Enhanced Adsorption of Methylene Blue Dye on Functionalized Multi-Walled Carbon Nanotubes.

Carbon nanomaterials are promising adsorbents for dye removal from wastewater also due to their possible surface functionalization that, in principle, can increase the adsorption rate and provide regeneration. To investigate the real advantages of functionalization, we synthesized and characterized through IR, TGA, TEM, XPS and DLS measurements a multi-walled carbon nanotube (MWCNT) derivative bearing benzenesulfonate groups (MWCNT-S). The obtained material demonstrated to have good dispersibility in water and better capability to adsorb methylene blue (MB) compared to the pristine MWCNT adsorbent. Adsorption kinetic studies showed a very fast process, with a constant significantly higher with respect not only to that of the unfunctionalized MWCNT adsorbent but also to those of widely used activated carbons. Moreover, the adsorption capacity of MWCNT-S is more than doubled with respect to that of the insoluble pristine MWCNT adsorbent, thanks to the dispersibility of the derivatives, providing a larger available surface, and to the possible electrostatic interactions between the cationic MB and the anionic sulfonate groups. Additionally, the reversibility of ionic interactions disclosed the possibility to release the adsorbed cationic pollutant through competition with salts, not only regenerating the adsorbent, but also recovering the dye. Indeed, by treating the adsorbed material for 1 h with 1 M NaCl, a regeneration capacity of 75% was obtained, demonstrating the validity of this strategy.

Data-Driven Predetermination of Cu Oxidation State in Copper Nanoparticles: Application to the Synthesis by Laser Ablation in Liquid.

Copper-based nanocrystals are reference nanomaterials for integration into emerging green technologies, with laser ablation in liquid (LAL) being a remarkable technique for their synthesis. However, the achievement of a specific type of nanocrystal, among the whole library of nanomaterials available using LAL, has been until now an empirical endeavor based on changing synthesis parameters and characterizing the products. Here, we started from the bibliographic analysis of LAL synthesis of Cu-based nanocrystals to identify the relevant physical and chemical features for the predetermination of copper oxidation state. First, single features and their combinations were screened by linear regression analysis, also using a genetic algorithm, to find the best correlation with experimental output and identify the equation giving the best prediction of the LAL results. Then, machine learning (ML) models were exploited to unravel cross-correlations between features that are hidden in the linear regression analysis. Although the LAL-generated Cu nanocrystals may be present in a range of oxidation states, from metallic copper to cuprous oxide (Cu2O) and cupric oxide (CuO), in addition to the formation of other materials such as Cu2S and CuCN, ML was able to guide the experiments toward the maximization of the compounds in the greatest demand for integration in sustainable processes. This approach is of general applicability to other nanomaterials and can help understand the origin of the chemical pathways of nanocrystals generated by LAL, providing a rational guideline for the conscious predetermination of laser-synthesis parameters toward the desired compounds.

Cold Plasma for Green Advanced Reduction/Oxidation Processes (AROPs) of Organic Pollutants in Water.

Cold plasma is gaining increasing attention as a novel tool to activate energy demanding chemical processes, including advanced reduction/oxidation processes (AROPs) of organic pollutants in water. The very complex milieu generated by discharges at the water/plasma interface comprises photons, strong oxidants and strong reductants which can be exploited for achieving the degradation of most any kind of pollutants. Despite the complexity of these systems, the powerful arsenal of mechanistic tools and chemical probes of physical organic chemists can be usefully applied to understand and develop plasma chemistry. Specifically, the added value of air plasma generated by in situ discharge with respect to ozonation (ex situ discharge) is demonstrated using phenol and various phenol derivatives and mechanistic evidence for the prevailing role of hydroxyl radicals in the initial attack is presented. On the reduction front, the impressive performance of cold plasma in inducing the degradation of recalcitrant perfluoroalkyl substances, which do not react with OH radicals but are attacked by electrons, is reported and discussed. The widely different reactivities of perfluorooctanoic acid (PFOA) and of perfluorobutanoic acid (PFBA) underline the crucial role played in these processes by the interface between plasma and solution and the surfactant properties of the treated pollutants.

Products, reactive species and mechanisms of PFOA degradation in a self-pulsing discharge (SPD) plasma reactor.

