Combining TiO2-photocatalysis and wetland reactors for the efficient treatment of pesticides

In the present work the photocatalytic and biological degradation of two commercial mixtures of pesticides (Folimat and Ronstar) and two fungicides (pyrimethanil and triadimenol) has been studied. The evolution of some components of these commercial products (dicofol, tetradifon and oxadiazon) and that of the two fungicides has been monitored by means of HPLC, GC-MS, TOC and toxicity (Lemna minor toxicity test) measurements. The photocatalytic method was able to degrade dicofol, tetradifon, pyrimethanil, triadimenol and the components of Ronstar with the exception of oxadiazon. In addition to this, the photocatalytic method eliminated pyrimethanil toxicity and reduced that of triadimenol by a 90%, Ronstar by a 78% and Folimat by an 87%. Nevertheless, the wetland reactors alone could reduce the toxicity of only the former. Finally, the proper dosage of the water containing the pesticides to a photocatalytic reactor followed by a wetland reactor resulted to be the most successful strategy for the detoxification of the studied compounds and their mixtures.     

Ground laser remote sensing measurements of a Saharan dust outbreak in Central Spain. Influence on PM10 concentrations in the lower and upper Spanish plateaus

This paper presents the hourly evolution of a severe Saharan dust outbreak, (SDO), affecting Central Spain over July 23-24, 2004 measured with a laser remote sensing device at a location close to the Guadarrama mountain range foothills and its impact on PM10 levels (particles with an aerodynamic diameter below 10 microm) recorded at four contrasting monitoring stations located in the upper and lower Spanish plateau, some 170km apart. During the period of study the Saharan dust layer, (SDL), presented significant hourly variability in height (3600-1500m), depth (1500-700m) and aerosol dust loading (extinction coefficient, EC, 0.22-1.28km(-1)). Overnight layering was generally observed whereas a well mixed layer prevailed in the afternoon. The (SDO) impact on the lower levels took place approximately 12h after the (SDL) was initially observed and triggered by a descending dust enriched, evidencing the important role of subsidence over the presence of dust in lower altitudes. During the event, PM10 levels at all the stations exceeded EU air quality daily mean standards, 50 microgm(-3), on 2-4days. The maximum values ranged from 185 to 245 microgm(-3) depending on the monitoring station. The impact on PM10 spread from 2days in the upper plateau to 3-4 in the lower plateau, in agreement with the geographical location of the monitoring stations with respect to the southwest origin of the intrusion. The impact was even more dramatic on PM10 hourly concentrations, leading to maximum hourly peaks ranging from 322 to 598 microgm(-3) again depending on the monitoring station. Correlations between EC vertical profiles and PM10 hourly concentrations at the monitoring stations showed the great influence of the (SDO) on surface concentrations. The best linear fits corresponded to the extinction coefficients in the lower altitudes (close to the lower range of the device 500-650m), EC2, yielding satisfactory correlation coefficients ranging from 0.68 to 0.71. The low variability of the slope of each individual linear fit, 19.2%, shows the similar impact of (SDO) on the PM10 hourly concentrations recorded in the area under study.     

Vegetation as an Indicator of Soil Properties and Water Quality in the Akarçay Stream (Turkey)

In this study, the relationship among water quality, soil properties, and plant coverage in the region of the Akarçay stream was examined. Correlation analyses were carried out between soil samples taken from each of four plant communities in the Akarçay basin and water in the Akarçay stream. The four plant communities in the study area are as follows: Limonium lilacinum (Boiss. et Bal.) Wag., Alhagi pseudalhagi (M. Bieb.) Desv. Peganum harmala L., and Hordeum marinum Huds. subsp. marinum. B, Cl, EC, K, Mg, Na, pH, and SO₄ data from both soil and water samples were subjected to statistical analysis, and significant correlations were obtained (p < 0.05). These correlations indicated that the chemical features of the soil had a major effect on water quality. The important parameters were B, Cl, EC, K, Mg, Na, pH, and SO₄ for Limonium lilacinum communities; Ca, K, and pV for Peganum harmala; and B, Cl, Mg, pH, and pV for Alhagi pseudalhagi. There were also statistically significant relationships (p < 0.05) among the parameters examined. These findings strongly suggested that these plant communities can be used as indicators for soil chemistry and water quality.     

