Taking advantage of moss’s nutrient absorption mechanism from the air, Prof. Dr. Le Hong Khiem used moss to monitor air pollution quality.
Since 2017, the method of using moss indicator to measure the level of heavy metal pollution in Hanoi and Hai Phong has been implemented by Vietnamese scientists. With more than 1,000 moss samples collected in these two cities, Professor Khiem and his colleagues have drawn an accurate air pollution map from 2017-2019. The product is the result of the project “Research on heavy metal pollution in the air through the Barbula indica moss indicator” by Prof. Dr. Le Hong Khiem and colleagues at the Institute of Physics, Academy of Science and Technology. Vietnam does.
Professor Khiem said, on average, each person breathes 10,000 liters of air per day. Air pollution is the main cause of many diseases. According to WHO in Vietnam, in 2016 more than 60,000 people died from heart disease, stroke, lung cancer, chronic obstructive pulmonary disease… all caused by air pollution. “It’s time for managers and scientists to act more aggressively to clean the air for people’s health,” he said.
Currently, to measure the level of air pollution, Vietnam has built automatic monitoring stations. The disadvantages of this method are the high cost, annual operating budget, easy damage due to outdoor placement, pollution data is only used for the area near the station location, long-term use of the data will not exactly… However, the number of installed stations is not significant, many stations have been “dead”, many provinces do not have any measuring stations. Another way to measure air quality is to use handheld meters, but with low accuracy, only used in cases of environmental problems.
Prof. Dr. Le Hong Khiem struggled to find a way to apply it to all provinces and cities at a low cost. After years of research, he found the answer was to use the moss indicator.
Mosses are lower plants that do not have cuticles. The roots of moss are false roots, the nutrients for its growth are mainly absorbed from the air. Moss absorbs most of the heavy metals and other trace elements from the air and rainwater. The upper part of the moss is completely exposed to the air, so it has the ability to catch dust particles, like air filters. The properties of the moss coat make it easier for metal ions to penetrate the cells. Moss plants can grow normally even in highly polluted environments. When using moss as a biological indicator, it is possible to determine the time it takes to accumulate elements (usually only the moss with 3 years old for analysis).
In places where there is no natural moss growth, the team will use the method of hanging moss bags. This is a natural moss taken in high mountain areas (usually more than 1,000 meters) and ensures no heavy metal contamination. This moss will be sewn into bags and hung at the locations to be surveyed. After a certain period of time (1, 2 or 3 months), moss samples will be analyzed to determine the content of heavy metal elements in the air.
Professor Khiem said that using moss to monitor the air is very simple. To know the air quality of a specific point, just take a moss sample at that location (200 grams/sample), take it to the laboratory for analysis to determine the content of elements in the moss. In a radius of about 4 km there will have to be a sample. For example, in Hanoi, to measure air quality, you will have to take samples at about 50 locations, 3-4 samples each. This method allows to measure 43 chemical elements in the air such as arsenic, mercury, chromium, silicon, molybdenum…
To analyze the chemical element composition in moss, the team used nuclear analysis methods. This technology includes neutron activation analysis, proton beam X-ray emission analysis and total reflectance X-ray fluorescence analysis to determine the composition of moss. Then apply statistical methods to analyze data sets on the content of elements present in moss samples. Finally, a mathematical model is applied to determine the source of emission of elements into the air in the study area.
According to Prof. Khiem, in addition to Barbula Indica moss, other mosses can be used. However, studies on their ability to absorb chemicals are needed. From this research result, Prof Khiem’s group was involved in the UK-based international moss-based air pollution research project (The ICP Vegetation, https://icpvegetation.ceh.ac .uk/).
Prof. Dr. Le Hong Khiem said that one of the difficulties of using moss as an indicator for air pollution in Vietnam is that there are no in-depth studies on this field. Analytical equipment in Vietnam has not yet achieved the necessary sensitivity to accurately determine the content of heavy metal elements in moss. To analyze the air in moss, it is necessary to use tools and chemicals used to make samples, sample mills, ultra-clean sample rooms, drying cabinets, furnaces, sample compressors… specialized. “These experiments will be completed by the research team in the near future,” said Prof. Khiem.
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