Pedological characterisation of sites along a transect from a primary cadmium/lead/zinc smelting works.

A pedological characterisation of seven sites along a transect from a smelter at Avonmouth, UK, was undertaken. Site locations comprised a mixture of both grassland (5 sites) and oak tree dominated (2 sites) areas. Geographically, sites were either low lying or on adjacent elevated ground. Across the transect, a severe gradient of metal concentrations was found with highest values for organic soil horizons from close to the factory. Comparisons with quality standards indicate that these metal levels are likely to be a major ecological stressor. In addition to the strong metal gradient, a number of other between site differences were also observed. These were firstly water regime, which at the low lying sites close to the smelter showed influence by both, groundwater and stagnant water, while at more distant sites indicated susceptibility to stagnant water only, and secondly soil pH, which showed large between site variations, although no consistent trend along the transect. Humus forms at sites more than 1.5 km from the smelter were characteristic for the soil conditions and land-use present, while those at sites within 1.5 km showed disturbed profiles. Indeed, the humus types present at these locations suggest that the activity of soil invertebrates may be inhibited. This is almost certainly due primarily to the high concentrations of metals that were present in mineral soil and organic horizons at the sites. However, the potential influences of water regime and pH could also be relevant factors influencing the results of any further studies conducted at these study sites.

Metal effects on soil invertebrate feeding: measurements using the bait lamina method.

Heightened concerns regarding the protection of terrestrial ecosystems at a national level has increased the need to develop a suite of indicators capable of assessing the quality, integrity and fertility of soils. Of the assays currently available, tests that measure aspects of soil function and associated parameters are among the most promising, since these integrate effects on soil quality at the highest level of organisation. In this study we describe results of the deployment of an indicator of soil functional integrity (the bait lamina test) that is designed to measure the feeding activity of soil invertebrates. Bait lamina was used at six grassland sites located along a transect from a smelter at Avonmouth (South-West England) used in the EU funded BIOPRINT II project. Results indicated highest bait removal (feeding) at sites furthest from the factory, intermediate feeding activity at intervening sites and extremely low activities at the two sites closest to the smelter. The strong decline in activity for the group of sites closest to the smelter corresponded with increasing metal concentrations suggesting a clear impact of metals on detritivorous invertebrate feeding. Comparisons of the results of the bait lamina study to previous invertebrate survey work suggested that the differences in observed bait removal can be attributed to direct effects of metals on the abundance and biodiversity of key decomposer groups such as earthworms, isopods, molluscs, myriapods, springtails and mites.