Gabriel Pérez-Lucas

Assessment of agro-industrial and composted organic wastes for reducing the potential leaching of triazine herbicide residues through the soil

In this study, we examined the effect of four different organic wastes--composted sheep manure (CSM), spent coffee grounds (SCG), composted pine bark (CPB) and coir (CR)--on the sorption, persistence and mobility of eight symmetrical and two asymmetrical-triazine herbicides: atrazine, propazine, simazine, terbuthylazine (chlorotriazines), prometon (methoxytriazine), prometryn, simetryn, terbutryn (methylthiotriazines), metamitron and metribuzin (triazinones). The downward movement of herbicides was monitored using disturbed soil columns packed with a clay loam soil (Hipercalcic calcisol) under laboratory conditions. For unamended and amended soils, the groundwater ubiquity score (GUS) was calculated for each herbicide on the basis of its persistence (as t½) and mobility (as KOC). All herbicides showed medium/high leachability through the unamended soils. The addition of agro-industrial and composted organic wastes at a rate of 10% (w:w) strongly decreased the mobility of herbicides. Sorption coefficients normalized to the total soil organic carbon (KOC) increased in the amended soils. These results suggest that used organic wastes could be used to enhance the retention and reduce the mobility of the studied herbicides in soil.

Photocatalytic transformation of sixteen substituted phenylurea herbicides in aqueous semiconductor suspensions: Intermediates and degradation pathways

The photocatalytic degradation of sixteen substituted phenylurea herbicides (PUHs) in pure water has been studied using zinc oxide (ZnO) and titanium dioxide (TiO(2)) as photocatalyst under artificial light irradiation. Photocatalytic experiments showed that the addition of these chalcogenide oxides in tandem with the oxidant (Na(2)S(2)O(8)) strongly enhances the degradation rate of these compounds in comparison with those carried out with ZnO and TiO(2) alone and photolytic tests. Comparison of catalysts showed that ZnO is the most efficient for the removal of such herbicides in optimal conditions and at constant volumetric rate of photon absorption in the photoreactor. Thus, the complete disappearance of all the studied compounds was achieved after 20 min of illumination in the ZnO/Na(2)S(2)O(8) system. The main photocatalytic intermediates detected during the degradation of PUHs were identified. The probable photodegradation pathways were proposed and discussed. The main steps involved: N-demethylation of the N,N-dimethylurea-substituted compounds followed of N-demethylation and N-demethoxylation of the N-methoxy-N-methyl-substituted ureas and hydroxylation of aromatic rings and their aliphatic side-chains of both, parent compounds and intermediates.

Assessment of the leaching potential of 12 substituted phenylurea herbicides in two agricultural soils under laboratory conditions.

In this study, the potential groundwater pollution of 12 substituted phenylurea herbicides (chlorbromuron, chlorotoluron, diuron, fenuron, fluometuron, isoproturon, linuron, metobromuron, metoxuron, monolinuron, Monuron, and neburon) was investigated under laboratory conditions. For this purpose, leaching studies were conducted using disturbed soil columns filled with two different agricultural soils, one hypercalcic calcisol (HC) and the other endoleptic phaeozem (EP). In the case of the HC, all of the studied herbicides were found in leachates, while for the EP only, chlorbromuron, chlorotoluron, isoproturon, monolinuron, and, especially, fenuron were recovered. For both soils, the groundwater ubiquity score (GUS) index was calculated for each herbicide on the basis of its persistence (as t(1/2)) and mobility (as K(OC)). The half-lives obtained were markedly higher in the EP (217-518 days) than in the HC (71-178 days). As a consequence, higher values of GUS indexes were observed for EP. The ratio of the GUS between the EP and the HC was about 1.3.

Reclamation of Water Polluted with Flubendiamide Residues by Photocatalytic Treatment with Semiconductor Oxides.

The photodegradation of flubendiamide (benzenedicarboxamide insecticide), a relatively new insecticide was investigated in aqueous suspensions binary (ZnO of and TiO2) and ternary (Zn2TiO4 and ZnTiO3) oxides under artificial light (300–460 nm) irradiation. Photocatalytic experiments showed that the addition of semiconductors, especially ZnO and TiO2, in tandem with an electron acceptor (Na2S2O8) enhances the degradation rate of this compound in comparison with those carried out with catalyst alone and photolytic tests. The photocatalytical degradation of flubendiamide using ZnO/Na2S2O8 and TiO2/Na2S2O8 followed first‐order kinetics. In addition, desiodo‐flubendiamide was identified during the degradation of flubendiamide. Finally, application of these reaction systems in different waters (tap, leaching and watercourse) showed the validity of the treatments, which allowed the removal of flubendiamide residues in these drinking and environmental water samples.

