Photocatalytic degradation of five sulfonylurea herbicides in aqueous semiconductor suspensions under natural sunlight

In the present study, the photocatalytic degradation of five sulfonylurea herbicides (chlorsulfuron, flazasulfuron, nicosulfuron, sulfosulfuron and triasulfuron) has been investigated in aqueous suspensions of zinc oxide (ZnO), tungsten (VI) oxide (WO₃), tin (IV) oxide (SnO₂) and zinc sulfide (ZnS) at pilot plant scale under natural sunlight. Photocatalytic experiments, especially those involving ZnO photocatalysis, showed that the addition of semiconductors in tandem with the oxidant (Na₂S₂O₈) strongly enhances the degradation rate of the herbicides in comparisons carried out with photolytic tests. The degradation of the herbicides follows a first order kinetics according to the Langmuir-Hinshelwood model. In our conditions, the amount of time required for 50% of the initial pesticide concentration to dissipate (t_½) ranged from 8 to 27 min (t_30W = 0.3-1.2 min) for sulfosulfuron and chlorsulfuron, respectively in the ZnO/Na₂S₂O₈ system. None of the studied herbicides was found after 120 min of illumination (except chlorsulfuron, 0.2 μg L⁻¹).     

Evaluating pharmaceuticals and caffeine as indicators of fecal contamination in drinking water sources of the Greater Montreal region

We surveyed four different river systems in the Greater Montreal region, upstream and downstream of entry points of contamination, from April 2007 to January 2009. The studied compounds belong to three different groups: PPCPs (caffeine, carbamazepine, naproxen, gemfibrozil, and trimethoprim), hormones (progesterone, estrone, and estradiol), and triazine herbicides and their metabolites (atrazine, deethylatrazine, deisopropylatrazine, simazine, and cyanazine). In the system A, B, and C having low flow rate and high TOC, we observed the highest detection frequencies and mass flows of PPCPs compared to the other compounds, reflecting discharge of urban contaminations through WWTPs and CSOs. However, in River D, having high flow rate and low TOC, comparable frequency of detection of triazine and their by-products and PPCPs, reflecting cumulative loads of these compounds from the Great Lakes as well as persistency against natural attenuation processes. Considering large differences in the removal efficiencies of caffeine and carbamazepine, a high ratio of caffeine/carbamazepine might be an indicative of a greater proportion of raw sewage versus treated wastewater in surface waters. In addition, caffeine appeared to be a promising indicator of recent urban fecal contaminations, as shown by the significant correlation with FC (R² = 0.45), while carbamazepine is a good indicator of cumulative persistence compounds.     

The chemical exploitation of nickel phytoextraction: An environmental, ecologic and economic opportunity for New Caledonia

Herein, we explore the outlines of an innovative method based on the chemical recovery of metal-rich biomass produced in phytoextraction technologies. Taking advantage of the adaptive capacity of some New Caledonian plants to hyperaccumulate Ni²⁺ cations in their aerial parts, this technique is based on the direct use of metals derived from plants as “Lewis acid” catalysts in organic chemistry. Metallic cations contained in New Caledonian nickel hyperaccumulators are recovered through a simple cost-effective process and serve the preparation of heterogeneous catalysts used in synthetic transformations allowing access to molecules with high added-value. The design of all processes is in line with the principles of green chemistry; it is adapted to the new economic constraints; it offers a new relevant outlet for metal-rich biomass; and it represents an alternative to non-renewable mineral materials.     

Acute toxicity tests with Daphnia magna, Americamysis bahia, Chironomus riparius and Gammarus pulex and implications of new EU requirements for the aquatic effect assessment of insecticides

Threshold concentrations for treatment related effects of 31 insecticides, as derived from aquatic micro-/mesocosm tests, were used to calibrate the predictive value of the European Tier-1 acute effect assessment on basis of laboratory toxicity tests with Daphnia magna, Chironomus spp., Americamysis bahia and Gammarus pulex. The acute Tier-1 effect assessment on basis of Daphnia (EC(50)/100) overall was protective for organophosphates, carbamates and most pyrethroids but not for neonicotinoids and the majority of insect growth regulators (IGRs) in the database. By including the 28-day water-spiked Chironomus riparius test, the effect assessment improves but selecting the lowest value on basis of the 48-h Daphnia test (EC50/100) and the 28-day Chironomus test (NOEC/10) is not fully protective for 4 out of 23 insecticide cases. An assessment on basis of G. pulex (EC(50)/100) is sufficiently protective for 15 out of 19 insecticide cases. The Tier-1 procedure on basis of acute toxicity data (EC(50)/100) for the combination of Daphnia and A. bahia and/or Chironomus (new EU dossier requirements currently under discussion) overall is protective to pulsed insecticide exposures in micro-/mesocosms. For IGRs that affect moulting, the effect assessment on basis of the 48-h Chironomus test (EC(50)/100) may not always be protective enough to replace that of the water-spiked 28-day C. riparius test (NOEC/10) because of latency of effects.     

Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate)/Polylactide Blends: Thermal Stability,Flammability and Thermo-Mechanical Behavior

Blends of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and polylactide (PLA) with different PHBV/PLA weight ratios (100/0, 75/25, 50/50, 25/75, 0/100) were prepared by melt compounding. Their mutual contributions in terms of thermal stability, flammability resistance, mechanical properties and rheological behavior were investigated. The study showed that the increase in PLA content in PHBV/PLA blends leads to enhanced properties. Consequently, thermal stability and flammability resistance were improved. Further, the rheological measurements indicated an increase in storage modulus and loss modulus of PHBV matrix by addition of PLA.     

