Fractionation of heavy metals in surface sediments of Taihu Lake, East China

The BCR (European Communities Bureau of Reference) three-step sequential extraction procedure was applied to fractionate heavy metals in the sediment of Taihu Lake. For the determination of total metal concentration of the sediments, sample digestion was achieved by using HF/H2O2/HNO3 (2/1/1) acid mixture in a microwave-irradiated closed vessel system. The concentrations of Cd, Ni, Cr, Zn, Cu and Pb in various extracts solutions were analyzed by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). The results obtained from the BCR three-step sequential extraction indicated relatively high mobility of Zn, Cu, Pb and Ni in the sediments while Cd and Cr were poorly mobile. Enrichment of heavy metals was found in the sediments collected in the northern parts of Taihu Lake. In the sediments collected in the southern and western sides of the Lake, heavy metal concentrations were relatively low. The relationship between total organic carbon (TOC) and heavy metals concentrations in the sediments is discussed.     

Effects of different concentrations of tetracycline and oxytetracycline on the growth and ecotoxicity in lettuce北大核心CSCD

四环素类抗生素(TCs)是目前我国应用广泛、用量最大的一类抗生素,畜禽粪便和土壤中存在TCs残留,影响蔬菜作物的生长发育. TCs因水溶性较高更容易被植物转运和积累,植物对TCs耐受性机理研究仍不足.为更全面探究土壤TCs对蔬菜的毒性作用,研究不同浓度四环素(TC)和土霉素(OTC)分别对生菜的抗生素残留、生长特征及抗氧化酶系统的影响.结果显示,在0(对照)、2、10、50、250 mg/kg 5个施用水平下,生菜叶片抗生素含量逐渐增加,且土霉素含量始终大于四环素含量.与对照相比,抗生素浓度在50 mg/kg以上时对生菜生长具有显著抑制作用,其中,株高、根长、地上部和地下部鲜重与叶片TC残留量具显著负相关.生菜叶片的脯氨酸含量随浓度增加呈先增加后降低的趋势,在10 mg/kg时达到最大.并且低浓度(2 mg/kg)促进抗氧化酶基因SOD、POD21和CAT的表达,高浓度抗生素(50、250 mg/kg)对其产生抑制作用,10 mg/kg的抗生素处理对SOD、POD21和CAT基因表达的影响在抗生素种类上存在差异.本研究表明抗生素浓度超过50 mg/kg对生菜生长产生抑制作用,脯氨酸和抗氧化酶SOD、POD、CAT的转录水平及其酶活性能快速响应抗生素胁迫,可作为生菜对抗生素抗性的辅助评价指标.(图8表3参19)     

Antioxidant effect of L-cysteine on sodium-valproate-induced oxidative stress in rat liver: biochemical and ultrastructural approaches

L-Cysteine has protective efficacy in cases of oxidative tissue injury. Sodium valproate is widely used as an anticonvulsant and an antidepressant in spite of hepatotoxicity as side effect. The aim of this study was to evaluate the protective role of L-cysteine in liver toxicity induced by sodium valproate overdose. Release of the hepatic enzymes, aspartate aminotransferase and alanine aminotransferase, and levels of lipid profiles, as well as the oxidative, enzymatic, and non-enzymatic antioxidant were assessed. Liver damage was judged histologically. L-Cysteine decreased the activity of alanine aminotransferase and aspartate aminotransferase, as well as improved the level of lipid profile, increased the enzymatic antioxidant (catalase, superoxide dismutase, glutathione peroxidase and glutathione reductase), and decreased the lipid peroxidation. L-Cysteine administration inhibited liver injury of sodium valproate.     

Nitrogen to phosphorus ratios of two understory plant species in response to nitrogen and phosphorus addition in tropical forest of southern China北大核心CSCD

The secondary tropical forests in southern China have suffered from frequent human disturbance and increasing high N deposition. In order to explore the nutrient limitation status in secondary tropical forests of South China, this 3-year field experiment of nitrogen (+N) and phosphorus (+P) addition investigated nitrogen (N) and phosphorus (P) concentrations of the aboveground tissue (leaf and branch) of two widely distributed understory native species Clerodendrum cyrtophyllum and Uvaria microcarpa in a secondary tropical forest of South China. The results showed that: 1) the N and P concentrations of the two species were significantly different (P < 0.001); N and P concentrations of different tissues in the same species were different; N&P addition greatly affected N and P concentrations in branch rather than new leaf and older leaf. 2) +N treatment had no significant effect on N or P concentrations of either species, but significantly decreased N:P ratios (P = 0.001), at the level of 9% for C. cyrtophyllum and 50% for U. microcarpa, respectively. 3) +P treatment had no significant effect on tissue N concentrations, but significantly increased plant P concentrations (P < 0.001), at 54% for C. cyrtophyllum and 88% for U. microcarpa, respectively; +P treatment significantly decreased plant N:P ratios (P < 0.001), at 28% and 60%, respectively. 4) The alterations of P concentrations of two species had significantly negative correlations with N:P alterations under +N/+P treatment (P < 0.001), suggesting that the alteration of P concentrations in plant tissue was the major driver for N:P alteration. Our results show that N and P addition would affect tissue N and P concentrations of the two species, with +P treatment having relatively greater effect on nutrient concentrations than +N treatment; the branch is more sensitive than new or older leaf in response to nutrient addition. Therefore, P availability may be the limiting factor for plant growth in the tropical forests.     

