Scientists search for plant KESIN to repair heavy metal pollution in soil

Due to the development of industrial and mining enterprises and sewage irrigation, heavy metal pollution in China and even in the world is becoming more and more serious Phytoremediation technology is one of the most effective methods for heavy metal pollution control, and the key to the success of this technology is to find super enriched plants Recently, under the guidance of Xia Hanping, a tutor, Zhang Xingfeng, a doctoral student in the research group of soil ecology and ecological engineering of South China Botanical Garden, Chinese Academy of Sciences, proposed for the first time to use the soil seed bank heavy metal concentration gradient method to screen heavy metal super enrichment plants, and successfully found a cadmium super enrichment plant, Solanum nigrum How do you find the little flower anemone? How to use new methods to search for super enriched plants? What should we pay attention to in the practical application of phytoremediation? With these questions, the author interviewed Xia Hanping, a researcher of South China Botanical Garden, Chinese Academy of Sciences Soil diseases: the polluted cultivated land area in China is 20 million hectares, including lead pollution in Fengxiang, Shaanxi, cadmium poisoning in Liuyang, Hunan and arsenic pollution in Linyi, Shandong Heavy metal pollution in the soil has a strong sting on people's nerves How much land in the country has been polluted by heavy metals, or is it facing a polluted cliff? With the continuous deterioration of environmental quality caused by mining and some industrial production, soil heavy metal pollution has become the focus of attention around the world Since 2009, there have been more than 30 heavy metal pollution incidents in China According to reports, China's polluted arable land covers 20 million hectares, accounting for about 1 / 5 of the total arable land area, of which heavy metal pollution accounts for about 30% - 40% of the polluted area China's annual grain output is up to 10 million tons due to soil pollution, with a direct economic loss of more than 10 billion yuan Heavy metals generally refer to metals with a specific gravity greater than 5 In terms of environmental pollution, heavy metals generally refer to metals with significant biological toxicity such as mercury, cadmium, lead, chromium and metalloid arsenic In the past decade, the heavy metal content in the Pearl River Delta has been increasing year by year, which has caused serious pollution problems In China, the pollution caused by heavy metals such as lead, zinc and cadmium is more serious When asked about the main source of heavy metal pollution in the soil, researcher Xia Hanping explained: "mining, metal smelting, electroplating, chemical industry, battery and other industries are the main industrial sources of heavy metal emission The" three industrial wastes "secretly discharged by some factories and enterprises make the concentration of lead, zinc and cadmium in the surrounding soil and water seriously exceed the standard; in addition, urban transportation The emission of automobile exhaust will also affect the content of heavy metals in the soil " Four questions: what's good about phytoremediation? Because of the characteristics of soil heavy metal pollution, such as wide range, long duration, concealment and irreversibility, it is very difficult to control it Xia Hanping said: "at present, scientists in related fields at home and abroad are studying the remediation technology of heavy metal contaminated soil In the process of treatment, physical method is time-consuming and chemical method is easy to cause secondary pollution Compared with the traditional treatment methods, phytoremediation technology has the advantages of permanent treatment effect, in-situ treatment process, low cost of treatment, compatibility of environmental aesthetics and so on, so it has become a research hotspot of heavy metal pollution treatment " "Phytoremediation technology is to plant plants with great extraction potential for heavy metals on the land polluted by heavy metals, and harvest the above ground parts of plants after a period of time to achieve the purpose of removing heavy metal pollution in the soil In addition, there are also some plants that can solidify the heavy metals in the soil, which can also play a role in reducing the toxicity of heavy metals " Referring to the principle of phytoremediation technology, Xia Hanping said: "phytoremediation technology can be divided into different parts according to the mechanism and process of phytoremediation, among which the contents related to phytoremediation of heavy metal contaminated soil mainly include plant extraction, plant fixation, plant volatilization and root filtration, etc." Are there some deficiencies in phytoremediation? Researcher Xia Hanping smiled and said, "of course, there are too few perfect things in the world In addition, the phytoremediation of soil can only be limited to the extension of plant roots In addition, the phytoremediation of heavy metals has certain selectivity to heavy metals, generally only one heavy metal can be enriched, and the heavy metal pollution of soil is mostly multiple pollution of several heavy metals Often associated with organic pollution and so on However, these problems are likely to be solved in further research " What is the key to phytoremediation? The researchers pointed out that the key to the success of phytoremediation technology is to find super enriched plants Therefore, screening plants with high tolerance to heavy metals and the ability of enrichment and super enrichment has become one of the important remediation methods for heavy metal contaminated soil "Hyperconcentrated plants refer to plants that can accumulate some chemical elements in excess Generally speaking, the amount of absorption of the chemical element by the aboveground tissue of these plants can be more than 100 times of that of ordinary plants, and it does not affect normal life activities " Xia Hanping, a researcher, explained, "however, a considerable part of the 400 kinds of heavy metal super enrichment plants found in the world have low biomass or strong specificity, and are difficult to reproduce, so it is difficult to really promote and apply them in a large area Therefore, the selection of high biomass, strong adaptability, strong enrichment ability, easy to cultivate super enrichment plants or relatively large absorption plant species is the focus of current and future research " How did Solanum nigrum, the "plant killer" of heavy metal cadmium, find out? Solanum nigrum is a cadmium enriched plant discovered by Zhang Xingfeng, a doctoral student in South China Botanical Garden of Chinese Academy of Sciences, under the guidance of Xia Hanping, a researcher Talking about her beloved apprentice, Xia Hanping said with a smile: "Zhang Xingfeng himself said that this research discovery was accidental When she collected soil in South China Botanical Garden for a heavy metal remediation study of herbage, she had an unexpected idea Maybe she could use the soil seed bank to screen the plants with heavy metal super enrichment characteristics, and then carry out the super enrichment characteristics through the heavy metal concentration gradient experiment Verification At that time, she was very excited to tell me this idea, and I thought this method was feasible, so next, we started a series of experiments " In the view of Xia Hanping, the method of soil seed bank heavy metal concentration gradient is superior to the previous methods "It is understood that at present, there are two main ways to search for super enriched plants at home and abroad One is field investigation, that is, to do field investigation in places polluted by heavy metals, such as in mining and industrial pollution areas; the other is special plant method, that is, to select some special plants according to some characteristics of plants to determine their heavy metal enrichment characteristics 。 However, there is an obvious disadvantage of both methods, that is, the plant species are relatively limited This makes people ignore some potential plants in the research In contrast, the soil seed bank is the Reserve Bank of plant reproductive body, which is very rich in plant species Using it to screen super enrichment plants can overcome the shortcomings of the above two methods, because the soil seed bank is almost everywhere, just collecting soil with rich seed resources for testing, and the experiment is simpler and easier to operate " What do you need to do to repair the soil? At present, many phytoremediation technologies are still in the stage of laboratory simulation research, from laboratory to practical application, there is still a long way to go Xia Hanping said: "because Solanum nigrum can withstand high cadmium pollution and accumulate a large amount of cadmium, and its provenance is relatively easy to obtain, reproduction and cultivation are relatively easy, and its biomass is relatively large, it is more suitable for repairing high cadmium pollution areas, such as industrial and mining enterprise parks and surrounding areas However, it is not suitable for large-scale promotion and application at present, because the scientific research achievements to promotion and application generally need to go through the pilot test process Therefore, it also needs to be tested in the field If it is successful, it can be proved that the plant can be used to solve the current cadmium contaminated soil remediation