BACKGROUND AND PURPOSES: The pathways used by microorganisms for the metabolism of every xenobiotic substrate are specific. The catabolism of a xenobiotic goes through a series of intermediate steps and lower intermediates (metabolites) appear in sequence. The structure of the metabolites can be similar to the parents due to kinship. The purposes of this study were to examine if the degradation pathways that were developed for a parent xenobiotic are effective to degrade the parent’s lower metabolites, and if the reverse is true. MATERIALS AND METHODS: The xenobiotic substrates, 2,4-dichlorophenoxyacetic acid (2,4-D, the parent xenobiotic) and its metabolite 2,4-dichlorophenol (2,4-DCP), were independently subjected to acclimation and degradation tests by the biomasses of mixed-culture activated sludge and a pure culture of Arthrobacter sp. RESULTS: Activated sludge and Arthrobacter sp. that were acclimated to 2,4-D effectively degraded 2,4-D and the lower metabolites of 2,4-D, typically 2,4-DCP. During the degradation of 2,4-D, accumulations of the lower metabolites of 2,4-D were not found. The degradation pathways acquired from acclimation to 2,4-D are effective for all the metabolites of 2,4-D. However, pathways acquired from acclimation to 2,4-DCP are not effective in the degradation of the parent 2,4-D. CONCLUSIONS: Microorganisms acclimated to 2,4-D evolve their degradation pathways by a scheme that is different from the scheme the microorganisms employ when they are acclimated to the metabolites of 2,4-D.

Continental-scale distribution and inter-continental transport of four polychlorinated biphenyl (PCB) congeners (28, 101, 153, 180) from 1950 to 2010 were studied using the global multicompartment chemistry transport model MPI-MCTM. Following identical primary emissions for all PCB congeners into air, most of the burden is stored in terrestrial (soil and vegetation) compartments. Thereby, PCB-28, PCB-101 and PCB-153 show a shift of the soil burden maxima from source to remote regions. This shift is downwind with regard to the westerlies for Eurasia and upwind for North America and more prominent for the lighter PCBs than for PCB-153 or PCB-180. In meridional direction, all congeners’ distributions underwent a northward migration in Eurasia and North America since the 1950s. Inter-continental transport from Eurasian sources accounts largely for contamination of Alaska and British Columbia and determines the migration of the PCB distribution in soil in North America. Trans-Pacific transport occurs mainly in the gas phase in boreal winter (December–January–February) at 3–4 km altitude and is on a multi-year time scale strongly linked to the atmospheric pressure systems over the Pacific. Inter-continental transport of the lighter, more volatile PCBs is more efficient than for the heavier PCBs.

This study evaluates the effect of integrated solar-assisted advanced oxidation process (AOP) and biological treatment on the extent of degradation of effluents from chlorination (C) and first alkaline extraction (E1) stages of soda pulp bleaching in agro-residue-based pulp and paper mill. Biodegradation of the effluents was attempted in suspended mode using activated sludge from the functional pulp and paper industry effluent treatment plant acclimatized to effluents in question. The photocatalytic treatment was employed using zinc oxide (ZnO) in slurry mode for decontamination of effluents in a batch manner and the degradation was evaluated in terms of reduction in chemical oxygen demand. The biological treatment (24 h) of C and E1 effluent resulted in 30 and 57 % of degradation, respectively. Solar-induced AOP of C and E1 effluents resulted in 53 and 43 % degradation under optimized conditions (2.5 g L−1 ZnO at pH 8.0) after 6 h of exposure. For C effluent, a short duration of solar/ZnO (1 h) prior to biological treatment reduced the time required at biological step from 24 to 12 h for almost same extent (92 %) of degradation. However, sequential biological treatment (24 h) followed by solar/ZnO (2 h) resulted in 85.5 % degradation. In contrast, in the case of E1 effluent, sequential biological (24 h)–solar/ZnO (2 h) system effectively degrades effluent to 95.4 % as compared to 84.8 % degradation achieved in solar/ZnO (2 h)–biological treatment (24 h) system. In the present study, the sequencing of photocatalysis with the biological treatment is observably efficient and technically viable process for the complete mineralization of the effluents.

PURPOSE: Exploratory data analysis (EDA) is applied in this research to study the behavior of radioactive aerosols present in the surface atmosphere of Granada, using 7Be as radiotracer. The reason for this study is to reduce the large number of parameters involved in understanding their behavior, given the complexity of the atmosphere. METHODS: Aerosol particles were collected weekly in Granada (Spain) over a 5-year period. Low-background gamma spectrometry was used to determine concentrations of 7Be-aerosol activity. The variables studied were: 7Be concentration, cosmic ray intensity, temperature, temperature interval, rainfall, relative humidity, and Saharan intrusions. Least significant difference test (LSD), hierarchical cluster analysis (HCA), and principal component analysis (PCA) with varimax rotation have been applied to study the datasets. RESULTS AND DISCUSSION: The results of our study reveal that aerosol behavior is represented by two principal components which explain 86.23 % of total variance. Components PC1 and PC2 respectively explain 74.61 and 11.62 % of total variance. PC1 explains the cyclical and seasonal pattern of the samples, while PC2 is related to the production of 7Be. In addition, PCA and HCA show good distribution of the samples by families with two groups, summer and winter, at the extremes and spring–autumn in the middle. This result corroborates that there are no differences between spring and autumn in the climate of Granada. CONCLUSIONS: EDA has been found to be quite useful in studying the behavior of radioactive aerosols in the surface atmosphere of a city with the climate and geographical characteristics of Granada.

