基于PCA和在线监测技术研究旅游活动对岩溶地下水水化学的影响

Influences of Tourism Activities on Hydrochemistry of Karst Groundwater Revealed by Principal Component Analysis and On-line Monitoring Technique

岩溶地下水极易遭受污染且响应迅速,单靠几次取样难以揭示这种快速的动态过程。本研究采用高分辨率在线示踪技术确定了重庆金佛山水房泉的污染源位置,利用高密度监测获取了水房泉2014-12-01至2015-03-27期间水化学信息,同时定期获取流域内的大气降水、土壤水、景区假日酒店生活用水(以下简称宾馆用水)及污水样品。结果表明:投放在假日酒店卫生间的荧光素钠在水房泉的回收率为82%,示踪剂到达水房泉的最短时间和平均时间分别为26.8 h、90.3 h;水房泉泉水(以下简称泉水)在监测前期(2014-12-01至2014-12-14)和监测后期(2015-03-05至2015-03-27)大部分水化学指标的数值接近,监测中期出现的3次较大幅度的波动,与游客高峰期契合。主成分分析(PCA)提取了能代表75.0%信息量的2个主成分,旅游活动引起的pH值、溶解氧降低及电导率、盐度、浊度、K^+、Na^+、Ca^(2+)、Mg^(2+)、Sr^(2+)、全Fe、全Mn、SiO_2、HCO_3~–、Cl~–、PO_4^(3–)的上升,对本次监测信息的贡献率为61.2%;大气降水则导致泉水流量增加、水温降低,NO–3、Al^(3+)可能受到活塞效应的影响而增加,对本次监测信息贡献率为13.8%。旅游活动是影响该时段泉水水化学特征变化的主要因素。

Karst groundwater is easy to be contaminated and respond quickly, and thus it is unreasonable to reveal the fast variation processes only based on several times of sampling. In this study, the position of pollution resources of Shuifang spring was confirmed by high-resolution online tracer test, and the geochemical information of Shuifang spring from December I, 2014 to March 27, 2015 was acquired via high-resolution monitoring. Furthermore, the precipitation, soil water and tap-water of Jinfo Mountain Holiday Hotel and wastewater in this basin were sampled bimonthly. The results show that the recovery of uranium injected in the holiday hotel＇s toilet is 82%, the shortest time and the mean time of the tracer transport from the injected point to Shuifang spring are 26.8 h and 90.3 h respectively. The values of geochemical parameters in the spring were close between the first monitoring stage （from December 1, 2014 to December 14, 2014） and the last monitoring stage （from March 5, 2015 to March 27, 2015）, whereas three fluctuation periods occurred during the middle monitoring stage and this phenomenon coincided well with the peak of tourism activities. PCA analysis yielded 2 principal components accounting for 75.0% of the total variance. The first component indicated the influences of tourism activities （i.e., the decrease in pH value, dissolved oxygen and the increase in specific conductivity, salinity, turbidity, K＋, Na＋, Ca2＋, Mg2＋, Sr2＋, TFe, TMn, SiO2, HCO3, C1-, PO34 ） , which accounted for 61.2% of the variability in the data. The second component represented the influences of precipitation （i.e. the increase in flow, NO3, A13＋ and the decrease in water temperature）, which contributed 13.8% to the total variance. Therefore, tourism activities were the primary factor responsible for the variation of geochemical parameters in Shuifang spring during the monitoring period.