Immobilization of Heavy Metals by Co-pyrolysis of Contaminated Soil with Woody Biomass

We investigated the potential application of pyrolysis treatment to a mixture of woody biomass and a metal-contaminated soil as an alternative eco-friendly option to stabilize metals in soils. Our specific objective was to test the optimum combination of high heating temperature (HHT) and heating time to effectively encapsulate metals in a contaminated soil into a biochar. For this purpose, we used a laboratory bench batch reactor to react a mixture of multi-element metal contaminated soil with 0% (control) 5%, 10%, and 15% (w/w) sawdust. Each mixture was reacted at 200°C and 400°C HHT for 1 and 2 h heating times. Physicochemical and morphological characterization along with standard EPA Synthetic Precipitation Leaching Procedure (SPLP) test were conducted to assess the effectiveness of the heat treatment to immobilize the metals in the contaminated soil. Compared to controls, we recorded up to 93% reduction in Cd and Zn leachability after 1 h heat treatment at 400°C, with the addition of 5–10% biomass. Pb leaching was reduced by 43% by the same treatment but without the addition of biomass. At lower pyrolysis temperature (200°C), however, there was a substantial increase in both As and Zn leaching compared to the untreated controls. Our study suggests that several factors such as the type of metal, heating temperature, heating period, and the addition of biomass influence the efficiency of pyrolysis to immobilize metals in the contaminated soil.     

Nutrient leaching from clay soil monoliths with variable past manure inputs

Overall, arable soils in Sweden are currently generally close to phosphorus (P) balance, but excessive P accumulation has occurred on animal fur farms, i.e., those rearing mink (Mustela vison) and foxes (Alopex lagopus and Vulpes vulpes). Manure P from these farms has sometimes regarded as sparingly soluble. Laboratory lysimeter topsoil trials with simulated rain demonstrated that potential leaching of P in dissolved reactive form (DRP) can be very high, even for heavy clay (50%–65%) soils. The Swedish/Norwegian soil test P‐AL (soil P extracted with acid NH₄ lactate, AL) proved useful as a potential indicator of DRP leaching risk (regression coefficient [R²] = 0.89) from fur farms. The upper 5‐cm soil layer, with 190% higher (median) soil P status than the 5–20 cm layer, was the major source of potential DRP leaching through soil columns at the site, despite having been under grass or green fallow for the past 8 y. In percolate from topsoil lysimeters, DRP concentration increased by 0.29 mg L^–1 after the long‐term manure application but only by 0.14 mg L^–1 after the single slurry application when compared to no addition of slurry. Therefore, the build‐up to a high soil P status due to the long‐term application of mink manure was more important than a single application of pig slurry at a rate corresponding to 22 kg P ha^–1 with respect to soil leachate DRP losses in this lysimeter study. The study stresses the importance of precision farming, in which the amount of slurry‐P applied is based on testing the already existing soil P content.     

Effects of tillage depth on organic carbon content and physical properties in five Swedish soils

The soil tillage system affects incorporation of crop residues and may influence organic matter dynamics. A study was carried out in five 15–20 year old tillage experiments on soils with a clay content ranging from 72 to 521 g kg⁻¹. The main objective was to quantify the influence of tillage depth on total content of soil organic carbon and its distribution by depth. Some soil physical properties were also determined. The experiments were part of a series of field experiments all over Sweden with the objective of producing a basis to advise farmers on optimal depths and methods of primary tillage under various conditions. Before the experimental period, all sites had been mouldboard ploughed annually for many years to a depth of 23–25 cm. Treatments included primary tillage to 24–29 cm depth by mouldboard plough (deep tillage) and to 12–15 cm by field cultivator or mouldboard plough (shallow tillage). Dry bulk density, degree of compactness and penetration resistance profiles clearly reflected the depth of primary tillage and substantially increased below that depth. Compared to deep tillage, shallow tillage increased the concentration of organic carbon in the surface layer but decreased it in deeper layers. Total quantity of soil organic carbon and carbon–nitrogen ratio were unaffected by the tillage depth. Thus, a reduction of the tillage depth from about 25 cm to half of that depth would appear to have no significant effect on the global carbon cycle.     

Isolates of fungi from symptomatic carthorses in Awassa, Ethiopia.

Samples were collected from clinically infected carthorses in Awassa. Fungus species affecting the carthorses were identified. Eight genera of fungal groups were isolated from swabs and skin scrapes taken from symptomatic horses. These included Aspergillus spp., Histoplasma spp., Penicillium spp., Microsporum spp., Trichophyton spp., yeast cells of Candida spp., Cryptococcus spp. and Geotrichum spp. The most frequent isolates were from the genera Aspergillus (48%), Penicillium (39.2%) and Trichophyton (31.6%). Clinical findings are reported, the economic, zoonotic and pathogenetic importance of fungi causing dermatomycoses is discussed, and further studies are recommended.