To eliminate mercury vapor from gas streams, three major methods are used: condensation, absorption, and adsorption. This work deals with adsorption, using elemental sulfur as an active phase supported on sepiolite and palygorskite fibrous clays. Sulfur loads of 5–30% were deposited by catalytic oxidation of hydrogen sulfide at temperatures of <200°C, the clays acting first as a catalyst of the reaction and then as a carrier of the obtained sulfur. The ability of the sulfurized clay adsorbents to retain mercury was studied at 45°C and 1 mm Hg pressure. The high values found, about 4 g Hg/g S supported on clays, compared with 1.69 g Hg/g S on activated carbon under the same conditions are related to a more appropriate pore size distribution, with more of the pore widths >6 nm for the sulfurized silicates. Also, the allotropic state of the deposited sulfur, where Sπ (octo-catena) is better than Sλ (octo-cycle), may also be a contributing factor.

Owing to their large and chemically active surface, hydroxy-intercalated and pillared clays can be potent sorbents for organic compounds. The sorption behavior of Al and Zr-hydroxy-intercalated bentonite (HAl-, HZr-MX80), Al and Zr-pillared bentonite (Al-MX80, Zr-MX80), and a commercial Al-pillared bentonite (EXM 534) for 3-chloroaniline (3-CA), atrazine (AT), and 3-chlorophenol (3-CP) was investigated. The results were compared with the sorption behavior of the untreated Na-rich bentonite (MX80) and granulated activated carbon (GAC). Also the influence of the salinity of the sorbate and the age of the sorbents was studied.

Al and Zr-hydroxy-intercalated and pillared bentonites sorbed higher amounts of 3-CA, AT, and 3-CP than the untreated bentonite. The quantities sorbed related to the electron-donating properties of the sorbate and the acidity of the sorbents. Sorbed quantities increased from the hydroxy-intercalated to the pillared species, and from the Al to the Zr forms. The organic bases, 3-CA and AT, were sorbed in higher quantities than the organic acid 3-CP. For AT, the sorbents exhibited a high affinity. Aging of the samples and a high ionic strength of the sorbate reduced the sorption of 3-CA, whereas the sorption of AT was not affected greatly. The sorption capacity of GAC for organic bases was generally higher than that of the hydroxy-intercalated and pillared bentonites.

The data suggest that at initial concentrations at a ppm level, 3-CA and AT can be entirely removed from aqueous solutions by Al and Zr-hydroxy-intercalated and pillared bentonites. These materials, especially Zr-pillared bentonites, represent potent alternative sorbents for atrazine, chloroanilines, and probably a wide range of other organic bases.

Previous studies have demonstrated that emergence and growth of Powell amaranth is inhibited in soils where buckwheat has been grown and incorporated. The primary objectives of this research were to (1) evaluate the possible role of allelopathy in explaining that suppression; (2) distinguish between suppression caused by incorporation of fresh buckwheat residues from suppression caused by changes in soil during buckwheat growth; and (3) quantify the relative importance of buckwheat root vs. shoot tissues in suppression. When all buckwheat plant parts were removed from soil in which buckwheat was grown, Powell amaranth emergence was not suppressed, but growth was reduced 70% compared to bare soil. Addition of buckwheat shoots, but not roots to these soils reduced emergence by 80%, and contributed to additional reduction in growth. Addition of chemically activated carbon did not increase emergence or growth in buckwheat-amended soil. However, thermally activated carbon resulted in greater adsorption of phenolics than chemically activated carbon and alleviated suppression of Powell amaranth in buckwheat-amended, high organic-matter soils. However, suppression was not overcome on mineral soils. In addition to adsorbing phenolics, activated carbon changed the nitrogen (N) content and electrical conductivity of soil extracts. Aqueous shoot extracts of buckwheat stimulated Powell amaranth germination slightly, but inhibited radicle growth. Aqueous soil extracts from buckwheat-amended soil inhibited germination of Powell amaranth compared with extracts from unamended soil. Results suggest that emergence suppression of Powell amaranth by buckwheat residues might be due to allelopathic compounds concentrated in the shoot tissues. However, these inhibitory effects appear to depend on interactions of buckwheat residues with soils. In contrast, suppression of growth of Powell amaranth appears to be associated primarily with lower N availability in buckwheat-grown soils.

In many countries, male pigs are castrated to prevent boar taint, but this practice raises concerns about animal welfare and reduces the production efficiency of pork. The objective of this study was to develop dietary manipulations to prevent boar taint. We evaluated the effectiveness of adding activated carbon (AC) or Tween-60 (Tween; polyoxyethylene sorbitan monostearate) to pig finishing diets to reduce levels of androstenone (AND) and skatole in plasma and fat of entire male pigs. Boars (159 ± 2 days of age at the start of the experiment) were fed diets supplemented with either 5% AC or 5% Tween for 28 days followed by either 14 or 28 days of recovery. Plasma samples were collected at experimental days 0, 7, 14, 21, 28, 42 and 56, and backfat biopsies were taken at experimental days 0, 28, 42 and 56. Feeding AC significantly (P < 0.05) reduced the levels of AND in plasma by day 28 compared to day 0 and by day 42 in fat compared to day 0. AC treatment also decreased levels of oestrone sulphate (E1S) in plasma by day 7 compared to day 0. Treatment with Tween significantly decreased (P < 0.05) the levels of plasma AND by day 28 from levels at day 0. Tween treatment did not significantly affect levels of fat AND or plasma E1S compared to day 0; however, fat AND levels decreased between days 28 and 42 following treatment with Tween (P < 0.05). Levels of plasma E1S, plasma AND and fat AND for control boars remained constant throughout the experiment. Skatole plasma concentrations were very low and did not vary significantly (P > 0.05) from day 0 for any treatment, but fat skatole levels decreased by day 42 in the Tween treatment group. Importantly, there was no difference in growth rate between the control and experimental groups. We conclude that adding AC or Tween to finishing diets for boars can reduce the levels of plasma and fat AND, but further work is needed to confirm the effects of these treatments on reducing fat skatole levels.

