Effect of humic acids on physicochemical property and Cd(II) sorption of multiwalled carbon nanotubes

Zinc pyrithione is used as an antifouling agent. However, the environmental impacts of zinc pyrithione have recently been of concern. Zinc induces diverse actions during oxidative stress; therefore, we examined the effect of zinc pyrithione on rat thymocytes suffering from oxidative stress using appropriate fluorescent probes. The cytotoxicity of zinc pyrithione was not observed when the cells were incubated with 3 μM zinc pyrithione for 3 h. However, zinc pyrithione at nanomolar concentrations (10 nM or more) significantly increased the lethality of cells suffering from oxidative stress induced by 3 mM H₂O₂. The application of zinc pyrithione alone at nanomolar concentrations increased intracellular Zn²⁺ level and the cellular content of superoxide anions, and decreased the cellular content of nonprotein thiols. The simultaneous application of nanomolar zinc pyrithione and micromolar H₂O₂ synergistically increased the intracellular Zn²⁺ level. Therefore, zinc pyrithione at nanomolar concentrations may exert severe cytotoxic action on cells simultaneously exposed to chemicals that induce oxidative stress. If so, zinc pyrithione leaked from antifouling materials into surrounding environments would be a risk factor for aquatic ecosystems. Alternatively, zinc pyrithione under conditions of oxidative stress may become more potent antifouling ingredient.     

Electrogeneration of H(2) for Pd-catalytic hydrodechlorination of 2,4-dichlorophenol in groundwater

A novel electrolytic groundwater remediation process, which used the H₂ continuously generated at cathode to achieve in situ catalytic hydrodechlorination, was developed for the treatment of 2,4-dichlorophenol (2,4-DCP) in groundwater. Catalytic hydrodechlorination using Pd supported on bamboo charcoal and external H₂ showed that 2,4-DCP was completely dechlorinated to phenol within 30 min at pH ? 5.5. In a divided electrolytic system, the catalytic hydrodechlorination of 2,4-DCP in cathodic compartment by H₂ generated at the cathode under 20 and 50 mA reached 100% at 120 and 60 min, respectively. Two column experiments with influent pHs of 5.5 (unconditioned) and 2 were conducted to evaluate the feasibility of this process. The 2,4-DCP removal efficiencies were about 63% and nearly 100% at influent pHs of 5.5 and 2, respectively. Phenol was solely produced by 2,4-DCP hydrodechlorination, and was subsequently degraded at the anode. A low pH could enhance the hydrodechlorination, but was not necessarily required. This study provides the preliminary results of a novel effective electrolytic process for the remediation of groundwater contaminated by chlorinated aromatics.     

Historical change of mercury pollution in remote Yongle archipelago, South China Sea

We collected three ornithogenic coral sand sedimentary profiles from Jinyin Island, Jinqing Island and Guangjin Island of Yongle archipelago, South China Sea and reconstructed the deposition flux of anthropogenic Hg over the past 700 years in the study area. On the whole, the anthropogenic Hg flux is relatively low; it remained at a low level before the Industrial Revolution with a small peak at about 1450-1550 AD, which may record the enhanced metallurgy activity in Ming Dynasty of China. During the 20th century, the deposition flux of anthropogenic Hg increased rapidly, but two troughs occurred during the periods around 1940s and 1970s, corresponding to the economic depression caused by World War II, Civil War in China (1945-1949), and the Culture Revolution (1966-1976) in China. Since the 1970s the deposition flux of anthropogenic Hg has been persistently increasing, apparently the result of fast economic development in East and Southeast Asia countries around South China Sea.     

Chronic toxicity of copper on embryo development in Chinese toad, Bufo gargarizans

This study examined the effects of copper exposure on embryonic development of Chinese toad, Bufo gargarizans. Firstly, the LC₅₀ values from 24 to 96 h of exposure were 3.61 × 10⁻⁶ M, by means of a 4 d toxicity test with B. gargarizans embryos. Secondly, Chinese toad embryos were exposed to 10⁻⁹-10⁻⁶ M copper from mid gastrula stage to operculum completion stage. Measurements included mortality, tadpole weight, tadpole total length, growth retardation, duration of different embryo stages and malformation. Embryonic survival was not affected by copper. Relative to control tadpoles, significantly decreased weight and total length were found at 10^-9-10^-6 M reduced percentage of the embryos in right operculum stage after 10 d exposure to copper and reduced percentage of embryos in operculum completion stage after 12 d exposure to copper were also observed. Moreover, the duration of embryonic development increased at neural, circulation and operculum development stage in copper-treated groups. For the scanning microscope and histological observation, the abnormalities were malformation of wavy dorsal fin, flexural tail, curvature body axis, yolk sac oedema and reduced pigmentation in the yolk sac. Histopathological changes in olfactory, retinal epithelium and skin were also observed. DNA strand breaks exposed to the copper were analyzed by DNA ladder. In conclusion, copper induced toxic effects on B. gargarizans embryos. The present study indicated chronic toxicity tests may provide more accurate way in formulating the “safe levels” of heavy metals to amphibian.     