Influence of soil properties on bioaccumulation of 14C-simazine in earthworms Eisenia foetida

The toxicity of pesticides has been evaluated by several methods including tests with earthworms in both artificial and natural soils treated with the compounds. The ecological niches of earthworms make them good bioindicators of soil contamination. The bioaccumulation of 14C-simazine (6-chloro-N2-N4-diethyl- 1,3,5-triazine-2,4-diamine) was evaluated in earthworms (Eisenia foetida) maintained during three months in two substrates with different physical-chemical characteristics. The substrates were treated with 3.0 mg and 330 kBq of 14C-simazine kg(-1) substrate. Results indicated that worms did not influence simazine dissipation in both substrates as indicated by similar recoveries and with no statistical differences with and without earthworms. The radiocarbon recoveries were 86.8 and 95.3%, respectively in the substrates with lower and higher organic matter contents with earthworms, and 91.0 and 107.4% in the same substrates without worms. However, in earthworms the recoveries were statistically higher when they were maintained in the substrate with lower amount of organic matter (0.89%) than from the higher one (0.33%). Consequently, 14C-simazine bioconcentration factor (BCF) was also greater in the substrate with lower organic matter (6.89+/-1.55) than in the substrate with higher organic matter content (0.88+/-0.06). The results suggest that the higher soil organic matter content will cause lower probability of contamination of soil organisms with simazine.     

Ecotoxicological assessment for receiving waters with the premetamorphic tadpoles acute assay

The toxicity of receiving waters was evaluated by means of the young tadpoles assays. The sentinel organism was Bufo arenarum, an indigenous anuran species. The assayed water samples were taken from a highly polluted urban watercourse (Reconquista River, Buenos Aires, Argentina), characterized by high concentration of nitrites, phosphates and heavy metals. The toxicity of water samples was assessed performing the pass-fail test and by means of the NOEC and LC(50); TUs (toxic units) were also calculated. The effect of the addition of a positive control (Cd) on the toxicity of the river water samples was also examined. Water samples of three sites, characterised by their different degree of pollution, were assayed. The lethal response had a clear cut correspondence with the water quality of the sample evaluated by means of physicochemical parameters. In most cases, the dilution of the samples resulted in a significant reduction of their toxicity to TU values compatible to those stated by the USEPA for industrial effluents. It was concluded that (a) the used Bufo arenarum bioassay was an adequate method for assessing the toxicity of natural polluted water samples and (b) the three considered endpoints showed no important differences after 48 or 96 h of exposure, therefore we concluded that it may not be necessary to extend the assay for a longer period than 48 h.     

Pressurised liquid-liquid extraction. An approach to the removal of inorganic non-metal species from used industrial oils

Modified pressurised hot water is used for the development of a high pressure liquid-liquid extraction method for the decontamination of used industrial oils from inorganic non-metal species (chlorine, fluorine and sulphur). The oils were subjected to dynamic extraction with water modified with 5% v/v HNO3 at 200 degrees C as extractant. Under these working conditions the analytes were transferred to the aqueous phase. Spontaneous separation of the two immiscible liquid phases (the used oil and extract) takes place in the collection flask after extraction. The treated and untreated oil samples were oxidised and the chloride, fluoride and sulphate thus formed were determined by ion-chromatography. The method was applied to four oil samples from different locations in Spain. A residence time of approximately =10 min provided oil samples from which 88.3%, 89.4% and 89.4% of chloride, fluoride and sulphate, respectively, have been removed with respect to the initial concentration of each analyte in the oil. The repeatability, expressed as relative standard deviation (RSD), was of 11.9%, 13.7% and 7.2% for Cl(-), F(-) and SO4(2-), respectively; whilst the within-laboratory reproducibility yielded RSDs of 6.2%, 7.9% and 6.2% for the same analytes. The proposed approach has proved to be efficient, simple, easily transferable to industrial scale, cheap, fast and environmentally friendly.     

