Use of native and transplanted mosses as complementary techniques for biomonitoring mercury around an industrial facility

Terrestrial mosses were used simultaneously in passive (native species, Scl eropodium purum and Hypnum cupressifomre) and active (S. purum transplants in moss bags) biomonitoring techniques in a study that aimed to demonstrate the compatibility of the two methods by detailed investigation of the spat ial distribution of mercury in the surroundings of a chlor-alkali plant. Na tive mosses were sampled and transplants exposed (for periods of 30 days) a t two different times of the year in order to take into account different e nvironmental conditions (precipitation, temperature, prevailing winds, etc. ). The concentrations of Hg in the native mosses ranged between 0.04 and 11 .78 mu g g(-1) in February and 0.26 and 12.7 mu g g(-1) in September; in th e transplants the concentrations ranged between 0.39 and 1.9 mu g g(-1) in June and 0.036 and 2.75 mu g g(-1) in November. These values are all within the ranges reported in the literature. The total concentrations were trans formed into either contamination factors (CF) (by taking into account the b ackground levels of Hg in the native mosses) or enrichment factors (EF) (by taking into account the initial concentrations in the transplants). In bot h cases, there was a clear relationship with the distance from the source o f emission, irrespective of the time of year. Within the range of distances for which data were available for natives and transplants, the CF and EF w ere highly correlated. This implies that transplants sited in the area imme diately surrounding the plant, where the density of native mosses was very low, can be used to determine the degree of contamination in this area. The study also illustrated that the native moss appeared to adapt to the surro unding environment because at an equal distance (> 500 m) from the source o f emission the value of the CF for native mosses fell to 1, but the EF for transplanted mosses remained still high (5.2). (C) 2000 Elsevier Science B. V. All rights reserved.