The "14th Five-Year Plan" period is a critical period for improving the quality of the ecological environment from quantitative change to qualitative change. Faced with the need to achieve green and low-carbon development and the goal of carbon peak and carbon neutrality , it is particularly important to carry out greenhouse gas emission monitoring work in my country. The "14th Five-Year Plan for Ecological Environment Monitoring" released by the Ministry of Ecology and Environment clearly states that it is necessary to make up for the shortcomings in carbon monitoring technology, build a greenhouse gas monitoring technology system and a quality control system, and at the same time promote carbon monitoring and evaluation pilot projects and carry out other compliance monitoring such as substances that consume ozone layer. This clarifies the future development priorities of my country's greenhouse gas emission monitoring work.
The experience gained in greenhouse gas emission monitoring in California, the United States can provide reference for the development of relevant work in my country.
takes regional scale, obtain emission data from multiple sites and multiple means
California Air Resources Commission (CARB) is a government agency responsible for air quality management and climate change in the California region of the United States. It launched a greenhouse gas monitoring network in 2010 to study and evaluate the greenhouse gas emission trends in the California region and help establish a more accurate regional greenhouse gas emission inventory. In addition to monitoring greenhouse gases, the monitoring network also monitors the artificial combustion emission source indicator carbon monoxide , and includes meteorological parameters such as wind speed, wind direction and temperature into the monitoring indicators.
Image source: canva
Greenhouse gas monitoring network analyzes the location of known greenhouse gas emission source, regional wind rail analysis, existing greenhouse gas emission monitoring location and other information , sets monitoring points, and functionally partitions the monitoring points according to different monitoring functions.
Its independent monitoring points are mainly distributed in the central valley and the southern coastal areas: the Tuscan Buttes Monitoring Points (TSB) and Sutter Buttes Monitoring Points (STB) are located in the northern part of the central valley, and the Madera Monitoring Points (MAD), Tranquility Monitoring Points (TRA) and Arvin Monitoring Points (ARV) are located in the southern part of the central valley for methane emission monitoring.
Among them, the MAD, TRA, and ARV monitoring points are used to measure methane released by mixed emission sources in the central valley. The Mt. Wilson Monitoring Point (MWO) is located in the San Gabriel Mountain area and is used to observe and evaluate urban gas pollutants spreading from the southeast and west-southwest. The San Bernardino monitoring point (SBC) is located above the tower. can cover a larger area and collect air samples from different heights to analyze the vertical distribution of monitoring gases.
CARB Greenhouse Gas Monitoring Network Distribution
CARB Greenhouse Gas Monitoring Station Basic Information
In addition to ground monitoring and tower monitoring devices, the greenhouse gas monitoring network also uses high-altitude monitoring methods such as satellite , small aircraft to more comprehensively understand the source of greenhouse gas emissions. For example, in the monitoring of methane emissions, the greenhouse gas monitoring network uses small aircraft telemetry to extract methane point sources at different altitudes and shares data with other scientific research institutions to better understand the data gap between the calculation and the emission list.
serves the construction of emission inventory, helping to achieve regional emission reduction targets
After obtaining monitoring data, CARB uses atmospheric inversion method to combine the greenhouse gas concentration measured on site or remote sensing and simulated meteorological conditions to obtain an independent greenhouse gas emission inventory and evaluate greenhouse gas emissions from bottom up. The specific operation is as follows:
Step 1, using the Lagrangian particle diffusion model (LPDM) to obtain the particle trajectory, and then using the atmospheric transport model and particle trajectory to calculate the atmospheric emission footprint of the site. Emission footprints characterize the sensitivity of the concentration of a site to changes in unit emission flux per grid cell and can be used to represent the amount of changes in the concentration of a site as local surface emissions change by one unit.
The second step is to multiply the emissions estimated by the historical greenhouse gas emission list with the emission footprint, and to obtain the growth of the greenhouse gas concentration emitted by the upwind emission source, and after adding the upwind background concentration, a simulated greenhouse gas emission concentration is obtained.
The third step is to compare the simulated greenhouse gas emission concentration data with the monitoring data, and then use statistical techniques (such as Bayesian model) to optimize the greenhouse gas flux to make the simulated atmospheric greenhouse gas concentration better match the observed values, and finally obtain the emission source emission data.
reverse modeling system framework diagram
emission traceability technical analysis methods can help to understand regional emissions more accurately and comprehensively. CARB conducted source analysis on the concentrations of 21 compounds (including carbon monoxide, carbon dioxide , methane, alkane , olefin , benzene, ethylbenzene and xylene ) in the air samples collected from 2014 to 2016 at the MWO monitoring point. The analysis determined that the main sources of methane emissions include landfills, petroleum gas , industrial processes, fossil fuel combustion, petroleum refining, natural gas and biological sources.
Source: pexels
tracer -Tracturing analysis is another technical analysis method used by CARB. The premise of using this analysis method is that the atmospheric air mass in the monitoring area is well mixed. CARB found that the ratio of methane and carbon monoxide collected at the MWO monitoring point was consistent, and it was inferred that methane and carbon monoxide were fully mixed before reaching the monitoring site, and the emission source contribution of the two substances was relatively constant.
Therefore, CARB uses tracer-trace analysis to calculate greenhouse gas emissions in the Los Angeles Basin . Since methane and carbon monoxide do not react chemically on the time scale of diffusion in urban Los Angeles, and their emission source distribution is similar and affected by atmospheric transport and dilution at similar scales, CARB uses the linear regression model to derive the statistical relationship between methane and carbon monoxide concentrations in the environment, and then calculates methane emissions in the Los Angeles Basin based on known carbon monoxide emissions.
CARB shares methane data obtained by the monitoring network with regulators or law enforcement departments , expanding the scope of data usage to other areas, supporting a larger scope of emission reduction work, and putting forward policy suggestions to help regulatory departments achieve emission management goals.
In addition, CARB also cooperates with government departments and oil and gas production enterprises to carry out telemetry of methane emissions at infrastructure project points, quickly locking out leakage emissions, and helping relevant parties take timely measures.
This article is compiled based on the speeches of Jorn Dinh Herner, director of the Research Planning, Administration and Emission Reduction Department of the California Air Resources Commission, at the 2022 Hangzhou Bay Coordinated Control Symposium on Air Pollution and Greenhouse Gases and related materials provided by the institutions. The original text is published in China Environment APP, click below to read the original text.
Edit: Asian Clean Air Center Li Hongchao
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