Effect of ultra-micro powder Dendrobium officinale on the molecular diversity of intestinal bacteria in mice with spleen-deficiency constipation北大核心CSCD

This research aimed to study the effect of ultra-micro powder Dendrobium officinale on the molecular diversity of intestinal bacteria in mice with spleen-deficiency constipation, in order to provide scientific basis for ultra-micro D. officinale therapy. The mice with spleen-deficiency constipation in treatment groups were respectively given the traditional decoction of D. officinale and 50% dose ultra-micro powder D. officinale. The metagenome DNA of intestinal flora was extracted from intestinal contents. Then ARDRA analysis was made after PCR by universal primer of bacteria. The results showed that OTUs, Shannon index and Brillouin index were the same between the normal group and the 50% dose ultra-micro powder group, and between the model group and the traditional decoction group, but greater in the former two groups than the latter ones. The similarity coefficient (0.500 0) was bigger between the 50% dose ultra-micro powder group and the normal group than between the model group and the traditional decoction group, which was 0.181 8. Both cluster analysis and principal components analysis showed that the molecular diversity of intestinal microbiotia in mice of 50% dose ultra-micro powder group was the closest to that in the normal group. The results showed that the weakened molecular diversity of intestinal bacteria in mice with spleen-deficiency constipation can be regulated by the two kinds of D. officinale treatments to different extent. The efficacy of 50% dose ultra-micro powder D. officinale is better than the traditional decoction.     

Toxicity evaluation of 10 oil gelling agents北大核心CSCD

Oil gelling agents are widely used in emergency response of marine oil spills. However, the biological toxicity of oil gelling agents is not well understood. This research aimed to evaluate the environmental safety of oil gelling agents used for rapid removal and cleanup of marine oil spills. We used luminescent bacteria (Acinetobacter sp. Tox2 and Acinetobacter sp. RecA) combined with exposure experiment using marine medaka (Oryzias melastigma) juveniles to detect the acute toxicity and genotoxicity of 10 oil gelling agents. As a result, a certain level of acute toxicity was detected from the oil gelling agent FOA and GMN-01 (the toxicity equivalent to 0.067 mg/L and 0.084 mg/L of HgCl2, respectively), and a certain level of genotoxicity was detected from the oil gelling agent NORSOREX (the toxicity equivalent to 0.307 mg/L of MMC) by the luminescent bacteria test. However, no obvious acute toxicity or genotoxicity was detected from the above three oil gelling agents in fish-exposure experiments. Our results suggest that the 10 oil gelling agents have no obvious acute toxicity or genotoxicity to higher organisms (including marine medaka). The luminescent bacteria test is more sensitive in detecting biological toxicity of oil gelling agents. This study provides a reference for environmental safety evaluation of the oil gelling agents used in the cleaning up of the marine oil spills.     

Review on the study of mercury/silver ions-pyrimidine base pairs in DNA duplexes and their application in detection technology北大核心CSCD

Nucleic acids and their analogues are getting more and more attention. Metal-mediated base pairs as a kind of simple and functionalized nucleic acids in special positions have widened the scope of application of functional nucleic acids and their analogues. In this type of base pairs, the representative is the interaction between metal ions and pyrimidine bases, especially the research on thymine-Hg2+-thymine (T-Hg2+-T) and cytosine-Ag+-cytosine (C-Ag+-C) base pairs. This review summarizes the structure and mechanism of metal-mediate pyrimidine base pairs as well as the application in the biochemical analysis. It explores the mode and ratio of coordination between metal ions and base pairs, the effects on the stability of DNA helical structure, the related crystal structure and the three-dimensional configuration information in the DNA helix. The analytical application mainly includes various probes of metal ions, small molecules, protein and the detection of single nucleotide polymorphism. Among them the most widely used metal ions detection, and its combination with spectrum technology, visualization and amplification technology greatly promoted the rapid development of sensitive detection technology. In further studies, it is necessary to reveal the mechanism of interaction between T-Hg2+-T and C-Ag+-C, and more attention should be paid to combining of T-Hg2+-T and C-Ag+-C base pairs with other new technologies. The scope of practical application should also be further extended.     

