ANALISIS PERAN SENYAWA NITROGEN OKSIDA (NOx) DAN FAKTOR METEOROLOGI TERHADAP FENOMENA NIGHTTIME OZONE ENHANCEMENT (NOE) (STUDI KASUS: DKI JAKARTA 2014–2025)

Abstract

Konsentrasi ozon (O3) permukaan umumnya mencapai maksimum pada siang hari dan menurun setelah matahari terbenam. Namun, peningkatan konsentrasi pada malam hari atau nocturnal ozone enhancement (NOE) secara konsisten teramati di DKI Jakarta. Penelitian ini menganalisis karakteristik spasiotemporal O3 dan NOx serta mengidentifikasi kejadian NOE dari lima SPKUA di DKI Jakarta selama tahun 2014–2025. Hasil menunjukkan tren rata-rata maksimum 8 jam (MDA8) O3 menurun di seluruh SPKUA, kecuali DKI5 Kebon Jeruk, sementara NOx lebih bervariasi secara spasial. NOE terjadi secara persisten di DKI Jakarta (142 kejadian/tahun) dengan tren meningkat di DKI5 Kebon Jeruk, serta dominan terjadi pada musim kemarau dan pancaroba. NOE ditandai oleh pelemahan titrasi NO, konsentrasi O3 sore hari yang lebih tinggi, serta peningkatan rasio NO2/NOx yang signifikan (p-value < 0,001). Kejadian NOE juga terjadi saat kondisi lebih panas dan kering dengan kecepatan angin yang lebih tinggi (kecuali di DKI1 Bundaran HI) dibandingkan kejadian non nocturnal ozone enhancement (NNOE). Hubungan antara O3 dan parameter meteorologi melemah secara signifikan pada kejadian NOE (p-value < 0,001), dengan hasil multiple linear regression yang juga menunjukkan penurunan kemampuan parameter meteorologi dalam menjelaskan variabilitas O3 pada kejadian NOE (R² = 0,033–0,130) dibandingkan kejadian NNOE (R2 = 0,067–0,296).

Surface ozone (O3) concentrations typically peak during the daytime and decrease after sunset; however, a nighttime increase known as nocturnal ozone enhancement (NOE) is consistently observed in DKI Jakarta. This study analyzes the spatiotemporal characteristics of O3 and NOx, and identifies NOE events using data from five AQMS in DKI Jakarta during 2014–2025. Results show that the maximum daily 8-hour average (MDA8) O3 concentration exhibits an overall decreasing trend, except at DKI5 Kebon Jeruk, while NOx varies spatially. NOE occurs persistently in DKI Jakarta (142 events/year), with an increasing frequency at DKI5 Kebon Jeruk and the highest occurrence during the dry and transition seasons. NOE events are characterized by a significant weakening of NO titration, higher afternoon O3 concentrations prior to events, and a higher NO2/NOx ratio. Furthermore, NOE events are associated with hotter, drier conditions and higher wind speeds (except at DKI1 Bundaran HI) compared to non nocturnal ozone enhancement (NNOE) events. Relationship between O3 and meteorological factors weakens significantly during NOE events (p-value < 0.001). Multiple linear regression confirms a reduced ability of meteorological variables to explain nighttime O3 variability during NOE (R2 = 0.033–0.130) compared to NNOE (R2 = 0.067–0.296).