The 2′,7′-dichlorofluorescin (DCFH) assay is widely used to measure particle-bound reactive oxygen species (ROS), which are considered as a major contributor leading to the adverse health effects upon exposure to atmospheric particulate matter. DCFH, a non-fluorescent substance that can be oxidized to highly fluorescent dichlorofluorescein (DCF) in the presence of horseradish peroxidase (HRP), is usually used as a probe for ROS determination due to its response to diverse and relevant oxidant species. However, there is limited literature that reports the effects of different experimental conditions in the performance of this assay. In our work, various experimental conditions, such as pH value, incubation temperature, reagent concentration and stability, reaction time, linearity range, and extraction method, were examined and optimized as a pilot study for developing an online system for atmospheric ROS measurement. The results showed that pH value, reagent concentration, and extraction method significantly affect the performance of DCFH assay, while incubation at a specified temperature (37 °C) did not increase the oxidization extent of DCFH. After optimization, some practical samples were measured using different experimental parameters to check the performance of the optimized assay. The comparisons of these measurements showed that optimization can greatly improve the detection limit and reproducibility of the DCFH assay, which can then be employed to better the accuracy of offline and online ROS measurement.

The implantation of wastewater treatment systems aims to minimize environmental impacts, but ultimately generates waste materials, such as sewage sludge, which must be properly discarded. Final disposal in landfills, and incineration are the most commonly used disposal methods, but both constitute a threat to the soil, water, air, and food chain. The most suitable alternative for the disposal of sewage sludge is its use as fertilizer, due to the nutrients in its composition, such as nitrogen, phosphorus, and organic carbon. However, the presence of potentially toxic metals is the main factor that limits such use. Many techniques have been employed in attempt to remove these toxic metals, including physical, chemical, and biological treatments, but the high cost of the physical and chemical treatments, as well as the risk of causing secondary pollution, makes this type of sewage sludge treatment an unsatisfactory option. Therefore, removing toxic metals through biological treatments has become an increasingly popular choice, as such treatments have been shown to be the most economically and environmentally beneficial methods. The aim of the present study was to provide a review of some of the most common alternative treatments for the incineration and disposal of sludge in landfills, emphasizing the physical, chemical, and biological processes that enable the removal of potentially toxic metals, for the purpose of obtaining a final product which can be used as fertilizers in farm soils.

To investigate the effect of different sizes, sex, and exposure time on Cu uptake capacity, mussels Mytilus galloprovincialis of different shell sizes were exposed to different Cu concentrations in different aquariums. In another experiment, mussels were exposed to stable dissolved Cu for 6 days in the laboratory. All mussels tissue concentrations were analyzed using energy dispersive X-ray fluorescence (EDXRF) spectrometry. At the end of uptake, the rate of increase of Cu level in the soft tissues of mussels in different aquariums was 3.84–7.92 times higher than before exposure. While the results of Cu concentrations were negatively correlated with the shell sizes in the control and second groups (r cₒₙₜᵣₒₗ = −0.862, r ₛₑcₒₙd = −0.851 p < 0.05), this relation was not observed in the other groups (p > 0.05). Also, results showed no significant difference between male and female (p > 0.05). On the other hand, Cu concentration values in soft tissue were monitored daily and observed to be increasing up to the third day but afterwards to be descending, thus indicating a significant effect of the exposure time-related Cu uptake by mussels. Therefore, the exposure time to Cu metal of the mussel should be taken into account in the marine pollution investigations. In addition, by using the obtained Cu heavy metal concentration results, the heavy metal intake by the human population was calculated by taking into account daily mussel consumption. The results were examined for potential human health risks and discussed. These results would be helpful to understand factors controlling Cu accumulation in mussels.

To analyze the daytime and phenological variations of canopy O₃ and CO₂ uptake of winter wheat, the canopy fluxes of wheat plants were measured using a chamber system with four different O₃ levels (0, 40, 80, and 120 nmol mol⁻¹) being applied. During the daytime (7:30–18:00 hours), canopy fluxes usually peaked around noon in early growing stages, while a generally decreasing trend from morning to afternoon was observed in the later stages. O₃ and CO₂ fluxes were positively and negatively correlated with O₃ concentration, respectively. Significant differences were observed in O₃ fluxes but CO₂ fluxes among O₃ treatments. Photosynthetically active radiation (PAR) and vapor pressure deficit (VPD) could affect canopy gas uptake in opposite ways. On the phenological timescale, both O₃ and CO₂ fluxes followed the variation of leaf area index (LAI) with the maximum occurring simultaneously at the booting stage. The daytime mean fluxes varied from −10.6 to −17.2 nmol m⁻² s⁻¹ for O₃ and from −5.9 to −19.6 μmol m⁻² s⁻¹ for CO₂. Quantitatively important O₃ deposition (−3.1∼−11.6 nmol m⁻² s⁻¹) was also observed at night with the ratios being about 40∼70 % relative to the daytime O₃ fluxes for most measuring days, which indicates a significant contribution from non-stomatal components to canopy O₃ removal. This study confirms that environmental variables and plant phenology are important factors in regulating canopy O₃ and CO₂ uptake. O₃ exposure (≤120 nmol mol⁻¹) could not significantly affect the CO₂ uptake of wheat canopy in a short time (ca. 10 min).

