Ratios of acid volatile sulfides (AVS) and simultaneously extracted metals (SEM) have been used extensively for predicting bioavailability of divalent metals (i.e., Cd, Cu, Pb, Ni, Zn) in sediments of aquatic environments. However, the role of sulfides (as AVS) as a toxicant has been largely ignored. The aim of this research was to measure relationships of AVS (as sodium sulfide [Na₂S]-amended sediment) and toxicity to a sensitive benthic amphipod Hyalella azteca to evaluate the exposure-response relationships among a series of sulfide exposures. The specific objectives were to (1) measure SEM/AVS ratios in a series of sodium sulfide (Na₂S·9H₂O)-amended sediments producing a range of sulfide concentrations and (2) measure responses of H. azteca (as mortality) in 96-h static sediment toxicity tests to exposures of Na₂S-amended sediments. Amended sediments had a predictable increase in AVS concentrations and a concomitant decrease in ∑SEM/AVS ratios. Increasing concentrations of AVS resulted in a range of ∑SEM/AVS ratios that varied over more than an order of magnitude from 0.185 to 0.006. H. azteca survival decreased with increasing concentrations of “excess” AVS, with 96-h no observable effect concentration (NOEC) and LC₅₀ of 0.041 and 0.019 ∑SEM/AVS, respectively. Clearly, the SEM/AVS model provides a useful tool for evaluating potential bioavailability of divalent metals and predicting ecological risk; however, this study demonstrates the need to consider sulfide (as AVS) as a potential source of toxicity in situations with low [<<1] ∑SEM/AVS ratios.

Eight wheat cultivars were grown in soil amended with arsenate (Asⱽ) at a concentration of 15 mg As kg⁻¹ soil, with or without a triple super phosphate amendment of 40 mg P kg⁻¹ soil. All eight wheat cultivars accumulated higher As in stems/leaves (9–23 μg As g⁻¹) and chaff (9–22 μg As g⁻¹) compared with the grain (0.6–1.6 μg As g⁻¹). The As present in stems/leaves, grain and chaff was found as inorganic As species—Asⱽ or arsenite (Asᴵᴵᴵ). For most cultivars, increased P availability had minimal influence on As accumulation in chaff tissues. If this data is reflective of what occurs in situ, then As can accumulate in chaff at similar concentrations to stem and leaf tissues which are much higher than in grain. Further research is required to determine the risks of As accumulation in livestock products (meat and dairy) when fed with As-contaminated wheat chaff.

The study of the time series from the township of Campo Grande in the State of Mato Grosso do Sul (from January 2004 to 31 December 2010) is presented. Various statistical methods were used for the data analysis. Using robust statistics, very pronounced skewness of the ozone volume part distribution during each month of the year was obtained. The variability in data is the largest during a month of September. The average annual values have asymmetrical distribution of the ozone volume fraction. Within the measured period, these averages are between 15 and 20 ppb. Particularly pronounced ozone distribution asymmetry throughout the year 2007 could be explained by observing meteorological parameters. Principal component analysis (PCA) presented here clearly shows that air temperature and wind speed are contributing factors in ozone formation, while relative humidity and atmospheric pressure cause the decrease in the ozone volume fraction in the air. Further, the hierarchical cluster analysis (CA) was performed for meteorological and ozone data using the Ward’s methods. The correlation between ozone and the effective temperature index (TEv) showed a development of the ozone with high temperature of air. From the Pearson’s correlation coefficients, it is clear that the relative humidity and the air temperature have a negative effect on respiratory system, causing respiratory illnesses.

