Air Negative Ions Characteristics of 7 Economic Forests in Beijing

To reasonably evaluate the value of air negative ions that provided by economic forests, the diurnal variation of negative air ions in the forest was monitored from May to October in 2015, and the quality and quantity of the economic forests were evaluated. The results showed that the peak of negative air ions appeared at around 9: 00 to 11: 00 and 17: 00, low value appeared at around 15: 00 among 7 species, and the average daily concentration was 746-2 056 ions/cm³. The monthly changes were as follows: September > August > July > June > May > October, and the negative ions in each month were extremely different. The strongest ability to provide negative ions among 7 economic forests species was Malus pumila, and the weakest was Ziziphus jujuba. The ions quality of economic forests was 2.09 × 10¹⁸-3.13 × 10¹⁸ ions/(hm²·a), the value of each year was 7.84-18.17 yuan /(hm²·a).