Impact of rhizosphere microorganisms on arsenic (As) transformation and accumulation in a traditional Chinese medical plant.

Panax notoginseng is an important traditional medicinal plant, but the commercial value is threatened by root-rot disease caused by rhizosphere microbes and a potential health risk caused by plant arsenic (As) accumulation. Whether rhizospheric microbes isolated from P. notoginseng rhizosphere soil could impact As uptake and transport into P. notoginseng is not yet known. Among the three root-rot disease-causing pathogens Fusarium flocciferum (PG 1), Fusarium oxysporum (PG 2), and Fusarium solani (PG 3) and one root-rot disease biocontrol fungus Trichoderma koningiopsis (FC 1) and five biocontrol-exerting bacterial species Bacillus siamensis (BC 1), Delftia acidovorans (BC 2), Brevibacillus formosus (BC 3), Mortierella alpine (BC 4), and Bacillus subtilis (BC 5), one As-resistant pathogen and four biocontrol microorganisms with As-resistant ability were identified. The As-transforming ability of the identified fungi and bacteria was ranked in the order of FC 1 > PG 1 and BC 2 > BC 3 > BC 1, respectively. Then, the As-resistant biocontrol and pathogenic microbes were initiated to colonize the rhizosphere of 1-year-old P. notoginseng seedlings growing in artificially As(V)-contaminated soil to evaluate the impact of microbe inoculation on P. notoginseng As uptake and transport capacity. Concentration of As in P. notoginseng tissues decreased in the order of the sequence stem > root > leaf. Compared to treatment without colonization by microorganism, inoculation with microorganisms increased As root uptake efficiency and root As concentration, especially under treatment of inoculation by BC 2 and PG 1 + BC 2. As transport efficiency from root to stem decreased by inoculation with microorganism, especially under treatment with inoculation of BC 2 and PG 1 + BC 2. However, the impact of microorganism colonization on As stem to leaf transport efficiency was not obvious. In summary, inoculation with rhizosphere microbes may increase As accumulation in P. notoginseng root, especially when using bacteria with high As transformation ability. Therefore, it is necessary to evaluate the As transformation capacity before applying biological control microorganism to the rhizosphere of P. notoginseng.

Assessment of metal mobility in sediment, commercial fish accumulation and impact on human health risk in a large shallow plateau lake in southwest of China.

Sediment heavy metal pollution in the Dianchi Lake has been a long-term environmental problem of concern. This study investigated the lake sediment heavy metal contamination level, mobility, commercial fish metal accumulation and its impact on human health. The results show high As, Hg and Cd concentration in the sediment, while Pb and Cr contamination are insignificant. Sediment sequential extraction analysis shows that Hg in sediment has the highest portion of mobile fraction, followed by As, while the portion of mobile fractions of Cd, Pb and Cr in sediment is very low. The high concentrations of Hg and As in surface water and porewater were consistent with the chemical fraction composition of the two elements in sediment. Three major commercial fish species, Culterichthys erythropterus, Carassius auratus and Hypophthalmichthys molitrix, were collected for analysis of metal concentrations in their muscles. Among the same size of fish, C. auratus has the highest As concentration due to its bottom habitat and omnivorous feeding habits. On the other hand, C. erythropterus has the highest Hg concentration due to its relatively high trophic level position. The average THQ value of metals in fish tissue decrease in the order of As > Hg > Pb > Cd > Cr and the total THQ of average metal concentration in fish species decreased in the order of C. auratus > C. erythropterus > H. molitrix. Both THQ and total THQ is below 1, suggested no non-carcinogenic human health risk of fish consumption. However, TR of As in C. auratus was above 1.00E-04 threshold value, indicated potential carcinogenic human health risk. The results from this study indicate that although moderately to heavily contamination of Hg, As, and Cd occurred in Dianchi Lake sediment, only Hg and As tend to transport to surface water and accumulate in commercial fish due to their higher mobility in sediment.

Correction to: Bioaccumulation and growth characteristics of Vallisneria natans (Lour.) Hara after chronic exposure to metal-contaminated sediments.

The correct name of the 9th Author is shown in this paper.

Bioaccumulation and growth characteristics of Vallisneria natans (Lour.) Hara after chronic exposure to metal-contaminated sediments.

Metal-contaminated sediments in lakes is a global concern that poses toxicological risk to aquatic organisms. This study performed bioassays using the submerged macrophyte, Vallisneria natans (Lour.) Hara, exposed to contaminated sediments collected from five locations in Dianchi Lake, Yunnan, China. Among the sediments collected, Igeo showed enrichment of As and Cd in Dianchi Lake sediments. In spite of enriched toxic metals at some locations, laboratory bioassays found no significant difference in leaf biomass or leaf photosynthesis rate between the sites. Root biomass and root activity showed significant differences between locations and were negatively correlated with the concentration of As, Cd, Hg, and Pb in sediment but not related to Cr. The above correlations were strongest for Hg and As, respectively. Accumulation of Cd and Pb to leaves of bioassay plants was observed, but this was not evident for As and Cr. Overall, the results indicate that V. natans can be used as a bioassay organism and measures of root toxicity are sensitive to metal concentrations present in Dianchi Lake sediments. Furthermore, the study species holds promise for use as a biomonitor of Cd and Pb sediment metal content.