Dispersal and mobility of metal contamination across a salt marsh from coastal landfill sites using ammonium nitrateextractions as an indicator

Abstract

Landfills have been the primary method of waste disposal within the UK for many years, and are often associated with land reclamation. The landfill in Christchurch Harbour, considered in this study, has a straight artificial channel which runs from the edge of the landfill to the estuary. This channel has increased the levels of metals in the marshland and acts, in effect, as a drainage system. The degree of metal mobility in soils and sediments is typically determined by using sequential extraction schemes (SESs), but the effectiveness and precision of these procedures are disputed. A simpler and more resilient approach is the application of partial/single extraction schemes (PESs). Both schemes, however, can only assess the theoretical readiness of a metal to migrate at a certain time/place and under certain conditions—they do not gauge the actual migration and therefore can only have predictive abilities at best. In this study, the metal distribution in an intertidal area between a landfill and an estuary has been determined using the actual distribution patterns in the ground and comparing them with the theoretical mobility based on the standardised PES procedure DIN 19730. It was found that this procedure can predict the actual migration in the marshland rather well; however, in the vicinity of the channel no correlation between the mobility and dispersion could be detected and the actual movement is much higher than the PES outcomes generally indicated.