Hourly concentrations of non-methane hydrocarbons (NMHCs) recorded between June and August 2006, at two monitoring sites (Gijang and Jin) in Busan were analyzed to examine the characteristics and photochemical reactivity of NMHC sources. The two sites represent urban (Jin) and suburban (Gijang) Busan, which is a typical Korean city. Positive matrix factorization (PMF), applied to identify and apportion the sources of NMHCs, revealed nine sources for Gijang and ten sources for Jin. To explore the contribution of each NMHC source to ozone formation at the two sampling sites, the ozone formation potential was estimated for each source. The largest contributors to ozone formation were sources characterized by 1,2,3-trimethylbenzene (26.4%) at Gijang and by toluene, ethylbenzene, and xylenes (22.5%) at Jin, which were composed mostly of heavy hydrocarbons and aromatics. Secondary sources included two coating sources (20.9%, 12.2%) and vehicle exhaust (10.3%) at Gijang and a source represented by toluene (17.4%), vehicle exhaust (15.9%), and a coating-2 source (9.6%) at Jin. Conditional probability function (CPF) and potential source contribution function (PSCF) analysis methods were used to identify the directions of local sources and to locate potential source regions, respectively. The CPF and PSCF results agreed well for the majority of sources resolved by PMF and thus were very useful in identifying the major sources contributing to ozone formation at the two study sites.

Application of one-dimensional transport considering multiple member of decay chain in a single rock fracture has been studied. Input sources for constant, pulse, impulse, Heaviside, and exponential decay have been used to demonstrate the suitability of relevant solutions. It shows that the breakthrough curves of dimensionless concentration for the three-member decay chain for Np-237 and the seven-member chain for Cm-246 can be well presented in the temporal and spatial domains. The analytical solutions of this study can clearly demonstrate the general form of contaminant transport with complete multiple-member decay chain in one-dimensional fractured or porous media of arbitrary analytical input sources without considering the matrix diffusion, which the conceptual model provides an alternative type to demonstrate the fate of radionuclide transport in the geosphere. The solutions are conservatively used to support the performance assessment for disposal site of radioactive waste. An application to a hybrid test site for the final disposal of spent nuclear fuel is newly demonstrated. Proposed solution to simulate the transport of nuclides in the one-dimensional pathway of host rock becomes feasible, so that the simulation and prediction of radionuclide transport of fractured media existing in geosphere can be conservatively performed in the future.

Hexavalent chromium is a heavy metal used in a variety of industrial applications which is highly toxic to humans, animals, plants and microorganisms. Moreover, it is a well-established human carcinogen by the inhalation route of exposure and a possible human carcinogen by the oral route of exposure. Therefore, it should be removed from contaminated waters. Its reduction to trivalent chromium can be beneficial because a more mobile and more toxic chromium species is converted to a less mobile and less toxic form. During the last two decades, there has been important interest in using zero-valent iron (ZVI) as a Cr(VI)-reducing agent. A considerable volume of research has been carried out in order to investigate the mechanism and kinetics of Cr(VI) reduction with ZVI, as well as the influence of various parameters controlling the reduction efficiency. Therefore, the purpose of this review was to provide updated information regarding the developments and innovative approaches in the use of ZVI for the treatment of Cr(VI)-polluted waters.

Mining operations are potential sources of airborne metal and metalloid contaminants through both direct smelter emissions and wind erosion of mine tailings. The warmer, drier conditions predicted for the Southwestern USA by climate models may make contaminated atmospheric dust and aerosols increasingly important, with potential deleterious effects on human health and ecology. Fine particulates such as those resulting from smelting operations may disperse more readily into the environment than coarser tailings dust. Fine particles also penetrate more deeply into the human respiratory system and may become more bioavailable due to their high specific surface area. In this work, we report the size-fractionated chemical characterization of atmospheric aerosols sampled over a period of a year near an active mining and smelting site in Arizona. Aerosols were characterized with a ten-stage (0.054 to 18 μm aerodynamic diameter) multiple orifice uniform deposit impactor (MOUDI), a scanning mobility particle sizer (SMPS), and a total suspended particulate collector. The MOUDI results show that arsenic and lead concentrations follow a bimodal distribution, with maxima centered at approximately 0.3 and 7.0 μm diameter. We hypothesize that the sub-micron arsenic and lead are the product of condensation and coagulation of smelting vapors. In the coarse size, contaminants are thought to originate as Aeolian dust from mine tailings and other sources. Observation of ultrafine particle number concentration (SMPS) show the highest readings when the wind comes from the general direction of the smelting operations site.

This study aimed to optimize two process variables, namely extractant concentration, i.e., di-2-ethylhexylphosphoric acid concentration ([D2EHPA]) and equilibrium pH (pHeq), in Cu(II) extraction from aqueous solutions with a soybean-oil-based organic solvent using response surface methodology by maximizing the percentage extraction (%E). A central composite design was applied, and a regression model for %E was developed. Adequacy of the model was examined, and it was found to be statistically significant. The optimum conditions were determined as follows: [D2EHPA] of 84.71 mM and pHeq of 4.46, which resulted in 99.78% of %E. The experimental value of %E (98.17%) obtained is found to agree satisfactorily with that (99.78%) predicted from the model.

