Observations of black/brown carbon concentrations in the Amazon using the Aethalometer and SP2

 

Authors

Arthur J Sedlacek — Brookhaven National Laboratory
Paulo Castillo — Brookhaven National Laboratory

Category

Absorbing Aerosol

Description

As part of the Green Ocean Amazon (GOAmazon) field campaign, the ARM Mobile Aerosol Observing System (MAOS) was deployed outside the city of Manacapuru (Brazil). This site, also referred to as the T3 site within the GOAmazon program, commenced operation in late January 2014 and will continue its 24/7 acquisition of until December 2015. This site was chosen because its location downwind of Manaus provides an ideal opportunity to investigate how anthropogenic and biogenic emissions interact. Additionally, Brazil is characterized by a distinct wet and dry season and therefore offers the prospect of studying the impact of seasonality on these interactions. Two climatologically important aerosols that are found in this region are black carbon (BC) and brown carbon (BrC). Sources of BC include Manaus, several brick kilns that are located downwind of Manaus but upwind of the T3 site, and biomass burning events. The primary brown carbon source is biomass burning. In an effort to better characterize and quantify these aerosols, a Single Particle Soot Photometer (SP2) and a 7 wavelength Aethalometer were deployed as part of the MAOS instrument suite. The SP2 provides an incandescence-based measurement of the refractory Black Carbon (rBC) mass concentration as well data on the rBC size distribution and enables analysis of the rBC-containing particle mixing state. The 7-Aethalometer (λ = 370 nm, 430 nm, 470 nm, 520 nm, 565 nm, 700 nm, and 880 nm) is a filter-based measurement that exploits the wavelength dependence of BrC to collect information about this aerosol type. In this poster, data from the Aethalometer and SP2 are analyzed to glean insights into the daily, weekly, and seasonal behavior of BC and BrC. Preliminary analysis results show that the wet season is characterized by clean atmospheric conditions where the average rBC mass concentration loading is 150 ng/m3. During the course of the sampling period, the black carbon dataset is punctuated with episodic and sporadic events. Episodic events, defined here as those events lasting > 4 hours, exhibiting an enhanced absorption at short wavelengths, and primarily found during the dry season are attributed to local biomass burning. In contrast, sporadic events, which are defined by very short lifetime, very large black carbon concentrations, and characterized by an absorption Angstrom exponent ~1, are likely due to the T3 site generator.