Influence of ageing of residues on the availability of herbicides for leaching

Losses by leaching of chlorotoluron, isoproturon and triasulfuron from small intact columns of a structured clay loam and an unstructured sandy loam soil were measured in five separate field experiments. In general, losses of all three herbicides were greater from the clay loam than from the sandy loam soil and the order between herbicides was always triasulfuron > isoproturon > chlorotoluron. Differences between experiments were also consistent for every soil/herbicide combination. There was no relationship between total loss and either total rainfall or cumulative leachate volume. When weighting factors were applied to the rainfall data to make early rainfall more important than later rainfall, there were significant positive relationships between cumulative weighted rainfall and total losses. Also, there were significant negative correlations between total losses and the delay to accumulation of 25 mm rainfall (equivalent to one pore volume of available water) in the different experiments. In laboratory incubations, there was a more rapid decline in aqueous (0.01 M calcium chloride) extractable residues than in total solvent extractable residues indicating increasing sorption with residence time. However, the rate of change in water extractable residues could not completely explain the decrease in leachability with ageing of residues in the field. Short-term sorption studies with aggregates of the two soils indicated slower sorption by those of the clay loam than by those of the sandy loam suggesting that diffusion into and out of aggregates may affect availability for leaching in the more structured soil. Small scale leaching studies with aggregates of the soils also demonstrated reductions in availability for leaching as residence time in soil was increased, which could not be explained by degradation. These results therefore indicate that time-dependent sorption processes are important in controlling pesticide movement in soils, although the data do not give a mechanistic explanation of the changes in leaching with ageing of residues.     

Simultaneous enhancement of sludge dewaterability and removal of sludge-borne heavy metals through a novel oxidative leaching induced by nano-CaO2

Environmental Science and Pollution Research - The production of sewage sludge with the presence of various contaminants has been a serious issue for the operation of wastewater treatment plants on...     

A lysimeter experiment to investigate temporal changes in the availability of pesticide residues for leaching

Leaching of three pesticides (isoproturon, chlorotoluron and triasulfuron) and a tracer (bromide) were determined in four contrasting soils ranging in texture from sandy loam to clay. The compounds were applied to undisturbed columns of soil and four columns for each soil were randomly selected and leached with 24-mm equivalent of water at prescribed time intervals (3, 9, 24, 37 and 57 d after application). A rapid decline in leached loads of isoproturon and chlorotoluron as time from application to irrigation increased was observed in all soils. In contrast, triasulfuron and bromide loads only decreased rapidly in the clay soil. Bromide losses decreased with decreasing clay contents of the soil and therefore with a decrease in structural development. Magnitudes of pesticide losses varied from soil to soil, depending on structural development and the organic carbon content. Pesticide degradation experiments on disturbed and undisturbed soil samples showed that the rapid decline of leached loads with time was faster than could be explained by degradation alone. Five physico-chemical processes are put forward to explain the different patterns of pesticide leached loads observed in the soils: (1) relative extent of preferential flow, (2) sorption capacity of the compounds to the different soils, (3) extent of degradation of the compounds in the soil, (4) variation in sorption kinetics between compounds associated with pesticide diffusion into soil aggregates, and (5) protection of the compounds by a combination of intra-aggregate diffusion and the presence of preferential flow pathways.     

Remediation of heavy metal polluted sediment by suspension and solid-bed leaching: estimate of metal removal efficiency

Remediation of heavy metal polluted sediment by extracting the metals with sulfuric acid can be performed as follows: abiotic suspension leaching, microbial suspension leaching, abiotic solid-bed leaching, and microbial solid-bed leaching. Abiotic leaching means that the acid is directly added, while microbial leaching means that the acid is generated from sulfur by microbes (bioleaching). These four principles were compared to each other with special emphasis on the effectiveness of metal solubilization and metal removal by subsequent washing. Abiotic suspension leaching was fastest, but suspending the solids exhibits some disadvantages (low solid content, costly reactors, permanent input of energy, high water consumption, special equipment required for solid separation, large amounts of waste water, sediment properties hinder reuse), which prevent suspension leaching in practice. Abiotic solid-bed leaching implies the supply of acid by percolating water which proceeds slowly due to a limited bed permeability. Microbial solid-bed leaching means the generation of acid within the bed and has been proven to be the only principle applicable to practice. Metal removal from leached sediment requires washing with water. Washing of solid beds was much more effective than washing of suspended sediment. The kinetics of metal removal from solid beds 0.3, 0.6 or 1.2m in height were similar; when using a percolation flow of 20lm(-2)h(-1), the removal of 98% of the mobile metals lasted 57-61h and required 8.5, 4.2 or 2.3lkg(-1) water. This means, the higher the solid bed, the lower the sediment-mass-specific demand for time and water.     