Wastewaters from pulp and paper mills are highly toxic and around 250 xenobiotic compounds have been reported in the effluents. Tannic acid degrading bacterium, Enterobacter sp. was isolated from soil by tannic acid enrichment. This isolate was used for bioremediation of pulp and paper mill effluents. Parameters like temperature, agitation, inoculum size and treatment duration were optimized by using Qualiteck-4 software. Reduction in lignin 73% and colour up to 82% was also observed. Encouraging results were observed is reduction of COD, BOD with 16-h retention time in batch culture.

Critical loads of nitrogen (N) from atmospheric deposition were determined for alpine lake ecosystems in the western US using fossil diatom assemblages in lake sediment cores. Changes in diatom species over the last century were indicative of N enrichment in two areas, the eastern Sierra Nevada, starting between 1960 and 1965, and the Greater Yellowstone Ecosystem, starting in 1980. In contrast, no changes in diatom community structure were apparent in lakes of Glacier National Park. To determine critical N loads that elicited these community changes, we modeled wet nitrogen deposition rates for the period in which diatom shifts first occurred in each area using deposition data spanning from 1980 to 2007. We determined a critical load of 1.4 kg N ha−1 year−1 wet N deposition to elicit key nutrient enrichment effects on diatom communities in both the eastern Sierra Nevada and the Greater Yellowstone Ecosystem.

Diatoms are good indicators of water quality in lotic systems. Unlike in the temperate region, the effect of substrate on diatom-based water quality assessment in tropical streams is not fully understood. The purpose of this study was to assess the effect of substrate on diatom-based multivariate water quality assessment. Epilithic, epiphytic, epipsammic and epipelic diatom community and water quality sampling was done four times at 10 sites during the dry season (2008 and 2009). Artificial substrates (brick and glasses) were also placed at the sampling sites during this period and sampled after 1 month. Cluster analysis was performed to show the main differences and similarities in community composition amongst substrates sampled and amongst sampling sites. The IndVal method was used to identify indicator species characterising different substrates. Canonical correspondence analyses (CCAs) were performed to relate the structure of diatom communities from different substrates to predictor variables. A gradient of increasing metal and organic pollution, eutrophication and ionic strength was observed from the agricultural/forested area to the urban area. Diatom community structure closely reflected this gradient, with communities from polluted sites (8, 9 and 10) being different from other communities. Polluted sites were associated with such species as Nitzschia palea, Plantago lanceolata, Achnanthes exigua, Caloneis hyaline, Cyclotella meneghiniana, Gomphonema parvulum, Fallacia monoculata, Luticola goeppertiana, Pinnularia microstauron, Pinnularia subcapitata and Sellaphora pupula. Indicator species analysis showed that common diatom species were not restricted to a single substrate, though preference was generally high for natural (especially macrophytes) compared to artificial substrates. Six CCAs corresponding to six substrates performed to relate diatom community structure to simultaneous effects of predictor variables explained ∼50% of the diatom species variance in all cases and roughly separated highly polluted sites from the rest of the sites. This indicates that the results of diatom-based multivariate water quality assessment based on different substrates may be interchangeable. Only one substrate has to be collected at each site for water quality assessment surveys, thus avoiding unnecessary expensive and time-consuming oversampling. Given the limitations of artificial substrates, sampling of natural substrates is highly recommended.

Sediment and porewater samples from an enclosed bay receiving stormwater discharge (Skutviken) near the centre of Luleå, northern Sweden were analysed for major and trace elements and 16 polycyclic aromatic hydrocarbons (PAHs). Among the studied metals Cd, Cu, Pb and Zn were enriched at Skutviken. Also, the PAH content was enriched, in particular for phenantrene, anthracene, fluoranthene and pyrene which are regarded as common constituents in stormwater. The use of trace metal ratios provided indications about pollutant sources for the sediment. Cs-137 dating was used to determine historical changes in metal and PAH fixation in the sediment. The bay Skutviken is enclosed through the construction of a road bank since 1962. The enclosure led to reduced water circulation in the bay that promotes the occurrence of anoxic conditions with sulphate reduction within the bay. As a consequence of these conditions, metals are trapped in the sediments as sulphides. This study suggests that enclosed bays with restricted water circulation may be efficient traps for urban pollutants, reducing the present-day input of pollutants to the sea. In areas with postglacial land uplift, where such bays are common, bay sediments are a potential future source of pollutants when uplift results in erosion and oxidation of the sediments.

Imidacloprid is a new insecticide that mimics nicotine, combining its insecticidal activity with a reduced persistence in the environment. The toxicity of imidacloprid to Chironomus riparius Meigen using the formulated product Confidor® from Bayer®, in pulse and continuous exposure, was evaluated in this study. The behavioural response of the midge after toxicant exposure using an online biomonitor was also investigated. Early second-instar C. riparius larvae were exposed in either constant (10 days) or pulse (4 days, followed by 6 days post exposure in clean medium) conditions. Imidacloprid constant exposure resulted in a decrease in growth and impairment of the behavioural pattern of the midge larvae. Pulsed exposure followed by a recovery period revealed a recovery of midge physiological conditions, by reaching a stabilisation of normal behavioural activities and growth among treatments. Moreover, ventilation showed to be a more sensitive parameter by revealing a faster recovery than locomotion. Behaviour alterations may weaken the ability to escape from predators, and reduce food acquisition with consequent growth impairment. These effects may have an impact at the population and community level.