Non-thermal plasma is a promising tool for novel technologies to treat water contaminated by recalcitrant pollutants. We report here on products, reactive species and mechanisms of the efficient degradation of perfluorooctanoic acid (PFOA) achieved with a self-pulsing discharge developed previously in our lab. Air or argon were used as plasma feed gas, ultrapure or tap water as aqueous medium. Identified organic intermediate products arise from chain-shortening and defluorination reactions, the latter achieving not only C-F to C-H exchange (hydro-de-fluorination), as reported in the literature, but also C-F to C-OH exchange (hydroxy-de-fluorination). In contrast with chain-shortening, yielding lower homologues of PFOA via selective cleavage of the C-C bond at the carboxylate group, defluorination occurs at various sites of the alkyl chain giving mixtures of different isomeric products. Plasma generated reactive species were investigated under all experimental conditions tested, using specific chemical probes and optical emission spectroscopy. Cross-analysis of the results revealed a striking direct correlation of energy efficiency for PFOA degradation and for production of plasma electrons. In contrast, no correlation was observed for emission bands of either Ar+ or OH radical. These results indicate a prevalent role of plasma electrons in initiating PFOA degradation using self-pulsing discharge plasma above the liquid.

Highly efficient degradation of PFAS and other surfactants in water with atmospheric RAdial plasma (RAP) discharge.

Atmospheric plasma offers a viable approach to new water remediation technologies, best suited for the degradation of persistent organic pollutants such as PFAS, per- and polyfluoroalkyl substances. This paper reports on the remarkable performance of a novel RAdial Plasma (RAP) discharge reactor in treating water contaminated with PFAS surfactants, notably the ubiquitous perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). RAP proved to be versatile and robust, performing very well over a wide range of pollutants concentrations. Thus, PFOA degradation was most satisfactory with regard to all critical indicators, kinetics (≥99% PFOA conversion in less than 2.5 min and 30 min in solutions with initial concentrations of 41 µg/L and 41 mg/L, respectively), byproducts, and energy efficiency (G50 greater than 2000 mg/kWh for 41 µg/L - 4.1 mg/L PFOA initial concentrations). Likewise for PFOS as well as for Triton X-100, a common fluorine-free non-ionic surfactant tested to explore the scope of applicability of RAP to the degradation of surfactants in general. The results obtained with RAP compare most favourably with those reported for state-of-art plasma systems in similar experiments. RAP's excellent performance is attributed to the dense network of radial discharges it generates, randomly spread over the entire exposed surface of the liquid thus establishing an extended highly reactive plasma-liquid interface with both strongly reducing and oxidizing species. Mechanistic insight is offered based on the observed degradation products and on available literature data on the surfactants properties and on their plasma induced degradation investigated in previous studies.

Atmospheric plasma-based approaches for the degradation of dimethyl phthalate (DMP) in water.

Cold plasma based treatment of contaminated water is becoming a promising novel green remediation option. This study assessed the performance of two different cold plasma reactors, using, respectively, a self-pulsing discharge (SPD) and a multipin corona discharge (MCD), in the degradation of dimethyl phthalate (DMP), a persistent and ubiquitous pollutant of the aquatic environment. The process kinetics and energy efficiency, as well as the main plasma generated reactive species were determined under various operating conditions concerning the plasma feed gas and flowrate, the voltage polarity, the input power, the DMP initial concentration, the liquid conductivity, and the aqueous matrix used to prepare DMP solutions for these experiments. The MCD reactor, operated with air as plasma feed gas and negative voltage polarity, gave the best results in terms of rate and energy efficiency. Moreover, variations in plasma input power and in the liquid conductivity have limited effect on DMP degradation rate, making this reactor suitable for treating liquids with a range of initial conductivities The effects of DMP initial concentration on its rate of degradation and on the process energy efficiency were also investigated. Differences in the efficiency of production and distribution of plasma generated reactive species, notably •OH and H2O2, observed for the two tested reactors are discussed in terms of different extension of the plasma/liquid interface and diffusion into the bulk solution. It is proposed that among the reactive species, •OH foremost, and O3 to a lesser extent, play a pivotal role in DMP degradation, while the contribution of H2O2 appears to be limited. The rate of DMP degradation was not drastically different in Milli-Q water and in tap water, a positive outcome in view of practical applications of the technology. The lower rate observed in tap than in Milli-Q water is attributed to the presence of bicarbonate and carbonate, which are known scavengers of hydroxyl radicals.

Chemical and Antimicrobial Effects of Air Non-Thermal Plasma Processing of Fresh Apple Juice with Focus on Safety Aspects.