EPR characterization of the catalytic activity of clays for PCE removal by gamma-radiation induced by acid and thermal treatments

Clays from tidal flat sediments showed efficient catalytic activity in the decomposition of PCE by gamma-radiation. The highest PCE removal of 98.6% was obtained with clays heated to 700 degrees C after acid treatment. The improved catalytic activity was identified by electron paramagnetic resonance (EPR) spectroscopy. The EPR spectra of clays were significantly changed by the acid and thermal treatments. The intensity of a narrow signal at g=2 (signal III) was decreased with increasing thermal treatment temperature and this increased the PCE removal efficiency. The acid treatment completely removed a broad signal at g=2 (signal II), decreased the intensity of signal III, and improved the gamma-radiation treatment of PCE.     

Comparison of techniques for estimating PAH bioavailability: uptake in Eisenia fetida, passive samplers and leaching using various solvents and additives

The aim of this study was to evaluate different techniques for assessing the availability of polycyclic aromatic hydrocarbons (PAHs) in soil. This was done by comparing the amounts (total and relative) taken up by the earthworm Eisenia fetida with the amounts extracted by solid-phase microextraction (SPME), semi-permeable membrane devices (SPMDs), leaching with various solvent mixtures, leaching using additives, and sequential leaching. Bioconcentration factors of PAHs in the earthworms based on equilibrium partitioning theory resulted in poor correlations to observed values. This was most notable for PAHs with high concentrations in the studied soil. Evaluation by principal component analysis (PCA) showed distinct differences between the evaluated techniques and, generally, there were larger proportions of carcinogenic PAHs (4-6 fused rings) in the earthworms. These results suggest that it may be difficult to develop a chemical method that is capable of mimicking biological uptake, and thus estimating the bioavailability of PAHs.     

Repeated use of MAP decomposition residues for the removal of high ammonium concentration from landfill leachate

The residues of magnesium ammonium phosphate (MAP) decomposed by heating under alkali conditions were repeatedly used as the sources of phosphate and magnesium for the removal of high ammonium concentration from landfill leachate. Up to 96% of ammonium in MAP powder could be released under the following conditions: NH4(+):OH- molar ratio, 1:1; temperature, 90 degrees C; heating time, 2 h. Fourier transform infrared spectra and X-ray diffraction analysis of MAP before and after heating demonstrated that MAP was mainly transformed to amorphous magnesium sodium phosphate (MgNaPO4), which makes it possible for the NH4(+) to replace Na+ in MgNaPO4 to form more stable struvite. Successful ammonium removal was achieved by using the MAP decomposition residues as the sole phosphate and magnesium sources. The ammonium removal decreased gradually following the increase of MAP reuse cycles, and in the 6th cycle, ammonium removals of 84% and 62% were achieved for synthetic wastewater and landfill leachate, respectively. Analysis of the surfaces of MAP powders acquired at different reuse cycles using scanning electron microscopy with energy dispersive X-ray suggested that the existence of calcium, kalium and aluminum ions in landfill leachate might have inhibited the formation of MAP through competition with ammonium ions for phosphate ions. It is estimated that reuse of MAP for 3 cycles could save about 44% chemical costs.     

