Applied to the glass slides of Vaseline, it stuck to the dust and pollen invisible to the naked eye. Gong Ayuan/Photo
Author | Gong Ayuan
Edit | Qin Zhenzi
As it floated past a transparent slide in the city, the pollen was stuck.
It was supposed to go with the wind or be picked up by insects, creating the next chance to blossom and bear fruit. Along the way, inadvertently, pollen will invade people's nostrils, eyes or throats, making people prone to allergies feel uncomfortable ebbing and tears, falling into a painful spring.
This time, the pollen was deliberately intercepted by humans. Some of the pollen came in from 20 kilometers away and ended up glued to a slide 24 mm wide and 50 mm long.
Beautiful ammunition depot
In recent springs, every 24 hours, at 9 a.m., staff at Beijing Tongren Hospital, affiliated to Capital Medical University, have replaced the pollen collector erected in the garden on the top floor of the outpatient building with new slides. The pollen collector is a bit old, with only two pieces of metal on a two-meter-high shelf that protects the slide in the middle.
In order to allow more pollen to stop on the slide, the pollen collector is usually located in a place of 15-25 meters high without any obstruction around. It's best to avoid the park as much as possible in this place, so as not to collect data that is too special, and then just wait for the wind to bring the pollen.
Recently, the most that stopped on the slides was pollen from pine plants. Their oval bodies, with their characteristic small airbag "wings", drift with the wind from far away. The April days in Beijing end in the air with pine pollen.
Old slides that have been replaced for a day of "standing guard" will be sent to the reader. Soon, they will be dyed pink, and under the chemical action, the pink particles are easily distinguished from the impurities, and the pollen surrounded by two walls gradually appears under the microscope. Single grains of pollen are not visible to the naked eye, and their diameter generally does not exceed 40 microns.
After the pollen is magnified to tens of thousands of times, each grain will be three-dimensional. Even if it is all "balls", the spring pollen of the Xylariaceae family is a hollowed-out three-lobed circle with a clear mesh pattern on the surface and grooves; the pollen of the Asteraceae family is covered with spikes; and the amaranth pollen of the Amaranth family is recessed granular on the surface. "It's like a work of art." A pharmacist who makes dyes can't help but sigh when he first sees the pollen ornament under an electron microscope.
In order to monitor pollen, Ye Caihua, deputy director of the Beijing Meteorological Service Center, began to be busy early in the morning. As soon as she arrived during working hours, her computer received data from pollen monitoring points placed at weather stations in 12 different districts of Beijing.
Ye Caihua skillfully used the new data collected to edit the WeChat public account and mini program push of this day. Other staff will enter the pollen concentration collected from the previous day into the set forecast model together with the average of the same period in history, and calculate the pollen concentration forecast for the new day. Experts from the Beijing Academy of Landscape Architecture will also classify the pollen collected the day before to find out the most active molecules in the near future.
Before 12 noon, a pollen monitoring forecast will be freshly baked as a war report recording the previous day's pollen attack and the next enemy situation forecast.
Pollen collector in the garden on the top floor of the outpatient building of Beijing Tongren Hospital affiliated to Capital Medical University. Gong Ayuan/Photo
More and more people with allergies
This year, information about pollen in Beijing came after the last heavy snow melted. Although the sharp cooling of the early spring delayed the confrontation between man and plant for a week, it did not affect the subsequent attack of the pollen army.
In March, in a slide from Beijing's Shijingshan District, readers counted out more than 5,000 pollen particles. Among them, the pollen concentration of Cyprinidae is more than 4 times that of other plants of the family, more than 2000 grains.
As one of the trees in Beijing, the cypress is the most planted tree in the city, with about 7 million trees. Zhongshan Park, Temple of Heaven Park and Xiangshan Park, which are good places to go, add up to nearly 5,000 cypress trees, many of which are ancient trees rooted for more than 300 years.
When March arrives, the staff of the Temple of Heaven have to use spray trucks to "compress" them with clean water to control the dispersion of pollen as much as possible. Under the trouble of more than 10,000 cypress trees, the students of Tsinghua University specially produced a "Campus Cypress Distribution Map". Allergic rhinitis sufferers joke on social networks that "I want to be a noseless 'Voldemort' (the villain of the novel "Harry Potter" - reporter's note)".
Within a month, nearly 23,000 people poured into the newly established "Pollen Health Treasure" backstage, a pollen monitoring and forecasting platform jointly released by the Beijing Meteorological Bureau and Beijing Tongren Hospital in March 2021. From January to March, it "sucks powder" on the Internet and also "sucks powder" in the air.
March came, elm plants were the first to arrive on the battlefield, and within two weeks, the willow family also joined the war, with the most remarkable white "smoke".
However, in the eyes of experts from the Beijing Municipal Bureau of Landscaping, a large number of poplar trees planted in the 1960s and 1970s are a "green skyline" that can grow to 30 meters high, and there is no tree in the north that is taller and has a better shading effect. Without poplar trees, this "skyline" would have descended 5-10 meters. The willow tree, which sprouts the earliest and the last to fall leaves, can single-handedly extend the "greenery" of Beijing by one month.
Under the conditions at that time, the willow trees solved the problem of wind and sand, which can be regarded as "the hero of saving Beijing's natural environment". In order to make the "hero" more popular, in addition to the daily high-pressure water gun washing, pruning and other measures, the landscaping department has long stopped planting new female plants of the willow family, and gradually replaced them with more abundant plant varieties.
