X-ray microtomographic characterization of highly rough titanium cold gas sprayed coating for identification of effective surfaces for osseointegration

A highly rough titanium coating obtained by Cold Gas Spray (CGS) has been characterized by means of high-resolution 3D microtomography (micro-CT) with the aim to evaluate its open and close porosity for possible use in orthopaedic implants to promote osseointegration. Micro-CT allowed a qualitative and quantitative description of the main features, morphology of the pores and surface roughness of the coating. Several numerical values were obtained to describe size, form and distribution of the closed/inner and open/outer pores. Additionally, surface roughness and open porosity were image-analyzed to find the effective surface for osseointegration.

Comparison of three pesticide fate models with respect to the leaching of two herbicides under field conditions in an irrigated maize cropping system

The ability of three models (PEARL, MACRO and PRZM) to describe the water transfer and leaching of the herbicides S-metolachlor and mesotrione as observed in an irrigated maize monoculture system in Toulouse area (France) was compared. The models were parameterized with field, laboratory and literature data, and pedotransfer functions using equivalent parameterization to better compare the results and the performance of the models. The models were evaluated and compared from soil water pressure, water content and temperature data monitored at 0.2, 0.5 and 1 m depth, together with water percolates and herbicide concentrations measured in a tension plate lysimeter at 1 m depth. Some hydraulic (n, θ(s)) parameters and mesotrione DT50 needed calibration. After calibration, the comparison of the results obtained by the three models indicated that PRZM was not able to simulate properly the water dynamic in the soil profile. On the contrary, PEARL and MACRO simulated generally quite well the observed water pressure head and volumetric water content at the three different depths during wetting periods (e.g. irrigated cropping period) while a poorest performance was obtained for drying periods (fallow period with bare soil and beginning of crop period). Similar water flow dynamics were simulated by PEARL and MACRO in the soil profile although in general, and due to a higher evapotranspiration in MACRO, PEARL simulated a wetter soil than MACRO. For the whole simulated period, the performance of all models to simulate water leaching at 1m depth was poor, with an overestimation of the total water volume measured in the lysimeter (ranging from 2.2 to 6.6 times). By contrast, soil temperature was properly reproduced by the three models. The models were able to simulate the leaching of herbicides at 1m depth in similar appearance time and order of magnitude as field observations. Cumulative observed and simulated mesotrione losses by leaching were consistently higher than the observed and simulated losses of the less mobile herbicide, S-metolachlor. In general, PRZM predicted the highest concentrations for both herbicides in the leachates while PEARL simulated the observed herbicide concentrations better than MACRO and PRZM.

COP-compost: a software to study the degradation of organic pollutants in composts

Composting has been demonstrated to be effective in degrading organic pollutants (OP) whose behaviour depends on the composting conditions, the microbial populations activated and interactions with organic matters. The fate of OP during composting involves complex mechanisms and models can be helpful tools for educational and scientific purposes, as well as for industrialists who want to optimise the composting process for OP elimination. A COP-Compost model, which couples an organic carbon (OC) module and an organic pollutant (OP) module and which simulates the changes of organic matter, organic pollutants and the microbial activities during the composting process, has been proposed and calibrated for a first set of OP in a previous study. The objectives of the present work were (1) to introduce the COP-Compost model from its convenient interface to a potential panel of users, (2) to show the variety of OP that could be simulated, including the possibility of choosing between degradation through co-metabolism or specific metabolism and (3) to show the effect of the initial characteristics of organic matter quality and its microbial biomass on the simulated results of the OP dynamic. In the model, we assumed that the pollutants can be adsorbed on organic matter according to the biochemical quality of the OC and that the microorganisms can degrade the pollutants at the same time as they degrade OC (by co-metabolism). A composting experiment describing two different (14)C-labelled organic pollutants, simazine and pyrene, were chosen from the literature because the four OP fractions simulated in the model were measured during the study (the mineralised, soluble, sorbed and non-extractable fractions). Except for the mineralised fraction of simazine, a good agreement was achieved between the simulated and experimental results describing the evolution of the different organic fractions. For simazine, a specific biomass had to be added. To assess the relative importance of organic matter dynamics on the organic pollutants' behaviour, a sensitivity analysis was conducted. The sensitivity analysis demonstrated that the parameters associated with organic matter dynamics and its initial microbial biomass greatly influenced the evolution of all the OP fractions, although the initial biochemical quality of the OC did not have a significant impact on the OP evolution.

