Spatial Distribution of Mercury in Vegetation and Soil in a Conservation Unit Near Highways
摘要
Mercury (Hg) is a potentially toxic element with bioaccumulation and biomagnification properties. Plants can be used to assess environmental Hg contamination, leaves serve as bioindicators of atmospheric Hg concentration. However, during litter formation, the incorporated Hg is released into the environment. Here, we performed an analysis of the spatial distribution of Hg concentration in the vegetation and soil of the Águas Emendadas Ecological Station, considering the highways as potential sources of Hg. We collected samples at 33 points, starting from the edges towards the center of the Esecae. Quantification of total mercury (THg) was performed by thermal decomposition atomic absorption spectrometry with a portable instrument RA-915 + coupled to a pyrolysis chamber. Ordinary kriging and cokriging were used to produce soil and vegetation THg trend surfaces. The contribution of leaf Hg to soil was inferred by multiplying leaf THg concentrations to regional litterfall estimates. Kriging analysis showed elevated THg concentrations at the station edges. In vegetation, greater accumulation toward the north coincides with prevailing wind direction and higher elevation. The species Miconia sp., Caryocar brasiliense, and Qualea parviflora were most responsive to traffic-related Hg emissions. Soil showed elevated Hg within the station, possibly due to Hg leaching and mobility. Vegetation contributes to soil Hg through litterfall, adding approximately 13.6 µg m⁻2 of THg annually. Vegetation acts as a barrier to atmospheric dispersion of Hg within the station, retaining significant amounts from roads, so it is recommended to plant trees in buffer zones to filter atmospheric pollution.