Arsenic(V) removal with a Ce(IV)-doped iron oxide adsorbent

The removal of arsenic(V) by a new Ce-Fe adsorbent was evaluated under various conditions. Under an initial As(V) of 1.0 mg l(-1), the adsorption capacity of the Ce-Fe absorbent was constant around a value of 16 mgg(-1) over a wide pH range (3-7), while a maximum adsorption capacity of 8.3 mgg(-1) was obtained over a narrow pH range around 5.5 for activated alumina, a conventional adsorbent. Kinetics of adsorption obeys a pseudo-first-order rate equation with the rate constant K(ad) as 1.84 x 10(-3) min(-1). The pattern of adsorption of As(V) by the adsorbent fitted well both the Langmuir and Freundlich models. A Langmuir Q(0) of 70.4 mgg(-1) was obtained at an initial pH of 5.0 and temperature of 20 degrees C, significantly higher than those of other adsorbents reported. Phosphate seriously inhibited the removal of As(V) while fluoride did not compete with As(V) even at an F/As molar ratio as high as 30, suggesting that the adsorption sites for As(V) and fluoride were different. Salinity, hardness, and other inorganic anions such as Cl(-), NO(3)(-), and SO(4)(2-) had no apparent effect on As(V) adsorption. Fourier transform infrared spectra of Ce-Fe adsorbent before and after As(V) adsorption demonstrated that M-OH groups plays an important role for As(V) ions removal in the adsorption mechanisms of Ce-Fe adsorbent.     

Photostabilizers for azadirachtin-A (a neem-based pesticide)

Photostability of azadirachtin-A (a neem based pesticide) has been studied without and with adding stabilizers such as ter. butyl-p-cresol, 8-hydroxy quinoline and ter. butyl hydroquinone as thin film on glass surface and on leaf surface under sunlight and UV light. Half-life of azadirachtin has been found to be 48 min and 3.98 days as thin film under UV light and sunlight and 2.47 days on leaf surface, respectively. 8-Hydroxy quinoline and ter. butyl hydroquinone have been found effective in controlling degradation of azadirachtin under both sunlight and UV light with half-life of 44.42 and 35.90 days under sunlight, and 55.80 and 48.50 h under UV light, respectively. Whereas ter. butyl-p-cresol has been found effective A only under sunlight. Significant decreases in antifeedant and insect growth regulatory activity against third instar larvae of Spodopterra litura has been observed with azadirachtin when exposed to sunlight and UV light. However, by the addition of above stabilizers, the biological activity of azadirachtin-A has been retained even after 24 h of irradiation under UV light and up to 30 days of exposure to sunlight.     

Equilibrium partitioning of (14)C-benzo(a)pyrene and (14)C-benazolin between fractionated phases from an arable topsoil

Equilibrium partitioning of hydrophobic (14)C-benzo(a)pyrene and hydrophilic (14)C-benazolin between fractionated phases from an arable topsoil of Merzenhausen (Germany) was investigated. Topsoil samples were collected from lysimeters which were incubated with different residual crops. A physical soil fractionation based on sedimentation and centrifugation steps was performed after water extraction. Four soil phases were obtained designated sediment (SED) phase (>20 microm), microaggregate (MA) phase (2 microm-20 microm), colloid (COL) phase (<2 microm) and electrolyte (EL) phase. The distribution of (14)C-benzo(a)pyrene, (14)C-benazolin and organic carbon between the soil phases was established. Enrichment factors for the two chemicals and organic carbon are higher in the COL and MA phases than in the SED phase. The distribution constant K(d) of chemicals for Merzenhausen topsoil was calculated according to two-phase or three-phase partitioning models. The three-phase partitioning model presumes the contribution of the organic carbon for the binding of chemicals. A log K(oc) of 5.55 can be calculated in the case of (14)C-benzo(a)pyrene, which is typical of the hydrophobic association with the soil organic carbon. In the case of (14)C-benazolin, much higher K(d) and K(oc) values were calculated than found with parent molecules after short-time experiments. Long-term aging processes must be considered. Specific effects on the chemical distribution due to the different crop residues were not detected.     