Simulation of Organic Matter and Pollutant Evolution during Composting: The COP-Compost Model

Organic pollutants (OPs) are potentially present in composts and the assessment of their content and bioaccessibility in these composts is of paramount importance. In this work, we proposed a model to simulate the behavior of OPs and the dynamic of organic C during composting. This model, named COP-Compost, includes two modules. An existing organic C module is based on the biochemical composition of the initial waste mixture and simulates the organic matter transformation during composting. An additional OP module simulates OP mineralization and the evolution of its bioaccessibility. Coupling hypotheses were proposed to describe the interactions between organic C and OP modules. The organic C module, evaluated using experimental data obtained from 4-L composting pilots, was independently tested. The COP-Compost model was evaluated during composting experiments containing four OPs representative of the major pollutants detected in compost and targeted by current and future regulations. These OPs included a polycyclic aromatic hydrocarbon (fluoranthene), two surfactants (4--nonylphenol and a linear alkylbenzene sulfonate), and an herbicide (glyphosate). Residues of C-labeled OP with different bioaccessibility were characterized by sequential extraction and quantified as soluble, sorbed, and nonextractable fractions. The model was calibrated and coupling the organic C and OP modules improved the simulation of the OP behavior and bioaccessibility during composting.

Spatial distribution of Lindane concentration in topsoil across France

Lindane [γ-hexachlorocyclohexane (γ-HCH)] is an organochlorine pesticide with toxic effects on humans. It is bioaccumulative and can remain in soils for long periods, and although its use for crop spraying was banned in France in 1998, it is possible that residues from before this time remain in the soil. The RMQS soil monitoring network consists of soil samples from 2200 sites on a 16 km regular grid across France, collected between 2002 and 2009. We use 726 measurements of the Lindane concentration in these samples to (i) investigate the main explanatory factors for its spatial distribution across France, and (ii) map this distribution. Geostatistics provides an appropriate framework to analyze our spatial dataset, though two issues regarding the data are worth special consideration: first, the harmonization of two subsets of the data (which were analyzed using different measurement processes), and second, the large proportion of data from one of these subsets that fell below a limit of quantification. We deal with these issues using recent methodological developments in geostatistics. Results demonstrate the importance of land use and rainfall for explaining part of the variability of Lindane across France: land use due to the past direct input of Lindane on cropland and its subsequent persistence in the soil, and rainfall due to the re-deposition of volatilized Lindane. Maps show the concentrations to be generally largest in the north and northwest of France, areas of more intensive agricultural land. We also compare levels to some contamination thresholds taken from the literature, and present maps showing the probability of Lindane concentrations exceeding these thresholds across France. These maps could be used as guidelines for deciding which areas require further sampling before some possible remediation strategy could be applied.

Composting in small laboratory pilots: performance and reproducibility

Small-scale reactors (<10 l) have been employed in composting research, but few attempts have assessed the performance of composting considering the transformations of organic matter. Moreover, composting at small scales is often performed by imposing a fixed temperature, thus creating artificial conditions, and the reproducibility of composting has rarely been reported. The objectives of this study are to design an innovative small-scale composting device safeguarding self-heating to drive the composting process and to assess the performance and reproducibility of composting in small-scale pilots. The experimental setup included six 4-l reactors used for composting a mixture of sewage sludge and green wastes. The performance of the process was assessed by monitoring the temperature, O(2) consumption and CO(2) emissions, and characterising the biochemical evolution of organic matter. A good reproducibility was found for the six replicates with coefficients of variation for all parameters generally lower than 19%. An intense self-heating ensured the existence of a spontaneous thermophilic phase in all reactors. The average loss of total organic matter (TOM) was 46% of the initial content. Compared to the initial mixture, the hot water soluble fraction decreased by 62%, the hemicellulose-like fraction by 68%, the cellulose-like fraction by 50% and the lignin-like fractions by 12% in the final compost. The TOM losses, compost stabilisation and evolution of the biochemical fractions were similar to observed in large reactors or on-site experiments, excluding the lignin degradation, which was less important than in full-scale systems. The reproducibility of the process and the quality of the final compost make it possible to propose the use of this experimental device for research requiring a mass reduction of the initial composted waste mixtures.

