Distribution and assessment of Pb in the supergene environment of the Huainan Coal Mining Area,Anhui, China

Coal mining area is highly subject to lead (Pb) pollution from coal mining activities. Several decades of coal mining and processing practices in dozens of coal mines in the Huainan Coal Mining Area (HCMA) have led to the accumulation of massive amounts of coal gangue, which piled in dumps. In order to investigate the impacts of coal gangue dumps on Pb level in the supergene media of the HCMA, a systematic sampling campaign comprising coal gangue, soil, wheat, and earthworm samples was conducted. The average Pb content in the coal mining area soil is 24 mg/kg, which is slightly higher than the associated coal gangues (23 mg/kg) and markedly higher than reference region soil (12.6 mg/kg). Soil in the HCMA present a slight to moderate Pb contamination, which might be related to the weathering and leaching of coal gangue dumps. Lateral distribution of Pb in HCMA soil differed among individual coal mines. The soil profile distribution of Pb depends on both natural and anthropogenic contributions. Average Pb content is higher in roots than in stems, leaves, and wheat husks, while the Pb level in seeds exceeded the maximum Pb allowance for foods (Maximum Levels of Contaminants in Foods of China, GB 2762–2012). Earthworms in the selected area are significantly enriched in Pb, suggesting higher bio-available Pb level in soil in the HCMA.     

Pollution magnet: nano-magnetite for arsenic removal from drinking water

Arsenic contamination in groundwater is a severe global problem, most notably in Southeast Asia where millions suffer from acute and chronic arsenic poisoning. Removing arsenic from groundwater in impoverished rural or urban areas without electricity and with no manufacturing infrastructure remains a significant challenge. Magnetite nanocrystals have proven to be useful in arsenic remediation and could feasibly be synthesized by a thermal decomposition method that employs refluxing of FeOOH and oleic acid in 1-octadecene in a laboratory setup. To reduce the initial cost of production, $US 2600/kg, and make this nanomaterial widely available, we suggest that inexpensive and accessible “everyday” chemicals be used. Here we show that it is possible to create functional and high-quality nanocrystals using methods appropriate for manufacturing in diverse and minimal infrastructure, even those without electricity. We suggest that the transfer of this knowledge is best achieved using an open source concept.     

Fourier analysis of the roll-up and merging of coherent structures in shallow mixing layers

The current study investigates the role of nonlinearity in the development of two-dimensional coherent structures (2DCS) in shallow mixing layers. A nonlinear numerical model based on the depth-averaged shallow water equations is used to investigate temporal shallow mixing layers, where the mapping from temporal to spatial results is made using the velocity at the center of the mixing layer. The flow is periodic in the stream-wise direction and the transmissive boundary conditions are used in the cross-stream boundaries to prevent reflections. The numerical results are examined with the aid of Fourier decomposition. Results show that the previous success in applying local linear theory to shallow mixing layers does not imply that the flow is truly linear. Linear stability theory is confirmed to be only valid within a short distance from the inflow boundary. Downstream of this linear region, nonlinearity becomes important for the roll-up and merging of 2DCS. While the energy required for the merging of 2DCS is still largely provided by the velocity shear, the merging mechanism is one where nonlinear mode interaction changes the velocity field of the subharmonic mode and the gradient of the along-stream velocity profile which, in turn, changes the magnitude of the energy production of the subharmonic mode by the velocity shear implicitly. The nonlinear mode interaction is associated with energy up-scaling and is consistent with the inverse energy cascade which is expected to occur in shallow shear flows. Current results also show that such implicit nonlinear interaction is sensitive to the phase angle difference between the most unstable mode and its subharmonic. The bed friction effect on the 2DCS is relatively small initially and grows in tandem with the size of the 2DCS. The bed friction also causes a decrease in the velocity gradient as the flow develops downstream. The transition from unstable to stable flow occurs when the bed friction balances the energy production. Beyond this point, the bed friction is more dominant and the 2DCS are progressively damped and eventually get annihilated. The energy production by the velocity shear plays an important role from the upstream end all the way to the point of transition to stable flow. The fact that linear stability theory is valid only for a short distance from the inflow boundary suggests that some elements of nonlinearity is incorporated in the mean velocity profile in experiments by the averaging process. The implicit nature of nonlinear interaction in shallow mixing layers and the sensitivity of the nonlinear interaction to phase angle difference between the most unstable mode and its subharmonic allows local linear theory to be successful in reproducing features of the instability such as the dominant mode of the 2DCS and its amplitude.     