Lignin-derived methoxyphenols (MPs) with Fe³⁺-reducing activity were used as potential mediators to increase the decolorization of dyes by classical Fenton (Fe²⁺/H₂O₂) and Fenton-like reactions (Fe³⁺/H₂O₂). In this study, several MPs such as vanillin, vanillic alcohol, syringaldehyde, ferulic, vanillic, and syringic acids were evaluated. The results showed that all MPs displayed similar prooxidant activities in the decolorization of methylene blue, chromotrope 2R, methyl orange, and phenol red. For example, the reaction performed with Fe³⁺/H₂O₂ decolorized 27 % of chromotrope 2R, whereas the treatments with Fe³⁺/H₂O₂/MP decolorized around 70 % of the same dye after 60 min. For Fe²⁺/H₂O₂ systems, two stages of decolorization were visibly observed. In the first stage, the MPs inhibited the treatments, and then they increased the decolorization rate in the second stage. Prooxidant and antioxidant properties were observed for decolorization of methylene blue performed in the presence of low and high concentrations of vanillin, respectively. Overall, the MPs increased dye decolorization without increasing the consumption of H₂O₂.

In this paper, we report on the development of a simple, fast, and environment-friendly UV/O₃-based method as an improved alternative to the conventional chemical methods using dichromate or permanganate for determining chemical oxygen demand (COD) in water. In the method through the continuous monitoring of O₃ and CO₂ (concentration and flow rate) before and after reaction, COD can be accurately determined. During the experiment, sample solutions with known COD concentration of 25, 12.5, 5, 2.5, and 1 ppm were first used to validate the feasibility of this new technique. These samples were treated under ambient temperature and pressure for 15 min before the complete digestion time for each sample was measured by analyzing the produced CO₂ concentration. After digestion, residual O₃ dissolved in solution was quantified by the indigo method. A linear relationship between the O₃ consumption and COD value was observed, and the slope of calibration curve was determined to be 0.34 with a R ² of 0.991. Detection limit of the current experimental setup is 0.81 ppm with a measurement range of 1–25 ppm. The precision of the COD measurement is within 5% of the actual concentration. This developed UV/O₃ method demonstrates viability in being applied to fast, reliable, and accurate COD monitoring.

The cleansing efficiencies of laundry detergents depend on composition and variation of ingredients such as surfactants, phosphate, and co-builders. Among these ingredients, surfactants and phosphate are considered as hazardous materials. Knowledge on compositions and micellar behavior is very useful for understanding their cleansing efficiencies and environmental impact. With this view, composition, critical micelle concentration, and dissolved oxygen level in aqueous solution of some laundry detergents available in Bangladesh such as keya, Wheel Power White, Tibet, Surf Excel, and Chaka were determined. Surfactant and phosphate were found to be maximum in Surf Excel and Wheel Power White, respectively, while both of the ingredients were found to be minimum in Tibet. The critical micelle concentration decreased with increasing surfactant content. The amount of laundry detergents required for efficient cleansing was found to be minimum for Surf Excel and maximum for Chaka; however, cleansing cost was the highest for Surf Excel and the lowest for Tibet. The maximum amount of surfactants and phosphate was discharged by Surf Excel and Wheel Power White, respectively, while discharges of both of the ingredients were minimum for Tibet. The maximum decrease of dissolved oxygen level was caused by Surf Excel and the minimum by Tibet. Therefore, it can be concluded that Tibet is cost-effective and environment friendly, whereas Surf Excel and Wheel Power White are expensive and pose a threat to water environment.

Within the Global Mercury Observation System (GMOS) project, long-term continuous measurements of total gaseous mercury (TGM) were carried out by a monitoring station located at Celestun, Yucatan, Mexico, a coastal site along the Gulf of Mexico. The measurements covered the period from January 28th to October 17th, 2012. TGM data, at the Celestun site, were obtained using a high-resolution mercury vapor analyzer. TGM data show values from 0.50 to 2.82 ng/m³ with an annual average concentration of 1.047 ± 0.271 ng/m³. Multivariate analyses of TGM and meteorological variables suggest that TGM is correlated with the vertical air mass distribution in the atmosphere, which is influenced by diurnal variations in temperature and relative humidity. Diurnal variation is characterized by higher nighttime mercury concentrations, which might be influenced by convection currents between sea and land. The back trajectory analysis confirmed that local sources do not significantly influence TGM variations. This study shows that TGM monitoring at the Celestun site fulfills GMOS goals for a background site.