Use of hairy roots extracts for 2,4-DCP removal and toxicity evaluation by Lactuca sativa test

2,4-Dichlorophenol (2,4-DCP) is widely distributed in wastewaters discharged from several industries, and it is considered as a priority pollutant due to its high toxicity. In this study, the use of different peroxidase extracts for 2,4-DCP removal from aqueous solutions was investigated. Tobacco hairy roots (HRs), wild-type (WT), and double-transgenic (DT) for tomato basic peroxidases (TPX1 and TPX2) were used to obtain different peroxidase extracts: total peroxidases (TPx), soluble peroxidases (SPx), and peroxidases ionically bound to the cell wall (IBPx). All extracts derived from DT HRs exhibited higher peroxidase activity than those obtained from WT HRs. TPx and IBPx DT extracts showed the highest catalytic efficiency values. The optimal conditions for 2,4-DCP oxidation were pH 6.5, H₂O₂ 0.5 mM, and 200 U mL^?1 of enzyme, for all extracts analyzed. Although both TPx extracts were able to oxidize different 2,4-DCP concentrations, the removal efficiency was higher for TPx DT. Polyethylene glycol addition slightly improved 2,4-DCP removal efficiency, and it showed some protective effect on TPx WT after 2,4-DCP oxidation. In addition, using Lactuca sativa test, a reduction of the toxicity of post removal solutions was observed, for both TPx extracts. The results demonstrate that TPx extracts from both tobacco HRs appear to be promising candidate for future applications in removing 2,4-DCP from wastewaters. This is particularly true considering that these peroxidase sources are associated with low costs and are readily available. However, TPx DT has increased peroxidase activity, catalytic efficiency, and higher removal efficiency than TPx WT, probably due to the expression of TPX1 and TPX2 isoenzymes.     

Appraisal of water matrix on the removal of fungicide residues by heterogeneous photocatalytic treatment using UV-LED lamp as light source

Environmental Science and Pollution Research - In this study, the photocatalytic degradation of four fungicides, myclobutanil, penconazole and difenoconazole (triazole compounds) and boscalid...     

Dissolved organic matter fractions formed during composting of winery and distillery residues: evaluation of the process by fluorescence excitation-emission matrix

The aim of the present paper is to assess the maturity degree reached by different samples of several mixtures from winery and distillery residues composted using the Rutgers composting system, by means of excitation-emission matrix (EEM) fluorescence spectroscopy. The composts were sampled once a week for about 200d. EEM spectra indicate the presence of different fluorophores. The fluorescence intensities of these peaks show trends related to the maturity of the composting samples selected. The "contour density" of EEM maps is strongly modified through time. We have used the quantitative method of fluorescence regional integration (FRI). The EEMs were delineated into five excitation-emission regions. The degree of compost maturity could be correlated with the percentage of the volumetric integration under the EEM within each region. Further refinement of these techniques should provide a relatively rapid method for assessing the suitability of the compost to soil application.     

Effect of initial pH control on biological phosphorus removal induced by the aerobic/extended-idle regime

Recently, it has been reported that biological phosphorus removal (BPR) can be induced by an aerobic/extended-idle (AEI) regime. This study further investigated the effect of initial pH ranging from 6.6 to 8.2 on BPR in the AEI process, and compared the BPR performance between the AEI and the anaerobic/oxic (A/O) regimes under their optimal initial pH value. Experimental results firstly showed that phosphorus removal linearly increased with initial pH increasing from 6.6 to 7.8, but slightly decreased when initial pH increased from 7.8 to 8.2. The optimal initial pH should be controlled at 7.8, and the phosphorus removal at initial pH 7.8 was approximately 1.7-time than that at initial pH 6.6. The mechanism studies showed that the biomass cultured at initial pH 7.8 contained more polyphosphate accumulating organisms (PAOs), lower glycogen accumulating organisms (GAOs), and had higher activities of exopolyphosphatase and polyphosphate kinase than that cultured at initial pH 6.6. Cyclic studies revealed that initial pH control affected the transformations of intracellular polyhydroxyalkanoates and glycogen, which might thereby influence microbial competition between PAOs and GAOs. Then, BPR performance between the AEI and the A/O regimes by adjusting initial pH at 7.8 was also compared. The results showed the AEI regime could drive a better BPR than the generally accepted A/O regime (98% vs 88%). Finally, controlling initial pH at 7.8 to promote BPR in the AEI process was confirmed for a municipal wastewater.     

