Abioye O. Fayiga

Effects of arsenic species and concentrations on arsenic accumulation by different fern species in a hydroponic system.

Two hydroponic experiments were conducted to evaluate factors affecting plant arsenic (As) hyperaccumulation. In the first experiment, two As hyperaccumulators (Pteris vittata and P. cretica mayii) were exposed to 1 and 10 mg L−1 arsenite (AsIII) and monomethyl arsenic acid (MMA) for 4 wk. Total As concentrations in plants (fronds and roots) and solution were determined. In the second experiment, P. vittata and Nephrolepis exaltata (a non-As hyperaccumulator) were exposed to 5 mg L−1 arsenate (AsV) and 20 mg L−1 AsIII for 1 and 15 d. Total As and AsIII concentrations in plants were determined. Compared to P. cretica mayii, P. vittata was more efficient in arsenic accumulation (1075–1666 vs. 249–627 mg kg−1 As in the fronds) partially because it is more efficient in As translocation. As translocation factor (As concentration ratio in fronds to roots) was 3.0–5.6 for P. vittata compared to 0.1 to 4.8 for P. cretica. Compared to N. exaltata, P. vittata was significantly more efficient in arsenic accumulation (38–542 vs. 4.8–71 mg kg−1 As in the fronds) as well as As translocation (1.3–5.6 vs. 0.2–0.5). In addition, P. vittata was much more efficient in As reduction from AsV to AsIII (83–84 vs. 13–24% AsIII in the fronds). Little As reduction occurred after 1-d exposure to AsV in both species indicates that As reduction was not instantaneous even in an As hyperaccumulator. Our data were consistent with the hypothesis that both As translocation and As reduction are important for plant As hyperaccumulation.

Chemical and physical characterization of lead in three shooting range soils in Florida

Abstract To better understand the environmental impact of lead (Pb) in shooting range soils, Pb levels in three berm soils were characterized via size distribution, total Pb concentration, water-soluble Pb, sequential extraction and X-ray diffraction (XRD). About 60% of the mid-berm soils of ranges-G and -O existed in grain sizes between 0.5 and 0.25mm (medium sand) while range-L was most abundant in the 0.25–0.106mm (fine sand) size fraction. All three range soils had the most accumulation of lead (60–70%) in the very coarse sand size (2.0–1.0 mm). In ranges-G and -L, the index shows a decreasing Pb enrichment with decreasing particle size, which may be a result of bullet fragmentation and abrasion in shooting range soils. Sequential extractions reveal that ranges-G and -L had the highest proportion of Pb bound to organic matter while range-O was dominated by the carbonate-bound fraction. However, a substantial proportion (one-third) of Pb in soil from the three shooting ranges was associated with carbonates. The XRD result revealed the dominance of carbonates in range-O soil, calcite in range-G soil and metallic lead in ranges-G and -O soil. The conversion of metallic lead to carbonates may be a mechanism for natural attenuation of lead in shooting range soils. Implications for remediation of shooting range soils are further discussed.