Optimization of sludge conditioning and dewatering is a continuing challenge for wastewater treatment plants. This study investigated the use of an in-line UV–vis spectrophotometer to optimize the polymer dose during sludge dewatering. The study established a relationship between the optimum polymer dose and residual polymer concentration in filtrate using UV–vis absorbance measurements at 191.5 nm. Experiments were carried out with four different polymers (FloPolymer CA 475, CAB 4500, FloPolymer CB 4350, and FloPolymer CA 4600), and similar results were obtained from all polymers. Detection limits of the polymers ranged from 0.35 to 0.95 mg/L in centrate. The optimum polymer dose was determined based on capillary suction time (CST) and filtration tests, and a relationship between the filtrate absorbance at 191.5 nm and optimum polymer dose was established. In the under-dose range, increasing the polymer dose resulted in a decrease in filtrate absorbance due to improvement in filtrate quality. The optimum polymer dose corresponded to the minimum filtrate absorbance at 191.5 nm. When the optimum dose was exceeded, absorbance values started to increase corresponding to the increase in the residual polymer concentration in filtrate in the over-dose range. These results indicate that real-time optimization of polymer dose can potentially be achieved at wastewater treatment plants using an in-line UV–vis spectrophotometer based on the absorbance of centrate or filtrate samples at 191.5 nm.

During an extended period from 2010–2012 ambient air quality researches, concentration of nitrogen dioxide (NO₂) in the air was measured applying the passive method. In order to evaluate the spatial distribution of pollutants and the major sources, 12 sampling sites across the region were chosen. Additionally, the seasonal changes of this pollutant under different meteorological conditions (air temperature, humidity, wind speed and direction) were investigated. The long-term study showed 3.8 times higher NO₂concentrations in the Mažeikiai urban area (24.2 μg m⁻³) as compared to other locations in the region (6.3 μg m⁻³). This confirms the assumption that the main source of NO₂in this area is motor vehicle exhaust fumes. The analysis of the results obtained in different seasons showed a significant difference (p < 0.05) in NO₂concentrations under different meteorological conditions. The increase in NO₂concentrations was recorded in the winter and late autumn seasons, due to reduced solar radiation and lower temperatures. Cluster analysis results showed that sampling sites can be grouped into different classes based on NO₂main source, motor vehicles and traffic intensity.

Forest ecosystems in the Eastern USA are threatened by acid deposition rates that have increased dramatically since industrialization. We utilized two watersheds at the Fernow Experimental Forest in West Virginia to examine long-term effects of acidification on ecological processes. One watershed has been treated with ammonium sulfate (approximately twice the ambient deposition rate) since 1989 to simulate elevated acidic deposition, while the other served as a control. Prior to treatment, both watersheds were similar in age and species composition. Ten dominant overstory Prunus serotina and Liriodendron tulipifera trees were selected and cored from each watershed to measure bolewood concentrations of essential elements through time. In addition, changes in tree species basal area were analyzed utilizing 50 long-term growth plots. Results of this experiment show lower calcium and magnesium concentration and increased acidic cation concentration for both species in the treated watershed, indicating a negative treatment effect. Growth response, measured through relative growth rates of cored trees and changes in basal area from growth plots, was not as conclusive and appeared to differ by species. The resulting difference in species response indicates that acidification sensitivity is something that land managers should consider when managing forests affected by acidification.