Organochlorine pesticides in soil under irrigated cotton farming systems in Vertisols of the Namoi Valley, north-western New South Wales, Australia

Organochlorine pesticides (OCPs) such as DDT and DDE have been detected in the surface 0.2 m of Vertisols in the lower Namoi Valley of north western New South Wales, Australia even though they have not been applied to crops since 1982. However, their presence in the deeper soil horizons has not been investigated. The objective of this study was to determine if OCPs were present to a depth of 1.2 m in Vertisols under irrigated cotton farming systems in the lower Namoi Valley of New South Wales. Soil was sampled from the 0-1.2 m depths in three sites, viz. the Australian Cotton Research Institute, ACRI, near Narrabri (149°36′E, 30°12′S), and two cotton farms near Wee Waa (149°27′E, 30°13′S) and Merah North (149°18′E, 30°12′S) in northern New South Wales, Australia. The OCPs detected and their metabolites were α-endosulfan, β-endosulfan, endosulfan sulphate, DDD, DDE, DDT and endrin. The metabolite DDE, a breakdown product of DDT, was the most persistent OCP in all depths analysed. Endosulfan sulphate was the second most persistent followed by endrin > α-endosulfan > β-endosulfan > DDT and DDD. DDT was sprayed extensively in the lower Namoi Valley up to the early 1980s and may explain the persistence of DDE in the majority of soil samples. Dicofol and Dieldrin, two OCPs previously undocumented in Vertisols were also detected. The movement of OCPs into the subsoil of Vertisols may occur when irrigation or rain transports soil colloids and organic matter via preferential flow systems into the deeper layers of a soil profile. Persistence of OCPs was closely correlated to soil organic carbon concentrations. The persistence in soil of OCP’s applied to cotton crops grown more than two decades ago suggests that they could enter the food chain. Their presence at depths of 1.2 m suggests that they could move into groundwater that may eventually be used for domestic and stock consumption.     

Detection of early effects of a single herbicide (diuron) and a mix of herbicides and pharmaceuticals (diuron, isoproturon, ibuprofen) on immunological parameters of Pacific oyster (Crassostrea gigas) spat

In the context of massive summer mortality events of the Pacific oyster Crassostrea gigas, the aim of this study was to investigate the early effects on genes, enzymes and haemocyte parameters implicated in immune defence mechanisms in C. gigas oysters exposed to a potentially hostile environment, i.e. to an herbicide alone or within a mixture. Following 2 h of exposure to the herbicide diuron at 1 μg L⁻¹, the repression of different genes implicated in immune defence mechanisms in the haemocytes and the inhibition of enzyme activities, such as laccase-type phenoloxidase (PO) in the plasma, were observed. The inhibition of superoxide dismutase (SOD) activity in the plasma was also observed after 6 and 24 h of exposure. In the mixture with the herbicides diuron and isoproturon, and the pharmaceutical ibuprofen, catecholase-type PO activity in the plasma and the percentage of phagocytosis in the haemocytes were reduced after 6 h of exposure. Our results showed that early effects on molecular, biochemical and cellular parameters can be detected in the presence of diuron alone or within a mixture, giving an insight of its potential effect in situations that can be found in natural environments, i.e. relatively high concentrations for short periods of time.     

Transformation of tetrabromobisphenol A in the presence of different solvents and metals

Solvent-based separation method is presumably an efficient and environmentally beneficial approach for elimination of brominated flame retardants (BFRs) from waste electrical and electronic equipment (WEEE). The overall goal of this study was to evaluate possible effects of organic solvent on the behavior of BFRs during solvent-based processing of WEEE. We initiated a set of batch experiments for examining the rates and possible pathways of transformation of a representative BFR (tetrabromobisphenol A, TBBPA) using acetone, toluene, and methanol as the solvents. Our results showed that toluene and methanol had no effect on the transformation of TBBPA, but approximately 20% of TBBPA (100 mg L⁻¹) was transformed by acetone within 2 h at 50 °C. Analysis of the products with GC-MS showed that two high-molecular-weight products (MW = 586) were major products of the transformation reactions. The role of acetone as a reactant in the transformation of TBBPA was further validated with dueterated acetone. In addition, the effects of co-existing metals in WEEE (i.e., Zn, Cu, and Ni) on the transformation of TBBPA in the solvent systems were investigated. These metals tested were found to greatly enhance the rates of TBBPA transformation. The metal facilitated solvent reactions with TBBPA may lower the extractability of TBBPA by formation of larger and less soluble products, hence potentially increasing the cost for separating the chemical from WEEE.     

