Worth attention! Where are the monitoring data of groundwater quality?
Open the website of the Ministry of Environmental Protection, you can see the real-time data of the national air quality, understand the dynamic monitoring of surface water quality, but hard to find real-time monitoring of groundwater quality data.
Turning to the "China State of the Environment 2015" bulletin released by the Ministry of Environmental Protection in June this year, groundwater quality occupies a short space. However, the data disclosed are startling: in China's 5,118 groundwater quality monitoring points, the water quality is poor and The proportion of extremely poor monitoring points were 42.5% and 18.8% respectively, accounting for more than 60% of the total number of monitoring points.
Ding Aizhong, vice dean of Beijing Normal University's Water Science Institute, admitted at a recent training seminar on simulation assessment and treatment and restoration of groundwater survey that the groundwater pollution in some cities and regions is aggravating. Even more worrisome to him is that currently, only remediation of the soil itself is considered in the remediation of contaminated sites and the evaluation and restoration of groundwater contamination under "poisonous land" is seldom involved.
In order to arouse the attention of all parties, Ding Aihong has always called for site management on various occasions to fully consider groundwater factors, but has repeatedly been questioned. "Some people think that poisonous soil will endanger human health through the exposure of dust and other means, and underground water will be buried underground, so long as it is not extracted, it will not cause any harm to people and no treatment is needed," Ding said.
In fact, the relationship between groundwater and soil is not fragmented. Ding Aizhong pointed out that the contaminated groundwater is untreated and the pollutants contained therein enter the soil above it by means of volatilization. Therefore, it is not enough to control the soil alone. Furthermore, groundwater is mobile, and the contaminants it contains can migrate as water flows, threatening nearby groundwater sensitive sites such as groundwater sources.
According to Huang Jinlou, associate researcher at the Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, one of the reasons why groundwater is less involved in remediation of contaminated sites in China is that the difficulty and cost of groundwater remediation are both high. Remediation of groundwater below the contaminated site, we must first clear the source of pollution and pollution. Some contaminated sites originally built chemical plant above, if there is detailed drawings to understand the factory process and sewage pipe network settings, the investigation of sources of pollution will be of great significance.
"Unfortunately, due to the age-old and other reasons, it is difficult to collect the raw materials related to chemical plants, increasing the difficulty of investigation.In addition, groundwater pollution may not be limited to a small place below the contaminated sites, and some even Involving a larger area near the plant, such a large amount of water is also very difficult to repair, the cost is also high. "Wong Kam Lau said.
In order to find out the situation of groundwater pollution at the venue, Ding Aizhong believes that in the first phase of the site investigation, in order to clarify the status of the water pollution, a network layout should be adopted to ensure scientific and objective assessment results. "The reality is that owners often demand short repair periods and low costs, so that fewer sample points are set up by the assessor at the site, and even the distribution according to the subjective needs of the owners affects the objectivity of the report."
At present, groundwater pollution can be roughly divided into two categories: remote treatment and in situ repair. Beijing Normal University Lecturer Cheng Lirong introduction, remote treatment is to remove contaminated groundwater away for processing. In situ remediation involves the treatment of groundwater bodies in physically contaminated areas such as physical isolation or biochemistry. Physical isolation is through the construction of walls to seal the contaminated water to prevent its further proliferation. Biochemical treatments include the injection of gas, microorganisms, chemicals, etc. into the ground to rehabilitate the body of water.
"Although there are many treatment technologies, there is currently no technology that can completely restore contaminated groundwater to its pre-contaminant status from domestic and international practices. In addition, the groundwater repair process takes a long time and can take decades, or even hundreds, of years This brings the high cost one can imagine a foreign case, run for 10 years is also difficult to achieve the default repair goals, had to lower expectations. "Cheng Lirong said.
"What is the effect of implementing groundwater pollution remediation?" Is the question that Ding Aizhong was most asked about at work. He said that as it is impossible to see directly, how to scientifically evaluate the effect of groundwater pollution repair is really a big problem. Abroad, there are ways to set up monitoring wells to assess the effect of groundwater pollution remediation based on concentration or pollutant reduction, which has not yet been adopted in domestic site restoration works. "We need to explore economically viable assessment methods, and a better assessment of the effectiveness of the groundwater pollution will help promote the work."
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