Combined chromium and phenol pollution in a marine prawn fishery

Genome sequencing reveals mechanisms for heavy metal resistance and polycyclic aromatic hydrocarbon degradation in Delftia lacustris strain LZ-C

Strain LZ-C, isolated from a petrochemical wastewater discharge site, was found to be resistant to heavy metals and to degrade various aromatic compounds, including naphenol, naphthalene, 2-methylnaphthalene and toluene. Data obtained from 16S rRNA gene sequencing showed that this strain was closely related to Delftia lacustris. The 5,889,360 bp genome of strain LZ-C was assembled into 239 contigs and 197 scaffolds containing 5855 predicted open reading frames (ORFs). Among these predicted ORFs, 464 were different from the type strain of Delftia. The minimal inhibitory concentrations were 4 mM, 30 µM, 2 mM and 1 mM for Cr(VI), Hg(II), Cd(II) and Pb(II), respectively. Both genome sequencing and quantitative real-time PCR data revealed that genes related to Chr, Czc and Mer family genes play important roles in heavy metal resistance in strain LZ-C. In addition, the Na(+)/H(+) antiporter NhaA is important for adaptation to high salinity resistance (2.5 M NaCl). The complete pathways of benzene and benzoate degradation were identified through KEGG analysis. Interestingly, strain LZ-C also degrades naphthalene but lacks the key naphthalene degradation gene NahA. Thus, we propose that strain LZ-C exhibits a novel protein with a function similar to NahA. This study is the first to reveal the mechanisms of heavy metal resistance and salinity tolerance in D. lacustris and to identify a potential 2-methylnaphthalene degradation protein in this strain. Through whole-genome sequencing analysis, strain LZ-C might be a good candidate for the bioremediation of heavy metals and polycyclic aromatic hydrocarbons.

Distributions and sources of polychlorinated biphenyls in the coastal East China Sea sediments

The Yangtze River estuary (YRE) and the adjacent East China Sea (ECS) inner shelf is an important sink of pollutants originated from mainland China. In this work, we studied the spatial and temporal variations and sources of polychlorinated biphenyls (PCBs) in sediments from the YRE and the ECS inner shelf. Total concentration of 23 PCBs (Σ23PCB) ranged between 24.3 and 343.3 pg/g (with a mean value of 126.7 pg/g), and higher values occurred in the estuarine region. The homolog profile was dominated by 3-5Cl CBs, accounting for 76.1% of Σ23PCB. The Cl proportion ranged from 45.1% to 58.8% (with a mean value of 49.9%); the lowest level appeared in the estuarine region, and it increased with distance from the YRE. Lower chlorinated congeners were carried mainly by the YR into the ocean, to be finally buried in sediments of the estuary region and vicinity. However, higher chlorinated ones were imported mainly via direct emission from local sources, to be finally buried in sediments farther away from the estuary. Of the PCBs in surface sediments, 40.1% came from the YR, 37.9% from the local sources and the rest 22.0% from atmospheric deposition. In a sediment core, we found that 81% of PCBs were technically produced and 19% unintentionally produced in the last century. Before the 1970s, PCB levels were influenced predominantly by the production and consumption of technical PCBs. While in recent decades, the effect of human activities on PCB levels has been increasing continuously.

Evaluation of genotoxicity of combined soil pollution by cadmium and phenanthrene on earthworm

The DNA-damaging effects of the combined pollution of heavy metal and organic contamination on earthworms were evaluated by single cell gel electrophoresis (SCGE) assay. Earthworms Eisenia andrei were exposed to single or combined test compounds in different doses of cadmium (Cd) 5, 10, 50 mg/kg and phenanthrene (Phe) 0.5, 2.5, 12.5 mg/kg with a treatment of 14 d. In SCGE assay, isolated coelomcytes and electrophoresis were employed to determine DNA damage degree after a 14-d treatment by test compounds. The results showed that there was a significant statistical difference between earthworms treated with Cd combined Phe with them treated alone with Cd or Phe. The Olive tail moment (OTM) of SCGE assay using earthworm coelomcytes appears to be a sensitive biomarker for evaluating exposure to genotoxic compounds. These tests also revealed that the interaction between Cd and Phe to DNA damaging effects was negative, and was strongly dependent on the concentration of pollution. This study corresponds to exploratory phase in order to reveal interaction effects of heavy metal and organic contamination on earthworms and then to set up more in-depth analysis to increase progressively the understanding of the genotoxicity mechanisms involved.

Single and joint toxicity of chlorimuron-ethyl, cadmium, and copper acting on wheat Triticum aestivum

Investigation of the toxicological effects of some agricultural pollutants on germination rate and on shoot and root elongation of wheat (Triticum aestivum) was carried out. Seeds of wheat were exposed to various concentrations of chlorimuron-ethyl with or without cadmium and copper addition. The inhibitory rates of seed germination and shoot and root elongation of wheat were calculated. Significant linear relationships between the root and shoot elongation and the concentration of chlorimuron-ethyl with or without copper or cadmium addition were observed. The interactive effects of the three pollutants on seed germination were not significant (P > 0.05), but on shoot and root elongation they were markedly significant (P < 0.01). When concentrations of added Cd2+ or Cu2+ reached the concentration under which the inhibitory rate of wheat root elongation was about 20%, cadmium (or copper) and chlorimuron-ethyl had an antagonistic effect on the inhibition of shoot and root elongation, although the interactive effects of copper were not significant (P > 0.05). However, cadmium (or copper) and chlorimuron-ethyl had significantly synergic effects on the inhibition of shoot and root elongation (P < 0.05) when concentrations of added Cd2+ and Cu2+ reached the concentrations under which the inhibitory rate of root elongation was about 70%. At the high concentration of added cadmium or copper, joint toxicity of chlorimuron-ethyl and the heavy metals was more dependent on the concentrations of the latter. The sensitivity of wheat to the toxicity of the three pollutants was in the following sequence: root elongation>shoot elongation>germination rate.

Joint effects of acetochlor and urea on germinating characteristics of crop seeds

In order to evaluate ecological risk of agrochemicals in common use, joint toxic effects of acetochlor and urea on germinating characteristics of Chinese cabbage (Brassica Pekinensis Rupr) seeds were investigated using the water-culture method and the soil-culture method. The results indicated that excessive application of acetochlor and urea, when the concentrations were higher than 31.3 mg x kg(-1) for acetochlor and 500 mg x kg(-1) for urea, had strong inhibitory effects on the rate of seed germination, root elongation and hypocotyl length of Chinese cabbage. The inhibitory rate of the germinating characteristics of Chinese cabbage seeds was significantly increased with an increase in the concentration of acetochlor or urea. The two agrochemicals in water had a stronger toxicity than these in the soil at the same concentration. Among the three indexes, hypocotyl length was the most sensitive to the toxicity of acetochlor and urea.