| Abstract |
To assess the role of salt-marsh plants on the vegetation-atmospheric Hg-0 fluxes, three salt marsh plant species, Halimione portulacoides, Sarcocornia, fruticosa and Spartina maritime were selected from a moderately contaminated site in the Tagus estuary during May 2012. Total mercury in stems and leaves for each plant as well as total gaseous mercury and vegetation-air Hg-0 fluxes were measured over two continuous days. Mercury fluxes were estimated with a dynamic flux Tedlar (R) bag coupled to a high resolution automated mercury analyzer (Teleran 2537A). Other environmental parameters such as air temperature, relative humidity and net solar radiation were also measured aside. H. portulacoides showed the highest total mercury concentrations in stems and, leaves and the highest average vegetation-air Hg-0 flux (0.48 0.40 ng Hg m(-2) h(-1)). The continuous measurements converged to a daily pattern for all plants, with enhanced fluxes during daylight and lower flux during the night. It is noteworthy that throughout the measurements a negative flux (air-vegetation) was never observed, suggesting the absence of net Hg deposition. Based on the above fluxes and the total area occupied by each species we have estimated the total amount of Hg emitted from this salt-marsh plants. A daily emission of 1.19 mg Hg d(-1) was predicted for the Alcochete marsh and 175 mg Hg d(-1) for the entire salt marsh area of the Tagus estuary. Crown Copyright (C) 2017 Published by Elsevier Ltd. All rights reserved. |
