Genesis of karst groundwater contamination based on system spatial feature recognition

Abstract

The karst groundwater system has a complex spatial structure, strong aquifer permeability and poor anti-pollution performance. Once pollution occurs, the pollutants spread rapidly, and the repair is difficult. This study takes the pollution of a large karst spring in South China as an example. On the basis of a karst hydrogeological survey, combined with hydrochemical characteristics and multiple-tracer technology, the boundary of karst groundwater system and the distribution of underground river pipelines were analyzed, and the main pollution sources and pollution routes of the karst spring were identified. In addition, the genetic model of karst groundwater pollution was also explored. These results showe that the Q1 karst groundwater system was a typical "multi-source, single-sink" groundwater circulation pattern with two main runoff channels in the north and south. Manganese, total bacterial counts, ammonia nitrogen and total phosphorus were the main substances exceeding the standard, which were 17, 14, 7.2 and 3.8 times the groundwater quality standard threshold, respectively. The construction waste blocked the original channel of the underground river, forcing the groundwater to divert and flow under the landfill. Engineering investigation and dynamic compaction activities destroyed the natural clay impermeable stratum under the landfill, resulting in the early transport of domestic garbage and leachate entered into the karst pipeline, both of which caused the pollution of karst groundwater. This study provides an important reference for the prevention and control of karst groundwater pollution.

Keywords

• groundwater contamination
• tracer test
• spatial structure
• genesis
• karst water system