Mercury speciation adsorption (MESA) method for combustion flue gas: Methodology,artifacts, intercomparison,and atmospheric implications

Chemical speciation of mercury (Hg) in a wide variety of combustion flue gas matrices has been determined using the mercury speciation adsorption (MESA) method. The MESA sampling system for gas phase Hg species employs a series of heated, solid phase adsorbent traps. Flue gas oxidized Hg species (Hg(II) and MMHg) are adsorbed by a potassium chloride (KCl) impregnated soda lime sorbent. Elemental Hg (Hg⁰) is collected by an iodated carbon sorbent after passing through the KCl/soda lime sorbent. Total Hg (Hg_t) is determined by summation of species. In the laboratory, cold vapor atomic fluorescence spectroscopy (CVAFS) is used for detection of Hg collected on the solid sorbents, after appropriate sample digestion and preparation. The MESA method has been evaluated for species stability, matrix effects, breakthrough, artifacts and precision. Based on eight duplicate samples a mean precision of 6.8% 11% and 4.5% (relative percent difference) has been calculated for Hg⁰, Hg(II) and Hgt respectively. Intercomparison of the MESA method with other methods shows very good agreement for Hgt. Mass balance calculations at 5 sites range from 75 to 140%, with a mean of 97±25%. Overall mean speciation results from 19 separate determinations suggest that Hg(II) has a 1 sigma range of 40 to 94% in coal combustion flue gas at, the inlet to pollution control devices.     

Conformational interpretation of vescalagin and castalagin physicochemical properties

Vescalagin and castalagin are two diastereoisomers. The variability of their principal physicochemical properties, compared with their small structural differences, suggests important conformational variations. This study shows, experimentally, that vescalagin has a greater effect on polarity, oxidizability in solution, and thermodegradability than castalagin. Conformational analysis by molecular mechanics demonstrated that vescalagin was more hydrophilic and was more reactive to electrophilic reagents than castalagin. Experimental results were thus explained and demonstrated the distinct behaviors of vescalagin and castalagin. These results were attributed to the C1 position of the two compounds because vescalin and castalin have comparable characteristics. Experimental data were confirmed and interpreted by molecular mechanics. This work represents one of the first attempts to correlate conformation and the properties of phenolic compounds. This step constitutes a predictive method for the pharmacology or chemistry of new compounds.     

Applicability of the soil gradient method for estimating soil–atmosphere CO2, CH4, and N2O fluxes for steppe soils in Inner Mongolia

For evaluating the applicability of the soil gradient method as a substitute for CO₂‐, CH₄‐, and N₂O‐flux measurements in steppe, we carried out chamber measurements and determined soil gas concentration at an ungrazed (UG99) and a grazed (WG) site in Inner Mongolia, China. The agreement of the concentration‐based flux estimates with measured chamber‐based fluxes varied largely depending on the respective GHG in the sequence CO₂ > CH₄ >> N₂O. A calibration of the gas‐transport parameter used to calculate fluxes based on soil gas concentrations improved the results considerably for CO₂ and CH₄. After calibration, the average deviation from the chamber‐based annual cumulative flux for both sites was 11.5%, 10.5%, and 59% for CO₂, CH₄, and N₂O. The gradient method did not constitute an adequate stand‐alone substitute for greenhouse‐gas flux estimation since a calibration using chamber‐based measurements was necessary and vigorous production processes were confined to the uppermost, almost water‐saturated soil layer.     

Usefulness of trunk diameter variations as continuous water stress indicators of pomegranate (Punica granatum) trees

Pomegranate trees (Punica granatum L.) is a deciduous fruit tree included in the so-called group of minor fruit tree species, not widely grown but of some importance in the south east of Spain. Pomegranate trees are considered as a culture tolerant to soil water deficit. However, very little is known about pomegranate orchard water management. The objective of this research was to asses the feasibility of using trunk diameter variation (TDV) indexes, obtained by means of LVDT sensors, as a plant water stress indicators for pomegranate trees. The experiment was carried out with mature trees grown in the field under three irrigation regimes: control well watered trees; trees continuously deficit irrigated at 50% of the control regime (SDI); and trees that had a summer water stress cycle being irrigated at 25% of the control rates only in July and August (RDI). The seasonal variations of maximum diurnal trunk shrinkage (MDS) and trunk growth rates (TGR) were compared with midday stem water potential (Ψstem) measurements. During the course of the entire season, control trees maintained lower MDS values than the SDI ones. In the RDI treatment, as water restrictions began, there was a slow increase in MDS, in correspondence with a decrease in Ψstem. When water was returned at full dosage, the RDI quickly recovered to MDS and Ψstem values similar to the control. However, lower MDS for a given Ψstem values were observed as the season advanced. The magnitude of differences between well watered and deficit irrigated trees was much larger in the case of MDS than for Ψstem. However, the tree-to-tree variability of the MDS readings was more than four times higher than for Ψstem; average coefficient of variation of 7.5 and 36% for Ψstem and MDS, respectively. On the other hand, TGR did not clearly reflect differences in tree water status. Overall, results reported indicated that MDS is a good indicator of pomegranate tree water status and it can be further used for managing irrigation. However, the seasonal changes in the MDS-Ψstem relationship should be taken into account when attempting to use threshold MDS values for scheduling irrigation.     