Freshly squeezed apple juice was subjected to air non-thermal plasma treatment to investigate the capability of this processing method to inactivate microorganisms and to evaluate its safety when applied to liquid food products. Two different configurations of a transient spark discharge in ambient air were tested: an electrospray system with the juice flowing directly through the high voltage needle electrode, and a batch system, where the discharge was generated onto the surface of the juice. The key physico-chemical parameters of the juice, such as pH, conductivity, color, transmittance, and Brix degree, did not significantly change upon treatment. The concentration of nitrate ions formed by the plasma was safe, while that of nitrite ions and hydrogen peroxide was initially higher than the safety limits, but decreased within 24 h post treatment. The plasma effect on individual natural components of the juice, such as sugars, organic acids, and polyphenols, treated in water solutions led to their partial or substantial decomposition. However, when these compounds were plasma-treated altogether in the juice, they remained unaffected. The antimicrobial effect of the plasma processing was evaluated via the inoculation of model microorganisms. A stronger (6 log) decontamination was detected for bacteria Escherichia coli with respect to yeast Saccharomyces cerevisiae. Plasma processing led to a substantial extension of the juice shelf-life by up to 26 days if refrigerated, which represents a promising application potential in food technology.

Application of Fluorescence-Based Probes for the Determination of Superoxide in Water Treated with Air Non-thermal Plasma.

Superoxide is one of the reactive oxygen species (ROS) in non-thermal plasmas generated by electrical discharges in air at room temperature and atmospheric pressure. One important application of such plasmas is the activation of advanced oxidation processes for air and water decontaminating treatments. When in contact with aqueous media, ROS and notably superoxide can react at the plasma/liquid interface or transfer and react into the liquid. While the detection of superoxide in plasma-treated water has been reported in the literature, to the best of our knowledge, quantitative determinations are lacking. We report here the determination of superoxide rate of formation and steady-state concentration in water subjected to air non-thermal plasma in a streamer discharge reactor used previously to treat various organic contaminants. After detecting the presence of superoxide by spin-trapping and electron paramagnetic resonance analyses, we applied superoxide-selective fluorescent probes to carry out quantitative determinations. The first probe tested, 3',6'-bis(diphenylphosphinyl) fluorescein (PF-1), was not sufficiently soluble, but the second one, fluorescein-bis-[(N-methylpyridinium-3-yl)sulfonate iodide] (FMSI), was applied successfully. Under typical plasma operating conditions, the rate of superoxide formation and its steady-state concentration were (0.27 ± 0.15) µM s-1 and (0.007 ± 0.004) nM, respectively. The procedure outlined here can be usefully applied to detect and quantify superoxide in water treated by different plasma sources in various types of plasma reactors.

Comment on "Water-Soluble Fluorescent Probe with Dual Mitochondria/Lysosome Targetability for Selective Superoxide Detection in Live Cells and in Zebrafish Embryos".

Recently, a new water-soluble, fluorescein-based probe for the detection of superoxide radical anion in aqueous media was developed by Lu et al. (ACS Sens. 2018, 3, 59-64). The probe was proven to be selective for superoxide and was used successfully also in cells and zebrafish embryos. To characterize the response of the probe to superoxide, Lu et al. used KO2 dissolved in deionized water as a surrogate. In testing this probe in different applications, we repeated some of these experiments and came to realize that the fluorescence signal observed by the Authors in their experiments with KO2 was incorrectly attributed to the reaction of the probe with superoxide and is due instead to its reactions with HO- and HO2-. We show that indeed under the conditions used in these assays KO2 undergoes very fast reaction with water to form HO- and HO2-. On the other hand, by using a proper surrogate, namely, KO2 dissolved in DMSO, and spin trapping experiments, we confirmed the ability of the probe to detect superoxide.

Radicals and Ions Formed in Plasma-Treated Organic Solvents: A Mechanistic Investigation to Rationalize the Enhancement of Electrospinnability of Polycaprolactone.