Photosynthetic responses to elevated CO(2) and O(3) in Quercus ilex leaves at a natural CO(2) spring

Photosynthetic stimulation and stomatal conductance (Gs) depression in Quercus ilex leaves at a CO(2) spring suggested no down-regulation. The insensitivity of Gs to a CO(2) increase (from ambient 1500 to 2000 micromol mol(-1)) suggested stomatal acclimation. Both responses are likely adaptations to the special environment of CO(2) springs. At the CO(2)-enriched site, not at the control site, photosynthesis decreased 9% in leaves exposed to 2x ambient O(3) concentrations in branch enclosures, compared to controls in charcoal-filtered air. The stomatal density reduction at high CO(2) was one-third lower than the concomitant Gs reduction, so that the O(3) uptake per single stoma was lower than at ambient CO(2). No significant variation in monoterpene emission was measured. Higher trichome and mesophyll density were recorded at the CO(2)-enriched site, accounting for lower O(3) sensitivity. A long-term exposure to H(2)S, reflected by higher foliar S-content, and CO(2) might depress the antioxidant capacity of leaves close to the vent and increase their O(3) sensitivity.     

Ice (photo)chemistry. Ice as a medium for long-term (photo)chemical transformations--environmental implications

This review accounts for the current knowledge about the distribution, accumulation, and chemical/photochemical transformations of persistent, bioaccumulative, and toxic compounds (PBTs) in water ice, especially in the connection with polar regions and atmospheric cloud particles. (Photo)reactions on/in ice are discussed in terms of photochemistry, photobiology, paleochemistry, as well as astrophysics. Authors propose a model, in which a significant amount of some PBTs are generated by (photo)chemistry of primary pollutants in ice, which may subsequently be released to the environment. It is argued that ice photochemistry might play an important role in the chemical transformations in cold ecosystems and in the upper atmosphere, particularly now when the ozone layer is partially depleted.     

Differential Sensitivity of a Coccal Green Algal and a Cyanobacterial Species to Dissolved Natural Organic Matter (NOM) (8 pp)

Background

and Aim. In non-eutrophicated freshwaters, humic substances (HS) pose chemical stresses on aquatic organisms and, hence, separating sensitive from less sensitive or even tolerant species. One of the stresses, identified so far, is the reduction of photosynthetic oxygen production and reduction in growth in freshwater macrophytes and algae. In a previous paper, it has been shown that even closely related coccal green algae responded differently upon identical stress by HS, which is consistent with the hypothesis above. Due to their much simpler cellular ultrastructure, cyanobacteria are supposed to be more sensitive to HS exposure than eukaryote should be. One coccal green algal species (Desmodesmus communis) and one cyanobacterium (Chroococcus minutus) were exposed to four natural organic matter (NOM) isolates. One NOM has been isolated from a brown water lake (Schwarzer See) in Brandenburg State; three were obtained from a comprehensive Scandinavian NOM research project and originated from Norway (Birkenes), Finland (Hietajärvi), and Sweden (Svartberget).

Methods

Cultures of D. communis and C. minutus were obtained from the Culture Collection of Algae, Göttingen, and maintained in a common medium. The cultures were non-axenic. The algae and cyanobacteria were exposed under identical conditions to environmentally realistic NOM concentrations. Cell numbers were counted microscopically in Neugebauer cuvettes in triplicates. To avoid limitation by nutrient depletion, the experiments were terminated after 14 to 15 days. Until culture day 12, no growth limitation has been observed in the controls.

Results

All NOM isolates modulated the growth of the algae and cyanobacteria. During the early culture days, there was a slight growth promotion with the coccal green alga and to a much lesser degree with the cyanobacterium. Yet, the major effect were significant reductions in cell yield in both primary producer cultures. C. minutus was much more affected than D. communis. This applies particularly to the three tested Scandinavian NOM isolates, which were effective at concentrations even below 1 mg L-1 DOC.

Discussion

The growth promoting effect may be due to an increase in bioavailability of some trace nutrients in the presence of NOM, the release of some growth promoting substances by microbial or photochemical processing of the NOM, and/or a hormetic effect. The growth reducing effect can be explained as a herbicide-like mode of action that affects the photosystem II most prevalent by blocking the electron transport chain, absorption of electrons, or production of an internal oxidative stress after processing the bioconcentrated HS. Furthermore, it may be postulated that also photo-toxicity of these HS in the algal cells contributes to the overall toxicity; however, experimental evidence is lacking so far.

Conclusions

Upon exposure to HS, cyanobacteria appear to be much more sensitive than coccal green algae and respond in growth reduction. This high sensitivity of cyanobacteria to HS may explain phytoplankton patterns in the field. Eutrophic, humic-rich lakes do not support the cyanobacterial blooms characteristic of eutrophic, but humic-poor lakes. In the humic-rich systems, raphidophytes or, less frequent, specific coccal greens are more common. Obviously, cyanobacteria appear to be unable to make advantage of their accessory pigments (phycocyanin) to exploit the reddish light prevailing in humic-rich lakes.