High prevalence of Hepatitis E virus in French domestic pigs

The importance of the domestic pig reservoir for Hepatitis E virus (HEV) was assessed by estimating the seroprevalence and prevalence of HEV contaminated livers in French slaughter-aged pigs. 6565 sera and 3715 livers were randomly sampled from 186 pig farms throughout the country. Taking the sampling design into account, the farm-level seroprevalence was 65% (95% CI 57–74) and 31% (95% CI 24–38) of the slaughter-aged pigs had antibodies against HEV. The individual prevalence of HEV RNA positive livers was 4% (95% CI 2–6) and 24% (95% CI 17–31) of the farms had at least 1 positive liver. Most isolates were of genotype 3f (76.7%) with smaller amounts of 3c (18.6%) and 3e (4.6%). The high prevalence of HEV in pigs and the similarities between HEV subtypes from pigs and humans corroborates the possible zoonotic origin of some HEV autochthonous infections.     

Impact of concentration of ellagitannins in oak wood on their levels and organoleptic influence in red wine

Some wood substances such as ellagitannins can be extracted during wine aging in oak barrels. The level of these hydrolyzable tannins in wine depends of some parameters of oak wood. Their impact on the organoleptic perception of red wine is poorly known. In our research, oak staves were classified in three different groups according to their level of ellagitannins estimated by NIRS (near infrared spectroscopy) online procedure (Oakscan). First, the ellagitannin level and composition were determine for each classified stave and an excellent correlation between the NIRS classification (low, medium and high potential level of ellagitannin) and the ellagitannin content estimated by HPLC-UV was found. Each different group of NIRS classified staves was then added to red wine during its aging in a stainless tank, and the extraction and evolution of the ellagitannins were monitored. A good correlation between the NIRS classification and the concentration of ellagitannins in red wine aging in contact with the classified staves was observed. The influence of levels of ellagitannins on the resulting wine perception was estimated by a trained judge's panel, and it reveals that the level of ellagitannins in wine has an impact on the roundness and amplitude of the red wine.     

What are the limits of the drilosphere? An incubation experiment using Metaphire posthuma

The near infrared reflectance spectroscopy (NIRS) method was used in the present study to compare earthworm-made soil aggregates to aggregates found in the surrounding bulk soil. After initially assessing the daily cast production of Metaphire posthuma, boxes with soil incubated with M. posthuma and control soils were subjected to wetting in order to reorganize the soil structure. After two months of incubation, soil aggregates produced by earthworms (casts and burrows), soil aggregates that were appeared to be unaffected by earthworms (bulk soil without visible trace of earthworm bioturbation from the earthworm treatment) and soil aggregates that were entirely unaffected by earthworms (control – no earthworm – treatment) were sampled and their chemical signatures analyzed by NIRS. The production of below-ground and surface casts reached 14.9 g soil g worm^?1 d^?1 and 1.4 g soil g worm^?1 d^?1, respectively. Soil aggregates from the control soils had a significantly different NIRS signature from those sampled from boxes with earthworms. However, within the earthworm incubation boxes the NIRS signature was similar between cast and burrow aggregates and soil aggregates from the surrounding bulk soil. We conclude that the high cast production by M. posthuma and the regular reorganization of the soil structure by water flow in and through the soil lead to a relatively homogenous soil structure. Given these results, we question the relevance of considering the bulk soil that has no visible activity of earthworm activity as a control to determine the effect of earthworms on soil functioning.     

Baseflow control on sediment flux connectivity: Insights from a nested catchment study in Central Mexico

In order to assess the extent of sediment connectivity between uplands and lowlands and to quantify the processes of in-channel deposition and remobilization, measurements of suspended sediment fluxes were conducted in a nested rural catchment of the Mexican Volcanic Belt. Data were collected over one year at three upland sites (3 to 12 km²) and two downstream stations (390–630 km²). Our results show that a structural discontinuity in the catchment (i.e. abrupt slope decrease at the junction between piedmonts and the alluvial plain from 2 to 10% to < 0.1%) could be compensated by functional continuity during floods. Direct conveyance of fine sediment to the outlet occurred when a high stream transport capacity was reached. Erosion of the streambed was observed on various occasions and accounted for up to 50% of the flux leaving the catchment during one event. Conversely, temporary in-channel storage was apparent on other occasions, amounting to up to 52% of the flux recorded upstream during one storm. These two distinct behaviours were approximately equally distributed along the rainy season and strongly driven by the extent of coupling between surface and subsurface water. This work indeed highlights the role of baseflow spatial variations in determining the extent of lowland sediment conveyance. Riverbed erosional processes occurred when large differences in pre-event baseflow values (i.e. at least a twofold longitudinal increase) were observed between the 5-km distant lowland stations. Our findings outline the importance of systematically taking into consideration the baseflow parameter in research focusing on fine sediment transport across scales.