We investigated the effects of road deicer runoff on benthic macroinvertebrate communities in Korean freshwaters focusing on the effects of CaCl₂deicer. Quantitative field sampling was conducted at eight sites (lakes and streams) in South Korea, and toxicity tests were conducted on 48-h lethal and effective concentrations (LC₅₀and EC₅₀) of road deicer (CaCl₂74 %) and high-grade CaCl₂(96 %) on five selected macroinvertebrate species (Gammarus sobaegensis, Caridina denticulata denticulata, Glyptotendipes tokunagai, Cloeon dipterum, and Ecdyonurus levis). Although Cl⁻concentrations were significantly different between the seasons (before and after snowfall) at most of the study sites, community values (species richness, density, dominance index, and diversity index) were not significantly different between the seasons. In the bioassay, 2.85 g L⁻¹CaCl₂elicited abnormal swimming behavior of test organisms based on EC₅₀values. The LC₅₀values of the five test species ranged from 3.54 to 20.73 g L⁻¹. For all tested species, the LC₅₀of road deicer was higher than that of high-grade CaCl₂. This study shows that despite the heavy application of road deicers during the snowy season, the deicer may not directly affect benthic macroinvertebrate communities over short time periods because Cl⁻concentrations in the field sites (<0.025 g L⁻¹) were much lower than the LC₅₀values. Because the quantity of deicers used in this region continues to increase, long-term research into the effects of deicers on benthic macroinvertebrates is needed.

Tropospheric ozone (O₃) has long been documented to cause an injury to plants, but a plants’ protectant, widely applicable in agronomical practice, does not exist. We evaluated the potential antiozonate efficacy of the antitranspirant di-1-p-menthene (Vapor Gard) compared with ethylenediurea (EDU) on Bel-W3 tobacco plants. Plants were treated either with water, or by EDU (10, 100, and 500 mg dm⁻³), or by vapor (1, 5, 10, and 50 ml dm⁻³) and were exposed either to O₃-enriched (90 ppb) or O₃-free air, for 12 days and 8 h day⁻¹. EDU when applied at 10 mg dm⁻³did not protect the plants against O₃, but when applied at 100 and 500 mg dm⁻³offered a significant protection to the plants. Vapor, when applied at 1 ml dm⁻³did not protect the plants against O₃, neither by terms of foliar visible injury nor by terms of aboveground biomass. In addition, when applied at 10 and 50 ml dm⁻³caused phytotoxicity to all the plants, which it was expressed as necrotic spots on the leaves’ surface, misshaping of the leaves, or short plants' height.It is obvious that vapor does not protect Bel-W3 tobacco plants against O₃. The antiozonate role of di-1-p-menthene is species-specific and probably occurs only under short-term exposures.

In order to determine human exposure to the indoor toxicant, selection of dust fraction and understanding dust particle size distribution in settled indoor dust are very important. This study examined the influence of dust particle size on the concentration of polybrominated diphenyl ethers (PBDEs) congeners, assessed the distribution of dust particle size and characterized the main indoor emission sources of PBDEs. Accordingly, the concentrations of PBDE congeners determined in different indoor dust fractions were found to be relatively higher in the order of dust particle size: 45–106 μm > (<45 μm) > 106–150 μm. The finding shows arbitrary selection of dust fractions for exposure determination may result in wrong conclusions. Statistically significant moderate correlation between the concentration of Σ₉PBDEs and organic matter content calculated with respect to the total dust mass was also observed (r = 0.55, p = 0.001). On average, of total dust particle size <250 μm, 93.4 % (m/m%) of dust fractions was associated with less than 150 μm. Furthermore, of skin adherent dust fractions considered (<150 μm), 86 % (v/v%) is in the range of particle size 9.25–104.7 μm. Electronic materials treated with PBDEs were found the main emission sources of PBDE congeners in indoor environment. Based on concentrations of PBDEs determined and mass of indoor dust observed, 150 μm metallic sieve is adequate for human exposure risk assessment. However, research in this area is very limited and more research is required to generalize the fact.

We analyzed, for the first time, the different fractions of metals present in the spent catalyst and changes they undergone during bioleaching and chemical leaching. Before bioleaching, Al (83.9 %) was found mainly in the residual fraction of the pretreated spent catalyst. Ni (61.3 %) was mainly present in the exchangeable fraction exhibiting its high environmental mobility. V (58.5) and Mo (49.3 %) mainly existed in the oxidizable fraction suggesting that highly oxidizing conditions would liberate these metals from the spent catalyst. During bioleaching with Acidithiobacillus thiooxidans, almost complete solubilization of the exchangeable as well as of reducible fraction was observed. Due to strong acidic conditions, part of oxidizable fraction of these metals was also solubilized. Bioleaching also affected the fractionation of metals remaining in the treated spent catalyst. At the end of the process, most of the metals remaining in the spent catalyst were found in the more stable fractions ensuring the safe disposal of spent catalyst. The leaching yields and fractionation behavior of metals during chemical leaching was found to be identical. The results of the present study strongly suggest that bioleaching is an effective method for removing metals from the spent catalyst.

