PM_(2.5)characterization of primary and secondary organic aerosols in two urban-industrial areas in the East Mediterranean

Primary and secondary organic aerosols in PM_(2.5)were investigated over a one-year campaign at Zouk Mikael and Fiaa,Lebanon.The n-alkanes concentrations were quite similar at both sites(26-29 ng/m^(3))and mainly explained by anthropogenic emissions rather than natural ones.The concentrations of total Polycyclic Aromatic Hydrocarbons(PAHs)were nearly three times higher at Zouk Mikael(2.56 ng/m^(3))compared to Fiaa(0.95 ng/m^(3)),especially for indeno[1,2,3-c,d]pyrene linked to the presence of the power plant.A characteristic indeno[1,2,3-c,d]pyrene/(indeno[1,2,3-c,d]pyrene+benzo[g,h,i]perylene)ratio in the range0.8-1.0 was determined for heavy fuel oil combustion from the power plant.Fatty acids and hopanes were also investigated and were assigned to cooking activities and vehicular emissions respectively.Phthalates were identified for the first time in Lebanon with high concentrations at Zouk and Fiaa(106.88 and 97.68 ng/m^(3) respectively).Moreover,the biogenic secondary aerosols revealed higher concentrations in summer.The total terpene concentration varied between 131 ng/m^(3) at Zouk Mikael in winter to 469 ng/m3 at Fiaa in summer.Additionnally,the concentrations of the dicarboxylic acids especially for adipic and phthalic acids were more influenced by anthropogenic sources.The analysis of molecular markers and diagnostic ratios indicated that the sites were strongly affected by anthropogenic sources such as waste open burning,diesel private generators,cooking activities,road transport,power plant,and industrial emissions.Moreover,results showed different pattern during winter and summer seasons.Whereas,higher concentrations of biogenic markers were clearly encountered during the summer period.

Comprehensive chemical characterization of PM_(2.5) in the large East Mediterranean-Middle East city of Beirut,Lebanon

The chemical composition of PM_(2.5) at two sites in Lebanon,a country in the East Mediterranean-Middle East region,is investigated in the spring and summer seasons.The average PM_(2.5) concentrations were of(29±16)μg/m 3 for Beirut urban site and(32±14)μg/m 3 for Beirut suburban site.This study showed that the geographic location of the East Mediterranean region,such as its proximity to the Mediterranean Sea and the dust storm intrusion are a significant contributor to the high PM levels from natural sources,which cannot be mitigated,rendering the PM_(2.5) WHO annual Air Quality guideline unattainable due to high natural background,which also applies to the entire Middle East region.Turkey and Eastern Europe are the dominant origin of air masses throughout our sampling days,suggesting the long-range transport as an important potential contributor to the high observed concentrations of V,Ni,and sulfate in this region most probably in other East Mediterranean countries than Lebanon too.Main local sources determined through the chemical speciation including organics are road transport,resuspension of dust and diesel private generators.A health risk assessment of airborne metals was performed and the carcinogenic risk for all the metals exceeded by 42(adults)and 14(children)times the acceptable risk level(10^(-6))at both sites.Vanadium was the predominant carcinogenic metal,emphasizing the need to replace energy production with cleaner energy on a regional level and highlighting the severe impact of air pollution on the health of inhabitants in this region’s main cities.

NitroMAC：An instrument for the measurement of HONO and intercomparison with a long-path absorption photometer

Nitro MAC（French acronym for continuous atmospheric measurements of nitrogenous compounds） is an instrument which has been developed for the semi-continuous measurement of atmospheric nitrous acid（HONO）. This instrument relies on wet chemical sampling and detection using high performance liquid chromatography（HPLC）-visible absorption at540 nm. Sampling proceeds by dissolution of gaseous HONO in a phosphate buffer solution followed by derivatization with sulfanilamide/N-（1-naphthyl）-ethylenediamine. The performance of this instrument was found to be as follows： a detection limit of around 3 ppt with measurement uncertainty of 10% over an analysis time of 10 min. Intercomparison was made between the instrument and a long-path absorption photometer（LOPAP） during two experiments in different environments. First, air was sampled in a smog chamber with concentrations up to 18 ppb of nitrous acid. Nitro MAC and LOPAP measurements showed very good agreement. Then, in a second experiment, ambient air with HONO concentrations below250 ppt was sampled. While Nitro MAC showed its capability of measuring HONO in moderate and highly polluted environments, the intercomparison results in ambient air highlighted that corrections must be made for minor interferences when low concentrations are measured.