Detection of a gas flaring signature in the AERONET optical properties of aerosols at a tropical station in West Africa

Abstract

The West African region, with its peculiar climate and atmospheric dynamics, is a prominent source of aerosols. Reliable and long‐term in situ measurements of aerosol properties are not readily available across the region. In this study, Version 2 Level 1.5 Aerosol Robotic Network (AERONET) data were used to study the absorption and size distribution properties of aerosols from dominant sources identified by trajectory analysis. The trajectory analysis was used to define four sources of aerosols over a 10 year period. Sorting the AERONET aerosol retrievals by these putative sources, the hypothesis that there exists an optically distinct gas flaring signal was tested. Dominance of each source cluster varies with season: desert‐dust (DD) and biomass burning (BB) aerosols are dominant in months prior to the West African Monsoon (WAM); urban (UB) and gas flaring (GF) aerosol are dominant during the WAM months. BB aerosol, with single scattering albedo (SSA) at 675 nm value of 0.86 ± 0.03 and GF aerosol with SSA (675 nm) value of 0.9 ± 0.07, is the most absorbing of the aerosol categories. The range of Absorption Angstrӧm Exponent (AAE) for DD, BB, UB and GF classes are 1.99 ± 0.35, 1.45 ± 0.26, 1.21 ± 0.38 and 0.98 ± 0.25, respectively, indicating different aerosol composition for each source. The AAE (440–870 nm) and Angstrӧm Exponent (AE) (440–870 nm) relationships further show the spread and overlap of the variation of these optical and microphysical properties, presumably due in part to similarity in the sources of aerosols and in part, due to mixing of air parcels from different sources en route to the measurement site.

Local air pollution from oil rig emissions observed during the airborne DACCIWA campaign

“…Among the techniques used to dispose of the gas associated with the crude oil extraction, one is the flaring, consisting of burning the gas in an open flame through a stack. This leads to a mixture of emitted gases which can reach the free troposphere if the meteorological conditions are favourable (Fawole et al, 2016b). The two targeted flights, on 10 and 14 July, consisted of about 3-4 h of meandering transects through emission plumes in the MBL about 300 m a.s.l.)…”

“…Third, the source temperature is deduced from the VIIRS measurements on a monthly mean. For the FPSO platform, it is set to 1600 K, which is a good order of magnitude, since the flame temperature can be as high as 2000 K (Fawole et al, 2016b). Fourth, for such a temperature, NO 2 is considered to be a primary pollutant coming from the rapid conversion of NO close to the source, and the inventory does not include any later transformation of the species.…”

“…Its impacts concern both the ecosystems (Nwaugo et al, 2006;Nwankwo and Ogagarue, 2011) and the air quality (Osuji and Avwiri, 2005). The pollutants can be transported into the free troposphere (Fawole et al, 2016b) or can reach coastal cities in the marine boundary layer (MBL). Flaring emissions can be derived from remote-sensing techniques (Elvidge et al, 2013) by the widely used Visible Infrared Imaging Radiometer Suite (VIIRS) Nightfire satellite product (Deetz and Vogel, 2017).…”

Dispersion of gas flaring emissions in the Niger delta: Impact of prevailing meteorological conditions and flare characteristics

“…According to 2009 estimates, the region's 75,000 km 2 landmass is occupied by about 31 million people (Young, 2013). (Fawole et al, 2016b). From the inception of oil exploration over four decades ago, gas flaring activities in the study area has been a persistent daily activity in the several flow stations and rigs.…”

Simulation of Black Carbon Emissions from Gas Flaring Activities in the Niger Delta Region, Nigeria

“…Nigeria also has a huge potential for gas, but due to lack of processing and storage infrastructure, a lot of these gas are flared and the gas flaring effects on the environment, ecosystem, socioeconomic and health of the residents of the flare area is multifaceted [3,4]. Among the deleterious effects of gas flaring activities is the release of carbonaceous substances such as black or elemental carbon (BC or EC), These sooty substances also called Black carbon [5,6,7], has been underestimated in emission inventories and models, as a result of which models are struggling to predict measurements of BC in regions of intense gas flaring [8]. BC is not the only substance emitted from incomplete combustion, and the climate impacts depend on the full range of co-pollutants emitted from a particular source.…”