Long-Term Fine Particulate Matter (PM<sub>2.5</sub>) Trends and Exposure Patterns in the San Joaquin Valley of California
Since 1989, California pollution control efforts have caused annual PM<sub>2.5</sub> averages to decrease. Despite the decline in ambient air concentrations of PM<sub>2.5</sub>, the San Joaquin Valley (SJV) of California continues to violate the federal standard for PM<sub...
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MDPI AG
2025-06-01
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| author | Ricardo Cisneros Donald Schweizer Marzieh Amiri Gilda Zarate-Gonzalez Hamed Gharibi |
| author_facet | Ricardo Cisneros Donald Schweizer Marzieh Amiri Gilda Zarate-Gonzalez Hamed Gharibi |
| author_sort | Ricardo Cisneros |
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| description | Since 1989, California pollution control efforts have caused annual PM<sub>2.5</sub> averages to decrease. Despite the decline in ambient air concentrations of PM<sub>2.5</sub>, the San Joaquin Valley (SJV) of California continues to violate the federal standard for PM<sub>2.5</sub>. This study evaluated PM<sub>2.5</sub> trends, diurnal and seasonal patterns, pollution sources, and air quality improvements from 2000 to 2022 in the SJV. Hourly and daily PM<sub>2.5</sub> data from CARB and EPA-certified monitors were analyzed using regression models, polar plots, and Air Quality Index (AQI) classification methods. Monthly PM<sub>2.5</sub> concentrations peaked in winter (November–January) and during commute periods, with higher levels observed on Fridays and Saturdays. In this study, the highest daily PM<sub>2.5</sub> levels observed in Fresno and Bakersfield occurred during the autumn, most likely due to agricultural activities and higher wind speeds, with daily values greater than 25 µgm<sup>−3</sup> and 50 µgm<sup>−3</sup>, respectively. In contrast, in Clovis, the highest daily PM<sub>2.5</sub> concentrations occurred in the winter during episodes characterized by low wind speeds, with values greater than 22 µgm<sup>−3</sup>. While PM<sub>2.5</sub> has declined since 1999, progress has slowed significantly since 2010. However, all sites exceeded the new EPA standard of 9 µgm<sup>−3</sup>. Without substantial changes to emission sources, meeting federal standards will be difficult. |
| format | Article |
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| institution | Kabale University |
| issn | 2073-4433 |
| language | English |
| publishDate | 2025-06-01 |
| publisher | MDPI AG |
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| series | Atmosphere |
| spelling | doaj-art-5655ba6b1ab04ff6b46f404632e668ea2025-08-20T03:26:49ZengMDPI AGAtmosphere2073-44332025-06-0116672110.3390/atmos16060721Long-Term Fine Particulate Matter (PM<sub>2.5</sub>) Trends and Exposure Patterns in the San Joaquin Valley of CaliforniaRicardo Cisneros0Donald Schweizer1Marzieh Amiri2Gilda Zarate-Gonzalez3Hamed Gharibi4Health Sciences Research Institute, University of California, Merced, CA 95343, USAHealth Sciences Research Institute, University of California, Merced, CA 95343, USAHealth Sciences Research Institute, University of California, Merced, CA 95343, USAHealth Sciences Research Institute, University of California, Merced, CA 95343, USAHealth Sciences Research Institute, University of California, Merced, CA 95343, USASince 1989, California pollution control efforts have caused annual PM<sub>2.5</sub> averages to decrease. Despite the decline in ambient air concentrations of PM<sub>2.5</sub>, the San Joaquin Valley (SJV) of California continues to violate the federal standard for PM<sub>2.5</sub>. This study evaluated PM<sub>2.5</sub> trends, diurnal and seasonal patterns, pollution sources, and air quality improvements from 2000 to 2022 in the SJV. Hourly and daily PM<sub>2.5</sub> data from CARB and EPA-certified monitors were analyzed using regression models, polar plots, and Air Quality Index (AQI) classification methods. Monthly PM<sub>2.5</sub> concentrations peaked in winter (November–January) and during commute periods, with higher levels observed on Fridays and Saturdays. In this study, the highest daily PM<sub>2.5</sub> levels observed in Fresno and Bakersfield occurred during the autumn, most likely due to agricultural activities and higher wind speeds, with daily values greater than 25 µgm<sup>−3</sup> and 50 µgm<sup>−3</sup>, respectively. In contrast, in Clovis, the highest daily PM<sub>2.5</sub> concentrations occurred in the winter during episodes characterized by low wind speeds, with values greater than 22 µgm<sup>−3</sup>. While PM<sub>2.5</sub> has declined since 1999, progress has slowed significantly since 2010. However, all sites exceeded the new EPA standard of 9 µgm<sup>−3</sup>. Without substantial changes to emission sources, meeting federal standards will be difficult.https://www.mdpi.com/2073-4433/16/6/721particulate matterair qualitySan Joaquin Valleytrendsdiurnal cyclepatterns |
| spellingShingle | Ricardo Cisneros Donald Schweizer Marzieh Amiri Gilda Zarate-Gonzalez Hamed Gharibi Long-Term Fine Particulate Matter (PM<sub>2.5</sub>) Trends and Exposure Patterns in the San Joaquin Valley of California Atmosphere particulate matter air quality San Joaquin Valley trends diurnal cycle patterns |
| title | Long-Term Fine Particulate Matter (PM<sub>2.5</sub>) Trends and Exposure Patterns in the San Joaquin Valley of California |
| title_full | Long-Term Fine Particulate Matter (PM<sub>2.5</sub>) Trends and Exposure Patterns in the San Joaquin Valley of California |
| title_fullStr | Long-Term Fine Particulate Matter (PM<sub>2.5</sub>) Trends and Exposure Patterns in the San Joaquin Valley of California |
| title_full_unstemmed | Long-Term Fine Particulate Matter (PM<sub>2.5</sub>) Trends and Exposure Patterns in the San Joaquin Valley of California |
| title_short | Long-Term Fine Particulate Matter (PM<sub>2.5</sub>) Trends and Exposure Patterns in the San Joaquin Valley of California |
| title_sort | long term fine particulate matter pm sub 2 5 sub trends and exposure patterns in the san joaquin valley of california |
| topic | particulate matter air quality San Joaquin Valley trends diurnal cycle patterns |
| url | https://www.mdpi.com/2073-4433/16/6/721 |
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