Spatial Distributions and Release Risks of Calcium and Magnesium in Sediments from Jianhu Lake, Northwest Yunnan Province

In order to study the spatial distributions and release risks of calcium (Ca) and magnesium (Mg) in Jianhu sediments from northwest Yunnan Province, the sediment samples of Jianhu Lake were pretreated by the methods of microwave assisted digestion. The contents of Ca and Mg were determined by inductively coupled plasma-optical emission spectrometry (ICP−OES). Meanwhile, the methods of Kriging interpolation and phosphorus release contribution calculation were used to study the spatial distributions and release characteristics of Ca and Mg in Jianhu Lake. The results showed that the average contents of Ca and Mg in the surface sediments were 18.91 g/kg and 8.20 g/kg in Jianhu Lake, respectively, and the average contents of Ca and Mg in the wetland restoration areas were all low, and the horizontal spatial variation coefficients were all greater than 10%. The contents of Ca and Mg in the columnar sediments of Jianhu Lake were 2.03–42.55 g/kg and 1.30–73.60 g/kg, respectively, and the contents of Ca and Mg in the surface sediments (0–5 cm) were all higher than those in the bottom sediments (70–75 cm). At the same time, the average values of fast release contribution rates of Ca and Mg were 15.84%, 3.71%, and the mean values of slow release contribution rates of Ca and Mg were 20.93%, 4.20%, respectively. Therefore, Ca and Mg in the sediments from Jianhu Lake were all generally in the states of releasing in a short time (25 years) and a long time (150 years).