Recommendation

. At present, no effective structure can be figured out which may be responsible for the adverse effect on the cyanobacterial species. It is reserved to future research whether or not HS may be applied more specifically (for instance, with elevated moieties of the effective structures) as a natural geochemical to combat cyanobacterial blooms.

     

Cholinesterase characterization in Corbicula fluminea and effects of relevant environmental contaminants: a pesticide (chlorfenvinphos) and a detergent (SDS)

This study characterizes the cholinesterasic forms present in the bivalve Corbicula fluminea, through the analysis of differential affinity towards various substrates and inhibitors. This approach also permitted the validation of cholinesterase inhibition in the mentioned species for monitoring purposes by evaluating the inhibitory activity of a detergent (SDS) and a pesticide (chlorfenvinphos), both in vitro and in vivo. The cholinesterasic form present in the tissues of C. fluminea showed intermediate properties in terms of its relation with substrates and inhibitors. Furthermore, it was not inhibited by the detergent SDS under any of the test conditions, but was clearly inhibited by the selected organophosphate. The data show clearly that the main cholinesterasic form in C. fluminea is responsive to the organophosphate chlorfenvinphos, thus supporting the use of this biomarker for the environmental monitoring of specific contaminants such as anticholinesterasic pesticides. Despite not being commonly attained in the wild, the levels of chlorfenvinphos required to elicit a significant ChE inhibition were only one order of magnitude above actual values of aquatic contamination by this pesticide.     

Perfluorooctanoic acid (PFOA) acts as a tumor promoter on Syrian hamster embryo (SHE) cells

Perfluorooctane sulfonate (PFOS) (C(8)F(17)SO(3)) and perfluorooctanoic acid (PFOA) (C(8)HF(15)O(2)) are synthetic chemicals widely used in industrial applications for their hydrophobic and oleophobic properties. They are persistent, bioaccumulative, and toxic to mammalian species. Their widespread distribution on earth and contamination of human serum raised concerns about long-term side effects. They are suspected to be carcinogenic through a nongenotoxic mode of action, a mechanism supported by recent findings that PFOS induced cell transformation but no genotoxicity in Syrian hamster embryo (SHE) cells. In the present study, we evaluated carcinogenic potential of PFOA using the cell transformation assay on SHE cells. The chemical was applied alone or in combination with a nontransformant concentration of benzo[a]pyrene (BaP, 0.4?μM) in order to detect PFOA ability to act as tumor initiator or tumor promoter. The results showed that PFOA tested alone in the range 3.7?×?10(-5) to 300?μM did not induce SHE cell transformation frequency in a 7-day treatment. On the other side, the combination BaP/PFOA induced cell transformation at all PFOA concentrations tested, which revealed synergistic effects. No genotoxicity of PFOA on SHE cells was detected using the comet assay after 5 and 24?h of exposure. No significant increase in DNA breakage was found in BaP-initiated cells exposed to PFOA in a 7-day treatment. The whole results showed that PFOA acts as a tumor promoter and a nongenotoxic carcinogen. Cell transformation in initiated cells was observed at concentrations equivalent to the ones found in human serum of nonoccupationally and occupationally exposed populations. An involvement of PFOA in increased incidence of cancer recorded in occupationally exposed population cannot be ruled out.     

Development of a biotic ligand model (BLM) predicting nickel toxicity to barley (Hordeum vulgare)

A biotic ligand model (BLM) was developed to predict nickel toxicity, affecting root growth of barley (Hordeum vulgare), in nutrient solutions. The extent to which Ca(2+), Mg(2+), Na(+), K(+) ions and pH each influenced nickel toxicity was determined. Higher activities of Mg(2+) linearly increased the 4d EC50 Ni (2+) , while Ca(2+), Na(+), K(+) and H(+) activities did not significantly influence Ni(2+) toxicity. Stability constants for the binding of Ni(2+) and Mg(2+) to the biotic ligand were obtained: logK(NiBL)=5.27 and logK(MgBL)=3.47. Further, it was calculated that on average 57% of the biotic ligand sites needed to be occupied by nickel to induce 50% root growth inhibition. Auto-validation of the BLM indicated that predicted EC50s differed from the observed EC50s by a factor of less than 2, indicating that the BLM concept may also be used to predict metal toxicity to terrestrial plants.     

