Surface water quality at Ashfield Flats Reserve, Western Australia
Elemental (including Al, As, B, Ba, Ca, Co, Cr, Cu, Fe,Gd, K, La, Mg, Mn, Mo, Na, Nd, Ni, P, S, Si, Sr, V, Zn) concentrations, selected nutrient ion concentrations (nitrate+nitrite (NOx), filterable reactive phosphate (FRP)), pH, electrical conductivity, Longitude-Latitude and UTM Zone 50 coordinates, sampling strata, and sample identification codes for 172 samples of surface water collected in 2019, 2020, and 2021 from Ashfield Flats Reserve, an urban nature reserve in Western Australia. Ashfield Flats Reserve (approx. 40 ha) is listed as a Western Australian Bush Forever Site (No. 214) and fringes the Swan-Canning Estuary. It is also listed in the Directory of Important Wetlands in Australia and contained a threatened ecological community of temperate saltmarsh plant species. It is the largest remaining salt marsh in the Swan-Canning Estuary, but is impacted by altered hydrology, several stormwater drains, and poor water quality from historical groundwater contamination. Sampling and analysis was conducted to assess the severity and extent of contamination of surface water with trace elements and nutrients. In particular it was of interest whether the water quality in wetland ponds was affected by stormwater drains which cross the reserve, and to what extent mixing of drain water with estuarine water affected water quality.
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Sampling was conducted was conducted on 15 March 2019, 13 March 2020, and 5 March 2021 with samples in transects along stormwater drains or across wetland ponds. Water sampling protocols followed Clesceri et al. (1998). Acid-washed plastic bottles were used to sample water at approximately mid-depth (and mid-stream for the drain samples). A portion (ca. 50 mL) of the water sampled was immediately removed, filtered through a 0.45 µm membrane into a separate clean plastic bottle, and acidified with 1∕100 volume of 5 mol/L HNO3. The acidified samples were stored in insulated containers prior to transporting to the laboratory within 4 hours, and were subsequently stored at 4 °C until analysis. Powder-free nitrile gloves were worn at all times while handling samples. The electrical conductivity of unfiltered water samples was determined using a calibrated conductivity cell electrode. The pH was measured on the same samples using a glass-reference pH electrode after a 2-point buffer calibration (Rayment and Lyons, 2010). The concentrations of 38 elements were measured on acidified samples by inductively coupled plasma–optical emission spectrometry (ICP-OES). Reagent blanks were included in analytical runs to check for contamination and for the calculation of lower limits of detection (LDL) from 3 × standard deviation of blank signals (Long & Winefordner, 1983). Measurement precision was assessed using analytical duplicates. Soluble reactive phosphate concentrations were determined spectrophotometrically at 880 nm following formation of the blue vanado-molybdate complex (Clesceri et al. 1998). Nitrate concentrations were determined spectrophotometrically at 540 nm following reduction to nitrite with NADH and nitrate reductase, then reaction with sulphanilamide and napthylethylenediamine which forms a deep pink coloured complex (Campbell et al. 2006). Campbell, W.H., Song, P., Barbier, G.G., 2006. Nitrate reductase for nitrate analysis in water. Environmental Chemistry Letters, 4: 69-73, doi:10.1007/s10311-006-0035-4. Clesceri, L.S., Greenberg, A.E., Eaton, A.D. (Eds.), 1998. Standard Methods for the Examination of Water and Wastewater, 20th Edition. American Public Health Association/American Water Works Association/Water Environment Federation, Washington, DC. Long, G.L., Winefordner, J.D., 1983. Limit of detection: A closer look at the IUPAC definition. Analytical Chemistry, 55: 712A-724A, doi:10.1021/ac00258a724. Rayment, G.E., Lyons, D.J., 2010. Soil Chemical Methods - Australasia. Australian Soil and Land Survey Handbooks Series. CSIRO Publishing Clayton, Victoria, Australia.