Cryptogamic Packed Biofilter as Potential Adsorbent for CO2, NH3, and H2S Impurities from Biogas

The presence of elevated concentrations of carbon dioxide, hydrogen sulfide, ammonia, and trace impurities in biogas affect its caloric value as well as causes corrosion and is extremely toxic. There are various methods in existence for removal of these impurities, but most are chemically based and expensive and are limited in use. In our work, cryptogams (moss) integrated with soil and biochar packed in a filter have been employed for simultaneous removal of CO2, H2S, and NH3, from biogas. Different soil types rich in metallic oxides at different masses of 100 g, 150 g, and 200 g with a fixed mass of moss and biochar were tested in an on-site experiment to determine the removal efficiency (RE) and sorption capacity (SC). The adsorption dynamics of the filters were investigated at two flow rates, 80 ml/min and 100 ml/min, by determining removal efficiency. For the contribution of each substrate, sorption capacity and breakthrough time were determined by considering 5 g of each substrate that made up the filter. The soils with a high content of extractable cations showed excellent adsorption capacity for H2S by about 20 g S/100 g, which was higher than other adsorbents tested. It was found that integrated biofilter made up of bed arrangement of the soil, biochar, and moss plant improved the quality of biogas with SC of 11 g S and RE of 93% for H2S, 72% for NH3, and 68% for CO2.

Infection and damage potential of Meloidogyne javanica on Sesbania sesban in different soil types

An experiment in western Kenya tested the effects of six inoculum levels (0, 80, 400, 800, 2000 and 4000 eggs per 100 cm3 soil) of Meloidogyne javanica on nematode infection and growth of two Sesbania sesban provenences (Kakamega and Kisii) in six soils with sand contents of 26 to 82%. At 1 month after sowing, nematode infection, gall index and seedling mortality increased with inoculum level and sand/clay ratio. Gall index decreased and seedling growth improved with extractable cations, particularly calcium. At 3 months, nematode infection and damage were affected neither by soil texture nor by extractable cations. However, nodulation and plant growth decreased with increasing inoculum levels in all soils. Soils with higher cations and inherent fertility were less prone to nematode infestation and sustained better Sesbania growth irrespective of soil texture. It appears that as Sesbania grows it develops tolerance to M. javanica, suggesting that nematode infection is important at seedling stage primarily in determining stand establishment and early growth. Kisii provenance was more tolerant to the nematode and more productive than Kakamega. There is a need for screening a wide range of Sesbania germplasm for nematode resistance to select appropriate provenances and exploring low cost methods to minimise nematode damage to Sesbania at establishment stage. In einem Versuch in Westkenia wurde die Wirkung von sechs Inokulumstufen (0, 80, 400, 800, 2000 und 4000 Eier je 100 ml Boden) von Meloidogyne javanica auf die Nematodeninfektion und auf das Wachstum von zwei Herkünften von Sesbania sesban (Kakamega und Kisii) in sechs verschiedenen Böden mit Sandanteilen zwischen 26 und 82% untersucht. Einen Monat nach der Aussaat stiegen die Nematodeninfektion, der Vergallungsindex und die Keimlingssterblichkeit mit der Inokulumsgrösse und dem Sand/Lehm-Verhältnis an. Der Vergallungsindex nahm ab, und das Keimlingswachstum verbesserte sich mit dem Gehalt an extrahierbaren Kationen, insbesondere Kalzium. Nach 3 Monaten wurden Nematodeninfektion und Schaden weder durch die Bodentextur noch durch die extrahierbaren Kationen beeinflusst. Die Gallbildung und das Pflanzenwachstum nahmen jedoch in allen Böden mit steigenden Inokulumsstufen ab. Böden mit einem böheren Gehalt an Kationen und natürlicher Fruchtbarkeit neigten weniger zu Nematodeninfektionen und unterstützten das Wachstum von Sesbania unabhängig von der Bodentextur. Anscheinend entwickelt Sesbania mit zunehmendem Wachstum eine Toleranz gegenüber M. javanica. Das weist daraufhin, dass eine Nematodeninfektion im Keimlingsstadium in erster Linie wichtig ist für die Entwicklung des Standplatzes und für das frühe Wachstum. Die Herkunft Kisii war toleranter gegenüber den Nematoden und auch produktiver als Kakamega. Es muss eine breite Palette von Sesbania-Genplasmen auf Nematodenresistenz geprüft werden, um geeignete Herkünfte zu selektieren und preiswerte Methoden zur Minimierung des Nematodenschadens an Sesbania im frühen Entwicklungsstadium auszuprobieren.