Exposure assessment of pesticides in a shallow groundwater of the Tagus vulnerable zone (Portugal): a multivariate statistical approach (JCA)

Purpose

To assess groundwater exposure to pesticides, in agricultural areas of ??Ribatejo?? region (Portugal), and the influence of some key factors in that exposure, field, laboratory and modelling studies were carried out.

Methods

The study was performed in maize, potato, sugar beet, tomato and vegetables agricultural areas, located in a shallow aquifer, with pesticides use and, in most cases, with irrigation practices. Pesticides used in the studied agricultural areas and having leaching potential were selected, being considered also other pesticides included in priority lists, defined in Europe. Evaluation of groundwater exposure to pesticides was carried out by successively: (1) groundwater sampling in seven campaigns over the period 2004?C2006; (2) pesticide analysis [including isolation and concentration from the groundwater samples and further determination by gas chromatography?Cmass spectrometry (GC?CMS) of 14 herbicides, four insecticides and two metabolites]; and (3) analysis and discussion of the results by applying joint correspondence analysis (JCA).

Results

From the 20 pesticides and metabolites selected for the study, 11 were found in groundwater. Pesticides and metabolites most frequently detected were atrazine, alachlor, metolachlor, desethylatrazine, ethofumesate, ??-endosulfan, metribuzine, lindane and ??-endosulfan. The results showed that groundwater exposure to pesticides is influenced by local factors??either environmental or agricultural, as precipitation, soil, geology, crops and irrigation practices. Spring and autumn were more associated with the detection of pesticides being more likely to observe mixtures of these compounds in a groundwater sample in these transition seasons.

Conclusions

This work evidences the importance of models, which evaluate pesticides environmental behaviour, namely their water contamination potential (as Mackay multicompartimental fugacity model) and, specially, groundwater contamination potential (as GUS and Bacci and Gaggi leaching indices), in pesticide selection. Moreover, it reveals the importance to adapt proper statistical methods according to level of left-censored data. Using JCA was still possible to establish relations between pesticides and their temporal trend in a case study where there were more than 80% of data censored. This study will contribute to the Tagus river basin management plan with information on the patterns of pesticide occurrence in the alluvial aquifer system.     

Fate of benzo(a)pyrene-C during brew process

Benzo(a)pyrene-¹⁴C (1 ppm) was applied to wort and boiled with hops in a brew process. The wort after filtration was subjected to fermentation. The hops and yeast were found to contain more than 99 % of applied radioactivity and consisted of benzo(a)pyrene. The radioactivity dissolved in beer was less than 1 % and the chemical nature could not be identified.     

Photochemical studies of a polybrominated diphenyl ethers (PBDES) technical mixture by solid phase microextraction (SPME)

In this work the photochemical behaviour of a technical mixture of polybrominated diphenyl ethers (PBDEs) (BDE-47, BDE-99, BDE-100, BDE-153 and BDE-154) has been studied. The mixture of BDEs was extracted from aqueous solutions using SPME fibers that were subsequently exposed to different UV irradiation times, procedure so-called Photo-SPME. PBDEs photochemical studies in such medium have been accomplished for the first time. Twenty one different photoproducts, all of them generated by successive bromine atoms losses, have been identified, being their photoformation-photodegradation curves easily determined by the Photo-SPME technique.     

Freshwater Ulva (Chlorophyta) as a bioaccumulator of selected heavy metals (Cd, Ni and Pb) and alkaline earth metals (Ca and Mg)

We analyzed the ability of freshwater taxa of the genus Ulva (Ulvaceae, Chlorophyta) to serve as bioindicators of metal in lakes and rivers. Changes in heavy metal (Ni, Cd and Pb) and alkaline earth metal (Ca and Mg) concentrations in freshwater Ulva thalli were investigated during the period from June to August 2010. The study was conducted in two ecosystems in Western Poland, the Malta lake (10 sites) and the Nielba river (six sites). Three components were collected for each sample, including water, sediment and Ulva thalli. The average concentrations of metals in the water sample and in the macroalgae decreased in the following order: Ca > Mg > Ni > Pb > Cd. The sediment revealed a slightly altered order: Ca > Mg > Pb > Ni > Cd. Ca and Mg were found at the highest concentrations in thalli due to the presence of carbonate on its surface. Among the examined heavy metals in thalli, Ni was in the highest concentration, and Cd found in the lowest concentration. There were statistically significant correlations between the levels of metals in macroalgae, water and sediment. Freshwater populations of Ulva exhibited a greater efficiency to bioaccumulate nickel as compared to species derived from marine ecosystems.     

