Publications·March 09, 2022
In March 2022, the Hainan Academy of Environmental Sciences and the Institute of Atmospheric Physics at the Chinese Academy of Sciences jointly released this research report about how the island province that has already enjoyed highest-level air quality in China can further reduce its air pollution in the next five years. The report was written with the support of Energy Foundation China.
After an analysis of Hainan’s current air quality status and the remaining problems after the 13th Five-Year Plan period of 2016–2020, the report compiles and updates the province’s emission inventories, investigates its air pollution sources, adopts a WRF-CMAQ model, conducts a scenario analysis, and proposes feasible air quality improvement targets and pollutant mitigation strategies for the 14th Five-Year Plan period of 2021–2025. The authors hope the report can provide science-based evidence, as Hainan adopts its provincial five-year plan for environmental protection and action plan for air quality improvement. They also hope it can help lay a foundation for the achievement of the province’s goal of world-class environmental quality by 2035.
This executive summary from the Hainan Academy of Environmental Sciences and the Institute of Atmospheric Physics (CAS) assesses Hainan’s current air quality, quantifies sources, and builds WRF–CMAQ scenarios to test how different control packages would lower PM₂.₅/PM₁₀/NO₂/SO₂/CO while keeping rising ozone (O₃) in check during the 14th Five-Year Plan. It also evaluates uncertainties (meteorology, external transport) and ties the findings to the province’s Free Trade Port build-out. Bottom line: Hainan already meets China’s Class II standards with wide margin, but must push further on PM₂.₅ and pivot hard to O₃/precursor control to protect the island’s clean-air advantage.
Where air quality stands (levels, trends, seasons)
2020 annual means were SO₂ 5 μg/m³, NO₂ 7 μg/m³, PM₁₀ 25 μg/m³, PM₂.₅ 13 μg/m³; CO (95th) was 0.8 mg/m³ and O₃ (90th) was 105 μg/m³—all comfortably below national Class II limits (SO₂ 60, NO₂ 40, PM₁₀ 70, PM₂.₅ 35, CO 4 mg/m³, O₃-8h (P90) 160 μg/m³). Year-on-year from 2019→2020: PM₂.₅ −18.8%, PM₁₀ −10.7%, NO₂ −12.5%, O₃ −11%, SO₂/CO essentially flat. Over the longer arc, PM₁₀ and NO₂ have fallen steadily since 2013, while PM₂.₅ and CO have decreased since 2015.
Seasonality. In the island’s two key cities (Haikou, Sanya), PM₂.₅/PM₁₀ peak in winter (heavier background and weaker dispersion), while O₃ peaks in spring–summer (roughly April–September); NO₂/SO₂ show milder seasonal swings. These patterns are consistent with maritime meteorology (sea breezes, monsoon flow), shallow mixing layers in winter, and photochemistry in the warm season.
Spatial gradients. Maps for 2020 show relatively uniform PM₂.₅ at low levels island-wide, with O₃ showing stronger spatial contrast that coincides with urbanized corridors and prevailing wind/photochemical regimes.
What’s emitting: sources at a glance
On-road vehicles contribute materially to NOₓ and primary PM; the report disaggregates emissions by emission standard stage, highlighting that older standards contribute disproportionately to NOₓ/PM even as their fleet share declines.
Industrial point sources remain modest compared with mainland heavy-industry provinces but are important locally where present; upgrades in combustion/process control curb SO₂/NOₓ/PM.
Dust (扬尘)—construction, roads, stockpiles—dominates coarse PM contributions in urban areas; managing surfaces and logistics is critical for PM₁₀.
Residential/“life” sources matter mainly via VOCs (solvents, coatings, consumer products, small catering combustion), which interact with NOₓ to drive O₃.
How the team tested policies (models & scenarios)
The analysis uses WRF–CMAQ with MEIC emissions (0.1°) to simulate a 2019 baseline and three forward-looking control suites: Conventional, Enhanced, and Super-Enhanced. Each suite tightens combustion/process controls, vehicle and non-road controls, dust management, and VOCs measures with increasing ambition. (WRF v3.9.1; multiple sensitivity runs isolate component effects.)
Results (province-wide averages):
Conventional: PM₂.₅ −9.5% (≈ −1.5 μg/m³), PM₁₀ −7.1%, NO₂/SO₂ −11%, O₃ −3%.