The rapid increase in anthropogenic nitrogen (N) load in urbanized environment threatens urban sustainability. In this study, we estimated the amount of reactive N (Nr) as an index of N pollution potential caused by human activities, using the megacity of Beijing as a case study. We investigated the temporal changes in Nr emissions in the environment from 2000 to 2012 using a multidisciplinary approach with quantitative evaluation. The Nr emissions presented slightly increasing during study period, and the annual emission was 0.19 Tg N, mainly resulting from fuel combustion. Nevertheless, the Nr output intensity resulting from inhabitants’ livelihoods and material production had weakened over the study period. The evaluation results showed that the environmental measures to remove Nr in Beijing were efficient in most years, suggesting that progress in mitigating the growth of the Nr load in this urban environment was significant. Further measures based on N offset are suggested that could help alleviate the environmental pressure resulting from anthropogenic Nr emissions. These could provide theoretical support for the sustainable development of megacities.

A bacterial strain CMGCZ was isolated from an abandoned oil field soil sample and identified as Rhodococcus sp. by 16S rRNA sequencing. Rhodococcus sp. CMGCZ was investigated for the degradation of model polycyclic aromatic hydrocarbons (PAHs) and Iranian light crude oil (ILCO) as a sole carbon source in minimal medium. Biodegradation enhancement was attained by supplementing the minimal medium with yeast extract (YE). Rhodococcus sp. CMGCZ was capable to degrade 13.2 % naphthalene (Nap), 13.1 % phenanthrene (Phe), and 99.3 % fluoranthene (Fla) in 1 week and 11 % aliphatic fraction of ILCO in 2 weeks as a sole carbon and energy source. Effect of YE supplementation on degradation potential of Rhodococcus sp. CMGCZ depended upon the added hydrocarbon in the medium. YE completely inhibited Nap degradation, slightly enhanced degradation of Phe (14.8 %) and ILCO aliphatics (13.2 %), and promoted a more rapid degradation of Fla (100 %). YE addition promoted rapid degradation of Fla and eliminated delay of 24 h in Fla degradation that was observed in minimal medium. Rhodococcus sp. CMGCZ was capable to degrade high concentrations of Fla (1000 mg l⁻¹). Rieske [Fe₂-S₂] center was amplified in Rhodococcus sp. CMGCZ that exhibited homology with Rieske [Fe₂-S₂] domain protein of Mycobacterium species and pahAC gene of uncultured bacterium clones.

In this work, an analytical method for the determination of the 16 polycyclic aromatic hydrocarbons (PAHs), classified as priority pollutants by the US Environmental Protection Agency (EPA), on bitter orange leaves has been optimised and validated. The method has been applied to the evaluation of the applicability of leaves of bitter orange tree as a bioindicator of urban atmospheric pollution by these contaminants. Leaves of bitter orange trees were collected from 13 sampling points in Seville city (South of Spain). Sampling points were located in high-density traffic streets (n = 5), in low-density traffic streets (n = 5) and in urban parks (n = 3). Fourteen of the 16 PAHs monitored were detected in bitter orange leaves. The highest mean concentrations corresponded to BaA, Phen, Pyr and Flt. The concentrations in high-density traffic streets were similar to those in low-density traffic streets. Lower concentrations were found in leaves from parks. PAH diagnostic ratios were applied to identify and to assess pollution emission sources. Diagnostic ratios obtained were consistent with traffic emissions as the main source of PAH to urban air. Based on the obtained results, leaves from bitter orange trees appears to be a promising inexpensive passive sampler suitable for extensive sampling in time and space that can be applied to evaluate risk assessment of urban population to PAH air pollution.