Photodegradation of the herbicide Norflurazon sensitised by Riboflavin. A kinetic and mechanistic study

The kinetics and mechanism of the Riboflavin (Rf)-promoted photochemical degradation with visible light of the herbicide Norflurazon (NF) has been studied by time-resolved and stationary techniques. Using light of wavelength higher than 400 nm--a region where NF is totally transparent--and with concentrations of Rf and NF of ca. 0.02 and 1 mM, respectively, only the excited triplet state of Rf ((3)Rf*) is quenched by NF, in competition with dissolved ground state triplet oxygen, O(2)((3)Sigma(g)(-)). NF degradation mainly occurs by reaction with superoxide radical anion O(2)(-) formed through two electron transfer steps: from NF to (3)Rf*, yielding Rf radical anion, and from this anion to O(2)((3)Sigma(g)(-)), regenerating ground state Rf. Although singlet molecular oxygen is also produced, NF only quenches this oxidative species in a physical mode. The global result is the photoprotection of the sensitiser and the photodegradation of NF.     

Ecological implications of anti-pathogen effects of tropical fungal endophytes and mycorrhizae

We discuss studies of foliar endophytic fungi (FEF) and arbuscular mycorrhizal fungi (AMF) associated with Theobroma cacao in Panama. Direct, experimentally controlled comparisons of endophyte free (E-) and endophyte containing (E+) plant tissues in T. cacao show that foliar endophytes (FEF) that commonly occur in healthy host leaves enhance host defenses against foliar damage due to the pathogen (Phytophthora palmivora). Similarly, root inoculations with commonly occurring AMF also reduce foliar damage due to the same pathogen. These results suggest that endophytic fungi can play a potentially important mutualistic role by augmenting host defensive responses against pathogens. There are two broad classes of potential mechanisms by which endophytes could contribute to host protection: (1) inducing or increasing the expression of intrinsic host defense mechanisms and (2) providing additional sources of defense, extrinsic to those of the host (e.g., endophyte-based chemical antibiosis). The degree to which either of these mechanisms predominates holds distinct consequences for the evolutionary ecology of host-endophyte-pathogen relationships. More generally, the growing recognition that plants are composed of a mosaic of plant and fungal tissues holds a series of implications for the study of plant defense, physiology, and genetics.     

A method for simplifying the analysis of traffic accidents injury severity on two-lane highways using Bayesian networks

Introduction

This study describes a method for reducing the number of variables frequently considered in modeling the severity of traffic accidents. The method's efficiency is assessed by constructing Bayesian networks (BN).

Method

It is based on a two stage selection process. Several variable selection algorithms, commonly used in data mining, are applied in order to select subsets of variables. BNs are built using the selected subsets and their performance is compared with the original BN (with all the variables) using five indicators. The BNs that improve the indicators’ values are further analyzed for identifying the most significant variables (accident type, age, atmospheric factors, gender, lighting, number of injured, and occupant involved). A new BN is built using these variables, where the results of the indicators indicate, in most of the cases, a statistically significant improvement with respect to the original BN.

Conclusions

It is possible to reduce the number of variables used to model traffic accidents injury severity through BNs without reducing the performance of the model.

Impact on Industry

The study provides the safety analysts a methodology that could be used to minimize the number of variables used in order to determine efficiently the injury severity of traffic accidents without reducing the performance of the model.     

Carbon paste electrodes modified with biosolids, soils and biocomposites utilized to study the interaction between organic matter and copper

Carbon paste electrodes (CPEs) modified with a biosolid, two types of soils with different amounts of organic matter (OM), and two biocomposites (soils mixed with a biosolid) were used to assess and compare the Cu(II) ion retention properties of the organic matter contained in the samples. The accumulation of Cu(II) on the surface of the modified carbon paste electrodes (MCPEs) was performed under open-circuit conditions. When comparing the response of the MCPEs while assessing parameters such as pH, preconcentration time, and adsorption/desorption capacity, it was found that the reaction mechanism of the two soils is different between the soils and dissimilar from the biosolid; while the biocomposites show reaction mechanisms that are intermediate between those of the soils and the biosolid. This was proven with the use of infrared spectroscopy, since the FTIR spectra show similarities between the two soils and significant differences between the soils and the biosolid.