Trace metals in mussels from mariculture zones, Hong Kong

In 1997, concentrations of cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb) and nickel (Ni) were analysed in green-lipped mussels (Perna viridis) from three mariculture zones located in the north-east (Kat O), south (Lo Tik Wan) and to the west (Ma Wan) of Hong Kong. Spatial differences in the concentration of metals were found, chromium and copper were higher at Ma Wan and Lo Tik Wan compared to Kat O in the north-east. In contrast, the highest levels of lead (mean = 4.37 microg/g dry wt) were recorded at Kat O. There were no differences in the level of nickel between the study sites. A comparison of the metal concentrations in mussels with the results of a previous study seven years before, in 1990, showed a twofold increase in the mean levels of cadmium for all three sites. However, levels of the other metals in 1997 were lower by 12-32% for chromium, 32-39% for copper and 24-25% for nickel. The greatest reductions were recorded for lead: Kat O (39%), Ma Wan (51%) and Lo Tik Wan (75%). This may be related to the introduction of lead-free petrol in 1991. Despite the apparent reduction in some heavy metal bioaccumulation between 1990 and 1997, from a public health risk perspective, the data suggest a continued need for monitoring of heavy metals in mussels from mariculture zones.     

Same but different: sources of natural resource management advice for lifestyle oriented rural landholders

Amenity migration to attractive and accessible non-metropolitan areas changes social and environmental relations with consequences for natural resource management and landscape composition and trajectories. Lifestyler oriented rural landholders are often cast as a problem for land management and extension. Managers and some researchers see them as a cause of landscape and social fragmentation and report difficulties in engaging such landowners on natural resource management issues and responsibilities. In contrast, limited existing research indicates that lifestylers do join and form networks of personal and other contacts for advice and support in land management. We contribute to this research with a survey of rural landholders in southeastern New South Wales (NSW). We explicitly compare the sources of advice for land management for lifestylers with those of farmers. We focus on the types of sources available to rural landholders in Australian regions and their relative importance to these two landholder groups. We find that lifestylers and farmers are different in their sources of advice but that both prefer personal sources rather than sources such as agencies. We reflect on the significance of the differences for engagement with lifestyle oriented rural landowners and for understanding landscape change.     

Identification of a new Irgarol-1051 related s-triazine species in coastal waters

A previously unknown s-triazine species present in commercially available Irgarol-1051, a booster biocide additive in copper-based antifouling paints for the replacement of organotin-based antifoulants, has been identified in the coastal aquatic environment. After careful isolation, purification and characterization by high resolution MS-MS and (1)H NMR, the molecular structure of that unknown species is found to be N,N'-di-tert-butyl-6-methylthiol-s-triazine-2,4-diamine (designated as M3). Levels of Irgarol-1051, its major degradation product (M1) and the newly identified M3 in the coastal waters of Hong Kong, one of the world's busiest ports located in the southern coast of China, were monitored by SPME-GC-MS and SPME-GC-FID. Water samples from five locations within Hong Kong waters were analysed and the levels of Irgarol-1051, M1 and M3 were found to be 0.1-1.6 microg l(-1), 36.8-259.0 microg l(-1) and 0.03-0.39 microg l(-1), respectively. Our results indicate that M3 is relatively stable against photo- and bio-degradation and may pose considerable risk to primary producer communities in the coastal marine environment.     

Field depuration and biotransformation of paralytic shellfish toxins in scallop<Emphasis Type="Italic"> Chlamys nobilis</Emphasis> and green-lipped mussel<Emphasis Type="Italic"> Perna viridis</Emphasis>

Under laboratory conditions, the scallop Chlamys nobilis and the mussel Perna viridis were exposed to N-sulfocarbamoyl toxins (C2 toxin), a paralytic shellfish toxin (PST), by feeding a local toxic strain of the dinoflagellate Alexandrium tamarense (ATDP) that produced C2 toxin exclusively. The bivalves were subsequently depurated in the field, and their depuration kinetics, biotransformation and toxin distribution were quantified. Depuration was characterized by a rapid loss within the first day, followed by a secondary slower loss of toxins. In the fast depuration phase, scallops detoxified PSTs more quickly than the mussels (depuration rate constants for scallops and mussels were 1.16 day^–1 and 0.87 day^–1, respectively). In contrast, the mussels detoxified PSTs more quickly than the scallops in the slow depuration phase, and the calculated depuration rate constants (mean+SE) from day 2 to day 13 were 0.063+0.009 day^–1 and 0.040+0.019 day^–1 for mussels and scallops, respectively. The differences in the appearances of gonyautoxins, GTX2 and GTX3, and their decarbamoyl derivatives, dcGTX2, dcGTX3 and GTX5, which are all derivatives of C2 toxin, indicated active and species-specific biotransformation of the algal toxins in the two bivalves. In both species of bivalves, the non-viscera tissue contained fewer toxins and lower concentrations than the viscera-containing tissue compartment. In scallops, very little toxin was distributed in the adductor muscle. In mussels, most of the PSTs were found in the digestive gland with significant transport of toxins into the digestive gland from other tissues during the course of depuration. The toxin profiles of scallops and mussels differed from each other and from that of the toxic algae fed. A significant fraction of GTX5 was detected in the mussels but not in the scallops. Our study demonstrates a species specificity in the depuration kinetics, biotransformation and tissue distribution of PSTs among different bivalves.Communicated by T. Ikeda, Hakodate     