Comparing modelled and observed effects of ash additions on chemistry of a highly acid soil

The chemical composition of soil solutions (field percolates collected in situ and laboratory saturation extracts) and the amount of salt-extractable cations were measured at several microsites (unburnt, moderately burnt, and intensely burnt ashbeds) after a fuel reduction burning in a subalpine Eucalyptus pauciflora forest. Soil samples were collected 1, 58, 375, 745, and 1095 days after the fire, and soil percolates were obtained on 17 occasions during the initial year. A model of coupled equilibria, which includes insoluble salts, multiple cation exchange, and inorganic complexation, was used to describe soil chemical changes after fire and ash addition. The model was able to describe temporal changes in cation concentrations of held percolates and soil exchangeable cations. Measurements of extractable cations using unbuffered salt solution on samples taken immediately after fire suggest immediate changes in exchangeable cations which were related to solubilisation of cations from ash, and not to changes in exchangeable cations in soils. Modelling suggests that under natural conditions the differences in solubility of cations in ash result in slow changes in exchangeable cations extending over a period of 6 years or more. The time required to reacidify the surface layer of ashbed soil was estimated to be 45 years when annual acid input was 0.5 kmol H+/ha.

Implications of soil type, pasture composition and mineral content of pasture components for the incidence of grass tetany in the South East of South Australia

The occurrence of grass tetany related deaths in cattle grazing pasture in the South East of South Australia is related to soil type. The greatest losses occur on the solodised solonetz soils, with few, if any, on the rendzina or siliceous sand soils in the region. Pastures from 3 soil types were sampled on 2 occasions during the growing period, and soils were sampled once. Comparisons were made for the pasture components of potassium (K), calcium (Ca) and magnesium (Mg) concentrations in soils, and K, Ca, Mg, nitrogen (N) and sulfur (S) concentrations in plants. In the July sampling, the mean herbage K/(Ca + Mg) ratio for both annual and perennial grass species grown on the solodised solonetz soils exceeded 2.2 but was below 2 for the other 2 soil types. At the same time the mean K/(Ca + Mg) ratio for soil-extractable cations was 0.10 for the solodised solonetz soils but only 0.058 and 0.025 for the rendzina and siliceous sand soils. A critical value for the K/(Ca + Mg) ratio for the soil extractable cations of 0.07-0.08 is suggested. Of the 22 sites in the investigation, grass tetany deaths had occurred on 9 within the previous 5 years; all of these were classified as solodised solonetz soils. Deaths were reported in late autumn and winter, and in all cases the dominant pasture species growing at these sites in July were grasses. It is suggested that deaths ceased in spring because there was either a change to legume dominance or an increase in air temperature.

INCREASE IN NEUTRAL SALT EXTRACTABLE CATION EXCHANGE CAPACITY OF SOME ACID SOILS AS AFFECTED BY CaSO4 APPLICATIONS

The equilibration of acid soils, a Sombric Ferro-Humic Podzol (CSSC-2) from British Columbia, an Orthic Ferro-Humic Podzol (CSSC-19) from Quebec and two horizons of a Dystric Brunisol (SSD-330, SSD-331) from British Columbia, with CaSO4 solution demonstrated that SO4 ions reacted with components of these soils. These reactions increased soil pH, ion activity product (Al)(OH)3 and neutral salt extractable exchangeable cations. The increase in pH and ionic activity product (Al)(OH)3 were noticeable on a single equilibration; however, increase in neutral salt extractable cations was only observed after subsequent equilibrations. After three equilibrations, the sums of NaCl extractable cations were 6.56, 11.99, 5.62 and 4.31 meq/100 g for soil samples CSSC-2, CSSC-19, SSD-330 and SSD-331, respectively. The corresponding values for the unequilibrated soils were 5.20, 7.49, 4.30 and 2.50 meq/100 g. On further equilibration there was no increase in total extractable cations for sample CSSC-2; however, for the other three samples there were increases which became progressively smaller. The reaction of SO4 ions with aluminum hydroxy clay complexes seems to be the mechanism for the increase of negative sites. Key words: Cation exchange capacity, CaSO4, acid soils

Atomic Absorption Methods for Analysis of Soil Extracts and Plant Tissue Digests

The principles of operation and basic equipment of atomic absorption spectroscopy are described. Its advantages over flame emission include higher specificity, fewer interferences, improved detection limits, lower flame temperature requirements, and simpler instrumentation. Analysis procedures which have proved successful in our laboratories are detailed. They include dry ashing and wet digestion for analysis of plant tissues, and exchangeable cations, extractable cations, and acid dissolution for soils analysis.