Nitrogen (ammonium, nitrate and nitrite) is the most common nutrient in urban waters that impact water quality. Excess nutrient loading to water bodies can affect many aquatic organisms and, ultimately, contribute to the degradation of freshwater, estuarine, and coastal marine ecosystems. Furthermore, high concentrations of nutrients in drinking water sources can cause health impacts to human beings. Due to the potential sporadic nature of the contamination sources, grab sampling may fail to identify contamination events, and hence requires accurate, valid approaches to monitor loads and concentration of nutrients. The diffusive gradients in a thin film (DGT) technique is a well-establish time-integrated, in situ and passive sampling technique, which has been utilized to trace metals (Cu, Fe, As, Cd), measure dissolved reactive phosphorus in rivers, coastal waters and sulphide in sediment. Analyte species diffuse through a diffusive layer (δ) of known thickness and are immobilized by the binding layer (∆r). Analytes are passively accumulated within the sampling device over a given deployment time. The accumulation process is derived from Fick’s First Law of Diffusion and calculated using the DGT equation. A new diffusive gradient in a thin film (DGT) technique, using an anion ion exchange resin A520E adsorbent, has been developed and evaluated for the measurement of nitrate in the laboratory. NO3-N was found to be quantitatively accumulated by the adsorbent A520E resin over a range of concentration. Laboratory DGT experiments gave a good linear mass uptake over time (R2≥0.9950) for NO3-N. NO3-N uptake was predictable with various pH (3.5-8.5) and ionic strength (0.0001-0.015 mol L-1 NaCl). For the future work, DGT samplers with three diffusive layer thicknesses will be deployed in the field to calculate the diffusive boundary layers to confirm the use of the technique in situ and an accurate measurement of nitrate in natural waters.

New diffusive gradients in a thin film technique for measuring nitrate using ion exchange resin

249th National Meeting (2015)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.