Emission from field burning of agricultural crop residue is a common environmental hazard observed in northern India. It has a significant potential health risk for the rural population due to respirable suspended particulate matter (RSPM). A study on eight stage size segregated mass distribution of RSPM was done for 2 wheat and 3 rice crop seasons. The study was undertaken at rural and agricultural sites of Patiala (India) where the RSPM levels remained close to the National Ambient Air quality standards (NAAQS). Fine particulate matter (PM_2.5) contributed almost 55% to 64% of the RSPM, showing that, in general, the smaller particles dominated during the whole study period with more contribution during the rice crop as compared to that of wheat crop residue burning. Fine particulate matter content in the total RSPM increased with decrease in temperature. Concentration levels of PM₁₀ and PM_2.5 were higher during the winter months as compared to that in the summer months. Background concentration levels of PM₁₀, PM_2.5 and PM_10−2.5 were found to be around 97±21, 57±15 and 40±6 μg m⁻³, respectively. The levels increased up to 66, 78 and 71% during rice season and 51, 43 and 61% during wheat crop residue burning, respectively. Extensive statistical analysis of the data was done by using pair t-test. Overall results show that the concentration levels of different size particulate matter are greatly affected by agricultural crop residue burning but the total distribution of the particulate matter remains almost constant.

Electrochemical behavior of anthrone derivatives 1 (1-(2,7-dioxo-3,7-dihydro-2H-naphtho[1,2,3 de]quinolin-1-yl)-1′-heptyl-4,4′-bipyridine-1,1′-diium) and 2 (1-(2,7-dioxo-3,7-dihydro-2H-naphtho[1,2,3-de]quinolin-1-yl)-[4,4′-bipyridine]-1-ium functionalized with viologen group are inspected extensively using cyclic voltammetry. Colorimetric studies indicate their selectivity towards anions like cyanide, acetate and fluoride. Cation selectivity of anthrone derivative changes to anions because of the viologen group. Anthrone derivative stabilizes viologen through conjugation, reducing one of its two redox couples which are characteristic of viologen group for molecule 1. Mechanisms are proposed and supported by theoretical studies carried out using Guassian 03W for the electrochemical behaviour of compounds 1 and 2. Voltammograms of dicationic viologen derivative 1 show near quenching of anodic peaks (a decrease of almost 90% of current) as well as cathodic peaks (a decrease of almost 100% current) in the presence of 1 equivalent of cyanide ions. The molecule 2 undergoes quenching of the cathodic peak while anodic peak survives in the presence of the anions, cyanide, acetate and fluoride. The proposed electrochemical sensors are selective for CN⁻, OAc⁻ and F⁻ based on binding constants which are much larger than for anions like Cl⁻, Br⁻, I⁻, HSO₄ ⁻. The proposed voltammetric method for the cyanide determination is compared with potentiometric and spectrophotometric methods for cyanide determination. The proposed voltammetric method has also been used for quantitative determination of cyanide in unknown samples.