The Effects of Depth and Hydrological Connectivity on Heavy Metal Loading in Riparian Zones

Abstract: The area between a stream and land is known as a riparian zone. These zones are highly dynamic whichcarry and accumulate heavy metals and environmental contaminants. Discrete Riparian Input Zones(DRIPs) are a subset of such zones that carry concentrated amounts of water into streams at discrete points.These are more active in their ability to channel water than riparian zones. These areas are important sincethey may retain or release metals and thereby affect the stream chemistry. To test if DRIPs accumulatemetals, 7 DRIPs and 4 Non-DRIPs were sampled along the C5 stream in the Krycklan Catchment. Soilsamples were taken from the surface down to 0.5 m depth at 0.1 m increments and were analysed for totalmercury, metals and loss on ignition. Three metals (vanadin, iron and zinc) were identified as having significant differences in concentration between DRIP and Non-DRIPS. Vanadin and Fe had significantlyhigher concentrations in Non-DRIPs, whereas iron had higher concentrations in DRIPs. Mercury,cadmium, iron, and loss on ignition (LOI) were found to decrease as depth increased, whilst Al was foundto increase with depth. Finally many elements are inter-related, but those with the strongest correlation areLOI and mercury, and iron and cadmium, both r > 0.85. LOI and mercury are strongly related as mercurybinds strongly to organic matter. The relationship of Fe and Cd is likely due to the Fe-oxide and Cdrelationship.