Contamination due to improper disposal of oilfield drilling waste is a serious environmental problem all over the world. This study used bench-scale experimental columns to investigate the effectiveness of combining soil vapor extraction (SVE) with bioremediation (bioaugmentation plus biostimulation) in treating drilling waste from onshore oil wells. The drilling waste used in this study was heavily contaminated with a total petroleum hydrocarbon (TPH) concentration of 2.5 × 10⁴ mg/kg. After 154 h of SVE operation, the TPH concentrations decreased by 4.7–23.6 %, and continuous SVE operation did not significantly reduce the concentration of residual contaminants. Then, microbial consortium and inorganic nutrients (urea and K₂HPO₄) were employed further to enhance bioremediation, and after 216 h of bioremediation and SVE, 70 % of the residual TPH was removed. Bioremediation enhanced the overall pollutant removal efficiency by fully degrading low volatile compounds and transforming them into more volatile compounds which were extracted by SVE. Results from GC-MS analysis corroborated TPH concentration data showing the occurrence of biotransformation during SVE and bioremediation treatment. Overall, this study demonstrates that SVE combined with bioremediation is an effective technique for handling petroleum drilling waste.

Advanced oxidation of bisphenol A (BPA) in aqueous system by O₃/Na₂S₂O₈ was investigated, the degradation of BPA was affected by ozone concentration, persulfate dosages, initial pH, and BPA concentration. Experimental results indicated that the degradation of BPA was proved to follow the pseudo-first order kinetics model and was enhanced with the increase of O₃ concentration and the decrease of initial BPA concentration. pH played a significant role in the BPA removal especially under the alkaline condition. Free radical species in the O₃/Na₂S₂O₈ system were identified by using tertiary butyl alcohol (TBA) and ethanol (ETOH) as two probes, the results found that the major free radical was SO₄ ⁻ · at acidic condition (pH = 3), and the concentration of ·OH increased with the pH increased. Eight products were detected during the reaction according to liquid chromatograph-mass spectrometry analysis. Most of the intermediates contained quinonoid derivatives, carboxylic acid, and the relevant mechanism for BPA degradation by O₃/Na₂S₂O₈ system were proposed.

This study assessed potential bioaccumulation of various trace elements in grasses and earthworms as a consequence of soil incorporation of organic amendments for in situ remediation of an orchard field soil contaminated with organochlorine and Pb pesticide residues. In this experiment, four organic amendments of differing total organic carbon content and quality (two types of composted manure, composted biosolids, and biochar) were added to a contaminated orchard field soil, planted with two types of grasses, and tested for their ability to reduce bioaccumulation of organochlorine pesticides and metals in earthworms. The experiment was carried out in 4-L soil microcosms in a controlled environment for 90 days. After 45 days of orchardgrass or perennial ryegrass growth, Lumbricus terrestris L. were introduced to the microcosms and exposed to the experimental soils for 45 days before the experiment was ended. Total trace element concentrations in the added organic amendments were below recommended safe levels and their phytoavailablity and earthworm availability remained low during a 90-day bioremediation study. At the end of the experiment, total tissue concentrations of Cu, Cd, Mn, Pb, and Zn in earthworms and grasses were below recommended safe levels. Total concentrations of Pb in test soil were similar to maximum background levels of Pb recorded in soils in the Eastern USA (100 mg kg⁻¹ d.w.) because of previous application of orchard pesticides. Addition of aged dairy manure compost and presence of grasses was effective in reducing the accumulation of soil-derived Pb in earthworms, thus reducing the risk of soil Pb entry into wildlife food chains.

The automobile exhausts are one of the major sources of particulate matter in urban areas and these particles are known to influence the atmospheric chemistry in a variety of ways. Because of this, the oxidation of dissolved sulfur dioxide by oxygen was studied in aqueous suspensions of particulates, obtained by scraping the particles deposited inside a diesel truck exhaust pipe (DEP). A variation in pH showed the rate to increase with increase in pH from 5.22 to about ∼6.3 and to decrease thereafter becoming very slow at pH = 8.2. In acetate-buffered medium, the reaction rate was higher than the rate in unbuffered medium at the same pH. Further, the rate was found to be higher in suspension than in the leachate under otherwise identical conditions. And, the reaction rate in the blank reaction was the slowest. This appears to be due to catalysis by leached metal ions in leachate and due to catalysis by leached metal ions and particulate surface both in suspensions. The kinetics of dissolved SO₂ oxidation in acetate-buffered medium as well as in unbuffered medium at pH = 5.22 were defined by rate law: k ₒbₛ = k ₀ + k cₐₜ [DEP], where k ₒbₛ and k ₀ are observed rate constants in the presence and the absence of DEP and k cₐₜ is the rate constant for DEP-catalyzed pathway. At pH = 8.2, the reaction rate was strongly inhibited by DEP in buffered and unbuffered media. Results suggest that the DEP would have an inhibiting effect in those areas where rainwater pH is 7 or more. These results at high pH are of particular significance to the Indian subcontinent, because of high rainwater pH. Conversely, it indicates the DEP to retard the oxidation of dissolved SO₂ and control rainwater acidification.

The present laboratory study was conducted in pot soil taken from forest. The leaching of calcium (Ca), magnesium (Mg), and potassium (K) (plant macronutrients) due to the application of a nitrogen phosphate-based long-term fire retardant (LTFR) (Fire Trol 931) was investigated. The concentrations of Ca²⁺, Mg²⁺, and K⁺ were measured in the resulting leachates from pots with forest soil and pine tree alone and in combination with fire. Magnesium is a minor component of Fire Trol 931. The leaching of Ca²⁺, Mg²⁺, and K⁺ from treated soils with the retardant pots was significantly greater than that from control pots. The leaching of Mg²⁺ was found to be of small percentage of the initially applied Mg quantities. Fire Trol 931 application resulted in the leaching of Ca²⁺, Mg²⁺, and K⁺ from a typical Mediterranean forest soil in pots, following the application of simulated annual precipitation probably due to ammonium (one of the major retardant components) soil deposition that mobilizes base cations from the soil. It seems that LTFR application may result in chemical leaching from the soil to the drainage water.