Phytoremediation of lead and arsenic by green onions, potatoes, and Chinese brake ferns and arsenic speciation in moonlight ferns using x-ray absorption/x-ray fluorescence spectrometry

Phytoremediation of lead and arsenic by green onions, potatoes, and Chinese brake ferns and arsenic speciation in moonlight ferns using x-ray absorption/x-ray fluorescence spectrometry

Barber's Orchard (N.C.)

Phytoremediation

Soil remediation

X-ray spectroscopy

Cho, Youngsoo

2007

Butcher, David J.

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61730

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Barber Orchard was contaminated by pesticide usage for approximately eighty years during its time as an apple orchard. The contamination was not discovered until the late I 990s, approximately ten years after its development into a residential community. Conventional remediation of a portion of the development by an excavation procedure cost four million dollars. Phytoremediation has been studied to cleanse contaminated soil as an alternative to excavation. Green onions (Allium fistulosum) and potatoes (Solanum tuberosum) were investigated in this work. Arsenic and lead compounds were added to potting soil and mixed well. Green onions were planted in arsenic and lead spiked soil. EDTA and PDTA were applied as chelating reagents to examine their potential to enhance the concentrations of lead and arsenic in plant tissues. Lead uptake was low in the absence of chelating reagents. However, ethylenediaminetetraacetic acid (EDTA) significantly enhanced the concentration of lead in the stems of green onions (210 mg/kg), while propylenediaminetetraacetic acid (PDTA) did not induce lead absorption. Green onions planted in arsenic (III) and arsenic (V) mixed soil (1+2 on a molar basis) extracted arsenic compounds in the absence of chelating reagents. When PDTA was added into arsenic (V) spiked soil, arsenic accumulated in stems at a high concentration (120 mg/kg). Green onions, potatoes, and Chinese brake ferns were also planted in Barber Orchard soil. The extraction of lead from the soil by the entire plant was between 1.43% and 8.43%. The corresponding figure for arsenic was between 2.33% and 4.23% in the presence of EDTA. Moonlight ferns (Pteris cretica cv Mayii) were planted in a hydroponic system to which arsenic (III), arsenic (V), and monomethylarsenate (MMA) were added along with hydroponic solution. X-ray absorption/X-ray fluorescence spectrometry was performed to evaluate the chemical forms of arsenic present in the ferns (speciation). The absorption edges were located at 11862.44 eV, 11867.61 eV, 11865 eV, and 11868.38 eV for arsenic (0), MMA, arsenic (III), arsenic (V), respectively. Freshly cut fronds of moonlight ferns showed the same absorption edge energies (11865 eV) as arsenic (III). Dried fronds of moonlight ferns had an absorption edge energy corresponding to indicating oxidation of arsenic during the drying process. The analyses of moonlight fern fronds exposed to the arsenic solutions were performed by ICP-OES. Ferns exposed to arsenic (III) showed the highest concentration followed by ferns exposed to arsenic (V). The concentration of arsenic was higher when arsenic (III) was mixed with arsenic (V) than the combination of arsenic (III) and MMA.

2014-09-22

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