Abstract
Mercury pollution has become an important current issue as a result of its environmental effects on a global scale. The Oak Ridge Reservation, established in 1942, was the designated site for the construction of the atomic bomb. During a 20-year period from 1944-1963 radioactive and toxic chemical pollutants, especially mercury compounds were released into the surrounding waterways.A germination study was conducted to investigate the ability of three tree species, American sycamore (Platanus occidentalis),shortleaf pine (Pinus echinata), and loblolly pine (Pinus taeda) seeds to germinate in mercuric nitrate (Hg(NO3)2 and methylmercury chloride (CH3HgCl) solutions. A subsequent greenhouse study was conducted to assess the phytotoxic effects of different mercuric solutions on Platanus occidentalis (American Sycamore), inoculated with soils from East Fork Poplar Creek.We also measured vegetation stress by Near Infrared (NIR) spectroscopy.The wavelengths examined were those thatare specific to chlorophyll and several carotenoids, which are involved in photosynthesis: 430 nm (Chl a), 448 nm (Chl b, carotenoids), 471 nm (carotenoids), 642 nm (Chl b), 662 & 680 nm (Chl a). Principal component analysis (PCA) was performed to identify patterns in sycamore leaf spectral data.Under in vitro conditions, as mercury concentration increased above 100 mg·kg-1, germination of all species decreased, with P. echinata being the least sensitive. Germination was inhibited more when seeds were exposed to methyl mercury chloride than to mercuric nitrate. Organic species of mercury proved to be more toxic than inorganic species of mercury in our greenhouse study. Significant changes occurred in levels of all pigments sampled (p430, p448, p471, p642, p662, and p680) over the course of the experiment. NIR spectroscopy was not sensitive enough to detect other chemical changes to foliage following mercury application.
Highlights
Mercury pollution is of particular importance due to its deleterious effects on aquatic plants and animals [1,2,3], soil microbial, plant and fungal communities [4,5,6]
A germination study was conducted to investigate the ability of three tree species, American sycamore (Platanus occidentalis), shortleaf pine (Pinus echinata), and loblolly pine (Pinus taeda) seeds to germinate in mercuric nitrate (Hg(NO3)2 and methylmercury chloride (CH3HgCl) solutions
Mercury compounds were discharge into East Fork Poplar Creek (EFPC), from the US Department of Energy Y-12 site in Oak Ridge, Tennessee USA [7,8]
Summary
The chronic presence of Hg exposure over the past 50 years. Several authors have investigated the seed developmental stage of the plant life cycle and the ways how essential and non-essential metal ions can affect developmental processes in vegetation [12,13,14]. We evaluate the ability of, American sycamore (Platanus occidentalis), loblolly pine (Pinus echinata), and shortleaf pine (Pinus taeda) to germinate in various mercury solutions. We initially determine lethal and non-lethal concentrations for each species and test whether germination rate for each species decreases as mercuric concentration increases. The results of this germination study were used to develop the appropriate Hg treatments solutions for the subsequent greenhouse study. We test whether an inoculation treatment using EFPC soils enhance tolerance to different mercuric applications [20], monitor early seedling survivaland measure the leaves of American sycamore using Near Infrared Spectroscopy (NIR) as a tool to monitor changes in leaves due to mercury exposure
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