Tracking bioaccumulation in aquatic organisms: A dynamic model integrating life history characteristics and environmental change

We have developed a dynamic model to track the evolution of contaminant concentration in an aquatic organism as a function of season and ontogeny throughout its life cycle. We have focused our analysis on the round goby (Apollonia melanostoma), a globally distributed invasive forage fish. By integrating bioenergetics with a bioaccumulation model, we illustrate how life history characteristics interact to influence contaminant accumulation. We use uncertainty and sensitivity analyses to assess how the model output is affected by uncertainty and variability in model parameters. We then demonstrate the influence of important physiological characteristics on contaminant accumulation with two scenarios. First, we probe the influence of sexual dimorphism by comparing gender-specific accumulation of a standard polychlorinated biphenyl congener, PCB153, in male and female round gobies. We hypothesize that lipid loss in female gobies during spawning season leads to a decrease in the PCB body burden compared to male gobies. Second, we compare PCB accumulation in the round goby and in the mottled sculpin (Cottus bairdi), the native forage fish that the round goby displaced in southern Lake Michigan, to determine whether the invasive species has an intrinsically different bioaccumulation potential than the native one. Our non-intuitive findings from these simulations illustrate how the interaction of growth rate with other life history characteristics lead to unexpected bioaccumulation patterns. The model we present is a flexible tool that integrates complex and dynamic interactions among environmental parameters, thus providing a means to better assess the potential for chemical accumulation in human and wildlife populations, and aiding the development of ecological forecasts.     

Arsenicosis status and urinary malondialdehyde (MDA) in people exposed to arsenic contaminated-coal in China

The current arsenic exposure condition, arsenicosis prevalence, urinary arsenic and MDA (malondialdehyde) concentrations in people were studied. The study area, a village in Xing Ren County in Guizhou Province, PR China, is a coal-borne arsenicosis endemic area that was identified several decades ago. The residents in Xing Ren have been using coal containing high arsenic levels all their life. Urinary arsenic levels of villagers were 192.2+/-22 microg/g creatinine (n=113) in the coal-borne endemic area (Xing Ren county) and were significantly higher than 63.6+/-5.9 microg/g creatinine (n=30) in a neighbouring control site (a village in Xing Yi county). The urinary MDA concentrations of villagers from the endemic area were also significantly higher compared to those of the control area. There was a strong correlation between age and urinary arsenic and MDA concentrations in the endemic area of Xing Ren; urinary arsenic and MDA levels decreased with age. Fifty out of 113 (44.3%) villagers in the endemic area had arsenicosis symptoms and the prevalence in villagers older than 40 y was 100% in male (92.2% overall). Urinary MDA concentration was significantly higher in people with arsenicosis symptoms in the endemic areas. Oxidative stress (urinary MDA concentration) was strongly related to arsenic exposure but not to the age and smoking habit. Higher urinary arsenic and MDA levels in younger villagers from the endemic area suggest that they are having a higher exposure to coal-borne emitted arsenic because they spend more time indoor. There is an urgent need to develop proper intervention methods in the Guizhou endemic areas in order to reduce the risk to the local communities who are still using arsenic contaminated-coal.     

Effect of membrane type and material on performance of a submerged membrane bioreactor

This study evaluated the impact of membrane type and material on filtration performance in a submerged membrane bioreactor (MBR) for municipal wastewater treatment. Three types of microfiltration membranes with similar pore size of 0.1 microm but different materials and types, phase-inversed polytetrafluoroethylene (PTFE), track-etched polycarbonate (PCTE) and track-etched polyester (PETE), were used. Changes in permeability with time for the PCTE and PTFE membranes appeared similarly, whereas the PETE membrane exhibited the most rapid flux decline. Lower TOC in the permeate compared to the supernatant was probably due to a combination of biodegradation by the biofilm (cake layer) developed on the membrane surface and further filtration by cake layer and narrowed pores. The faster permeability decline and higher TOC removal rate of the PETE membrane were attributed to an initial permeate flux higher than an average design flux, which led to a faster rate of fouling and thicker cake layer. Therefore, an MBR should not be operated at a flux higher than the average design flux for a specific type of membrane. A gradual increment of biomass concentration did not significantly affect membrane permeability of each membrane investigated. Dissolved organic carbon fractionation results showed that the composition of each fraction between the supernatant and permeates did not change significantly with time, suggesting that membrane hydrophobicity was not a dominant factor affecting MBR fouling in this study. The organic foulants desorbed from the PCTE membrane contained approximately 60% of hydrophobic fraction, which was probably attributable to the extracellular polymeric substances proteins released from the biomass attached to the membrane. While the total filtration resistance of the PTFE membrane was influenced by a higher surface roughness, those of the PETE and PCTE membranes, which had a similar and lower roughness, were affected by the initial operating flux.     

Association of arsenic and kidney dysfunction in people with diabetes and validation of its effects in rats

We studied villagers with and without diabetes from arsenic-endemic areas and a nearby control site in Xinjiang Autonomous Region, PR China. Water and urinary arsenic were assayed for exposure measurement. Urinary NAG (N-acetyl-beta-glucosaminidase), a kidney function test, blood glucose, triglyceride, cholesterol, high density lipid and low density lipid were measured. Villagers from endemic areas were found to have higher urinary arsenic concentrations. The NAG results also suggest that chronic arsenic exposure presents a significant adverse impact on the kidney function of villagers in the endemic areas. However, blood glucose levels of diabetes individuals were lower than those from the control site. These observations were validated in rats which were chronically exposed to arsenic in drinking water. The distinct relationship between chronic arsenic exposure and diabetes mellitus requires further investigation. A rodent model is a useful tool for study of this type.     

The fate and transport of arsenic species in the aquatic ecosystem: a case study on Bestari Jaya,Peninsular Malaysia

The field of arsenic pollution research has grown rapidly in recent years. Arsenic constitutes a broad range of elements from the Earth’s crust and is released into the environment from both anthropogenic and natural sources due to its relative mobility under different redox conditions. The toxicity of arsenic is described in its inorganic form, as inorganic arsenic compounds can leach into different environments. Sampling was carried out in the Bestari Jaya catchment while using a land use map to locate the site, and experiments were conducted via sequential extraction and inductively coupled plasma optical emission spectroscopy to quantify proportions of arsenic in the sediment samples. The results show that metals in sediments of nonresidual fractions, which are more likely to be likely released into aquatic environments, are more plentiful than the residual sediment fractions. These findings support the mobility of heavy metals and especially arsenic through sediment layers, which can facilitate remediation in environments heavily polluted with heavy metals.     

Selective catalytic reduction of NO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> using RDF char and municipal solid waste char based catalyst

Experiments were performed in order to investigate the possibility for the development of catalysts for low-temperature selective catalytic reduction (SCR) using municipal waste char and RDF byproduct. Physical and chemical activations, using water, and HCl and KOH, were employed to increase the catalytic activities. The characteristics of the activated catalysts were investigated using N₂ adsorption–desorption and FT-IR. The catalysts activated chemically using basic treatment showed higher NO _x removal efficiencies than those activated physically or chemically using acidic treatment. The de-NO _x performance of the activated catalysts was dependent on the chemical properties, such as oxygen functional groups as well as physical properties, such as specific surface area and pore volume. In order to investigate the effect of MnO _x , which has been reported to be efficient for the removal of NO _x in low-temperature SCR processes, the chemically activated catalyst was impregnated with manganese. The Mn-impregnated catalyst had the highest NO _x conversion at all of the temperatures tested in this study.