Soil contaminated by pesticides and microorganisms to "counter"

■ Jiang Jiandong

Microbial remediation has the most potential

Data show that the amount of chemical pesticides used in China currently exceeds 1.

According to the testing data from the Nanjing Institute of Soil Science, Chinese Academy of Sciences and environmental monitoring stations across the country, there are about 16 million hectares of agricultural land contaminated by pesticides in the country, which accounts for more than 10% of China's arable land

It can be seen that the problem of pesticide residues in the ecological environment of farmland in China is already very serious

Microbial remediation technology is recognized as the most potential remediation technology, which plays an important role in solving the problem of non-point source pollution of pesticides and improving the quality and safety of agricultural products

Due to its wide variety and rich metabolism, microorganisms can completely decompose pollutants into carbon dioxide, water, inorganic compounds and other substances that are harmless to the environment and the human body

Two decryption technologies

Microbial remediation of pesticide-contaminated soil mainly uses two technologies, one is bioremediation technology, and the other is biological incentive technology

Bioremediation technology includes two technologies: bioenhancement of adding foreign bacteria and bio-incentive using original bacteria on site

Because the biological incentive technology uses the original strains of the contaminated site, there is no pollution problem caused by the addition of foreign microorganisms, and it has been applied in engineering in the United States, Japan and other countries

Bioaugmentation is achieved by adding a large number of high-efficiency degradation strains and forming a dominant flora within a certain period of time, so as to achieve the effect of rapid pollution repair, and is widely used all over the world

At present, the main research focus on the microbial remediation of pesticide-contaminated soil is also focused on two aspects of bio-enhancement and biological incentives.

The remediation effect of microorganisms on pesticide pollution depends on the degradation ability of strains, as well as the bioavailability of pollutants and the competitiveness between bacteria and indigenous microorganisms

The bioremediation factors of pesticide pollution also include the characteristics of pesticide pollutants, the ecological structure of microorganisms in the environment, and various environmental factors

In addition, factors such as the distribution characteristics and initial concentration of pesticide pollutants in the soil and other environments are also the main factors affecting their biodegradability

Supplementing electron donors and acceptors in the bioremediation process can also improve the repair effect, such as soil cultivation, direct oxygenation or injecting hydrogen peroxide to release free oxygen as electron acceptors for microbial oxidation in the soil

Establishment of strain germplasm resource bank

The prerequisite for bioremediation is strain resources that can efficiently degrade pollutants.

The types of pesticides that can be degraded by pesticide-degrading strains in the germplasm bank established by Nanjing Agricultural University basically cover the common pesticide varieties on the market in China

From thousands of samples collected by Nanjing Agricultural University from all over the country, they are enriched and domesticated through conventional triangular flask acclimation, activated sludge method, soil recirculation method, etc.
, and also adopts improved gradient dilution inoculation, resistance pressure, and simulated ecology.
Through methods such as separation and screening, more than 500 microbial strains that efficiently degrade chemical pesticides have been obtained, a complete germplasm resource bank of pesticide-degrading bacteria has been established, and a system of strain preservation, activation, inspection, and rejuvenation processes have been formed
.

These strains can efficiently degrade various organophosphorus, organic nitrogen, organochlorine pesticides, fungicides and herbicides in the farmland habitat environment in China.
A total of 62 degrading strains and their fermentation processes have obtained national invention patents, and they have published chemical pesticide degradation There were 27 new species of functional bacteria, accounting for 63% of the same type of new species in the same period
.