This paper reports and discusses the beneficial effects on the quality of electrospun polycaprolactone nanofibers brought about by pretreatment of the solvent with non-thermal plasma. Chloroform/dimethylformamide 9:1 (CHCl3:DMF 9:1) and pure chloroform were pretreated by a few minute exposure to the plasma generated by an atmospheric pressure plasma jet (APPJ). Interestingly, when pure chloroform was used, the advantages of plasma pretreatment of the solvent were way less pronounced than found with the CHCl3:DMF 9:1 mixture. The chemical modifications induced by the plasma in the solvents were investigated by means of complementary analytical techniques. GC-MS revealed the formation of solvent-derived volatile products, notably tetrachloroethylene (C2Cl4), 1,1,2,2-tetrachloroethane (C2H2Cl4), pentachloroethane (C2HCl5), hexachloroethane (C2Cl6) and, in the case of the mixed solvent, also N-methylformamide (C2H5NO). The chlorinated volatile products are attributed to reactions of ·Cl and Cl-containing methyl radicals and carbenes formed in the plasma-treated solvents. ·Cl and ·CCl3 radicals were detected and identified by EPR spectroscopy analyses. Ion chromatography revealed the presence of Cl-, NO 3 - , and HCOO- (the latter only in the presence of DMF) in the plasma-treated solvents, thus accounting for the observed increased conductivity and acidification of the solvent after plasma treatment. Mechanisms for the formation of these solvent derived products induced by plasma are proposed and discussed. The major role of radicals and ions in the plasma chemistry of chloroform and of the chloroform/dimethylformamide mixture is highlighted. The results provide insight into the interaction of plasma with organic solvents, a field so far little explored but holding promise for interesting applications.

A new rapid procedure for simultaneous determination of glyphosate and AMPA in water at sub µg/L level.

Glyphosate is the most used pesticide worldwide and its impact on the environment is becoming increasingly significant. Glyphosate and its main metabolite AMPA are frequently detected in streams and rivers. In this study, an analytical method is presented that combines Ultra-High Performance Liquid Chromatography with mass spectrometry (UHPLC-ESI-MS/MS) for glyphosate and AMPA analysis in environmental water samples. The method was developed starting from an application of Waters Corporation, and involves the use of an alternative derivatizing reagent, the commercially available AccQ·Tag™ Ultra Derivatization Kit (Waters Corporation, Milford, MA, USA). The kit contains the derivatizing reagent 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC). Derivatization takes place directly in the injection vial and no sample pre-concentration is needed. The derivatization is simple, quick and robust, which fits well within the needs of a routine method for the analysis of glyphosate and AMPA. Derivatized glyphosate and AMPA were recorded in positive ion mode. The method demonstrates a good linear relationship in the concentration range from 0.2 µg/L for glyphosate and 0.05 µg/L for AMPA to 100 µg/L and an accurate recovery. The method developed has been successfully applied to the determination of glyphosate and AMPA in 23 runoff water samples collected from a field in the Po Valley (North-East Italy), an agricultural area where glyphosate is widely used.

Air non-thermal plasma treatment of Irgarol 1051 deposited on TiO2.

The herbicide 2-(methylthio)-4-(tert-butylamino)-6-(cyclopropylamino)-s-triazine (tradename Irgarol 1051, abbreviated here as Irg), widely used in antifouling paints as biocide inhibiting seaweeds growth, is found in coastal waters in the vicinity of ports and harbors. In this work, Irg was subjected to air non-thermal plasma (NTP) treatment, alone and in the presence of TiO2. A dielectric barrier discharge reactor was used, powered by AC voltage (18 kV, 50 Hz) to produce air-NTP directly above the surface of the aqueous Irg solution to be treated. Due to the very fast degradation of Irg occurring under the experimental conditions used, the results of kinetic experiments failed to detect any rate enhancement due to titania induced photodegradation. We show, however, that pre-adsorption of Irg on titania provides a means to significantly increase Irg NTP-induced degradation throughput, a result which might have useful practical consequences. It is concluded that this phenomenon is due to the acidic character of TiO2 which brings more Irg in solution by increasing the value of the ionization ratio, [IrgH+]/[Irg]. Product analysis, performed by LC/ESI-MSn, allowed us to detect and identify numerous intermediates of Irg degradation and to propose different competing reaction pathways for the investigated NTP induced Irg advanced oxidation process. The extent of mineralization to CO2 was assessed by Total Carbon analysis. It was found to reach 95% after 5 h treatment of Irg solutions with an initial concentration of 5·10-6 M. These results confirm the capability of our NTP prototype reactor to mineralize persistent organic pollutants.

Dissipation of terbuthylazine, metolachlor, and mesotrione in soils with contrasting texture.