Long-term pollution by chlordecone of tropical volcanic soils in the French West Indies: A simple leaching model accounts for current residue

Chlordecone was applied between 1972 and 1993 in banana fields of the French West Indies. This resulted in long-term pollution of soils and contamination of waters, aquatic biota, and crops. To assess pollution level and duration according to soil type, WISORCH, a leaching model based on first-order desorption kinetics, was developed and run. Its input parameters are soil organic carbon content (SOC) and SOC/water partitioning coefficient (K_oc). It accounts for current chlordecone soil contents and drainage water concentrations. The model was valid for andosol, which indicates that neither physico-chemical nor microbial degradation occurred. Dilution by previous deep tillages makes soil scrapping unrealistic. Lixiviation appeared the main way to reduce pollution. Besides the SOC and rainfall increases, K_oc increased from nitisol to ferralsol and then andosol while lixiviation efficiency decreased. Consequently, pollution is bound to last for several decades for nitisol, centuries for ferralsol, and half a millennium for andosol.     

Performance evaluation and application of surface-molecular-imprinted polymer-modified TiO2 nanotubes for the removal of estrogenic chemicals from secondary effluents

The removal of estrogenic chemicals during wastewater reclamation has been a great concern. Current advanced treatment processes are inefficient for the removal of estrogenic chemicals from secondary effluents of municipal wastewater treatment plants (WWTPs) due to the coexistence of other pollutants with less environmental significance which are also removed simultaneously. The search for highly selective and low-cost removal methods is warranted. Therefore, surface-molecular-imprinted polymer-modified TiO₂ nanotube (S-MIP-TiO₂ NT) photocatalysts were fabricated, characterized, and tested for the removal of estrogenic pollutants from wastewater in this study for the first time. Scanning electron microscopy and Fourier-transform infrared spectroscopy studies showed that the TiO₂ NTs (with an average diameter of 60 nm) were successfully imprinted with functional groups (i.e., carboxyl). The adsorption selectivity and photocatalytic activity of the S-MIP-TiO₂ NTs towards template compound (17β-estradiol, E2) were improved, compared with neat TiO₂ NTs. Interestingly, S-MIP-TiO₂ NTs exhibited higher adsorption intensity and photocatalytic selectivity at low concentrations (from 10 ng/L to 100 μg/L, as normal estrogenic chemical concentrations in secondary effluents) of E2 than that at high concentrations (from 10 to 1,000 mg/L). It was also found that some representative estrogenic chemicals and estrogenic activity could be selectively and rapidly removed from secondary effluents of municipal wastewater treatment plants using S-MIP-TiO₂ NTs as photocatalysts. In addition, S-MIP-TiO₂ NT photocatalysts exhibited excellent regeneration characteristics. Photocatalytic treatment using S-MIP-TiO₂ NTs could be a promising approach for the effective removal of estrogenic chemicals from secondary effluents of municipal WWTPs.     

Adsorptive removal of ibuprofen to binary and amine-functionalized UiO-66 in the aquatic environment: synergistic/antagonistic evaluation

Environmental Science and Pollution Research - The removal of ibuprofen (IBP) from the aqueous solution by metal–organic frameworks such as UiO-66, UiO-66-NH2, and a binary MOF...     

Cyclodextrin-based adsorbents for the removal of pollutants from wastewater: a review

Environmental Science and Pollution Research - Water is a vital substance that constitutes biological structures and sustains life. However, water pollution is currently among the major...     

Uptake of nitrous acid and nitrogen oxides by nylon surfaces: Implications for nitric acid measurement

The interference in HNO₃ determination due to HNO₂ and NO_x retention on nylon filters has been evaluated in laboratory and field conditions. Nitrous acid is retained on nylon filters with efficiencies varying from 25% at 12ℓ min⁻¹ to 80% at 2ℓ min⁻¹, yielding NO₂⁻ ion. In ambient sampling performed during photochemical smog episodes, NO₂⁻ is oxidized to NO₃⁻ with conversion factors up to 100%, resulting in a positive bias in HNO₃ determination.NO₂ reacts heterogeneously with H₂O on nylon surfaces according to the reaction 2NO₂ + H₂O → HNO₂ + HNO₃ with a removal constant of about 1 × 10⁻⁴ ms⁻¹ at a H₂O concentration of 20,000 ppm. The resulting nitrite and nitrate are independent of the sampling flow rate, while NO₂ concentration, sampling time and exposed nylon surface area play a directly proportional role. Accordingly, the relative interference of NO₂ with respect to HNO₃ determination is almost negligible for nylon filters, usually run at relatively high flow rates, while it may be significant for nylon denuders, which are characterized by larger exposed surfaces and lower operating flow rates.     