PURPOSE: Persistent organic pollutants (POPs) are of global concern due to their ubiquitous presence and toxicity. The occurence of polychlorinated dibenzo-p-dioxins (PCDDs), -dibenzofurans (PCDFs), co-planar biphenyls (PCBs), hexachlorocyclohexanes (HCH), dichlorodiphenyltrichloroethanes (DDT), and organochlorine pesticides (OCPs) in forest soil collected from Taurus mountains may have adverse effects on the environment and health. The aim of the study was to investigate the outcome and distribution of POPs in the environment and the possible grasshopper effect along an altitude transect from sea level up to nearly 2,000 m a.s.l at a spatial distance of about 60 km in the southeastern Turkish Mediterranean Sea. METHODS: The samples were collected at a height of 121, 408, 981, 1,225, 1,373, 1,639, and 1,881 m above sea level from Taurus Mountains, Turkey. The results were confirmed using high-resolution gas chromatography–high-resolution mass spectrometry. RESULTS: The levels of the PCDD in forest soil from Taurus Mountains varied from nearly 4 to 12 pg g−1 dry weight (dw). PCDF concentrations ranged from 2 to 7 pg g−1 dw. Considerably high DDT levels detected in five stations indicated (3,223–24,564 pg g−1) its extensive local application or atmospheric transport. PCB levels were determined between 80 and 288 pg g−1 dw. HCH concentrations ranged from 141 to 1,513 pg g−1 dw. The other OCP was between 102 and 731 pg g−1. CONCLUSION: Although the use of POPs has been banned, our results show that they could still be found in Turkey. Their presence may be attributed to the degradation of pesticides which are newly banned and, as well as to the atmospheric migration and deposition. The lattitude of sampling sites, the chemical, and physical parameters of soil have observed no effect on the fate of POPs in the environment.

The purpose of this study was to link toxicokinetics/toxicodynamics (TK/TD) and bioavailability-based metal uptake kinetics to assess arsenic (As) uptake and bioaccumulation in three common farmed species of tilapia (Oreochromis mossambicus), milkfish (Chanos chanos), and freshwater clam (Corbicula fluminea). We developed a mechanistic framework by linking damage assessment model (DAM) and bioavailability-based Michaelis–Menten model for describing TK/TD and As uptake mechanisms. The proposed model was verified with published acute toxicity data. The estimated TK/TD parameters were used to simulate the relationship between bioavailable As uptake and susceptibility probability. The As toxicity was also evaluated based on a constructed elimination–recovery scheme. Absorption rate constants were estimated to be 0.025, 0.016, and 0.175 mL g−1 h−1 and As uptake rate constant estimates were 22.875, 63.125, and 788.318 ng g−1 h−1 for tilapia, milkfish, and freshwater clam, respectively. Here we showed that a potential trade-off between capacities of As elimination and damage recovery was found among three farmed species. Moreover, the susceptibility probability can also be estimated by the elimination–recovery relations. This study suggested that bioavailability-based uptake kinetics and TK/TD-based DAM could be integrated for assessing metal uptake and toxicity in aquatic organisms. This study is useful to quantitatively assess the complex environmental behavior of metal uptake and implicate to risk assessment of metals in aquaculture systems.

INTRODUCTION: Mercury is a high-priority regulatory concern because of its persistence and bioaccumulation in the environment and evidence of its having serious adverse effects on the neurological development of children. DISCUSSION: Mercury is released into the atmosphere from both natural and anthropogenic sources. Coal-fired utilities are considered to be one of the largest anthropogenic mercury emission sources. The period since the late 1990s has been marked by increasing concern over mercury emissions from combustion systems to the extent that a number of national governments have either already implemented or are in the process of implementing, legislation aimed at enforcing tighter control over mercury emissions and a reduction in mercury consumption. CONCLUSION: This review examines the most important national and international policies and agreements for controlling mercury emissions from coal-fired combustion systems. To provide a global perspective, this study lists the countries with the largest estimated mercury emissions and regulatory efforts to reduce them.

INTRODUCTION: The unhairing step, a part of the beamhouse process, is particularly polluting, generating an alkaline wastewater with high concentrations of organic and inorganic matter. The aim of this study was to evaluate the treatment of this industrial wastewater using a combination of biological and microfiltration processes. MATERIALS AND METHODS: The performance of the activated sludge system (AS) was evaluated under varying organic loading rate (OLR) from 0.9 to 3.4 kg chemical oxygen demand (COD) m−3 day−1 and decreasing hydraulic retention time (HRT) from 3 to 1.6 days. RESULTS: For an HRT of 3 days, the increase of OLR significantly affected the removal of organic matter. Therefore, the biological organic matter removal of unhairing wastewater decreased from 92% to 66% for COD and from 87 to 53% for biological oxygen demand (BOD5). GC-MS analyses showed that biological treatment of unhairing wastewater contributed to the removal of long chain fatty acids and their degradation products. Microfiltration of unhairing wastewater was performed using 0.2 μm pore-size membranes in tangential filtration. The highest removal efficiencies were obtained for bacteria (100%) and turbidity (98.4%) which confirmed the importance of the microfiltration step in treatment of unhairing wastewater. The result showed that the flux decay rate was greatest at the start of the microfiltration assay (90 L h−1 m2), becoming 60.7 L h−1 m2 after 32 min. CONCLUSION: This change indicated that fouling occurred rapidly once the membrane module was put into operation.