Simultaneous conversion of CHClF(2) and CH(3)Br to CH(2)CF(2)

Gas phase reaction of CHClF(2) with CH(3)Br in an alumina tube reactor at 773-1123 K as a function of various input ratios of CH(3)Br to CHClF(2) is presented. The major products detected include C(2)F(4), CH(2)CF(2), and CH(4). Minor products include CH(3)Cl, CHF(3), C(2)H(4), C(2)H(2), CH(2)CF-CF(3), and C(2)H(3)F. The reaction produces a high yield of CH(2)CF(2) (53% based on CHClF(2) feed) at 1123 K and an input molar ratio of CH(3)Br to CHClF(2) of 1.8, suggesting that the reaction potentially can be developed as a process to convert two ozone depleting substances (CHClF(2) and CH(3)Br) to a highly valuable chemical, CH(2)CF(2). The reaction of CHClF(2) with CH(3)Cl and CH(3)I was also investigated under similar reaction conditions, to assist in understanding the reaction chemistry involved in the reaction of CHClF(2) with CH(3)Br.     

Reduction of ferrate(VI) and oxidation of cyanate in a Fe(VI)-TiO2-UV-NCO- system

The aqueous photocatalytic degradation of cyanate (NCO(-)), which is a long-lived neurotoxin formed during the remediation of cyanide in industrial waste streams, was studied in the ferrate(VI)-UV-TiO2-NCO(-) system. Kinetics measurements of the photocatalytic reduction of ferrate(VI) were carried out as a function of [NCO(-)], [ferrate(VI)], [O(2)], light intensity (I(o)), and amount of TiO2 in suspensions at pH 9.0. The photocatalytic reduction rate of ferrate(VI) in the studied system can be expressed as -d[Fe(VI)]/dt=kI(o)(0.5) [NCO(-)] [TiO2]. The rate of photocatalytic oxidation of cyanate with ferrate(VI) was greater than the rate in the analogous system without ferrate(VI). The possibility of involvement of reactive ferrate(V) species for this enhancement was determined by studying the reactivity of ferrate(V) with NCO(-) in a homogeneous solution using a premix pulse radiolysis technique. The rate constant for the reaction of ferrate(V) and NCO(-) in alkaline medium was estimated to be (9.60+/-0.07) x 10(2) M(-1) s(-1), which is much slower than the ferrate(VI) self-decomposition reaction (k approximately 10(7) M(-1) s(-1)). An analysis of the kinetic data in the Fe(VI)-UV-TiO2-NCO(-) system suggests that ferrate(V) is not directly participating in the oxidation of cyanate. Possible reactions in the system are presented to explain results of ferrate(VI) reduction and oxidation of cyanate.     

Surface runoff and nitrogen (N) loss in a bamboo (Phyllostachys pubescens) forest under different fertilization regimes

Nitrogen (N) losses from agricultural fields have been extensively studied. In contrast, surface runoff and N losses have rarely been considered for bamboo forests that are widespread in regions such as southern China. The thriving of bamboo industries has led to increasing fertilizer use in bamboo forests. In this study, we evaluated surface runoff and N losses in runoff following different fertilization treatments under field conditions in a bamboo (Phyllostachys pubescens) forest in the catchment of Lake Taihu in Jiangsu, China. Under three different fertilization regimes, i.e., control, site-specific nutrient management (SSNM), and farmer's fertilization practice (FFP), the water runoff rate amounted to 356, 361, and 342 m³?ha^?1 and accounted for 1.91, 1.98, and 1.85 % of the water input, respectively, from June 2009 to May 2010. The total N losses via surface runoff ranged from 1.2 to 1.8 kg?ha^?1. Compared with FFP, the SSNM treatment reduced total nitrogen (TN) and dissolved nitrogen (DN) losses by 31 and 34 %, respectively. The results also showed that variations in N losses depended mainly on runoff fluxes, not N concentrations. Runoff samples collected from all treatments throughout the year showed TN concentrations greater than 0.35 mg?L^?1, with the mean TN concentration in the runoff from the FFP treatment reaching 8.97 mg?L^?1. The loss of NO₃ ^?–N was greater than the loss of NH₄ ⁺–N. The total loss of dissolved organic nitrogen (DON) reached 23–41 % of the corresponding DN. Therefore, DON is likely the main N species in runoff from bamboo forests and should be emphasized in the assessment and management of N losses in bamboo forest.