A combined chemical/size fractionation approach to study winter/summer variations, ageing and source strength of atmospheric particles.

We studied the size distribution of ions (Cl-, NO3-, SO4=, Na+, NH4+, K+, Mg++, Ca++) and elements (As, Ba, Cd, Co, Cs, Cu, Fe, Li, Mn, Ni, Pb, Rb, Sb, Se, Sn, Sr, Ti, Tl, V, Zn) during the winter and summer seasons of seven consecutive years (2008-2014) in an area of the Po Valley (Northern Italy) characterised by industrial, agricultural and urban settings. The study included the collection and analysis of 41 series of size-segregated samples (MOUDI sampler, 10 stages, cut sizes from 0.18 to 18 µm). Ions were analysed by ion chromatography; elemental analysis was carried out by ICP-MS, by applying a chemical fractionation method able to increase the selectivity of PM source tracers. Our results indicate that important winter/summer variations occurred in both the concentration and size distribution of most PM components. These variations were explained in terms of variations in the strength of the prevailing sources of each component. The contribution of biomass burning for domestic heating was highlighted by the well-known tracer K+ but also by the soluble fraction of Rb, Cs and Li. Biomass burning contribution to atmospheric PM was mostly contained in the fine fraction, with a broad size-distribution from 0.18 to 1.8 µm. This source also appreciably increased the concentration of other elements in fine PM (As, Cd, Co, Mn, Pb, Sb, Sn). A few PM components (tracers of sea-spray, brake lining and some industries) did not show marked seasonal variations in concentration and size distribution. However, during winter, for brake lining and industry tracers we observed an upward shift in the dimension of fine particles and a downward shift in the dimension of coarse particles, due to the ageing of the air masses.

Vertical and horizontal fall-off of black carbon and NO2 within urban blocks.

While exposure to traffic pollutants significantly decreases with distance from the curb, very dense urban architectures hamper such dispersion. Moreover, the building height reduces significantly the dispersion of pollutants. We have investigated the horizontal variability of Black Carbon (BC) and the vertical variability of NO2 and BC within the urban blocks. Increasing the distance from road BC concentrations decreased following an exponential curve reaching halving distances at 25 m (median), although with a wide variability among sites. Street canyons showed sharper fall-offs than open roads or roads next to a park. Urban background concentrations were achieved at 67 m distance on average, with higher distances found for more trafficked roads. Vertical fall-off of BC was less pronounced than the horizontal one since pollutants homogenize quickly vertically after rush traffic hours. Even shallower vertical fall-offs were found for NO2. For both pollutants, background concentrations were never reached within the building height. A street canyon effect was also found exacerbating concentrations at the lowest floors of the leeward side of the road. These inputs can be useful for assessing population exposure, air quality policies, urban planning and for models validation.

Seasonal variations in the chemical composition of particulate matter: a case study in the Po Valley. Part II: concentration and solubility of micro- and trace-elements.

Size distribution (fine and coarse fraction) and solubility distribution (extracted and residual fraction) of 20 elements (As, Ba, Be, Cd, Co, Cu, Fe, Li, Mn, Pb, Ni, Rb, S, Sb, Se, Sn, Sr, Ti, Tl, V) in atmospheric particulate matter (PM) were determined during a 5-year field study carried out in the Po Valley (peri-urban area of Ferrara, in Northern Italy). By studying the contribution of the two size fractions and the two solubility fractions to the atmospheric concentration of each element, it was possible to obtain interesting information about the variability of PM sources, to assess the role played by atmospheric stability in determining pollution episodes, and to obtain an estimate of the bio-accessible fraction. Atmospheric stability is confirmed to be one of the main causes of atmospheric pollution in this area and is to be responsible for the pronounced winter increase in both PM and elemental concentration. Long-range transport of natural and polluted air masses caused temporary increases in PM and elemental concentration, while local industrial emission seemed to play a secondary role. Regulated elements were well below their concentration limit, but many toxic elements were in the form of fine particles and soluble chemical species, more accessible to the environment, and the human body.

A dietary trial with a short-term low-sucrose diet in an Italian population: effects on colorectal mucosal proliferation.

Colorectal mucosal proliferation is supposed to predict colon cancer risk. We investigated whether a low-sucrose diet might reduce colorectal mucosal proliferation in a group of patients at higher risk of colorectal cancer after at least two colon adenoma resections. In a pilot phase, 14 patients [12 men and 2 women, 60.3 +/- 5 (SD) yr] were instructed to adopt a low-sucrose diet for one month. Colorectal biopsies were taken twice in the same patients, at the start and the end of the intervention period, and mucosal proliferation was measured by [3H]thymidine uptake in vitro and autoradiography. Although compliance of study participants to dietary modification was high, only a few agreed to two consecutive endoscopies; thus we carried out a randomized study, and 107 patients were assigned to a low-sucrose diet (50 treated patients: 31 men and 19 women, 59.7 +/- 7.5 yr) or instructed to continue their usual diet for one month (55 control patients: 32 men and 23 women, 59.6 +/- 7.7 yr). At the end of this period, colorectal biopsies were obtained. The results of the pilot phase and the randomized study showed that a low-sucrose diet for one-month did not affect proliferation or the distribution of proliferation activity along the crypt. The food-frequency questionnaires indicated that treated patients consumed significantly less sucrose (and fewer total calories) during the dietary modification. Urinary fructose, a measure of dietary sucrose intake, was also reduced at the end of the intervention period. In conclusion, we found no evidence that a low-sucrose diet for one month influences colorectal mucosal proliferation.