Modelling of organic matter dynamics during the composting process

Composting urban organic wastes enables the recycling of their organic fraction in agriculture. The objective of this new composting model was to gain a clearer understanding of the dynamics of organic fractions during composting and to predict the final quality of composts. Organic matter was split into different compartments according to its degradability. The nature and size of these compartments were studied using a biochemical fractionation method. The evolution of each compartment and the microbial biomass were simulated, as was the total organic carbon loss corresponding to organic carbon mineralisation into CO(2). Twelve composting experiments from different feedstocks were used to calibrate and validate our model. We obtained a unique set of estimated parameters. Good agreement was achieved between the simulated and experimental results that described the evolution of different organic fractions, with the exception of some compost because of a poor simulation of the cellulosic and soluble pools. The degradation rate of the cellulosic fraction appeared to be highly variable and dependent on the origin of the feedstocks. The initial soluble fraction could contain some degradable and recalcitrant elements that are not easily accessible experimentally.

Sorption and mineralization of organic pollutants during different stages of composting

The organic pollutant (OP) content is a key factor when determining compost quality. The OPs present in feedstock materials may either be degraded during composting or stabilized in the compost by sorption interactions with organic matter (OM), which may reduce the availability of OP to microorganism degradation. It is particularly important to identify the key stages during composting that are involved in OP mineralization so as to be able to optimize the composting process and determine whether OP sorption on OM is a limiting factor to OP mineralization. Four (14)C-labeled OPs were used during the study: a polycyclic aromatic hydrocarbon (fluoranthene), two surfactants (4-n-nonylphenol - NP and sodium linear dodecylbenzene sulfonate - LAS) and a herbicide (glyphosate). The potential for compost microflora to degrade OP, and compost sorption properties, were characterized at different stages of composting. The highest levels of LAS and glyphosate mineralization were found during the thermophilic stage, at the beginning of maturation for NP and at the end of maturation for fluoranthene. A specific microflora was probably involved in the biodegradation of fluoranthene while NP, LAS and glyphosate mineralization were linked to total microbial activity. OP sorption on compost was linked to their hydrophobicity, decreasing in the order: fluoranthene>NP>LAS>glyphosate. Moreover, sorption decreased as compost maturity increased, except for glyphosate. The sorption coefficients were positively correlated to mineralization kinetics parameters for NP, LAS and glyphosate, suggesting a positive effect of sorption on increasing mineralization rates.

Ageing processes and soil microbial community effects on the biodegradation of soil (13)C-2,4-D nonextractable residues

The biodegradation of nonextractable residues (NER) of pesticides in soil is still poorly understood. The aim of this study was to evaluate the influence of NER ageing and fresh soil addition on the microbial communities responsible for their mineralisation. Soil containing either 15 or 90-day-old NER of (13)C-2,4-D (NER15 and NER90, respectively) was incubated for 90 days with or without fresh soil. The addition of fresh soil had no effect on the mineralisation of NER90 or of SOM, but increased the extent and rate of NER15 mineralisation. The analyses of (13)C-enriched FAME (fatty acids methyl esters) profiles showed that the fresh soil amendment only influenced the amount and structure of microbial populations responsible for the biodegradation of NER15. By coupling biological and chemical analyses, we gained some insight into the nature and the biodegradability of pesticide NER.

Tracing 2,4-D metabolism in Cupriavidus necator JMP134 with 13C-labelling technique and fatty acid profiling

The use of stable isotope probing of fatty acid methyl esters (FAME-SIP) is a powerful tool to study the microorganisms involved in xenobiotic biodegradation in soil. Nevertheless, it is important to determine how representative these molecules are of microorganisms both qualitatively and quantitatively. Using Cupriavidus necator JMP134 as a simple experimental model, we showed that the (13)C-labelling technique can be used both at a global (here defined as cellular, medium and CO(2)) and molecular level to study the metabolism of 2,4-Dichlorophenoxyacetic acid (2,4-D). Although isotopic fractionation among substrate, biomass and FAME were observed, this technique could be used when using a highly (13)C-labelled substrate. Global (13)C analyses gave similar results to those obtained with traditional (14)C-labelling methods. After 10 days of incubation 59% of ring-C was mineralized and about 30% remained in the liquid medium. A maximum of 11% was incorporated into the biomass after 3 days. The assimilation yield of chain-C into the biomass was about half that of ring-C, suggesting a preferential use of chain-C for energy acquisition. Molecular analysis of the lipid fraction evidenced that the incorporation of the labelled 2,4-D did not correspond to a bioaccumulation of pesticide residues but to the metabolism of the 2,4-D carbons for FAME synthesis. Provided the labelling is located on the benzenic ring, the assessment of (13)C-FAME is a robust method to quantify the incorporation of (13)C into the whole microbial biomass. However, the variability of the (13)C incorporation among FAME due to physiological processes has to be considered in complex biological systems. The coupling of bulk and molecular studies with a simple model as C. necator JMP134 is a good approach for testing FAME-SIP.

