Abnormal interruption of water flow from an artesian well prior to 2008 Wenchuan earthquake

Water flow from an artesian well stopped on December 17, 2007 but recovered when the Wenchuan Ms 8.0 earthquake occurred on May 12, 2008. This well is located 90 km south of the epicenter in an extensional tectonic setting, where similar changes of water level and resistivity were observed at two other nearby sites. Our investigation suggests that this phenomenon was not caused by environmental disturbances, such as drought or borehole-drilling activity, but might be a precursor to the earthquake.

固相萃取液相色谱串联质谱法测定水中6种三嗪类除草剂

[背景]三嗪类除草剂是我国目前生产应用较多的除草剂之一,其很难被生物降解,具有持续高生态毒性,会对环境产生影响,包括对水生生物的慢性毒性、生态系统中的蓄积以及对人体健康的危害。[目的]将固相萃取法和液相色谱-串联质谱法相结合,建立检测水中莠去津、草净津、异丙甲草胺、草克津、扑草净、西玛津6种三嗪类除草剂的新方法。[方法]优化仪器条件和前处理条件,用Waters Oasis HLB萃取小柱净化,甲醇洗脱,90%甲醇水复溶,超高效液相色谱串联质谱法用电喷雾离子化源正离子模式进行多反应检测模式监测,对质谱测定的目标离子进行选择,外标法定量。应用建立的方法检测4份太湖水样、3份水源水样和10份生活饮用水样。[结果]6种三嗪类除草剂在0-250.0μg·L^(-1)范围内线性关系良好,相关系数均大于0.999,检出限为0.54-1.44μg·L^(-1),定量限为1.8-4.8μg·L^(-1),平均回收率为75.0%-93.3%,精密度为0.6%-5.0%。水源水和生活饮用水中均未检出三嗪类除草剂,某湖水样本中测得草克津质量浓度为0.16-0.17μg·L^(-1),其他5种物质未检出。[结论]方法操作简便,检出限低,灵敏度高,经实际湖水样品测试,可以满足水样中6种除草剂残留的同时分析测定。