In this study, the rainfall, pH, conductivity, and ionic component data for Guilin from 2015 to 2017 were analyzed. Specifically, the relationship between the pH value of the rainfall, the change of each ion in the rainfall, and the primary ion sources was examined. The main results obtained were as follows. During the 3-year study period, the average annual pH value of Guilin was 5.45 and exhibited a downward trend. The seasonal variation of rainfall acidity was pronounced, with high pH values and low frequencies of acid rain in summer, and low pH values and high frequencies of acid rain in winter. From 2015 to 2017, the relative order of the average concentrations of the ionic components in the rainfall was SO₄²⁻ > NO₃⁻ > Ca²⁺ > Cl⁻ > NH₄⁺ > Na⁺ > K⁺ > Mg²⁺ > F⁻, the annual average concentration of each ionic component displayed a downward trend, and seasonal changes were obvious. Only NH₄⁺ showed an upward trend in rainfall. The (SO₄²⁻)/(NO₃⁻) ratio was basically < 3 and manifested a downward trend; (Ca²⁺)/(NH₄⁺) rose sharply in August and September each year. Using correlation analysis and enrichment factor analysis, it was concluded that the rainfall in Guilin is mainly affected by SO₂, NO_x, and NH₃, with the geological conditions in the karst area also contributing a certain amount to the rainfall acidity. Calculating the enrichment factor revealed that most of the Ca²⁺ came from a crustal source; half the Mg²⁺ came from the ocean and half came from the crust; and most of K⁺ and Cl⁻ originated from the ocean. Human activities contributed most of the SO₄²⁻ and NO₃⁻ in the rainfall.

本研究对桂林市2015-2017年降雨量、pH值、电导率和离子成分数据进行了分析。具体地，考察了降雨的pH值、降雨中各离子的变化与一次离子源之间的关系。获得的主要结果如下。3年研究期内，桂林市年均pH值为5.45，呈下降趋势。降水酸度季节性变化明显，夏季pH值高、酸雨频率低，冬季pH值低、酸雨频率高。2015-2017年降雨中离子组分平均浓度的相对顺序为SO ₄ ²⁻ > NO ₃ ⁻ > Ca ²⁺ > Cl⁻ > NH ₄ ⁺ > Na ⁺ > K ⁺ > Mg ²⁺ > F ⁻，各离子组分年平均浓度呈下降趋势，季节性变化明显。只有NH ₄ ⁺的降雨量呈上升趋势。(SO ₄ ^2- )/(NO ₃ ^- )比值基本<3，呈下降趋势；(Ca ²⁺ )/(NH ₄ ⁺ ) 在每年的 8 月和 9 月急剧上升。通过相关分析和富集因子分析得出桂林降雨主要受SO ₂、NO_x , NH ₃ , 喀斯特地区的地质条件对降雨酸度也有一定的贡献。计算富集因子发现大部分Ca ²⁺来自地壳源；Mg ²⁺一半来自海洋，一半来自地壳；大部分K ⁺和Cl ^-来自海洋。人类活动贡献了降雨中的大部分 SO ₄ ^2-和 NO ₃ ^-。