Indoor-outdoor association of particulate matter and bounded elemental composition within coarse, quasi-accumulation and quasi-ultrafine ranges in residential areas of northern India

Abstract

Attempts have been made to comprehend size distribution pattern of Particulate Matter (PM) and associated elemental concentration within coarse (2.5–10μm), quasi-accumulation (q-Acc) (0.25–2.5μm) and quasi-ultrafine (q-UF) (<0.25μm) ranges at indoors and outdoors of residential homes of Agra. Overall, the average mass concentrations of PM10 and PM2.5 in indoors were found to be 263.24±59.24 and 212.01±38.06μgm−3 while in outdoors the concentrations accounted to 194.28±15.25 and 152.88±16.31μgm−3 respectively; exceeding WHO standards. In view of geographical variation, significantly higher (t=2.461; P=0.044) PM mass was found in outdoor samples of roadside location when compared to homes located far away from busy traffic; whereas indoor concentration exhibited non-significant relationship (t=1.887; P=0.095) between the two categorized homes. Findings of size partitioning trend through deployment of Sioutas Cascade Impactor evidenced presence of high proportion of PM and elemental concentrations within q-Acc and q-UF modes with their distribution pattern and probable emission sources conferred upon. Absence of modal peak in coarse range indicated predominance of anthropogenic emissions with presumed wash-out of coarse particles during frequent precipitation coincidental with sampling event. Seeming modal shifts for some elements (K, Cd, Zn) from q-Acc to q-UF were perceived during infiltration process. Presence of high traffic emission in homes near busy road stemmed the shifting of particles (Cu, K, Co, Zn) towards finer size (preferably q-UF mode) thus exposing residents to adverse health effects through their penetration (Finf=0.14) into indoor environment. Flat slopes (0.11) and poor correlation (8.4%) for metals in coarser range obtained through regression model hypothesized their high deposition velocities and low penetration efficiency. Our findings suggest enhanced resident exposure to fine particles (81%) especially q-UF range (37%) through indoor and outdoor (through infiltration) sources along with complexity of size distribution of airborne particles that prerequisites surplus consideration to achieve a healthier environment within residential area.