The number of people susceptible to pollen allergies is still increasing year by year. According to the 2013 study data, the prevalence of allergic rhinitis in 11 central cities in the mainland was 8%-16%, of which the prevalence rate in Urumqi exceeded 20%. In 2020, the multi-center epidemiological study in mainland China found that pollen allergens are the most important allergens in the north, with a population of up to 75 million.
Ouyang Yuhui, chief physician of the Department of Rhinal Allergy of Beijing Tongren Hospital affiliated to Capital Medical University, found in the outpatient clinic and data that the allergic population is getting younger and younger, and the incidence of children is increasing. She believes that environmental pollution has caused more people's mucous membranes to be damaged; the average temperature of the atmosphere has increased, and the amount of pollen released by plants has also increased; and people living modern lives have become nervous, tired and more prone to allergies.
On March 28, according to background data, more than 10,000 people read the pollen monitoring forecast for the day of the "Pollen Health Treasure", and some even read it several times. The tweet that day recorded that on March 27, 3,830 grains of pollen in Beijing's average of 1,000 square millimeters were scattered freely, far exceeding the maximum concentration standard of 800 grains.
Ten years ago, more than fifty plant samples provided by botanists are still stored in the research institute of Tongren Hospital. Gong Ayuan/Photo
The pollen that makes you allergic comes from the tree
As early as before the emergence of WeChat public accounts and mini program services, the Zhang Luo team and the meteorological department of Tongren Hospital began to monitor pollen for 10 years from 2011, starting in early spring and ending in late October.
In that year, Ouyang Yuhui, the main member of the team, summarized the data of patients treated for nearly 5 years and found that the onset time of hay fever patients was closely related to the concentration of pollen in the atmosphere, and established 13 pollen monitoring centers in Beijing. The doctor wanted to broadcast the same as the weather forecast, predict the pollen concentration, and provide defense and travel guidance for hay fever patients.
In order to obtain pollen concentration data in more areas of Beijing, Ouyang Yuhui sought the help of the Beijing Meteorological Bureau to install slides that intercept pollen on meteorological monitoring stations in various regions of Beijing and place them on improved pollen collectors. In the face of strong winds, it can stand more firmly, and most importantly protect the slide from raindrops, which wash away large amounts of pollen, which often occurs in the early stages of monitoring.
The method of calculating the total pollen concentration is not difficult, but the process is cumbersome, and for many years it relied on manual readings – to count clearly on slides, one by one.
Ouyang Yuhui's team once introduced a Japanese pollen counting device, the design of the machine is based on the identification of pollen particle size, as long as it is between 20-40 micron particles, will be automatically considered to be pollen, the result is often several times higher than the manual counting results of the comparison group, not accurate enough.
At first, Ouyang Yuhui, with the help of experts from the Institute of Botany, collected more than 50 kinds of plants from the sidewalk trees on the side of the road and the wet fields that few people go to. Botanical experts numbered them one by one, packed them into envelopes, wrote down their names and subjects, and formed the earliest database of pollen monitoring.
Prior to this, the Beijing Meteorological Bureau began pollen monitoring in 1998, and only monitored concentrations. In an era when there was no network channel to broadcast pollen concentrations, they inserted the weather forecast three times a day through the FM94.5 Beijing Radio and Television News Broadcasting Center to remind everyone of the arrival of the peak pollen season.
After the total number of pollen particles is used to update the daily pollen concentration, Tongren Hospital will collect slides from 25 monitoring centers established in different cities across the country since 2019 every ten days and half a month and start reading secondary reading. This time, they invited more specialized botanists to broadcast the varieties of pollen particles and make pollen concentration predictions for the second year, depending on weather conditions.
According to the classification data of Tongren Hospital and the Capital Landscaping Bureau, the Beijing Meteorological Bureau will also track the arrival, peak and disappearance of several types of pollen with high concentrations for a long time in addition to updating the pollen concentration on a daily basis. By subdividing the subjects of pollen, people who are prone to allergies can better resist "invasion" according to allergens.
In fact, even if an allergy-prone person walks into a room full of flowers, it does not necessarily produce an allergic reaction. Brightly blooming flowers often spread pollen through insects and do not cause allergies. What is more likely to make people allergic are spring trees and autumn grasses. The pollen they carry is light, and as soon as the wind blows, it begins to drift freely.
In addition to playing games with humans, the relationship between pollen and nature is more subtle. Pollen researchers have found that the amount of pollen increases during long days; when there is more rain, they naturally decrease. On thunderstorms, pollen can break through the usual flying height, be carried into the clouds, and under the action of the electric field, be decomposed into spore fragments. When they fall again, it aggravates people's allergic reactions to pollen. Also capable of enhancing sensitization are pollutants in the atmosphere. The harder the wind, the more "crazy" the pollen.
Right now, the second round of willow flying feathers is floating wildly in Beijing, accompanied by pollen from pine plants. Fortunately, in a month's time, the peak pollen period this spring will temporarily end with the end of the pine pollen period. By then, except for those who had a runny nose and sneezed every spring, no one would realize that the city had just experienced a "war."
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Produced by China Youth Daily and China Youth Network