Toxicological effect of MPA-CdSe QDs exposure on zebrafish embryo and larvae

Cadmium selenium (CdSe) quantum dots (QDs) are semiconductor nanocrystals that hold wide range of applications and substantial production volumes. Due to unique composition and nanoscale properties, their potential toxicity to aquatic organisms has increasingly gained a great amount of interest. However, the impact of CdSe QDs exposure on zebrafish embryo and larvae remains almost unknown. Therefore, the lab study was performed to determine the developmental and behavioral toxicities to zebrafish under continuous exposure to low level CdSe QDs (0.05-31.25 mg L⁻¹) coated with mercaptopropionic acid (MPA). The results showed MPA-CdSe exposure from embryo to larvae stage affected overall fitness. Our findings for the first time revealed that: (1) The 120 h LC₅₀ of MPA-CdSe for zebrafish was 1.98 mg L⁻¹; (2) embryos exposed to MPA-CdSe resulted in malformations incidence and lower hatch rate; (3) abnormal vascular of FLI-1 transgenic zebrafish larvae appeared after exposure to MPA-CdSe including vascular junction, bifurcation, crossing and particle appearance; (4) larvae behavior assessment showed during MPA-CdSe exposure a rapid transition from light-to-dark elicited a similar, brief burst and a higher basal swimming rate; (5) MPA-CdSe induced embryos cell apoptosis in the head and tail region. Results of the observations provide a basic understanding of MPA-CdSe toxicity to aquatic organisms and suggest the need for additional research to identify the toxicological mechanism.     

Effect of microbial siderophore DFO-B on Cd accumulation by Thlaspi caerulescens hyperaccumulator in the presence of zeolite

Hyperaccumulators are grown in contaminated soil and water in order that contaminants are taken up and accumulated. Transport of metals from soil to plant is initially dependent on the solubility and mobility of metals in soil solution which is controlled by soil and metal properties and plant physiology. Complexation with organic and inorganic ligands may increase mobility and availability of metals for plants. In this work the influence of desferrioxamine-B (DFO-B), which naturally is produced in the rhizosphere, and zeolite on Cd accumulation in root and shoot of Thlaspi caerulescens (Cd hyperaccumulator) was investigated. Plants were grown in pots with clean quartz sand, amended with 1% zeolite; treatment solutions included 0, 10, and 100 μM Cd and 70 μM DFO-B. Addition of zeolite to the quartz sand significantly reduced Cd concentration in plant tissues and translocation from root to shoot. On contrary, DFO-B considerably enhanced Cd sorption by roots and translocation to aerial part of plants. Treating the plants with zeolite and DFO-B together at 10 μM Cd resulted in reduction of the bioaccumulation factor but enhancement of Cd translocation from root to shoot at the rate of 13%. In contrast, at 100 μM Cd in the solution both bioaccumulation and translocation factors decreased. Total metal accumulation as a key factor for evaluating the efficiency of phytoremediation was highly influenced by treatments. Presence of zeolite in pots significantly decreased total Cd accumulation by plants, whereas, DFO-B clearly enhanced it.     

Ozonation as an advanced oxidant in treatment of bamboo industry wastewater

The present study employed ozonation process to treat the bamboo industry wastewater (BIWW). The impact of ozone dosage and initial organic concentration on color, COD and TOC removal rates were studied along with characterization of the major organics in raw and treated wastewater. The results suggested the ozone dosage of 3.15 g h⁻¹ (concentration 52.5 mg L⁻¹) was suitable for the treatment. After 25 min ozonation of 1 L raw wastewater, the color, COD and TOC removal efficiencies were 95%, 56% and 40%, respectively, with an influent COD concentration of 835 mg L⁻¹. The ratio of kg O₃ kg⁻¹ COD at 3.15 g h⁻¹ was 2.8 (<3), revealing that ozonation was a cost effective process for tertiary treatment of BIWW. Longer oxidization time was required to achieve similar results for raw wastewater with higher COD concentration. The chromatogram from gel permeation chromatography revealed that ozonation resulted in the breakdown of high molecular weight compounds into lower molecular weight components but could not completely mineralize the organic matter. The majority of these compounds were identified in both raw and ozonated samples via GC-MS analysis. In addition to ester derivatives as the main intermediates of ozonation, 1-chloroctadecane, methyl stearate, benzophenone and α-cyperone were identified as the by-products of ozonation.