Characterization and catabolic genes detection of three oil-degrading Rhodococcus spp.北大核心CSCD

Oil pollution is one of the major factors causing environmental deterioration. Bioremediation of oil contaminated environments by microorganisms attracts much research attention. This study aimed to screen efficient oil-degrading bacteria from oil contaminated soil and analyze their characteristics and catabolic genes. Oil-degrading bacteria were screened from oil contaminated soil in minimal medium containing crude oil and identified by morphological, physiological and biochemical characteristics and 16S rDNA sequence analysis. Their growth and degradation characteristics were studied with ultraviolet spectroscopy and GC-MS analysis. The surfactant production was studied by adopting culture method. The major oil-degrading related genes were detected by t he PCR a mplification. As a result, t hree oil-degrading bacteria strains named KB1, 2182 and JC3-47 were isolated from the oil contaminated soil samples. The strains could use crude oil as the sole carbon source to degrade oil with a degrading rate of 41.02%, 32.26% and 55.90%, respectively, when cultured in minimal medium containing crude oil for 3 days. The bacteria were identified to belong to genus Rhodococcus. With 100% similarity of 16S rDNA sequences of the three strains with known ones of Rhodococcus, KB1 was preliminarily identified as Rhodococcus erythropolis, 2182 as Rhodococcus equi, and JC3-47 as Rhodococcus qingshengii. They grew well at 10-50 °C, with the initial pH of 3-9 and the NaCl concentration of 0-5%. The optimal temperature for bacterial growth was 35 °C, 35 °C and 30 °C respectively. KB1 and 2182 could grow at pH 2 and 9.0% of NaCl. The bacteria grew well in broth containing different organic substrates as sole carbon source, such as n-dodecane, n-octadecane, benzene, methylbenzene, xylene and naphthaline. KB1 and JC3-47 could grow well in broth containing pyrene. GC-MS analysis revealed that the bacteria could effectively degrade medium- and long-chain alkane components in crude oil. The bacteria produced biosurfactants and decreased the surface tension of the culture broth. They also showed adhesion activities to n-hexadecane. The oil-degrading related genes such as alkane monooxygenase, aromatic-ring-hydroxylating dioxygenase and catechol dioxygenase genes were detected in all the three strains. Besides, biphenyl dioxygenase genes were detected in KB1 and 2182. The isolated Rhodococcus spp. strains could effectively degrade petroleum hydrocarbons with high adaptabilities to extreme environments such as high salt and low temperature. They are supposed to be applied broadly in the bioremediation of oil contaminated soil in such environments.     

Study of atrazine degradation in soil from Kenyan sugarcane-cultivated fields in controlled laboratory conditions

A study to compare the extent of atrazine mineralization in soils from Kenyan sugarcane-cultivated fields with and without history of atrazine use was carried out in the laboratory under controlled conditions. The study was testing the hypothesis that repeated atrazine application to soil will not result in enhanced atrazine mineralization. The study was carried out with ¹⁴C-uniformly ring-labeled atrazine in a laboratory under controlled conditions. Atrazine mineralization to ¹⁴CO₂ in soil with no history of atrazine use was negligible (0.16%) after 163 days of soil incubation. The three metabolites hydroxyatrazine, desisopropylatrazine, and desethylatrazine in the proportion of 17.7%, 1.3%, and 2.6%, respectively, were in the soil after 75 days. In the soil from the sugarcane-cultivated field with history of atrazine use, atrazine mineralization was 89.9% after 98 days. The same soil, amended with mature compost, showed a lag phase of eight days before rapid atrazine mineralization was observed.     

Methodological approach for metal pollution evaluation in sediments collected from the Taranto Gulf

The concentrations of Hg, Cd, Pb, Cu, Ni, V, and Sn were determined in marine sediments collected from Taranto Gulf (Ionian Sea, Southern Italy). The aim of this article is to study the methodological approach in order to evaluate total metal levels determined in marine sediments of a contaminated area (Taranto Gulf, Southern Italy), to identify contaminated areas and to predict adverse biological effects based on Sediment Quality Guidelines (SQGs). The results are discussed in relation to geological characteristics of sediments in order to define background levels and anthropogenic input. Experimental results were elaborated by multivariate statistical techniques and Geographical Information System (GIS) software. The geoaccumulation index I _geo and two sets of SQGs (in particular (a) the threshold effect level (TEL), the probable effect level (PEL) and (b) the effect range-low (ERL) and the effect range median (ERM)) have been used for environmental evaluation of metal concentrations. Results show that in Taranto coastal area, Mar Piccolo basin represents the most contaminated area. A comparison with results from other Mediterranean areas demonstrates that for some metals (such as Cd, Pb, and Hg) Taranto seas represent one of the most polluted areas in the Mediterranean Sea. A comparison of metal levels with SQGs also suggests an ecotoxicological risk for benthic organisms mainly in the first inlet of Mar Piccolo.