Physical Properties, Photo- and Bio-degradation of Baked Foams Based on Cassava Starch, Sugarcane Bagasse Fibers and Montmorillonite

The objectives of this work were to develop biodegradable trays from cassava starch, sugarcane fibers and Na-montmorillonite (Na-MMT) using a baking process and to study the effects of these components on the physical properties, photo- and bio-degradation of the trays. The sample F20 (produced with 20 g fiber/100 g formulation) showed the maximum yield production (100 %). All formulations resulted in well-shaped trays with densities between 0.1941 and 0.2966 g/cm³. The addition of fibers and Na-MMT resulted in less dense and less rigid trays compared to control samples (only starch). The studied processing conditions resulted in good nanoclay dispersion, leading to the formation of an exfoliated structure. The evaluation of the photo-degradation stability of the trays under UV exposure for 336 h showed that a sample produced with a specific combination of fiber and nanoclay (20 g fiber and 5 g nanoclay/100 g formulation) had the highest loss in stress at break (91 %). Biodegradation assays showed that Control trays (starch) and F20 (20 g fiber/100 g formulation) lost a greater percentage of their weight after 90 days of incubation in soil, with losses of up to 85.50 and 82.70 %, respectively.     

A field study on residues of four insecticides used in strawberry protection

Abstract

In 1986 strawberry plots were treated with dimethoate, malathion, permethrin and cypermethrin at 80% bloom of primary flowers. In 1987 the plots were sprayed with dimethoate, malathion and permethrin at 30% bloom. Residue analysis of these insecticides on the flowers were analyzed using solvent extraction and gas liquid chromatography. Residue analysis at 0 to 18 days on flowers and fruit showed an exponential decrease. Organophosphates tended to degrade more quickly than synthetic pyrethroids. The results are discussed in the context of an integrated pest management program.     

Potential of the microbial community present in an unimpacted beach sediment to remediate petroleum hydrocarbons

The potential of the microbial communities present in the intertidal zone of an unimpacted beach (a beach that did not suffer any significant oil spill) to degrade hydrocarbons was investigated. For that, laboratory-based microcosms (50-ml flasks) were set up with sandy beach sediment spiked with crude oil and incubated with local seawater for 15 days in the dark. Three bioremediation treatments were tested (biostimulation (BS), autochthonous bioaugmentation (AB), and combined treatment of biostimulation + bioaugmentation (BS + AB)) and the results were compared with natural attenuation (NA). Visual inspection showed clearly an oil solubility increase (confirmed by a higher hydrocarbons concentration in supernatant solutions) for all tested treatments when compared to NA. Significant degradation of the oil, shown by different profiles of petroleum hydrocarbons, was also observed for the different treatments particularly for BS + AB. Therefore, the microbial community of this unimpacted beach sediment could respond to an oil spill, degrading hydrocarbons. But to increase the natural attenuation pace, obtained results indicated that BS + AB is an appropriate approach for the bioremediation of beaches recently impacted by an oil spill. The autochthonous microbial cultures can be obtained “before” or “after” the contamination of the target site, being inoculated into the site right after it contamination.     

Accumulation of arsenic, lead, copper, and zinc, and synthesis of phytochelatins by indigenous plants of a mining impacted area

Several native plants, able to grow in an unconfined mining impacted area that is now in close vicinity with urban areas, were evaluated for their ability to accumulate heavy metals. The main soil contaminants were As, Pb, Cu, and Zn. Sampling of the rhizospheric metal polluted soil showed that Euphorbia prostrata Aiton, Parthenium incanum Kunth, and Zinnia acerosa (DC.) A. Gray were able to grow in the presence of high amounts of mixtures of these elements. The plants accumulated the metals in the above ground parts and increased the synthesis of thiol molecules. E. prostrata showed the highest capacity for accumulation of the mixture of elements (588 μg g DW^?1). Analysis of the thiol-molecules profile showed that these plants synthesized high amounts of long-chain phytochelatins, accompanied by low amounts of monothiol molecules, which may be related to their higher resistance to As and heavy metals. The three plants showed translocation factors from roots to leaves >1 for As, Pb, Cu, and Zn. Thus, by periodically removing aerial parts, these plants could be useful for the phytoremediation of semi-arid and arid mining impacted areas, in which metal hyper-accumulator plants are not able to grow.     

Partitioning, sources and variability of regional and local oxidant (OX = O3 + NO2) in a coastal rural area in the southwest of Iberian Peninsula

The purpose of this work is to investigate the behaviour and variability of oxidant levels (OX?=?NO₂?+?O₃), for the first time, in a rural coastal area in the southwest of the Iberian Peninsula, affected by several air masses types. Detailed database (built-up over the years 2008 to 2011, and containing around 500,000 data) from the Atmospheric Sounding Station “El Arenosillo” was used. The observed daily cycles of NO _x and OX were influenced by air masses coming from industrial and urban area. It can be seen that the concentration of OX is made up of a NO _x -independent ‘regional’ contribution (i.e. the O₃ background), and a linearly NO _x -dependent ‘local’ contribution from primary emissions, such as traffic. The local emission is very low in this area. Also, the regional contribution is similar to unpolluted sites and presents seasonal variation, being higher in May. However, our measurements showed that the proportion of OX in the form of NO₂ increases with the increase in NO _x concentration during the day. The higher proportion of NO₂ observed at night must be due to the conversion of NO to NO₂ by the NO?+?O₃ reaction. With regards to the source of the local NO _x -dependent contribution, it may be attributed to industrial emission, or the termolecular reaction 2NO?+?O₂?=?2NO₂, at high-NO _x levels and stagnant air during several days. Finally, we estimated the photolysis rate of NO₂, J _NO2, an important key atmospheric reaction coupled with ozone. We also present surface plots of annual variation of the daily mean NO _x and OX levels, which indicate that oxidants come from transport processes instead of local emissions associated as local photochemistry.