sourced from riverbank erosion and thaw slumps. In contrast, lowland rivers of the central and eastern MRB contribute larger shares of dissolved Hg (up to 78 %), likely from recent atmospheric deposition through precipitation. Using load modelling constrained by the new water quality dataset, we estimate that the three largest western tributaries (Liard, Peel and Arctic Red rivers) of the Mackenzie contribute 60 % of the annual MRB THg export and DHg export to the Beaufort Sea during freshet, as well as 51 % of DHg export, while supplying 60% of freshet discharge. Load modelling also reveals a sustained decline in DHg loads of similar to 13 kg yr(-1) between 2001 and 2016 in the lower Mackenzie River, which likely reflect a decreasing trend in atmospheric Hg deposition over most of northwestern Canada during this period. This study highlights the value of community-based water quality monitoring in helping to support assessments of riverine Hg in the MRB in support of the Minamata Convention on Mercury.

Nyckelord

Mercury; Arctic; Rivers; Canada; Permafrost; Climate change

Publicerad i

Science of the Total Environment
2022, Volym: 853, artikelnummer: 158674
Utgivare: ELSEVIER

SLU författare

• Campeau, Audrey

  • Institutionen för skogens ekologi och skötsel, Sveriges lantbruksuniversitet
    
  • Uppsala universitet

Globala målen

SDG6 Rent vatten och sanitet för alla


UKÄ forskningsämne

Klimatforskning
Oceanografi, hydrologi, vattenresurser


Publikationens identifierare

DOI: https://doi.org/10.1016/j.scitotenv.2022.158674

Permanent länk till denna sida (URI)

https://res.slu.se/id/publ/119413