This study evaluates the dissipation of terbuthylazine, metolachlor, and mesotrione at different depths in soils with contrasting texture. The field trial was conducted at the Padua University Experimental Farm, north-east Italy. The persistence of three herbicides was studied in three different soil textures (clay soil, sandy soil, and loamy soil) at two depths (0-5 and 5-15 cm). Soil organic carbon content was highest in the clay (1.10%) followed by loam (0.67%) and sandy soil (0.24%); the pH of soils was sub-alkaline. Terbuthylazine, metolachlor, and mesotrione were applied on maize as a formulated product (Lumax®) at a dose of 3.5 L ha-1. Their dissipation in the treated plots was followed for 2 months after application. The concentrations of herbicides were analyzed by liquid chromatography-mass spectrometry. The dissipation of terbuthylazine, metolachlor, and mesotrione could be described by a pseudo first-order kinetics. Terbuthylazine showed the highest DT50, followed by metolachlor and mesotrione. Considering the tested soil, the highest DT50 value was found in clay soil for terbuthylazine and metolachlor, whereas for mesotrione there was no difference among soils. Significant differences were found between the two soil depths for terbuthylazine and metolachlor, whereas none were found for mesotrione. These results suggest that soil texture and depth have a strong influence on the dissipation of terbuthylazine and metolachlor, whereas no influence was observed on mesotrione because of its chemical and physical properties.

Oxidation of clofibric acid in aqueous solution using a non-thermal plasma discharge or gamma radiation.

In this work, we study degradation of clofibric acid (CFA) in aqueous solution using either ionizing radiation from a60Co source or a non-thermal plasma produced by discharges in the air above the solution. The results obtained with the two technologies are compared in terms of effectiveness of CFA degradation and its by-products. In both cases the CFA degradation follows a quasi-exponential decay in time well modelled by a kinetic scheme which considers the competition between CFA and all reaction intermediates for the reactive species generated in solution as well as the amount of the end product formed. A new degradation law is deduced to explain the results. Although the end-product CO2 was detected and the CFA conversion found to be very high under the studied conditions, HPLC analysis reveals several degradation intermediates still bearing the aromatic ring with the chlorine substituent. The extent of mineralization is rather limited. The energy yield is found to be higher in the gamma radiation experiments.

Treatment of methyl orange by nitrogen non-thermal plasma in a corona reactor: The role of reactive nitrogen species.

Methyl orange (MO) azo dye served as model organic pollutant to investigate the role of reactive nitrogen species (RNS) in non-thermal plasma (NTP) induced water treatments. The results of experiments in which MO aqueous solutions were directly exposed to N2-NTP are compared with those of control experiments in which MO was allowed to react with nitrite, nitrate and hydrogen peroxide, which are species formed in water exposed to N2-NTP. Treatment of MO was also performed in PAW, Plasma Activated Water, that is water previously exposed to N2-NTP. Both direct N2-NTP and N2-PAW treatments induced the rapid decay of MO. No appreciable reaction was instead observed when MO was treated with NO3(-) and H2O2 either under acidic or neutral pH. In contrast, in acidic solutions MO decayed rapidly when treated with NO2(-) and with a combination of NO2(-) and H2O2. Thorough product analysis was carried out by HPLC coupled with UV-vis and ESI-MS/MS detectors. In all experiments in which MO reaction was observed, the major primary product was a derivative nitro-substituted at the ortho position with respect to the N,N-dimethylamino group of MO. The reactions of RNS are discussed and a mechanism for the observed nitration products is proposed.

Synthesis and Evaluation as Prodrugs of Hydrophilic Carbamate Ester Analogues of Resveratrol.

Resveratrol (3,5,4'-trihydroxy-trans-stilbene) is an unfulfilled promise for health care: its exploitation is hindered by rapid conjugative metabolism in enterocytes and hepatocytes; low water solubility is a serious practical problem. To advantageously modify the physicochemical properties of the compound we have developed prodrugs in which all or part of the hydroxyl groups are linked via an N-monosubstituted carbamate ester bond to promoieties derived from glycerol or galactose, conferring higher water solubility. Kinetic studies of hydrolysis in aqueous solutions and in blood indicated that regeneration of resveratrol takes place in an appropriate time frame for delivery via oral administration. Despite their hydrophilicity some of the synthesized compounds were absorbed in the gastrointestinal tract of rats. In these cases the species found in blood after administration of a bolus consisted mainly of partially deprotected resveratrol derivatives and of the products of their glucuronidation, thus providing proof-of-principle evidence of behavior as prodrugs. The soluble compounds largely reached the lower intestinal tract. Upon administration of resveratrol, the major species found in this region was dihydroresveratrol, produced by enzymes of the intestinal flora. In experiments with a fully protected (trisubstituted) deoxygalactose containing prodrug, the major species were the prodrug itself and partially deprotected derivatives, along with small amounts of dihydroresveratrol. We conclude that the N-monosubstituted carbamate moiety is suitable for use in prodrugs of polyphenols.

