Satellite Grid System Zeros In on Rogue Polluters
By Zhou Tailai, Chen Xinyue and Teng Jing Xuan
The Ministry of Environmental Protection’s Bureau of Environmental Supervision created more than 36,000 9-square-kilometer squares in the 28 cities in the Beijing-Tianjin-Hebei area. Using satellite remote sensing technology, the ministry identified over 3,600 hot spots that have high concentrations of PM2.5 pollution. Photo: Ministry of Environmental Protection’s Bureau of Environmental Supervision.
Every winter, Beijing, Tianjin and Hebei province battle choking pollution from vehicles, factories and household heating.
Local governments in the area, known as “Jing-Jin-Ji,” have long known that small, hard-to-spot polluters like workshops and illegal boilers contribute significantly to
poor air quality. Environmental inspectors are hoping to change that through a new satellite grid system, which can locate those small polluters with greater precision.
The grid system was first used the previous winter, from Dec. 30 to Jan. 7, when heavy pollution caused 60 cities in the region and its surrounding provinces to activate pollution alerts. Half of the cities activated the red alert — the highest warning level.
During this period, the national Ministry for Environmental Protection sent inspection teams to
Jing-Jin-Ji as well as neighboring provinces Henan and Shanxi. Every evening, each team would receive the coordinates of the day’s five most-polluted hot spots in their coverage area. Each hot spot had an area of 100 square kilometers (38.6 square miles), and appeared as a red rectangle on a mobile map app. Inspectors would focus on the highlighted hot spots for the next day’s inspections.
Liu Xiangmei, who led one of the teams sent to the city of Xintai in Hebei province, described a typical grid-assisted inspection: “After confirming the coordinates of the area we needed to inspect, we could see from the map image that a particular hot spot covered industrial parks.” In this hot spot, Liu’s team found a small coal yard in a glass factory where coal was improperly stored. Every time a vehicle passed the coal yard, it would cause a large dust cloud to rise up. After the coal yard was discovered, the local environmental agency was able to penalize its owners and demand a cleanup.
Three weeks into the new year, a new wave of
heavy pollution engulfed the Jing-Jin-Ji area. This time, the Ministry for Environmental Protection further refined the grid system. It divided the area’s 26 prefecture-level cities, as well as the provincial-level municipalities of Beijing and Tianjin, into a total of 36,000 squares, each covering 9 square kilometers.
In April, the ministry announced the largest-ever, national-level environmental protection operation in Jing-Jin-Ji, deploying 5,600 environmental law enforcement officers to inspect the air quality in the 28 cities over the course of a year. The satellite grid system will play a central role in this operation.
Blind spots
Pollution hot spots identified by the satellite grid system usually fall into one of three categories, Lei Ming, one of the inspectors sent to Jing-Jin-Ji, told Caixin. Some hot spots are in areas where large-scale, heavily-polluting industry — like steel factories, thermal power plants and coal mines — is located. Other hot spots are in city centers, where pollution comes primarily from car exhaust and central heating systems. The last category of hot spots includes areas with a high concentration of small-scale, pollutant-emitting businesses, and from delivery vehicles.
For many years, the small, scattered polluters were a blind spot in the Ministry for Environmental Protection’s data collection system, Chinese Academy of Engineering member He Kebin wrote in a recent essay.
These small polluters, usually factories or workshops, are often very well-hidden. “When we went to Shanxi province, we realized that some of these small polluters were hidden inside fruit orchards. There would be a small clearing inside the orchard, the site of a small oil refinery. From the outside, it looked like just trees, and you could enter only down a small winding path,” a ministry official told Caixin.
Before the satellite grid system was implemented, the ministry’s standard inspection methods were limited. Drones can travel for only short distances and are expensive to operate. Air-quality monitoring stations are good for measuring the overall air quality in a city, but aren’t precise enough for pinpointing specific rogue businesses, since even the best-equipped cities are home to only a few dozen such stations. Teams of inspectors can “carpet” an entire city and spot its biggest pollution offenders, but often miss harder-to-spot but more-numerous small polluters.