The nanoscale zero-valent iron grafted on acid-activated attapulgite (A-nZVI) was prepared by a liquid-phase reduction method and used for Cr(VI) removal from solution with enhanced efficiency. The structure of the composite A-nZVI was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller surface area analysis. nZVI was well-dispersed on the surface of acid-treated attapulgite, and no obvious aggregation was observed due to the support of rod-like structure of attapulgite, which is beneficial to Cr(VI) removal. Batch experiments revealed that the removal of Cr(VI) using A-nZVI was consistent with pseudo-first-order reaction kinetics, and removal efficiency was up to 98.73 % within 60 min for 100 mL 20 mg/L Cr(VI) at the initial pH 7.0 and 4.0 g/L A-nZVI. The pseudo-first-order rate constant kₒbₛwas independent of initial Cr(VI) concentration, but there was a good linearity (r² = 0.95) between kₒbₛand the A-nZVI dosage. This study demonstrates that A-nZVI has the potential to become a promising material for in situ groundwater remediation.

A mesocosm experiment was established to evaluate the effect of two organic wastes: fermented sugar beet residue (SBR) and urban waste compost on the stimulation of plant growth, phytoaccumulation of heavy metals (HM) and soil biological quality and their possible use in phytostabilization tasks with native (Piptatherum miliaceum, Retama sphaerocarpa, Bituminaria bituminosa, Coronilla juncea and Anthyllis cytisoides) and non-native (Lolium perenne) plants in a heavy metal-contaminated semiarid soil. Except R. sphaerocarpa, SBR increased the contents of shoot N, P and K and shoot biomass of all plants. The percentage of mycorrhizal colonization was not affected by the organic amendments. The highest increase in dehydrogenase and β-glucosidase activities was recorded in SBR-amended P. miliaceum. SBR decreased toxic levels of HM in shoot of P. miliaceum, mainly decreasing Fe and Pb uptake to plants. This study pointed out that the SBR was the most effective amendment for enhancing the plant performance and for improving soil quality. The combination of SBR and P. miliaceum can be regarded the most effective strategy for being employed in phytostabilization projects of this contaminated site.

In a study on the behaviour of pesticides in a soil–plant–water system, the quick, easy, cheap, effective, rugged and safe (QuEChERS) method for analysing pesticide or metabolite residues in soil and maize (leaves, roots and kernels) was optimized and validated. The pesticides bentazone, chloridazon and terbuthylazine and their metabolites bentazone-methyl, chloridazon-desphenyl, chloridazon-methyl-desphenyl, terbuthylazine-desethyl and terbuthylazine-2-hydroxy were selected in this study. The QuEChERS extracts obtained from soil and maize matrices and the collected leachate were analysed by liquid chromatography–electrospray ionization–tandem mass spectrometry (LC–ESI–MS/MS) using a high-performance liquid chromatography and an ultra-high-performance liquid chromatography (UHPLC) analytical column. As expected, shorter run times and higher sensitivity were achieved with the UHPLC column. Validation studies focused on recovery, repeatability, matrix effects, limits of detection and quantification. Recoveries (and repeatability relative standard deviation (RSD)) of the spiked samples were in the range of 55 to 98 % (7.4–18) in soil, 23 to 101 % (1.7–20) in maize and 82 to 105 % (4.4–25) in leachate. Quantification limits were lower than 3.0 μg kg⁻¹ in soil, 7.3 μg kg⁻¹ in maize and 0.080 μg l⁻¹ in leachate.