Boar taint, an off-odor and an off-flavor in the meat from some uncastrated male pigs, is due to high levels of the testicular steroid hormone, androstenone, and the indole, skatole. Thus far, there are no known methods for controlling both androstenone and skatole through dietary means. We tested the adsorbent agents, cholestyramine (CH), activated carbon (AC), tween-60 (Tween), bentonite (BNT) and polyvinylpolypyrrolidone (PVPP) for binding androstenone, estrone (E1), estrone sulfate (E1S) and skatole from buffer solutions in an in vitro system. The goal was to determine the potential utility of these binding agents as feed additives to control boar taint. Michaelis–Menten analysis was utilized to determine the effectiveness of the adsorbents. At pH 7.4, E1S was bound to AC and CH with the highest Bmax (maximum binding), whereas Tween and AC had the greatest Bmax for E1. The Bmax for skatole at pH 7.4 was highest for AC, CH and PVPP. AC had a higher Bmax for androstenone than CH and Tween. The Bmax values at pH 3.0 with E1S for AC and CH were essentially 100%, whereas the binding of Tween to E1S at pH 3.0 decreased by 49.5% from binding at pH 7.4 (P < 0.05). The Adint values, which represent efficiency of binding, illustrated that AC bound E1, androstenone and skatole with greater efficiency than the other binding agents at pH 7.4, whereas AC bound E1S as efficiently as CH. We conclude that AC was the most effective adsorbent agent for binding E1, E1S, androstenone and skatole in vitro, followed by CH, Tween, PVPP and lastly BNT. These adsorbent agents may be useful for binding boar taint compounds in in vivo studies to decrease the risk of boar taint.

Germination and survival of water-impermeable seeds of 11 species of Geraniaceae and Malvaceae were monitored during dry storage and during burial in soil for up to 2.5 years. During dry storage, seeds of annual Geraniaceae became permeable and also lost their physiological dormancy. However, during burial in natural conditions, most seeds remained impermeable and viable, with no seasonal change in germination capacity. Germination in only one species (Geranium robertianum) was enhanced by daily alternating temperatures when seeds were exhumed in spring. Drying of exhumed seeds broke physical dormancy. Seeds of the perennial Geranium pratense gradually became permeable in a prolonged germination test of 31 weeks. Most seeds of Malva remained impermeable during dry storage. Buried seeds gradually germinated in situ, and exhumed seeds had a low germination capacity in all seasons. We concluded that dormancy of hard seeds in natural conditions may be broken by drying during summer, by specific temperature regimes or by gradual softening of the seed coat, ensuring the spread of germination over many seasons.

Introduction. Le safoutier (Dacryodes edulis, Burseraceae) est un arbre dont les fruits sont très appréciés par les populations de son aire de répartition. Plante allogame, la multiplication par semis ne permet pas d'effectuer une multiplication conforme de l'arbre sélectionné. La présente étude a eu pour principal objectif de mettre au point une technique de régénération in vitro des bourgeons axillaires et apex prélevés sur de jeunes plants issus de la germination de graines, afin d'adapter ultérieurement cette technique au clonage d'arbres adultes par utilisation de repousses formées après recépage. Matériel et méthodes. Des nœuds et apex prélevés sur des plants de Dacryodes edulis issus de la germination de graines ont été mis en culture in vitro sur un milieu Murashige et Skoog dilué de moitié (MS 1/2). Les effets du charbon actif et de la benzyleadéninepurine (BAP) sur le débourrement des explants ont été étudiés, de même que l'influence de l'acide naphtalènacétique (ANA) et de la photopériode sur l'enracinement. Résultats. Le milieu MS 1/2 additionné de charbon actif à 2g × L-1 et de BAP à 2,22 µM ou 4,44 µM a provoqué le meilleur débourrement des bourgeons axillaires et une bonne croissance des tigelles. L'ANA à 5,37 µM a favorisé l'enracinement. Une période de 7 j à l'obscurité s'est révélée favorable à l'induction racinaire. Deux types de racines ont été observés : les racines néoformées (issues de cals) et les racines adventives. L'acclimatation a été faite avec succès sur substrat constitué de tourbe et vermiculite. La régénération des vitroplants à partir des nœuds et apex permet de distinguer le long de la jeune plante un gradient morphogénétique acropétale. Discussion et conclusion. Ces résultats pourront être exploités pour la mise au point d'une micropropagation conforme à partir de jeunes repousses formées après la taille d'un safoutier présentant des caractéristiques intéressantes.