Enhanced: PM₂.₅ −22.9% (≈ −3.7 μg/m³), PM₁₀ −17.3%, NO₂/SO₂ −28%, O₃ −9.5%.
Super-Enhanced: PM₂.₅ −34.3% (≈ −5.5 μg/m³), PM₁₀ −25.4%, NO₂/SO₂ −40%, O₃ −14%.
These response magnitudes are large relative to a very clean baseline, implying that ozone-focused controls (VOCs + NOₓ) can deliver additional PM₂.₅ benefits (secondary aerosol) even in a low-PM province.
Uncertainty matters: meteorology & external transport
Two big caveats temper any year-to-year comparison:
Meteorology. Weather conditions during 2020–2021 contributed materially to concentration changes across pollutants; a simplified attribution suggests ±1 μg/m³ swings in PM₂.₅ from meteorology alone at annual scale—non-negligible at Hainan’s low concentrations.
Regional transport. Despite island geography, inflow can raise background PM and O₃; the report documents upstream provinces/cities (e.g., Shanghai, Guangdong, Fujian, Hunan) having lowered PM₂.₅ by ~22–33% from 2017→2021, which helps Hainan’s attainment prospects when meteorology favours inflow.
Targets & attainability
Given 2020 PM₂.₅ = 13 μg/m³, the study evaluates the feasibility of reaching an ≈11 μg/m³ level under stronger measures by 2025, drawing on the scenario reductions and expected upstream improvements. On O₃, the report frames an 8-hour P90 target ≈120 μg/m³ and stresses a spring–summer (April–August) campaign on NOₓ + VOCs, coordinated with episode forecasting and sector-specific interventions.
Policy playbook for the 14th FYP (what to do, practically)
1) Lock in low PM with structural controls that also help ozone.
Continue deepening clean combustion/process controls in power/industry (where present), and keep automobile and non-road mobile standards/in-use compliance tight. These reduce NOₓ/SO₂/primary PM and curb secondary PM formation—preserving Hainan’s low PM₂.₅ while supporting O₃ management.
2) Make VOCs a first-class citizen.
Elevate VOCs alongside NOₓ: establish sector-specific substitution and low-solvent product lists, strengthen fugitive controls (LDAR) in petrochemical/solvent-use clusters, and integrate retail & small-business sources into routine inspections. This is pivotal for O₃ in coastal urban belts.
3) Keep dust down with logistics discipline.
Given the PM₁₀ contribution from dust, require enclosures/paving, wheel-wash, route cleaning, and real-time yard sensors in construction/port logistics to suppress resuspension.
4) Tune vehicle policy to real-world emissions.
Pair new-vehicle standards with in-use tools—remote sensing, OBD analytics, roadside tests—to find high emitters quickly; target legacy pre-China-6 gasoline/diesel vehicles for accelerated retirement; and tighten non-road controls at airports, ports, and construction sites.
5) Build ozone season operations.
Institutionalize a seasonal O₃ plan (April–August) with forecast-based responses, prioritizing NOₓ from mobile sources and VOCs from solvent-rich sectors; coordinate episode communications so the public and firms can act (work scheduling, coatings bans during heat waves, etc.).
6) Align the Free Trade Port with clean-air design.
In zones tied to the FT Port, adopt clean-site standards for logistics/warehousing, require shore-power for ships and electrified cargo handling, and apply low-VOC material requirements for new build-outs—so growth does not backslide on O₃/PM.
Why this matters now
Hainan is one of China’s cleanest provinces—but ozone is the emerging risk as PM recedes and the economy grows around the Free Trade Port. The modelling shows that PM₂.₅ can fall another ~2–6 μg/m³ under stronger packages and that O₃ can be bent downward by ~10–14% with NOₓ + VOCs controls—if operations are seasonal, data-driven, and backed by robust in-use compliance. Keeping focus on low-VOC products and fugitive control, mobile-source NOₓ, and dust management will protect Hainan’s competitive advantage in clean air and tourism/liveability.
Keywords
Hainan; PM₂.₅ attainment; ozone management; WRF–CMAQ scenarios; VOCs + NOₓ control; dust/PM₁₀; in-use vehicle compliance (remote sensing/OBD); Free Trade Port planning; meteorology & transport uncertainty; coastal urban corridors; seasonal ozone campaigns.