The microbiology of railway embankments and its relation to herbicide persistence

Herbicides have been shown to be very persistent in Swedish railway embankments. Half-lives in the range of several years have been reported. This is especially troublesome since embankments also have a very low adsorptive capacity. Herbicide residues have caused the unintended killing of pine trees along railways and have been found in groundwater several years after use. To address the problems related to long persistence an investigation into the microbiology of railway embankments has been undertaken. Preliminary results show that the microbial biomass, as estimated with Substrate-Induced Respiration (SIR), is about 10 times smaller than in normal agricultural soils. Furthermore, it would appear that the size of the microbial biomass, in all essential, was controlled by the organic matter content. Thus, microbial biomass increased with distance to track middle, as did organic matter content, probably owing to increased litter fall and less efficient weed control