| 27 Jul 2026
Field-tested emission factors and temporal allocation factors for air pollutants emitted from industrial sources in China
Abstract. High accuracy and hourly-resolved emission inventories of air pollutants rely on timely updates of emission factors (EFs) and reliable temporal allocation factors, yet both remain poorly constrained for industrial point sources. In this study, we combined a dilution sampling system with online monitoring instruments to obtain 1-hour resolved mass concentrations of PM10, PM2.5, PM1, black carbon (BC), NOx, SO2, and CO emitted from five industrial sectors (cement, medicine manufacturing, glass production, textile, iron and steel) in China. Product- and fuel-based EFs were updated, as well as sector-specific hourly allocation factors optimized for air quality modeling. Their emission amounts were calculated using the revised product-based EFs and further compared with those for widely adopted Multi-resolution Emission Inventory for China (MEIC). Our measured EFs deviated from previously reported literature values by 1–4 orders of magnitude. BC EFs ranged from 3.2 × 10−6 to 4.7 × 10−2 g kg−1, which sharply contrasts with the default zero value recommended by official technical guidelines for most industrial categories. The measured BC/PM2.5 mass ratios were 0.0136 and 0.0104 for cement and iron and steel sectors, respectively, both lower than literature-reported ratios, implying substantial overestimation of industrial BC emissions in existing studies. Compared with the activity-adjusted 2024 MEIC inventory, PM2.5 emissions estimated using our field-measured EFs were 29.6 and 255 times lower for cement and iron and steel, respectively, reflecting the deployment of advanced air pollution control technologies and the urgent need to update outdated EFs for industrial sources. Additionally, MEIC allocated emissions across 7,720 iron and steel grid cells, which drastically overrepresents real factory distribution. Our study adopted geolocated Point-Of-Interest data to identify only 216 actual sites, partially explaining the overestimation for industrial emissions by MEIC.
Hourly temporal allocation factors exhibited two distinct pollutant-specific diurnal patterns: with three distinct peaks for PM10, PM2.5, and PM1 within a single day and a single peak for BC, SO2, NOx, and CO. For PM2.5, normalized hourly allocation factors ranged from 0.016 to 0.055 (averaged as 0.0417 ± 0.0074). Conventional uniform temporal allocation assumptions (e.g., fixed 1/24 hourly weight) fail to capture nighttime and short-duration emission spikes, especially for particles. This work provides ground-truthed EFs and hourly allocation profiles for subcategory industrial sources, which can improve the accuracy and reliability of high-temporal-resolution emission inventories, and support the validation of industrial hourly-contribution partitioning from receptor and air quality model simulations.
This manuscript presents field measurements of PM10, PM2.5, PM1, BC, NOx, SO2, and CO from five industrial sectors in China. Based on these measurements, the authors derive updated emission factors and hourly allocation factors and compare the resulting emission estimates with the activity-adjusted MEIC inventory. The dataset is potentially valuable for improving the temporal representation of industrial emissions and for supporting future emission inventory and air quality modeling studies.
The manuscript is generally clear and falls within the scope of Earth System Science Data. However, several points should be clarified before publication. I noticed some inconsistencies among the main text, figures, and Supporting Information, particularly in the reported pollutant concentrations and in the treatment of cement SO2 and CO. The construction of the temporal profiles also needs further explanation. Figure 4 presents sector-specific hourly allocation factors, whereas Table S3 provides only one composite profile for each pollutant, and it is not clear how these profiles were combined or weighted. In addition, the meaning of the reported mean ± values and the temporal resolution represented by the individual data points in Figure 2 should be stated more clearly. These issues mainly concern the clarity and consistency of the dataset rather than the overall approach.
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