In vitro evaluation of cellular influences induced by stable fullerene C70 medium dispersion: Induction of cellular oxidative stress

Fullerene is one of the nanocarbons that is expected to have applications to life science, such as nanomedicines. An understanding of the cellular influences of fullerene is essential for its application to life science. Although C₆₀ and C₇₀ are both known as major fullerenes, most previous reports about the cellular influences of fullerene are about C₆₀. Thus we evaluated the cellular influences caused by C₇₀. A stable and uniform C₇₀-medium dispersion was prepared. The dispersion was stable for the experimental period. Mitochondrial activity (MTT assay), colony forming ability (clonogenic assay), induction of oxidative stress (intracellular ROS and lipid peroxidation levels) and cellular uptake (TEM observation) in human keratinocyte HaCaT and lung carcinoma A549 cells exposed to C₇₀ were examined. C₇₀ did not influence mitochondrial activity. On the other hand, C₇₀ dispersion inhibited colony formation at the concentration of 25.2 μg mL⁻¹. Exposure to C₇₀ dispersion caused an increase in intracellular ROS and lipid peroxidation levels. The induction of intracellular ROS level was inhibited by pre-treatment of the cells by antioxidants. TEM observations of C₇₀ exposed cells showed cellular uptake of C₇₀. These results were similar to the cellular influences caused by C₆₀ which were reported by us previously. Although C₇₀ did not cause cell death, it caused the induction of intracellular oxidative stress.     

Xenobiotics removal by adsorption in the context of tertiary treatment: a mini review

Many xenobiotics, including several pharmaceuticals and pesticides, are poorly treated in domestic wastewater treatment plants. Adsorption processes, such as with activated carbons, could be a solution to curb their discharge into the aquatic environment. As adsorbent-like activated carbon is known to be expensive, identifying promising alternative adsorbent materials is a key challenge for efficient yet affordable xenobiotic removal from wastewaters. As part of the effort to address this challenge, we surveyed the literature on pharmaceutical and pesticide xenobiotics and built a database compiling data from 38 scientific publications covering 65 xenobiotics and 58 materials. Special focus was given to the relevance and comparability of the data to the characteristics of the adsorbent materials used and to the operating conditions of the batch tests inventoried. This paper gives an in-depth overview of the adsorption capacities of various adsorbents. The little data on alternative adsorbent materials, especially for the adsorption of pharmaceuticals, makes it difficult to single out any one activated carbon alternative capable of adsorbing pesticides and pharmaceuticals at the tertiary stage of treatment. There is a pressing need for further lab-scale experiments to investigate the tertiary treatment of discharged effluents. We conclude with recommendations on how future data should best be used and interpreted.     

Photooxidative removal of the herbicide Acid Blue 9 in the presence of hydrogen peroxide: modeling of the reaction for evaluation of electrical energy per order (EEO)

The present work deals with photooxidative removal of the herbicide, Acid Blue 9 (AB9), in water in the presence of hydrogen peroxide (H₂O₂) under UV light illumination (30 W). The influence of the basic operational parameters such as amount of H₂O₂, irradiation time and initial concentration of AB9 on the photodegradation efficiency of the herbicide was investigated. The degradation rate of AB9 was not appreciably high when the photolysis was carried out in the absence of H₂O₂ and it was negligible in the absence of UV light. The photooxidative removal of the herbicide was found to follow pseudo-first-order kinetic, and hence the figure-of-merit electrical energy per order (E_Eo) was considered appropriate for estimating the electrical energy efficiency. A mathematical relation between the apparent reaction rate constant and H₂O₂ used was applied for prediction of the electricity consumption in the photooxidative removal of AB9. The results indicated that this kinetic model, based on the initial rates of degradation, provided good prediction of the E_Eo values for a variety of conditions. The results also indicated that the UV/H₂O₂ process was appropriate as the effective treatment method for removal of AB9 from the contaminated wastewater.