Solution for underground pollution detect

Soils and groundwater are the material basis upon which human beings depend. After 30 years of economic growth, China has greatly improved people’s living standards, but China also paid the price of serious pollutions in the natural environment. The “Communique on the Investigation of Soil Pollution in China” issued in 2014 and the exposure of many pollution incidents in recent years all indicate that the soil and groundwater pollution in China is becoming increasingly prominent and seriously endangering people’s health. Therefore, the remediation and control of soils and groundwater in contaminated sites admits of no delay. As General Secretary Xi has put forward, “lucid waters and lush mountains are invaluable assets.” China’s economic development is currently under transformation. The original development model at the expense of resources and environment has gradually been replaced by a new economic model which is green and healthy. While, the survey and restoration of contaminated soils and groundwater will be an important work for China in the coming years.

The ultimate goal of contaminated site remediation is to completely remove contaminants and restore lucid waters and lush mountains for people. Remediation of contaminated sites is more often than not conducted through soil replacement, mixing or clearing. Due to the different types of pollution, the difficulty of soil remediation varies. In the case of contaminated sites where only shallow soils are contaminated and groundwater is not influenced, such as some illegal landfills or small-scaled single oil spills, the remediation can be done by simply treating or replacing the contaminated soil. However, as pollution expands into the water table, it’s very difficult to know the movement of contaminants in groundwater, greatly adding difficulty to the remediation. At this point, the site remediation will face many blind spots and difficulties so that whether the repair agent has reached the expected range is uncertain. If the injected drugs can’t mix with contaminants and take effects, they will only fail to repair the pollution, but even cause secondary pollution. In this case, we can consider using geophysical methods to observe the change of soil resistivity before, during and after the agent injection to determine whether the contaminant has moved and whether the agent has reached the expected range. The value of early observation can be used as the background value to compare with those of later stages. Moreover, we can build a geophysical observation system to conduct continuous observation, and finally use the time-lapse data processing method to analyze the electric property difference in percentage, which is the online monitoring technique for contaminated site remediation.

The site of groundwater pollution, which can’t decompose because full replacement isn’t applicable as in sites of soil pollution, requires injecting drugs into wells to decompose the contaminants chemically or biologically. Under such circumstances, more wells need to be built according to the site conditions. In addition to being used to fill repair agents, these wells can also be used in such geophysical well-logging method as cross-hole resistivity imaging. The method upgrades the traditional 2D to 3D imaging and even 4D dynamic imaging effects with the time-lapse method. Since the location of repair well is fixed, if such equipment as trans-hole electrode is set up when building the repair well, the soil resistivity can be continuously monitored during the repair process, analyzing the flow direction and distribution of the repair agent; and, the agent, if found not as effective as expected, can also be timely adjusted.

The system mainly consists of the following modules:

1. Direct current electrical products
2. Rainfall sensor, etc.
3. Geomornitor controller
4. Power supply module
5. Geo Could server
6. Client software

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