Exposure to metals (Ca,K, Mn) and road salt (NaCl) differentially affect development and survival in two model amphibians

ABSTRACT

Human activity has led to widespread chemical alteration of natural environments. Aquatic ecosystems are especially susceptible to chemical changes, including those caused by runoff and invasive species. Here, we examined the effects of water chemistry, specifically sodium chloride as well as three metals (Ca, K, and Mn) known to differ between native and invasive wetland plant species’ leaf tissues, on the development of two model amphibians: the native Northern leopard frog, Lithobates pipiens, and the non-native African clawed frog, Xenopus laevis. We exposed frog eggs to metal treatment solutions and measured time to hatching (TTH), and following hatching, we exposed tadpoles to a lethal concentration of sodium chloride and recorded time to death (TTD). We found that increasing metal concentrations generally resulted in acceleration of TTH for Xenopus tadpoles, but had no effect on leopard frogs. However, increasing metal concentrations (Ca, Mn) increased leopard frog tadpole susceptibility to NaCl (decreased TTD), while increasing metal concentrations (Ca, K) generally resulted in decreased Xenopus tadpole susceptibility to NaCl. Overall, our data suggest that invasive amphibians may be more tolerant to chemical changes than native amphibians, including those driven by the introduction of invasive plant species.     

Human health risk assessment of organochlorines associated with fish consumption in a coastal city in China

Food consumption is an important route of human exposure to organochlorines (OCs). In order to assess the potential health risks associated with these contaminants due to fish consumption, five species of fish were collected from a local market in Zhoushan City, an island in the East China Sea. Dioxin-like compounds, such as polychlorinated dibenzo-p-dioxins/ dibenzofurans, in the fish samples were screened by H4IIE-luc cell bioassay, and the concentrations of specific organochlorines were measured by gas chromatograph-electron capture detector (GC-ECD). The bioassay results indicated that concentrations of dioxin-like compounds in the fish samples were below detection limit (0.64 pg/mL). The concentrations of OC pesticides and PCBs ranged from 0.67 to 13 and 0.24 to 1.4 ng/g wet wt., respectively. Significantly, concentrations of p,p'-DDE in fish meat were comparatively high (average 3.9 ng/g wet wt.) compared with the other OC pesticides. The daily fish consumption, based on a dietary survey conducted among 160 local healthy residents, was determined to be 105 g/person. The relevant cancer benchmark concentrations of HCB, dieldrin, chlordane, DDTs and PCBs were 0.36, 0.04, 1.6, 1.7, and 0.29 ng/kg per day, respectively, based on the local diet. The hazard ratios (HRs), based on non-cancer endpoints were all less than 1.0, while the HRs based on cancer were greater than 1.0 for certain contaminants based on the 95th centile concentration in fish tissue.     

A comparative investigation on the biosorption of lead by filamentous fungal biomass

The removal of lead from aqueous solutions by adsorption on filamentous fungal biomass was studied. Batch biosorption experiments were performed to screen a series of selected fungal strains for effective lead removal at different metal and biomass concentrations. Biosorption of the Pb²⁺ ions was strongly affected by pH. The fungal biomass exhibited the highest lead adsorption capacity at pH 6. Isotherms for the biosorption of lead on fungal biomass were developed and the equilibrium data fitted well to the Langmuir isotherm model. At pH 6, the maximum lead biosorption capacity of Mucor rouxii estimated with the Langmuir model was 769 mg/g dry biomass, significantly higher than that of most microorganisms. Biomass of Mucor rouxii showed specific selectivity for Pb²⁺ over other metals ions such as Zn²⁺. Ni²⁺ and Cu²⁺. This fungal strain may be applied to develop potentially cost-effective biosorbent for removing lead from effluents. The technique of scanning electron microscopy coupled with X-ray dispersion analysis shows that Pb²⁺ has exchanged with K⁺ and Ca²⁺ on the cell wall of Mucor rouxii, thereby suggesting ion exchange as one of the dominant mechanisms of metal biosorption for this fungal strain.