Recent Overview on the Abatement of Pesticide Residues in Water by Photocatalytic Treatment Using TiO2

The water bodies’ pollution with phytosanitary products can pose a serious threat to aquatic ecosystems and drinking water resources. The usual appearance of pesticides in surface water, waste water and groundwater has driven the search for proper methods to remove persistent pesticides. Although typical biological treatments of water offer some advantages such as low cost and operability, many investigations referring to the removal of pesticides have suggested that in many cases they have low effectiveness due to the limited biodegradability of many agrochemicals. In recent years, research for new techniques for water detoxification to avoid these disadvantages has led to processes that involve light, which are called advanced oxidation processes (AOPs). Among the different semiconductor (SC) materials tested as potential photocatalysts, titanium dioxide (TiO 2 ) is the most popular because of its photochemical stability, commercial availability, non-toxic nature and low cost, high photoactivity, ease of preparation in the laboratory, possibility of doping with metals and non-metals and coating on solid support. Thus, in the present review, we provide an overview of the recent research being developed to photodegrade pesticide residues in water using TiO 2 as photocatalyst.

Behavior of Triazole Fungicide Residues from Barley to Beer

Triazole fungicides (TZFs) are sterol biosynthesis inhibitors (SBIs). The mechanism of action of the azole (triazole and imidazole) fungicides lies in their ability to interfere with the biosynthesis of fungal biosteroids and inhibit ergosterol biosynthesis. They are classified as demethylation inhibitors (DMIs), the most important SBIs. Based on the current information, an overview on the behavior and fate of TZF residues during malting and brewing stages (mashing, boiling, and fermentation) is reviewed. In the first phase, TZF residues may remain into the malt. Later, TZF residues can be transferred from the malt to sweet wort and beer inducing in some cases of stuck/sluggish fermentation for both lager and ale beer. As a consequence, some organoleptic properties of the beer may be altered. Therefore, studies to examine the behavior of TZFs during beer brewing are necessary to assess the beer quality and perform a dietary risk assessment.

Solar reclamation of wastewater effluent polluted with bisphenols, phthalates and parabens by photocatalytic treatment with TiO2/Na2S2O8 at pilot plant scale

Investigations of anthropogenic contaminants in fresh- and wastewater have shown a wide variety of undesirable organic compounds such as Endocrine Disruptors (EDs). As a result, wastewater treatments using innovative technologies to remove those organic compounds are required. In this paper, the photodegradation of six EDs in wastewater at pilot plant scale is reported. The EDs were bisphenol A, bisphenol B, diamyl phthalate, butyl benzylphthalate, methylparaben and ethylparaben. Commercial TiO2 nanopowders (P25, Alfa Aesar and Kronos vlp 7000) were used as photocatalysts. The operating variables (type and loading catalyst, effect of electron acceptor and pH) were previously optimized under laboratory conditions. The results show that the use of TiO2 alongside an electron acceptor like Na2S2O8 strongly enhances the degradation rate of the studied compounds compared with photolytic tests, especially P25. The oxidation rates of the EDs at pilot plant scale were calculated following the disappearance of the target compound as a function of fluence (H). The ED degradation followed a pseudo-first order kinetics in all cases. In our experimental conditions, the half-fluence (H50) varied from 79 to 173 J cm-2 (photolytic test), 10-117 J cm-2 (TiO2 vlp 7000) and 3-58 J cm-2 (TiO2 P25), for bisphenol B and butyl benzylphthalate, respectively. It is concluded that solar photocatalysis using the tandem TiO2/Na2S2O8 can be considered as an environmental-friendly tool for water detoxification and a sustainable technology for environmental remediation, especially in the Mediterranean Basin, where many places receive more than 3000 h of sunshine per year. Although the cost depends on the nature of the pollutant, the treatment cost was estimate to be about 150 € m-3 for photocatalytic treatment with TiO2 P25.

Valorization of Organic Wastes to Reduce the Movement of Priority Substances Through a Semiarid Soil

In this work, we examined the effect of two different organic wastes, composted sheep manure and coir, on the sorption, persistence, and mobility of three pesticides (alachlor, chlorfenvinphos, and chlorpyrifos) included as priority substances in European Directive 2013/39/EU. With this aim, leaching studies were conducted using disturbed soil columns filled with a typical agricultural soil (hipercalcic calcisol) from a semiarid area (southeastern Spain) to determine their potential for groundwater pollution. The three compounds were found in leachates of unamended soil although in different proportions: 53% (alachlor), 9% (chlorfenvinphos), and 6% (chlorpiryfos). The addition of organic wastes significantly increased the sorption of the studied pesticides. As a consequence, the half-lives of the studied pesticides were higher in amended than in unamended soils. A marked reduction of the amount recovered in leachates was observed in the amended soils, except for chlorpiryfos, whose recoveries barely changed. According to their potential groundwater pollution calculated as the groundwater ubiquity score (GUS) index, alachlor and chlorfenvinphos show medium leachability while chlorpiryfos is unlikely to leach.