Deposition of airborne mercury from six Swedish chlor-alkali plants surveyed by moss analysis
The local contamination of airborne mercury caused by six Swedish chlor-alkali plants was studied by analyses of mercury accumulated in moss. Samples of the carpet-forming moss, Hypnum cupressiforme, were collected from an area radiating 15 km from each plant site. For the most part the sampling localities were distributed along five transects emanating from the emission source. The mercury content of the dry moss tissue was determined by neutron activation analysis. 
 
The fall-out pattern determined at each plant was found to be somewhat similar. The highest mercury levels, 1,000–15,000 ng/g, were obtained within close proximity to the plants; as the distance increased, the mercury level decreased. The background level of the region (90–150 ng/g) was reached at distances ranging from 9 to 15 km from the plant site. Estimates of the annual fall-out indicated that only a minor part of emitted mercury (usually ≲10%) was deposited locally. The major part seems to spread over very large areas and probably contributes to the global circulation as well as to regional background deposition.