重庆北温泉水化学特征对汶川8.0级地震的响应

Response of the Beiwenquan hot spring's hydrochemical features in Chongqing to the Wenchuan earthquake of magnitude 8.0 in Sichuan

2008年5月1日至7月4日汶川8.0级地震前后,对距震中约400 km的重庆北温泉7个泉点进行采样监测,发现其水温、水量及水化学特征均发生了较大变化:(1)所有泉点震后水温都下降了1℃左右;(2)海拔相对较高的BWQ-2、BWQ-3、BWQ-4泉点相继断流,而下游海拔较低的BWQ-1泉点水量则增加了15 L/s,BWQ-6泉点水量也有所增加;(3)海拔较低泉点泉水中K+、Na+、Ca2+浓度减少,Mg2+浓度增大,且K+、Na+、Ca2+浓度呈正相关;Fe3+、Mn2+浓度于地震当日成倍增长,随后逐渐减小,7月4日时浓度与5月1日相当;SO42-、F-浓度增大后逐渐减少。引起北温泉水物理化学变化的主因是:由于汶川强烈地震,导致北温泉区上覆盖层裂隙与下伏温泉含水层裂隙贯通,地表或上覆盖层低温水汇入含水层所致。

The Beiwenquan hot spring were continuously monitored from May 1 to July 4,2008.It proves that the temperature and discharge as well as hydrochemistry have obvious response to the earthquake of magnitude 8.0 in Wenchuan.（1） After the earthquake,temperature of these springs all dropped about 1℃.（2） Three higher elevation springs BWQ-2,BWQ-3,BWQ-4 ceased to flow,but BWQ-1,being located lower,increased its discharge by nearly 50%,and BWQ-6＇s discharge also increased.（3） Concentration of K＋,Na＋,Ca2＋ in those lower located hot springs reduced after the earthquake and has excellent linear correlation with the earthquake.But concentration of Mg2＋ increased.Concentration of Fe2＋,Mn2＋ increased several fold on May 12 and decreased gradually thereafter.On July 4,the Concentration of Fe3＋,Mn2＋ was the same with May 1.Concentration of SO2-4,F-changed anomalously.It is believed that the variation of physicochemical properties in hot springs results from the mixture of cold waters from surface or from overlying aquifer mixed with the hot water of the spring because the fractures connected the upper or overlying aquifer with the hot spring after the earthquake.