Effect of water temperature on internal nitrogen release from sediments in the Pearl River Delta region, China

Nitrogen (N) has received attention as an indicator of water quality and pollution. However, there is still a lack of systematic research on its influence of temperature. An experiment was conducted with five tanks containing sediments from the Pearl River Delta region of China and distilled water to assess the release of N from sediments under controlled conditions; temperatures from 10 to 30 °C were assessed. Results show that the effect of temperature on N in the water column and sediment is nonlinear. NO3-N was affected at temperatures between 20 and 25 °C in shallow sediments (1–3 cm below the sediment–water interface) with rapid increase concentration, while NH4-N concentration in water column was decreased significantly with increased temperature between 10 and 15 °C. NO3-N was dominant at temperatures from 25 to 30 °C. However, the presence of NH4-N in a water body can inhibit its release, thus the relationship between the diffusive flux with temperature is not linear. The relationship between N diffusive flux at the sediment–water interface was described by Polynomial2D and Lorentz2D models.