Microbial biomass and respiration in soils derived from lignite ashes: a profile study

Abstract

Microbial biomass C and soil respiration measurements were made in 17–20 yr old soils developed on sluiced and tipped coal‐combustion ashes. Topsoil (0–30 cm) and subsoil (30–100 cm) samples were collected from three soil profiles at two abandoned disposal sites located in the city area of Halle, Saxony‐Anhalt. Selected soil physical (bulk density and texture) and chemical (pH, organic C, total N, CEC, plant available K and P, and total Cd and Cu) properties were measured. pH values were significantly lower while organic C and total N contents and the C : N ratio were significantly higher in the topsoil than in the subsoil indicating the effects of substrate weathering and pedogenic C accumulation. Likewise, microbial biomass C, K2SO4‐extractable C, and soil respiration with median values of 786 μg biomass C g–1, 262 μg K2SO4‐C g–1, and 6.05 μg CO2‐C g–1 h–1, respectively, were significantly higher in the topsoil than in the subsoil. However, no significant difference was observed in metabolic quotient between the topsoil and the subsoil. Metabolic quotient with median values of 5.98 and 8.54 mg CO2‐C (g biomass C)–1 h–1 for the 0–30 cm and 30–100 cm depths, respectively, was higher than the data reported in the literature for arable and forest soils. Microbial biomass C correlated significantly with extractable C but no relationship was observed between it and total N, Cd, and Cu contents, as well as plant‐available K and P. We conclude that the presence of the remarkable concentration of extractable C in the weathered lignite ashes allowed the establishment of microbial populations with high biomass. The high metabolic quotients observed might be attributed to the heavy‐metal contamination and to the microbial communities specific to ash soils.

Contaminated Urban Soils

“…As seen in Table 5.17, the C content reached enhanced values in the subsoil as well independent of the kind of deposit. This context is transferable to the second element of concern, cadmium, which is presented in the same publications Machulla et al 2004). Looking at the cation exchange capacity (CEC) this parameter also showed higher results, demonstrating increasing CEC with the accumulation of technogenic carbon content.…”

Black (pyrogenic) carbon: a synthesis of current knowledge and uncertainties with special consideration of boreal regions

“…The possibilities for microbial degradation of charred biomass are likely to be similar to those occurring in forest sites that have shown microbial utilization of C from lignite combustion ash (Machulla et al, 2004), and from lignite in soils developed after open-pit coal mining Kögel-Knabner, 2002, 2004). The latter studies also showed increasing oxidative transformation of lignite into humic acids and the importance of co-metabolism for decomposition of lignite.…”

Reclamation and revegetation of fly ash disposal sites – Challenges and research needs

“…As a result, concomitant with the development of an above-ground plant community over time, there will be a corresponding accumulation of soil organic matter and increase in the size and activity of the microbial biomass below-ground. Machulla et al (2004) suggested that the microbial communities that developed in 17-20 year-old lignite ash deposits in Germany contained specific ash-tolerant populations that differed significantly from those in surrounding soils. They found that the metabolic quotient (CO 2 -C respired per unit of microbial biomass C) was notably high for ash communities suggesting that these microorganisms require a relatively larger amount of energy for biomass maintenance rather than biomass accumulation.…”

“…This clay material could also react with organic matter produced during revegetation of the site. Thus, the developing soil would effectively sequester C and this would result in a rapid accumulation of organic matter and formation of a large soil microbial community Machulla et al, 2004).…”