The effect of cadmium on the activity of nitrifying populations in two different grassland soils

Abstract

The effect of a laboratory addition of 10, 100 and 500 mg Cd kg~.~ soil on ammonification and nitrification was studied using soil samples of two unpolluted grassland soils. Calcareous and non-calcareous soil were selected for this purpose. Various parameters of nitrifying activity were investigated simultaneously: activity during long-term laboratory incubations in the presence and absence of a substrate, mineralization potentials, and potential activity of both ammonium and nitrite oxidizers during short-term incubations in soil slurries. Cadmium was added as aqueous CdC12.Additions of both 100 and 500 mg Cd kg~r ~ soil doses significantly lowered the ability of both soils to nitrify 100 ~g added NH+-N -l g,~y soil as a substrate, which was reflected in a decreased rate of nitrate formation (maximum inhibition reached 60% in the calcareous soil and 45% in the non-calcareous soil). Furthermore, these two concentrations of Cd caused an abnormal accumulation of nitrite immediately after incorporation, particularly in -1 the calcareous soil. The addition of 10 mg Cd k g~ ~oil intensified N-mineralization in both soils, probably as a consequence of a higher concentration of readily metabolized substrate originating from killed bacteria or fungi. An excess of nitrate was then formed as a final step. The harmful effect of cadmium was more pronounced in calcareous soil, probably due to the higher sensitivity of nitrite-oxidizers in these soil samples.

Potential Nitrification Rate as a Tool for Screening Toxicity in Metal-Contaminated Soils

“…for the oxidation to and Nitrobacter spp. The term ''nitrification potential'' is commonly used for nitrification in soil at saturating substrate concentrations, that is, the nitrification observed immediately after adding as the substrate ϩ NH 4 [2,3,5,6]. Nitrification is a process that is Ϫ Ϫ NO NO 2 3 affected by metals in soil [1][2][3][4][5].…”

“…Nitrification is a process that is Ϫ Ϫ NO NO 2 3 affected by metals in soil [1][2][3][4][5]. The accumulation of -N is also used as an Ϫ NO 2 endpoint, although this intermediate is found only in tests performed in suspensions [6] or in calcareous soils [2]. Because of its sensitivity to metal contamination and its key role in nitrogen cycling, nitrification is a process that can be used in hazard assessment of chemicals in soil.…”

Monitoring of population shifts in an enriched nitrifying system under gradually increased cadmium loading

“…Cadmium is widely known to be a very hazardous pollutant having toxic effects in various ecosystems [33]. On the molecular level, cadmium uptake is barely understood [13].…”

Are Fe and P availabilities involved in determining the occurrence and distribution of Calluna vulgaris (L.) Hull in semi-arid grasslands on calcareous soils?

“…Soil organic carbon contents (C o ) mostly range between 2.0% and 6.0% (m/m DW ), corresponding to carbon contents widespread in calcareous soils under temperate climatic conditions (e.g. Misra and Tyler 1999;Niklaus 1998;Dušek 1995).…”