" It is time to take action , " says yuan daoxian , a hydrogeologist at the institute of karst geology in guilin , china .
来自中国桂林喀斯特地质研究所的水文学家袁道县说，现在是时候采取行动了。
Other lab-based studies have suggested that sediments in deeper aquifers tend to keep arsenic out of the water , says william burgess , a hydrogeologist at the department of earth sciences at university college london .
