Commentary on “Arsenic mobility in the arsenic-contaminated Yangzonghai Lake in China” by Changliang Yang et al. [Ecotoxicology and Environmental Safety, 107(2014)321–327]

• Unreasonable sampling method for determining As concentration.
• Incorrect conclusion comes from the wrong lake water volume data.
• HCO3− cannot desorb As in the sediments.

This commentary concerns some inaccuracy in recently published paper “Arsenic mobility in the arsenic-contaminated Yangzonghai Lake in China”. Yang et al. raised an incorrect conclusion that after treatment with FeCl3 using the flocculation method, the sediments in the Yangzonghai Lake released As in the summer. The fundamental flaws of the paper which led to the incorrect conclusion were unreasonable sampling method for determining As concentration at various water depth and the wrong lake water volume of 6.04×108 m3 (actually 4.8×108 m3) for calculating inventory of As in Yangzhonghai in August 2012. Then the authors attribute the As release in summer to the high concentration of HCO3− without any support of experimental data. Meanwhile, the authors designed a microbiological experiment to illustrate that increasing capacity of anaerobic microorganism could lead to As releasing from sediments. In our view point, this microbiological experiment was nonsense for evaluating the stability of As in sediments of Yangzonghai lake since the experimental conditions were greatly different from the natural conditions. Therefore, we conclude that the conclusions put forward by YANG are incorrect.