“So we considered trying out satellites, to see what the effect was. We later realized it was viable, and added the hot spot grid system to our methods,” the ministry official said.
Satellites’ benefits are twofold, the official added. They cover large areas and they are relatively immune to human interference, which doesn’t always involve deliberately falsified data, but can also be caused by inexperienced maintenance staff, he said.
The grid system relies primarily on satellite remote sensing technology, which measures the sunlight reflected by the earth. Light is scattered and absorbed by pollutants in the air, so the difference in brightness between the light reaching the Earth and the light reflected back into space can be used to calculate pollutant concentration.
Human input
Once the satellite-generated figures are received by the Ministry of Environmental Protection, its environmental supervision bureau uses big data analysis and artificial intelligence to identify hot spots. But human experts haven’t been taken out of the equation.
“Looking from above, if a grid square’s pollutant concentration is very high, does it necessarily mean it contains pollutant-emitting factories? There are lots of other explanations that affect the pollutant concentration,” including the topology of the area, a ministry official told Caixin. Ultimately, an experienced environmental supervision official needs to step in to interpret the data.
“When you get a satellite image, if you rely entirely on machine identification, the process starts from zero, with no knowledge of what factors may be affecting the results. But if an environment specialist looks at the image, they can use their experience to judge that pollution from a particular direction may have been a cause,” the official said.
So far, the ministry has identified more than 3,600 hot spots from 36,000 squares on the grid. These hot spots make up approximately 10% of these cities’ land area but contribute to nearly 80% of the pollution they experience, the official said.
This year, local governments in Jing-Jin-Ji’s 28 cities will spend a year strengthening supervision of these 3,600 squares, lowering their concentration of the cancer-causing PM2.5 particulates. At the end of the year, the Environmental Supervision Bureau will grade 2017’s situation, find the year’s 3,600 worst offending squares to set as targets for next year, gradually lowering the entire region’s PM2.5 concentrations over the course of the next few years, the official added.
Cangzhou City
The Ministry for Environmental Protection’s satellite grid system isn’t just intended to simply provide inspectors with a new method for spotting polluters, but also to act as the basis of a new environmental regulation system. In February, the ministry began a pilot of this new regulation system in Cangzhou, Hebei.
Cangzhou has a population of around 740,000, distributed across 14,000 square kilometers, and is one hour away from Beijing by high-speed train. As of mid-July, Cangzhou had 6,000 small-business polluters, including plastic waste processors, and small foundries. In 2016, Cangzhou’s average concentration of PM2.5 air pollutants was 69 micrograms/cubic meter. It hopes to bring this year’s average down to 62.
Under the pilot program, the Cangzhou government matches hot spots with enforcement staff who are responsible for reducing pollution in their assigned areas. The ministry has identified 126 hot spots in Cangzhou, scattered across the city’s 19 districts.
This isn’t the first time supervision of pollution in Cangzhou is being staffed according to a grid layout. In 2014, China’s State Council issued a notice requiring municipal and county governments to split their jurisdictions according to a grid system, and assign three tiers of supervisors to each square.
But at the time, most cities’ implementation of this supervision system was superficial. Environmental grid regulation of a major difficulty is to fully roll out no focus. "A county environmental protection bureau may have up to 20 enforcement staff, but each county has an area of over 1,000 square kilometers,” meaning there was no way staff could thoroughly carry out inspections, a ministry official told Caixin.
But the satellite grid system marks a breakthrough for grid-based supervision. Hot spots of 3 kilometers by 3 kilometers are far easier to police, a Cangzhou city official said.
“This coming winter will be the real test of the new system’s effectiveness,” Wu Rongsheng, a senior official at Cangzhou’s environment protection agency, told Caixin.
Satellite Grid System Zeros In on Rogue Polluters - Caixin Global
