Diurnal changes in the negative ion concentration of the air for two Cryptomeria fortunei communities of National Nature Reserve of Mount Tianmu

Key words: 
• environment science /
• negative ion concentration in the air /
• Cryptomeria fortunei community /
• gray correlation analysis

Abstract: To study the diurnal changes in negative air ion concentration and their relationships with environmental factors within two Cryptomeria fortunei communities，growing at Yiliting and Zhuxiang Resort，in the Mount Tianmu Nature Reserve，measurements were made with an air ion measuring instrument，a microcomputer laser dust collecting instrument，and a temperature-humidity recorder. Then，diurnal variations（8 : 00 － 17 : 00） were monitored simultaneously during sunny days in summer of 2006 with a gray sequence analysis between negative air ions and 1）particle matter with aerodynamic diameter＜10 μm（PM10），2）relative humidity，3）air temperature，4） wind speed and 5） photons. Results showed that 1） the negative ion concentration in the air for Yiliting was significantly higher than（P＜0.001 during sunny days in early and mid-summer of 2006 respectively） Zhuxiang with two or three peaks during a day. Also，2） air cleanness degree for Yiliting was superior to Zhuxiang. Lastly，3） The sequence of the affection on the negative ion concentration by environment factors on a sunny day in early summer for C. fortunei community near Yiliting was air relative humidity＞air temperature＞wind speed. But in midsummer C. fortunei community near Zhuxiang，the sequence of the affection on the negative ion concentration by environment factors was air relative humidity＞air temperature＞PM10. For measurements on a day in midsummer，the most important meteorological factor affecting the negative ion concentration of the air in Yiliting and Zhuxiang was photons.［Ch，2 fig. 5 tab. 13 ref.］