Team:JACOXH China/Description
Description
Environmental concern
Mercury pollution is a typical type of heavy metal pollution in soil, which will cause serious adverse effects on ecosystem and human health. Mercury ion ingestion in the body can cause neurological diseases and damage to the bones, endocrine and immune systems. As a result of mining, exhaust emissions, sewage irrigation and the use of heavy metal products exceeding standards, many of China's arable land has been contaminated by heavy metal mercury. Mercury is unique in its nature and is more stable in the soil than other organic or inorganic pollutants, resulting in a cumulative chronic harm and a threat to human health and safety through soil crops.
Figure 1 Mercury emissions by sector
Survey data shows that the heavy metal pollution area of farmland soil in China has exceeded 10 million hm2, accounting for about 10% of the total cultivated land area. By comparing with the natural background value of soil nearly 30 years ago and calculating the accumulation index of heavy metals in cultivated land in various regions, it was found that many provinces covering China, such as Hunan, Guangxi, Yunnan and Guizhou, had the problem of high mercury content. Globally, mercury pollution has also been found in arable land around many mercury-zinc mines in South Korea, India and elsewhere.
Figure 2 Global Mercury emissions
Therefore, it is urgent to deal with the problem of mercury pollution in cultivated land. But with our firm faith, mercury pollution, a major environmental problem, will be improved to make the world a better place
Former Research of mercury pollution treatment.
At present, there are two main treatment methods for mercury pollution: microbial adsorption and plant enrichment. The application of microbial adsorption in soil environment is very limited: it is difficult to ensure the survival rate of microorganisms in the soil, also, the mechanism of adsorption indicates that microorganisms adsorbed heavy metals must be recovered and treated, which is a great challenge in the soil environment. Third, the contact between microorganisms and heavy metals in the soil environment is very limited, which causes the inefficiency. However, by using our new method, these problems will be solved.
Fixing mechanism selection.
Microbial remediation and phytoremediation alone cannot solve the problem of mercury pollution in cultivated land due to the limitation of mechanism and application conditions. Therefore, fixing the mineralization of mercury ion is an option worth trying. The hydrogen sulfide () is a kind of extremely stable insoluble substance, which also exists in the nature. Mercury ion mineralization has passed the US EPA standard certification, and the effective state of mercury ion cannot be extracted by TCLP leaching, which makes the mercury ion no longer pose a threat to the environment.
The advantages of earthworms
In order to address the limitations of traditional microbial treatments, we use earthworms a common ecological engineer in the soil to help us to spread the gene-engineered strain.
Figure 3 The Earthworms
1.The host with perfect mobility
Earthworm lives originally in soil and has strong mobility in soil. However, we cannot effectively address the soil pollution if we only use engineering bacteria, because the scope of action of engineering bacteria is limited. Therefore, by making earthworms carry engineering bacteria, engineering bacteria can move along with earthworms. Through earthworms, we provide a good carrier for the engineered bacteria to spread throughout the soil
2. An excellent host for engineered bacteria——The earthworm gut
The intestinal mucus of earthworm is rich in soluble organic carbon, with high humidity, low stable pH, which is generally considered as the most suitable habitat for microorganisms. Soil microorganisms enter the intestines of earthworms with the soil. The abundant available organic carbon, appropriate temperature and pH in the intestinal tract of earthworms can provide good living conditions for microorganisms, promote their growth
The general idea
For real-time monitoring and repair of heavy metal mercury pollution of soil, we designed a "walking" soil mercury pollution detection and governance: biological systems with mercury ion induction, mercury ion monitor color and mercury ions fixed prosthesis function of engineering bacteria in the soil, once found in the soil mercury ions can color expression and should be fixed to the stability of low toxicity HgS, and the engineering bacterium with soil by earthworms intake, will propagate in earthworm body, and follow the earthworm "walk" emissions, so the mobile of soil mercury pollution real-time monitoring and control.
Reference
[1]: ‘A review of the distribution of mercury pollution at home and abroad’ Hu Yuehong
[2]: ‘Mechanism and application of earthworm in bioremediation of organic contaminated soil’ Pan Zheng
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