Oxidation mechanisms of CF2Br2 and CH2Br2 induced by air nonthermal plasma.

Oxidation mechanisms in air nonthermal plasma (NTP) at room temperature and atmospheric pressure were investigated in a corona reactor energized by +dc, -dc, or +pulsed high voltage.. The two bromomethanes CF(2)Br(2) and CH(2)Br(2) were chosen as model organic pollutants because of their very different reactivities with OH radicals. Thus, they served as useful mechanistic probes: they respond differently to the presence of humidity in the air and give different products. By FT-IR analysis of the postdischarge gas the following products were detected and quantified: CO(2) and CO in the case of CH(2)Br(2), CO(2) and F(2)C ═ O in the case of CF(2)Br(2). F(2)C ═ O is a long-lived oxidation intermediate due to its low reactivity with atmospheric radicals. It is however removed from the NTP processed gas by passage through a water scrubber resulting in hydrolysis to CO(2) and HF. Other noncarbon containing products of the discharge were also monitored by FT-IR analysis, including HNO(3) and N(2)O. Ozone, an important product of air NTP, was never detected in experiments with CF(2)Br(2) and CH(2)Br(2) because of the highly efficient ozone depleting cycles catalyzed by BrOx species formed from the bromomethanes. It is concluded that, regardless of the type of corona applied, CF(2)Br(2) reacts in air NTP via a common intermediate, the CF(2)Br radical. The possible reactions leading to this radical are discussed, including, for -dc activation, charge exchange with O(2)(-), a species detected by APCI mass spectrometry.

Comparison of the rates of phenol advanced oxidation in deionized and tap water within a dielectric barrier discharge reactor.

Electric non-thermalizing discharges provide promising novel means to induce oxidation of organic pollutants in water. The decomposition of phenol in solutions prepared with deionized (milliQ) and tap water was studied and compared in a Dielectric Barrier Discharge (DBD) reactor. Interestingly, a significant rate increase was found in tap with respect to milliQ water. Control experiments proved that this was not the effect of conductivity or of traces of iron or of residual active chlorine from the depuration process operated in the aqueducts of Italian cities. The same increase in efficiency as observed in tap water was instead obtained when phenol was treated in solutions containing bicarbonate anions in the same concentration as present in tap water, an effect attributed to buffering of the solution pH. The role of pH has been investigated thoroughly by measuring the process efficiency over a wide pH range, from 2 to 10, by using different buffer systems to probe reactivity at near neutral pH, the most relevant for drinking water applications, and by testing the effect of different buffer concentrations. These latter experiments failed to detect any significant kinetic effect attributable to the well known reactivity of bicarbonate as quencher of OH radicals.

Effect of vegetative filter strips on herbicide runoff under various types of rainfall.

Narrow vegetative filter strips proved to effectively reduce herbicide runoff from cultivated fields mainly due to the ability of vegetation to delay surface runoff, promote infiltration and adsorb herbicides. A field trial was conducted from 2007 to 2009 in north-east Italy in order to evaluate the effectiveness of various types of vegetative filter strips to reduce spring-summer runoff of the herbicides mesotrione, metolachlor and terbuthylazine, widely used in maize, and to evaluate the effect of the rainfall characteristics on the runoff volume and concentration. Results show that without vegetative filter strip the herbicide load that reaches the surface water is about 5-6 g ha(-1)year(-1) for metolachlor and terbuthylazine (i.e. 0.5-0.9% of the applied rate), confirming that runoff from flat fields as in the Po Valley can have a minor effect on the water quality, and that most of the risk is posed by a few, or even just one extreme rainfall event with a return period of about 25-27 years, causing runoff with a maximum concentration of 64-77 µg L(-1). Mesotrione instead showed rapid soil disappearance and was observed at a concentration of 1.0-3.8 µg L(-1) only after one extreme (artificial) rainfall. Vegetative filter strips of any type are generally effective and can reduce herbicide runoff by 80-88%. Their effectiveness is steady even under severe rainfall conditions, and this supports their implementation in an environmental regulatory scheme at a catchment or regional scale.

Structure elucidation of the dye Acid Red 131: complete (1)H, (13)C and (15)N NMR data assignment.

The chemistry of dyes and pigments is relevant to the textile industry, because of the importance to establish the best conditions for the finishing process and to understand the interactions among various compounds to yield the correct hue and nuances. For this reason, the molecular structure of a monoazo acid dye, C.I. Acid Red 131, was elucidated and characterized by homo- and hetero-nuclear NMR, MS, IR and UV spectroscopy techniques.