Morphological Traits Influence the Uptake Ability of Priority Pollutant Elements by Hypnum cupressiforme and Robinia pseudoacacia Leaves

In this paper, a biomonitoring survey of airborne priority pollutant elements was carried out using leaves of native black locust and moss bags filled with Hypnum cupressiforme. The aims of the work were (i) to evaluate if mosses and leaves provide similar information regarding the accumulation of the elements of environmental concern (As, Be, Cd, Cr, Cu, Hg, Mo, Ni, Pb, Sb, Se, V, Zn, Tl); (ii) to evaluate if leaf traits are significantly involved in the uptake mechanisms. Hypnum transplants showed elemental contents generally higher than R. pseudoacacia leaves, despite the shorter exposure time. Moss accumulated larger amounts of elements linked to PM and the resuspension of soil dust. Based on the calculation of deposition flux for each element, R. pseudoacacia showed lower values for most elements—except Cr, Mo and Zn—indicating that uptake takes place both by deposition on the leaf surface and absorption via the root. Leaf traits (micromorphology of surface) play an important role in the interception and retention of PM-linked elements. Hypnum transplanted in bags was confirmed to be a powerful bio-accumulator of airborne elements; by contrast, R. pseudoacacia, with a smooth surface and scarce trichomes, showed a limited ability in airborne element retention. Therefore, widely diffused species, well-adapted to anthropized environments, such as black locust, not always can be considered as good biomonitors. The results are discussed in comparison to other vascular plant species used in biomonitoring studies.

Speciation, risks and isotope-based source apportionment of trace elements in soils of the northeastern Qinghai–Tibet Plateau

Trace elements in soils might cause contamination and ecological risks to the environment with increasing anthropogenic disturbance. This study investigated the distribution, speciation, risks and possible sources of 28 target trace elements in soils of the northeastern Qinghai–Tibet Plateau. The average concentrations of trace elements in soils of the study area ranged from 0.25 (Hg) to 697.38 mg kg−1 (Cr). The residual fraction was the dominant host of V, Cr, Cu, Sn, Sb Hg and REEs, while Co, Ni, Zn, Mo, Cd and Pb had large proportions in the non-residual fractions. Risk assessment code analysis showed that Cd should be recognized as a priority pollutant in the study area. Correlation analysis indicated that Pb, Cu, Zn, Cd and Sn might originate from the same or similar source. The 206Pb/207Pb and 208Pb/206Pb ratios of the soils were in the range of 1.166–1.224 and 2.031–2.122, respectively. The anthropogenic Pb contribution proportion was in the range of 0–53.92% for the study area. The anthropogenic Pb contribution was higher in the areas with more intensive anthropogenic activities. Heavy metals and excessive anthropogenic disturbance should be effectively controlled in the northeastern Qinghai–Tibet Plateau to maintain the ecological sustainability and human health of this fragile area.

Effect of Ni morphology on removal of pentachlorophenol with Fe/Ni nanomaterials

Chlorinated phenols are a kind of environmental priority pollutant that attract much attention. Nanosized Fe and Fe/Ni materials are considered as promising options for chlorinated phenol removal. The effect of Ni morphology on the removal of pentachlorophenol (PCP) with Fe/Ni nanomaterials was investigated in this study. Iron nanoparticles and nickel nanomaterials with different shapes were synthesized using a chemical reduction method and wet chemical techniques, respectively. The concentrations of PCP and chloride in solutions were measured with and without Ni present. The intermediates of PCP were also analyzed. The results showed that the dechlorination of PCP was promoted by Ni nanomaterials, among which the tubular porous Ni nanomaterials expressed the most promotion, then those with net shape and nanochains. However, the tubular porous Ni nanomaterials inhibited the removal of PCP, and the other two expressed a certain promotion. In the Fe/Ni system, Fe nanoparticles transformed into magnetite (Fe3O4) and/or maghemite (Fe2O3), and Ni nanomaterials were still pure Ni after reaction. The introduction of Ni nanomaterials would improve dechlorination of PCP, but the removal of PCP might be inhibited or improved as the morphology of Ni changed.

HipH Catalyzes the Hydroxylation of 4-Hydroxyisophthalate to Protocatechuate in 2,4-Xylenol Catabolism by Pseudomonas putida NCIMB 9866

ABSTRACTIn addition to growing onp-cresol,Pseudomonas putidaNCIMB 9866 is the only reported strain capable of aerobically growing on 2,4-xylenol, which is listed as a priority pollutant by the U.S. Environmental Protection Agency. Several enzymes involved in the oxidation of thepara-methyl group, as well as the corresponding genes, have previously been reported. The enzyme catalyzing oxidation of the catabolic intermediate 4-hydroxyisophthalate to the ring cleavage substrate protocatechuate was also purified from strain NCIMB 9866, but its genetic determinant is still unavailable. In this study, the genehipH, encoding 4-hydroxyisophthalate hydroxylase, from strain NCIMB 9866 was cloned by transposon mutagenesis. Purified recombinant HipH-His6was found to be a dimer protein with a molecular mass of approximately 110 kDa. HipH-His6catalyzed the hydroxylation of 4-hydroxyisophthalate to protocatechuate with a specific activity of 1.54 U mg−1and showed apparentKmvalues of 11.40 ± 3.05 μM for 4-hydroxyisophthalate with NADPH and 11.23 ± 2.43 μM with NADH and similarKmvalues for NADPH and NADH (64.31 ± 13.16 and 72.76 ± 12.06 μM, respectively). The identity of protocatechuate generated from 4-hydroxyisophthalate hydroxylation by HipH-His6has also been confirmed by high-performance liquid chromatography and mass spectrometry. Gene transcriptional analysis, gene knockout, and complementation indicated thathipHis essential for 2,4-xylenol catabolism but not forp-cresol catabolism in this strain. This fills a gap in our understanding of the gene that encodes a critical step in 2,4-xylenol catabolism and also provides another example of biochemical and genetic diversity of microbial catabolism of structurally similar compounds.