Ammonia nitrogen adsorption and release characteristics of surface sediments in Dianchi Lake, China

Abstract

To determine the ammonia nitrogen adsorption and release characteristics of surface sediments in Dianchi Lake, 36 surface sediment (0-10 cm) samples were collected in 2013. Results showed that compared with other lakes in China (e.g. Erhai Lake and Taihu Lake), Dianchi Lake had high levels of ammonia nitrogen (NH 4 ? -N) adsorption capacity, release rate and release capacity. The ammonia nitrogen release risk of Dianchi sediments was relatively high. Comparison of the equilibrium ammonium concentration (ENC 0 ) in surface sediments and the ammonium contents in the overlying water of Dianchi Lake indicated that ENC 0 was high for most lake sections. Therefore, the sediments of Dianchi Lake would be a pollution source, and ammonia nitrogen release risk was high because the surface sediments of Dianchi Lake were heavily contaminated with nitrogen. The total nitrogen (TN) and NH 4 ? -N contents of the sediments of Dianchi Lake greatly influenced the ammonia nitrogen adsorptionrelease process. Aside from TN, nitrogen fractions should also be studied when assessing pollutant release risk from lake sediments. NH 4 ? -N was the main fraction of nitrogen released from sediments, which was highly significant when evaluating sedimentary release capacity. The sedimentary release capacity and release potential of nitrogen provided important information to assess release risks.

Seasonal Release Potential of Sediments in Reservoirs and its Impact on Water Quality Assessment

“…NH 4 + –N solutions with gradient concentrations of 0, 1, 5, 10, 15, 25, 30, 40, 50, 60, 70, 90, and 100 mg/L were prepared by ammonium chloride, and the pH of all of them was adjusted to 7.0 by 0.01 mol/L HCL and 0.01 mol/L NaOH [4]. In a series of 100 mL centrifuge tubes, 1 g of sediments was placed and treated with 100 mL NH 4 + –N solution at various concentrations.…”

“…With the perennial accumulation of pollutants and mineralization of sedimentary organic matter, concentrations of a variety of constituents in sediments are many times greater than those in water. When the external environment condition is changed, constituents will be released from sediments into the water column through desorption, dissolution, mineralization, and microbe release, leading to algae over-blooming and water quality degradation [3,4,5,6]. Thus, sediments act as pollution sources to water.…”

Vertical distribution and release characteristics of nitrogen fractions in sediments in the estuaries of Dianchi Lake, China

“…During a governance process that has lasted nearly 30 years, a series of measures have been taken including wastewater interception, governance of rivers flowing into the lake, governance of agricultural and rural non-point source pollution, ecological restoration and construction, and desilting. By August 2013, although exogenous pollutants in Dianchi Lake had been essentially controlled, deterioration of its water quality was not improved and blue-green algae and algal blooms continued to occur once per year [25].…”

Seasonal and Spatial Distribution and Pollution Assessment of Nitrogen and Phosphorus in Sediments from One of the World’s Largest Tidal Reservoirs

“…Sediment, an irreplaceable component of water bodies, derives naturally from the weathering and erosion of bedrock minerals, organic matter, soil, and other river sources [1], and acts as both sink and secondary release source [2][3][4]. Most pollutants are retained in sediments because of their stability in the sedimentary column [5].…”