Distribution of Sulfidic Sediments in Wetlands along the Murray River

"February 2006".

Project Number: Acidification of Freshwater Wetlands - M/BUS/76.

MDFRC item.

31 pages.

The presence of sulfidic sediments was assessed for 30 wetlands along the Murray River (28 in NSW, 2 in Victoria) using a suite of diagnostic field and laboratory experiments. At least one sediment sample from seven of the wetlands contained sufficient reduced inorganic sulfur to be considered sulfidic and therefore of immediate concern. Of those, five were in NSW - Quatta Quatta Lagoon and Croppers Lagoon near Corowa, Bottle Bend Lagoon and Boeill Creek near Mildura, and Pollard/Malcolm. In addition, another 4 wetlands had sediment characteristics which suggest that they probably contain sulfidic sediments – Pattersons Swamp, State Forest Lagoon, Horseshoe Lagoon-Periccota and Benanee Lake. A decision support tool has been developed to help identify if a wetland may contain sulfidic sediments. Wetlands that receive irrigation return water or storm water are at risk of producing sulfidic sediments. Low pH (< 4) and/or high salinity (>1750 μS cm-1) and/or high sulfate (>10 mg S l-1) in the water column are also indicative of wetlands with sulfidic sediments. If the wetland does contain sulfidic sediments but the sediment pH (determined on a 1:5 soil: 1M KCl extract) is greater than 6.5, there is a reduced risk of acidification on drying.