Measurement of trifluralin volatilization in the field: Relation to soil residue and effect of soil incorporation

Volatilization may represent a major dissipation pathway for pesticides applied to soils or crops. A field experiment (September, 2002), consisted in volatilization fluxes measurements during 6 days, covering the periods before and after soil incorporation carried out 24 h after trifluralin spraying on bare soil. Evolution of concentration in soil was measured during 101 days, together with soil physical and meteorological variables. Volatilization fluxes were very high immediately after application (1900 ng m(-2) s(-1)), decreased down to 100 ng m(-2) s(-1) in the following 24 h. Soil incorporation strongly abated trifluralin concentration in the air. 99% of the total volatilization losses recorded over the 6 days following application occurred before incorporation. Volatilization fluxes evidenced a diurnal cycle driven by environmental conditions. Soil trifluralin residues could still be quantified 101 days after application. Our results highlight the caution required when using soil degradation half-life values in the field for volatile compounds.

A model for linking the effects of parathion in soil to its degradation and bioavailability kinetics

Parathion is an insecticide of a group of highly toxic organophosphorus compounds. To investigate the dissipation and toxicological impact of parathion [O,O-diethyl O-(4-nitrophenyl) phosphorothioate] and its highly toxic metabolite, paraoxon, soil laboratory experiments were conducted in columns during a 19-d experiment under variably saturated conditions. Water and pesticide transport, sorption, and biodegradation of parathion were measured in three soil pools (soluble phase, weakly and strongly sorbed phases) using C-labeled pesticide. The effects of parathion and its metabolite on the mobility of soil nematodes were observed and then modeled with an effective variable, which combined pesticide concentration and time of application. Results showed that parathion was highly sorbed and slowly degraded to a mixture of metabolites. The parent compound and its metabolites remained located in the top 0.06-m soil layer. A kinetic model describing the sorption, biodegradation, and allocation into different soil pools of parathion and its metabolites was coupled with heat and water transport equations to predict the fate of parathion in soil. Simulated results were in agreement with experimental data, showing that the products remained in the upper soil layers even in the case of long-term (11-mo) simulation. The strongly sorbed fraction may be regarded as a pesticide reservoir that regularly provides pesticide to the weakly sorbed phase, and then, liquid phase, respectively. From both modeling and observations, no major toxicological damage of parathion and paraoxon to soil nematodes was found, although some effects on nematodes were possible, but at the soil surface only (0.01- and 0.02-m depth).

Behavior of 14C-atrazine in Argentinean topsoils under different cropping managements

Atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine) behavior was studied in four surface soils during incubations in laboratory conditions. Soils were chosen in relation to their cropping management (tillage and no tillage) and crop rotation system (continuous soybean [Glycine mar (L.) Merr.] and maize (Zea mays L.)-soybean rotation). A natural soil under brushwood was sampled as a reference. Atrazine use in field conditions was associated with maize cropping, thus only one soil received atrazine every other year. Atrazine behavior was characterized through the balance of 14C-U-ring atrazine radioactivity among the mineralized fraction, the extractable fraction, and the nonextractable bound residues. Soil organic matter capacity to form bound residues was characterized using soil size fractionation. Accelerated atrazine mineralization was only observed in the soil receiving atrazine in field conditions. Atrazine application every other year was enough to develop a microflora adapted to triazine ring mineralization. Bound residue formation was rapid and increased with soil organic matter content. The coarsest soil size fractions (2000-200 and 200-50 microm) containing the nonhumified organic matter presented the highest capacity to form bound residues. No effect of tillage system was observed, probably because of the uniform sampling depth at 20 cm, hiding the stratification pattern of soil organic matter in non-tilled soils.

Modeling of sorption and biodegradation of parathion and its metabolite paraoxon in soil

To investigate the distribution of parathion [O,O-diethyl O-(4-nitrophenyl) phosphorothioate] and its highly toxic metabolite paraoxon [O,O-diethyl O-(4-nitrophenyl)phosphate] between the soluble and sorbed pools in the soil, batch experiments were conducted to evaluate the rate of adsorption and desorption of 14C-labeled parathion and paraoxon in soil. The mineralization and degradation of these products were also investigated during a 56-d experiment under controlled laboratory conditions. Adsorption patterns indicated initial fast adsorption reactions occurring within 4 h for both parathion and paraoxon. We also observed the formation of nonextractable residues. The paraoxon was more intensively degraded than the parathion, and production of p-nitrophenol and other metabolites was observed. A kinetic model was developed to describe the sorption and biodegradation rates of parathion, taking into account the production, retention, and biodegradation of paraoxon, the main metabolite of parathion. After fitting the parameters of the model we made a simulation of the kinetics of the appearance and disappearance of paraoxon. From the simulation we predicted a quantity of metabolite in the liquid phase amounting to 1% of the quantity of parathion initially applied. This is in agreement with the experimental data.

