1. Associate Professor, Department of Environmental Conservation, Faculty of Global Environmental Science, Kim Il Sung University, Pyongyang, the Democratic People's Republic of Korea (corresponding author: , )
2. Researcher, Department of Environmental Conservation, Faculty of Global Environmental Science, Kim Il Sung University, Pyongyang, the Democratic People's Republic of Korea
3. Postgraduate student, Department of Environmental Conservation, Faculty of Global Environmental Science, Kim Il Sung University, Pyongyang, the Democratic People's Republic of Korea