自然環境中的負離子濃度受到該區域微環境與即時天氣狀況的綜合影響，例如植物自行產出、人造或自然的電場、氣溫、相對濕度、風速、太陽輻射及宇宙射線等。許多醫學上的文獻在可控制的環境下，直接或間接地證實了負離子對人體的益處。不僅是生理及心理效益，也包含了清淨環境的效益，例如高效率除去懸浮粒子，因此在森林環境中的負離子被廣泛認為是有益於健康的。本研究於溪頭森林地區設置固定測站，監控即時的天氣狀況與負離子濃度變化。一年的監測結果顯示平均的負離子濃度依序為秋季410±212>冬季355±203>夏季228±129>春季184±132 個/立方公分。有太陽輻射條件下的平均負離子濃度皆大於無太陽輻射值的條件。四季的負離子濃度最大值都發生在有太陽輻射條件的天氣狀況下，無論有無太陽輻射條件，負離子濃度與氣溫皆呈顯著性正相關。在有太陽輻射條件下，負離子濃度與平均相對濕度呈顯著性負相關；在無太陽輻射值條件下，負離子濃度與平均相對濕度呈顯著性正相關。由複迴歸分析結果可以說明負離子濃度受氣溫、相對濕度、太陽輻射及風速等氣象因子的影響。本研究結果可以提供溪頭森林療癒對身體健康效益研究的參考。

In the natural environment, the concentration of negative ions (NAIs) is affected by the combined effects of the microenvironment and real-time weather conditions, such as plants as a source for generating NAIs, natural and artificial corona discharge, temperature, relative humidity, wind speed, solar radiation, cosmic rays, and etc. Many medical literatures have directly or indirectly confirmed the benefits of NAIs on human health under controlled environments. Not only the physiological and psychological benefits, the NAIs also provide benefits of environment cleaning, like the efficient removal of suspended particles. As a result, NAIs in the forest environment have been widely considered to help improve the health condition. This study set up a fixed monitoring station in the Xitou forest environment to monitor the variations of instantaneous weather conditions and NAIs concentration. The results of one year's monitoring showed that the average NAIs concentration (ions/cm3) followed the order of autumn (410±212) > winter (355±203) > summer (228±129) > spring (184±132). The average NAIs concentration in the presence of solar radiation was greater than the condition without solar radiation. The maximum NAIs concentration in the four seasons occurred under weather conditions with solar radiation. Regardless of the presence or absence of solar radiation, the NAIs concentration showed a significant positive correlation with air temperature. In the presence of solar radiation condition, the NAIs concentration had a significant negative correlation with the average relative humidity; in the absence of solar radiation condition, the NAIs concentration had a significant positive correlation with the average relative humidity. The multiple regression analysis showed that the NAIs concentration was affected by meteorological factors such as temperature, relative humidity, solar radiation and wind speed. This study can provide a reference for the study of health benefits of forest therapy in Xitou area.