The effects of heavy metal-rich sewage sludge on Collembola communities in grassland

[摘要] The purpose of this research was to investigate how the land application of sewage sludge (and particularly the heavy metals it contains) affects grassland Collembola. The effects of digested, undigested, copper-rich, zinc-rich and cadmium-rich sludges were investigated using a small plot trial established at SAC Auchincruive, South Ayrshire. An initial investigation was also conducted at a similar trial site established at Haitwood, Lanarkshire. The metal-rich sludges were derived from treatment works with naturally high inputs of the specific metal. Effects on euedaphic and hemiedaphic Collembola were examined in 1995 using litterbags as a sampling method, and effects on hemiedaphic and epigeal Collembola were investigated in 1995 and 1996 using pitfall trapping and suction sampling. The euedaphic Mesaphorura spp. and Neelus minimus were adversely affected by the application of zinc-rich sludge, and Mesaphorura spp. were also adversely affected by copper-rich sludge. Both suction samples and pitfall traps indicated that Lepidocyrtus cyaneus and Isotoma viridis were adversely affected by cadmium-rich sludge, and the pitfall traps also found Isotomurus maculatus and the total collembolan abundance to be adversely affected. Furthermore, the abundance of L. cyaneus, I. viridis and Heteromurus nitidis in suction samples was inversely related to the concentration of cadmium in the soil. The abundance of Isotoma anglicana in suction samples, on the other hand, tended to increase with soil cadmium concentration. This species was also more abundant in litterbags collected from the zinc-rich and copper-rich plots, hence suggesting that it was tolerant to all tliree metals investigated. Isotomurus palustris also appeared to be tolerant to heavy metals, and the abundance of this species (when sampled by suction) was highest in the zinc-rich and cadmium-rich plots. On the Auchincruive trial site, reproduction of Isotoma/Isotomurus species was promoted by the addition of sludge irrespective of metal contamination. At the Hartwood site, however, the abundance of juveniles was lowest in the cadmium-rich plots. Reproduction of Isotoma/Isotomurus species was therefore adversely affected by cadmium-rich sludge at Hartwood (but not at Auchincruive). The difference between sites was thought to be the result of differences in the composition of Isotoma/Isotomurus juveniles, with a larger proportion of the juveniles at Hartwood belonging to a metal sensitive species (e.g. I. viridis). All three sampling methods indicated that the effects of season (and succession in the case of litterbags) were more pronounced than those of treatment. Isotoma notabilis was found to be an early coloniser of decomposing oak leaves, while 1. palustris and 1. anglicana were late colonisers. The species diversity was found to increase as decomposition progressed. Seasonal peaks in abundance were also found to be species specific, with some species reaching their maximum density in April (e.g. Ceratophysella denticulata and Sminthurides malmgreni), others in May (e.g. Sminthurinus aureus and Isotoma/Isotomurus juveniles), and others in August (e.g. H. nitidis and L. cyaneus). Effects of grass cutting were apparent and several species (e.g. /. viridis, Sminthurides pumilis and Tomocerus longicornis) were more abundant following cutting. Furthermore, the abundance of I. viridis, S. pumilis and T. longicornis was inversely related to gi'ass height. This was thought to be the consequence of pitfalls and suction samplers being more efficient at sampling these species in shorter grass. In addition to the contaminated sludge experiment, initial research was also conducted to investigate the effects of the land application of pharmaceutical wastes on euedaphic and hemiedaphic Collembola. Two wastes, sodium ammonium sulphate (SAS) and aerobically treated sludge (ATS), were investigated using small plot trials. One year after SAS application, the collembolan community was more diverse and the species Folsomia Candida and Mesaphorura spp. were particularly favoured by SAS.(Abstract shortened by ProQuest.).

[发布机构] University:University of Glasgow

[关键词] Environmental engineering