Heavy metals are metals or metallic elements with low toxicity to animals and humans. However, they tend to accumulate in living things, such as plants and animals, so their ingestion can eventually pose a serious threat to human health. In addition, heavy metal-contaminated soils adversely affect the growth and development of plants and microorganisms, resulting in decreased crop productivity.

Among all kinds of heavy metals, lead has become a critical soil pollutant. Although Pb is not an essential element, crops can absorb it and inhibit plant growth. Much of the lead in soil may come from fertilizer and automobile exhaust. In addition, anthropogenic activities play an important role in the accumulation of lead pollution in the air, soil, and water. Higher Pb uptake affects crop quality, growth, and yield.

According to statistics, the area of heavy metal pollution in China's arable land has exceeded 1/5 (nearly 20 million hectares). Every year, about 10 million tons of grain is reduced due to heavy metal pollution in soil, and another 12 million tons of grain pollutants exceed the standard.

In recent years, the widespread use of plastic film caused the white pollution of soil, and added Cd, Pb containing heat stabilizer in the production process of plastic film, which increased the soil heavy metal pollution.

1. Heavy metals cannot be degraded by microorganisms and are long-term and potential pollutants of the environment;

2. Due to the adsorption of soil colloid and particulate matter, it has existed in the soil for a long time, and its concentration is vertically decreasing.

3. It interacts with chloride ions, sulfate ions, hydrogen and oxygen ions, and corrosives in the soil to generate complex or chelate, resulting in greater solubility and migration activity of heavy metals in the soil.

Heavy metal pollution seriously affects the quality of vegetables, and through the food chain, it also becomes a potential hazard source to biodiversity and human health.

Many measures alleviate heavy metal pollution, but most are not applicable in the practical application process.

The antagonism between elements can also inhibit plants' absorption of heavy metals

Selenium, for example, significantly reduces the accumulation of cadmium and lead. However, the application area of this mitigation method is not open, and the dosage must be careful.

Physical relief

For example, soil leaching, electric repair, electric repair, etc., not only require certain use of technology but also may bring other problems in the repair process.

Bio-organic fertilizer remediation

Heavy metal contamination can be remediated by adding bio-organic fertilizer/microbial fertilizer/microbial agent/organic material.

Remediation of microorganisms

Soil microorganisms are active colloids in soil. They have a large surface area, electric charge, and vigorous metabolic activity.

Remediation of organic matter

Organic compounds have many functional groups, which can be complexed with heavy metal ions and reduce the absorption of heavy metals by plants. On the one hand, organic compounds can enhance the tolerance of plants to heavy metals by regulating the physiological indexes of crops. On the other hand, organic matter can inhibit the transport of heavy metals from root to shoot and reduce the accumulation of heavy metals in a vegetable shoot.

We are committed to applying synthetic biology to the problem of heavy-metal (HM) pollution in soil. By the means of synthetic biology, our team has engineered genes into plants that can absorb residual metals in the soil. Heavy metals in soil are a serious hazard and a worldwide problem. As a result, we think that biotechnology will help to ameliorate the situation. The results of our research can benefit people in many different fields, such as helping farmers improve crop quality and yield, reducing the risk of disease among people who live in areas with contaminated soil for a long time, and helping companies develop new products to overcome the difficulties caused by the pandemic, while also contributing to global sustainable development. Thus, we combine synthetic biology with today's critical problems, hoping to find solutions for a better future.

Our team chose to work on this specific project because heavy-metal pollution is a growing environmental problem around the world. We specially studied and investigated environmental protection. Lead (Pb2+) is one of the most toxic heavy-metal contaminants has harmed agroforestry production, and also the health of humanity. In China, there are 20 million hectares of land which had suffered from heavy-metal pollution. It can lead to climate change and a series of severe consequences. Grain pollution is estimated to reach as high as 12 million tons per year, indicating that plants are robbed of nutrients, moreover, the toxicity would endanger the human race. The heavy-metals pollution has threatened the quality of human life profoundly. For the reasons mentioned above, we expect to accomplish effective absorption of lead (Pb2+) ions in deep soil using synthetic biology and try our best to improve the situation that's been going around on Earth right now.

Polaris Environmental Restoration Network，2019-02-14， https://zhuanlan.zhihu.com/p/225083060

Zhihu, Tianyun Network, 2020-9-7https://huanbao.bjx.com.cn/news/20190214/962648.shtml