Anthropogenic VOCs in Abidjan, southern West Africa : From source quantification to atmospheric impacts

Several field campaigns were conducted in the framework of the Dynamics-Aerosol-Chemistry-Cloud Interactions in West Africa (DACCIWA) project to measure a broad range of atmospheric constituents. Here we present the analysis of an unprecedented and comprehensive dataset integrating up to 56 volatile organic compounds (VOCs) from ambient sites and emission sources. VOCs were collected on multi-sorbent tubes in the coastal city of Abidjan, Côte d'Ivoire, in winter and summer 2016 and later analysed by gas chromatography coupled with flame ionization and mass spectrometer detectors (GC-FID and GC-MS) at the laboratory. The comparison between VOC emission source profiles and ambient profiles suggests the substantial impact of two-stroke motorized two-wheel vehicles and domestic fires on the composition of Abidjan's atmosphere. However, despite high VOC concentrations near-source, moderate ambient levels were observed (by factors of 10 to 4000 lower), similar to the concentrations observed in northern mid-latitude urban areas. Besides photochemistry, the reported high wind speeds seem to be an essential factor that regulates air pollution levels in Abidjan. Emission ratios (ΔVOC/CO) were established based on real-world measurements achieved for a selected number of representative combustion sources. Maximum measured molar mass emissions were observed from two-wheel vehicles, surpassing other regional sources by 2 orders of magnitude. Local practices like waste burning also make a significant contribution to VOC emissions, higher than those from light-duty vehicles by 1.5 to 8 orders of magnitude. These sources also largely govern the VOC's atmospheric impacts in terms of OH reactivity, secondary organic aerosol formation (SOAP), and photochemical ozone creation potential (POCP). While the contribution of aromatics dominates the atmospheric impact, our measurements reveal the systematic presence of anthropogenic terpenoids in all residential combustion sectors. Finally, emission factors were used to retrieve and quantify VOC emissions from the main anthropogenic source sectors at the national level. Our detailed estimation of VOC emissions suggests that the road transport sector is the dominant source in Côte d'Ivoire, emitting around 1200Gg yr-1 of gas-phase VOCs. These new estimates are 100 and 160 times larger than global inventory estimations from MACCity or EDGAR (v4.3.2), respectively. Additionally, the residential sector is largely underestimated in the global emission inventories, by factors of 13 to 43. Considering only Côte d'Ivoire, these new estimates for VOCs are 3 to 6 times higher than the whole of Europe. Given the significant underestimation of VOC emissions from the transport and residential sectors in Côte d'Ivoire, there is an urgent need to build more realistic and region-specific emission inventories for the entire West African region. This might be true not only for VOCs, but also for all atmospheric pollutants. The lack of waste burning, wood fuel burning and charcoal burning, and fabrication representation in regional inventories also needs to be addressed, particularly in low-income areas where these types of activities are ubiquitous sources of VOC emissions

Policy findings from the DACCIWA Project

Report on the policy-relevant. findings of the DACCIWA projec

Key lessons from the DACCIWA project for operational meteorological services

This document describes the conclusions of the EU-funded project Dynamics- Aerosol-Chemistry-Cloud Interactions in West Africa (DACCIWA) directly relevant to operational meteorological services. DACCIWA produced the most comprehensive observational dataset of the atmosphere over densely populated southern West Africa to date and used this dataset to foster our understanding of atmospheric processes, and to evaluate dynamical models and satellite data. With this document DACCIWA aims to help improve atmospheric predictions across time-scales, which are important for the development of greater resilience of the West African population to hazardous weather and climate change

Réduire la pollution de l’air à Abidjan. De l’ambition scientifique à la fabrique du terrain : la science en train de se faire.

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Development of a Micro-hotplate for different Metal Oxide Gas Sensors with High Operating Temperatures

International audienceThe main goal of this work is to realize a metal oxide gas sensor with stable operating temperature. This article describes our approach and the technological process used to reach a high and stable operating temperature (650-700°C), with low consumption (100mW) and good thermal homogeneity all over the active area

High performances of new microhotplate for gas sensors

International audienceThe main goal of this work is to improve significantly performances of microhotplate for gas sensors. This article describes technological optimizations (materials and design) used to reach high and stable operating temperature, in reducing intrinsic drift problems (linked to standard polySilicon heater). Our heating platforms present low buckling effect, low consumption and good thermal homogeneity all over the active area

CONTROLLED ZnO DEPOSITS FOR GAS SENSORS

International audienceZinc oxide (ZnO) is widely used for its capability to detect gases. There are several known methods to synthetize and deposit ZnO for gas sensor applications. We have developed a new process based on ZnO nanoparticles from Sigma Aldrich manufacturer deposited by an inkjet technique. The process achieved is based on stable ZnO nanoparticles ink obtained by mixing 10% weight of commercial powder with diethylene glycol (DEG). This ink has been deposited on Pamela Yoboué et al. 56 a microhotplate that can operate up to 550°C with a low power of consumption (less than 60mW). The gas tests presented in this article show good results concerning the sensor response and its stability in the presence of gases

Particulate pollution in Korhogo and Abidjan (Cote d'Ivoire) during the dry season

International audienceParticulate pollution in West African cities seriously impacts public human health. Assessing the levels of pollution to which populations are exposed is problematic, as to date very few countries in Africa have an air quality monitoring network in place. However, given the specific anthropogenic sources present in West African countries and the increase in their projected emissions in the coming years if no regulations are put in place, solutions must be found. This study evaluates with a simple existing methodology particulate air pollution in two West African cities (Korhogo and Abidjan in Cote d'Ivoire) which have different population practices and local meteorology. From two measurement campaigns at about ten sites during the dry season and using the inverse distance-weighted interpolation method, maps of spatial variation in PM10 and PM2.5 concentrations are obtained at the scale of each of these cities, which provide a snapshot of the concentration levels to which populations are actually exposed. The results of this study showed that populations in low-and middle-income areas are exposed to higher concentrations than those in high-income areas. The analysis of the relative contribution of fine particles to coarse particles shows that PM2.5 contributes to PM10 at less than 40% in Korhogo but more than 50% in Abidjan. Daily average concentrations of PM2.5 are all above WHO standards, and are 2 to 8 times higher in Korhogo, while in Abidjan they are up to 4 times higher. The daily profiles of the mean hourly concentrations of the sites are similar across all sites in Korhogo, while in Abidjan, that of some sites show some differences. This study, by the methodology used, offers an opportunity for different research teams to assess at lower cost the population's exposure levels to urban particulate pollution