Ring 20 chromosome syndrome with epilepsy and dysmorphic features: a case report

Relatively few cases of the 20 ring chromosome [r(20)] syndrome have been reported. Epileptic seizures, behavioral problems, mental retardation, and absence of definite dysmorphic features characterize this syndrome. We present a patient with the classic genetic and phenotypic findings. A 42-month-old boy with mild dysmorphic features and psychomotor retardation has had generalized tonic-clonic seizures, resistant to antiepileptic drug therapy since he was 26 months old. Electroencephalography (EEG) was performed on several occasions, as were brainstem auditory evoked potentials (BAEPs), magnetic resonance imaging (MRI), and cytogenetic studies. The EEG showed slow waves in anterior regions intermingled with spikes in temporal areas. The BAEPs were abnormal, and neuroimaging studies were normal. The chromosome r(20) appeared in 100 metaphases studied. Parental chromosomes were of normal karyotype. The genetic and EEG finding from this patient strongly suggest that epilepsy associated with 20 ring chromosome syndrome is a distinct new entity, although the clinical manifestations may be broader than previously recognized.

Soil surface structure effect on isoproturon and diflufenican loss in runoff

Because soil surface structure has a considerable influence on infiltration rate, the sealing process is postulated to have a significant effect on herbicide loss through runoff. We evaluated the effect of degraded soil surface structures on herbicide loss in runoff, and used the experimental data to test the uniform mixing zone concept and two-site sorption kinetics for modeling herbicide transfer to runoff. The experiments were done with simulated rainfall on 10-m2 plots in the field and 0.25-m2 plots in the laboratory after a surface application of 1.5 kg ha(-1) of isoproturon [3-(4-isopropylphenyl)-1,1-dimethylurea] and 0.187 kg ha(-1) of diflufenican [2',4'-difluoro-2-(alpha,alpha,alpha-trifluoro-m-tolyloxy) nicotinanilide]. Isoproturon (IPU) and diflufenican (DFF) concentrations were very high in the first runoff (up to 60 mg L(-1) for IPU and 2 mg L(-1) for DFF) when simulated rainfall was applied 24 h after the treatment. The concentrations decreased very rapidly with total rainfall depth. Degradation of the structural state of the soil surface increased the ratio of pesticide loss to application rate from 0.3 to 10% for IPU and from 0.7 to 7.8% for DFF for a runoff depth of less than 1 mm. The structural state of the soil surface influences the rapidity at which runoff begins after the onset of rain, and the runoff coefficient at steady state. Furthermore, the development of a surface seal seems to limit the depth of soil-runoff interaction and thus influences the dynamics of herbicide mobilization. Concentrations of IPU in the runoff were satisfactorily described with a model incorporating a uniform mixing zone and two-site sorption-desorption.

Sorption of weak organic acids in soils: clofencet, 2,4-D and salicylic acid

The sorption behaviour of a new wheat hybridising agent (clofencet, 2-4-(chlorophenyl)-3-ethyl-2,5-dihydro-5-oxopyridazine-4-carboxylic acid) was investigated in batch equilibrium experiments and compared to that of two other organic acids (2,4-D and salicylic acid). Sorption coefficients Kd for the three compounds were determined in 18 Cambisols and Ferralsols. Kd values for clofencet were 0.3-9.4 l/kg for Cambisols and 2.1-68 l/kg for Ferralsols. Sorption of clofencet was strongly related statistically to that of salicylic acid. Sorption of clofencet and salicylic acid decreased exponentially with increasing solution pH in Cambisols whereas a bell-shaped curve was obtained for the sorption of salicylic acid in Ferralsols. Sorption of 2,4-D (2,4-dichlorophenoxyacetic acid) was not statistically related to the pH of the different soils. Positively charged oxide surfaces were shown to play a significant role in the sorption of clofencet and salicylic acid. The use of simple correlation and multiple linear regressions suggested that the main sorption mechanisms of clofencet in soils were likely to be ligand exchange on oxide surfaces and, to a lesser extent, cation bridging. Differences in the sorption behaviour of clofencet/salicylic acid and 2,4-D might be attributed to the possibility of the two former compounds forming bidentate complexes with metals.