Source apportionment studies to identify particulate matter from crop residue burning affecting human health

Abstract

Rice and wheat are the major crop in the North-Western part of the country, which generate a large amount of leftover crop residue, intensified with the usage of mechanical combine harvester technology, which is further, subjected to open field crop residue burning. It is a human initiated activity for the purpose of preparing the fields for the next crop quickly and inexpensively. The burning of agricultural residues leads to significant emissions of chemically and radioactively important trace gases such as methane (CH4), carbon monoxide (CO), nitrous oxide (N2O), oxides of Nitrogen (NOX) and Sulphur (SOX) and particulate matter (PM) to the atmosphere. Size, concentration, composition, and toxicity of particulate matter are vital features that greatly affect the possible human health problems related to their exposure. This research provides insight on effects of particulate matter fractions (PM10, PM2.5 and PM1) on lung efficiency of school children and was conducted from September 2014 to December 2015 covering one wheat and two rice crop seasons. The effects on children are more severe than other age groups due to their body structure and constraints. The children are unaware of their surrounding environment and their organs are in development phase. Due to comparatively weaker immune system, even short-term exposure could lead to harmful health effects on children. The study was undertaken at 3 rural sites in the districts of Patiala, Fatehgarh Sahib and Sangrur (Malwa region of Punjab) with no nearby another source except national highway at Fatehgarh Sahib. The monthly average values of PM10, PM2.5 and PM1 were about 3–4 times higher than the National Ambient Air Quality Standards (NAAQS) given by Central Pollution Control Board during the crop residue burning periods. The MODIS data images of crop residue burning events confirmed the active fire operations over the region. The lung function parameters (Forced Vital Capacity, Forced Expiratory Volume in one second) of children (10–16 years) decreased with increase in particulate matter concentration while no significant effect was observed on Oxygen saturation level of children. The decrease in Forced Vital Capacity was slightly more in male subjects as compared to the female population. The sharp decrease in Pulmonary Function Test parameters during the crop residue burning period indicated the severity of the episodic burning events on the health of the children. The more decrease in lung efficiency was observed during rice crop residue burning periods as compared to wheat crop residue burning period, associated it with increased concentration levels of particulate matter during that time period. The establishment of adverse health effects of increased particulate matter concentrations leads to the inquiry about the composition of the particulate matter. To determine the contribution of different particulate sources in PM10 mass concentration at semi urban site of Thapar Institute of Engineering and Technology, Patiala, source apportionment study was carried out from 7 May 2015 to 9 June 2016. For source apportionment, particulate matter (PM10) was collected on glass microfiber filter which was extracted and analysed for metals (Al, Ti, Ca, Mn, Fe, Mg, V, Cr, Ni, Cu, Zn, Ba and Pb) and ions (Na+ , K+ , SO4 2- , Cl- , NO3 - ). To know the variability in sources, PM10 was collected in daytime-nighttime paired samples for 24 hours. The study was specifically designed to apportion the sources of air pollution where main exposure is from crop residue burning. The particulate matter (PM10) samples were analyzed for mass and chemical composition, with Potassium as biomarker for crop residue burning. Sulfate (SO4 2- ) and potassium ion (K+ ) species dominated the concentration of characterized species. K+ and Clwere identified as reliable markers for crop residue burning while Zn, Pb, Al, Ni and Cu were identified as markers for vehicular exhaust. The results of Positive matrix factorization (PMF) model gives the five major sources as probable sources of PM10 pollution. The highest contribution in PM10 mass concentration was found to be sulfate (24.39±10.42), and potassium (24.02±09.56) and chloride (07.07±05.47), which combined accounts for nearly 60% of the total PM10 mass fraction. The highest source contribution was from Industrial emission source (22.9%), with almost same contribution from biomass burning (21.2%), and resuspended dust (20.7%) and followed by vehicular emissions (19.0%) and least from secondary aerosols (16.2%). Nighttime concentrations were always higher than day time levels due to descend of the boundary layer height at night time period. The measured species mass concentration represents 65% mass fraction of the PM10. The results of the study provide an approximate indication of which anthropogenic and natural sources of particulate pollution could be responsible for poor health quality in rural and semi urban areas in Punjab. Based on the results of the study, emissions cut off from industrial and biomass burning are required in the region as biomass burning and industrial emissions are the biggest contributor in PM concentrations (21.2% and 22.9%, respectively). Further, wide range of markers including trace gases, particulate matter and various Volatile organic compounds (VOCs) should be studied for better understanding of origin of the sources and GIS (Geographic Information System) should be used along with modeling and satellite data for representing real picture of the pollutants origin and their transport