Volatilization and oxidative artifacts of PM bound PAHs collected at low volume sampling (1): Laboratory and field evaluation.

Laboratory and field studies were carried out to assess the effects of oxidative degradation and volatilization on PM10 bound polycyclic aromatic hydrocarbons (PAHs), collected at low volume condition according to the EU sampling reference method EN12341:2014 (flow rate 2.3 m3 h-1), on 47 mm quartz filters. For the laboratory experiments, pairs of twin samples were collected in field and, after treatments favoring decomposition or/and volatilization of PAHs on one sample, the PAH amount was compared with that of the corresponding untreated sample. Ozone exposure caused a general PAHs decay with more marked effects on benzo [a]pyrene, perylene and benz [a]anthracene; these compounds showed, similarly to benzo [ghi]perylene, correlations between ozone dose and losses. Treatments with zero air exhibited losses due to volatilization even for 5-ring PAHs up to benzo [a]pyrene, whereas a linear dependence was observed between filter PAH load and losses for benzo [a]anthracene, chrysene and benzofluoranthenes. Concentrations on samples collected simultaneously over 48, 24, 12 and 6 h were compared. Results confirmed a lack of temporal auto-consistency in the PAHs sampling methodology here adopted. In particular higher atmospheric PAH concentrations were ascertained on samples constituted by cumulative filters exposed over shorter sampling times. When 24-h and 2 × 12-h samples were compared, comparable losses were evaluated in the hot and cold seasons. This finding shows that, although in summer meteorology conditions favor sampling artifacts, the effectiveness of these phenomena continue in the winter, probably due to the larger amount of PAH available on the sampling filter (total PAHs ∼ 10 vs 0.5 ng m-3).

Volatilization and oxidative artifacts of PM bound PAHs at low volume sampling (2): Evaluation and comparison of mitigation strategies effects.

The artifacts induced by oxidative degradation and volatilization were assessed with regards to determination of particulate atmospheric PAHs collected at low volume conditions (2.3 m3 h-1) according to the EU Reference Method EN 12341:2014. In order to evaluate the oxidative degradation, PAH measures carried out through collecting airborne particulate with and without ozone denuders were examined. Simultaneously, the influence of volatilization was investigated by comparing concentrations of PAHs in particulate samples collected over 24-h and 12-h using conventional instruments. Summer and winter/spring campaigns were carried out in order to assess the influence of environmental contour on the artifact processes. Oxidative degradation led to a general decrease of PAH concentrations in both periods; in particular, the highest losses were observed for benzo[a]pyrene and perylene reaching, in average, ca. 20%. In the summer, the effect of volatilization exceeded that of oxidative degradation for light PAHs up to benzo[e]pyrene. In the winter/spring time, the influence of both artifact typologies could be mitigated by splitting the normal 24-h collection interval starting at midnight into two 12-h intervals. A mitigation of the losses could even be obtained by fixing the start time sampling fixed at noon or in the first hours of the day. Finally, the feasibility of collecting PAHs through prolonged sampling (>1 month) at the flow rate of 1.1 L min-1 was preliminarily investigated. Results indicated that this approach is unsuitable for minimizing the oxidative artifacts.

Emission of submicron aerosol particles in cement kilns: Total concentration and size distribution.

Cement plants are responsible for particle and gaseous emissions into the atmosphere. With respect to particle emission, the greater part of is in the range from 0.05 to 5.0 µm in diameter. In the last years attention was paid to submicron particles, but there is a lack of available data on the emission from stationary sources. In this paper, concentration and size distribution of particles emitted from four cement kilns, in relationship to operational conditions (especially the use of alternative fuel to coal) of the clinker process are reported. Experimental campaigns were carried out by measuring particles concentration and size distribution at the stack of four cement plants through condensation particle counter (CPC) and scanning mobility particle sizer spectrometer (SMPS). Average total particle number concentrations were between 2000 and 4000 particles/cm³, about 8-10 times lower that those found in the corresponding surrounding areas. As for size distribution, for all the investigated plants it is stable with a unimodal distribution (120-150 nm), independent from the fuel used.