P. S. Khillare

Pattern, sources and toxic potential of PAHs in the agricultural soils of Delhi, India.

Surface soil (0-5 cm) from various agricultural sites in Delhi was analyzed to discern the contents of 16 priority polycyclic aromatic hydrocarbons (PAHs). Reference and deuterated standards were used for identification and quantification of PAHs by high performance liquid chromatography (HPLC) with UV detection. summation operator(16)PAHs ranged from 830 to 3880 microg kg(-1) (dry wt.) with an arithmetic mean of 1910+/-1020 microg kg(-1) summation operator(16)PAHs values at the urban sites were 2-5 times higher as compared to the rural sites. In general, low molecular weight PAHs were predominant. Total organic carbon (TOC) was found to be significantly correlated with summation operator(16)PAHs. Isomer pair ratios and Principal component analysis (PCA) suggested biomass and fossil fuel combustion as the main sources of PAHs. The toxic equivalency factors (TEFs) were used to estimate benzo[a]pyrene-equivalent concentration (B[a]P(eq)). Therewith, PAH content of urban agricultural soil was found to have more carcinogenic potential.

Particle size distribution and its elemental composition in the ambient air of Delhi.

This study examines the chemical composition of PM10, the thoracic fraction of the atmospheric particulate matter. An eight-stage Anderson impactor is used to separate the PM10 from other fractions with different aerodynamic behaviour at three different area representative sites in Delhi from February to May 1998. PM10 particulate are subdivided into two fractions, coarse (> 2.1-10 microns) and fine (< 2.1 microns). The concentrations of major heavy metals such as Pb, Zn, Cd, Ni, and Fe are determined by atomic absorption spectrophotometer. The average concentration of coarse fraction of PM10 is found to be 68.3 +/- 17 micrograms/m3 while the fine fraction of PM10 is 71.3 +/- 15 micrograms/m3 for Delhi. Metal concentration (except Fe) in fine fraction exceeds by a factor of up to 6, as compared to that in the coarse fraction. In order to identify the major sources of fine and coarse fraction of PM10, principle component analysis (PCA) was undertaken and three major sources were identified, namely vehicular emissions, industrial emission, and soil resuspension.

SPATIAL AND TEMPORAL VARIATION OF HEAVY METALS IN ATMOSPHERIC AEROSOL OF DELHI

The levels of Suspended Particulate Matter (SPM) and heavy metals viz. Pb, Cd, Cr, Ni and Fe were measured. Aerosol samples from fourdifferent locations in Delhi were collected by High-volume samplers for a period of one year from July 1997 June 1998. Metal concentration was determined by Atomic Absorption Spectrometry. The annual average concentration of SPM in Delhi was found to be 416.34 ± 223 μg m-3. The atmospheric aerosol samples were highly enriched with elements viz. Pb and Cd, which originate from various human activities like transportation and industrial processes. Principal Component Analysis (PCA) showed vehicular traffic and industrial emission as the major contributors of metals. The annual average concentration of Pb did not exceed the national standard of 0.75 μg m-3.

Assessment of PAHs in soil around the International Airport in Delhi, India.

Present study was undertaken to determine the level of PAH contamination due to jet turbine exhaust in the peripheral soil of the International Airport in Delhi, India. Densely populated residential areas surrounding the airport come directly under both the landing and take-off flight paths. Twelve priority polycyclic aromatic hydrocarbons (PAHs) were analyzed in the <2 mm surface soil fraction. Identification and quantification of PAHs was done by high performance liquid chromatography (HPLC). The sum of 12 PAHs ranged from 2.39 microg g(-1) to 7.53 microg g(-1) with a mean concentration of 4.43+/-1.45 microg g(-1). PAH levels observed in the present study were found to be higher as compared to most of the literature values. Among the three sampling sites selected around the International Airport, the site near landing point revealed maximum concentration of PAHs, while minimum concentration was observed at the site near take-off point. Predominance of pyrene was observed in the airport soil. Factor analysis and isomer pair ratios suggest pyrogenic origin of PAHs in the study area.

Metallic species in ambient particulate matter at rural and urban location of Delhi.

In the present study 14 metallic species (six crustal and eight trace metals) were quantified in the suspended particulate matter (SPM) at a rural and urban location of Delhi, India. Particulate matter was collected on glass fiber filters for a period of one year (from September 2003 to August 2004). Rank sum test revealed that the TSP concentration at the urban site was significantly (P=0.47) higher as compared to the rural site. Urban site showed highest SPM concentration during winter while rural site during summer. Enrichment factor (EF) and coefficient of variation (CV) were calculated to assess the variability of elemental concentration data. Trace metals viz. Pb, Cd, Cu and Zn were observed to be highly enriched at both the sites, but EF for Zn and Cu was 2-3 times higher at the urban site as compared to the rural site. Trace and crustal metal concentration displayed less variability at the urban site. In the urban area, metals were mainly found to come from construction and industrial activities in surrounding. At the rural site, re-suspended and wind-blown dust appeared to be the source of observed elemental concentration.

Health risk assessment of polycyclic aromatic hydrocarbons and heavy metals via dietary intake of vegetables grown in the vicinity of thermal power plants.

Six different vegetables grown in the vicinity of three thermal power plants and a background site in Delhi, India were analyzed for 16 priority polycyclic aromatic hydrocarbons (PAHs) and 7 heavy metals (Cd, Cu, Cr, Ni, Zn, Fe and Mn). Annual mean concentrations of PAHs and all metals were found to be significantly higher (ANOVA, p<0.001) at power plant sites as compared to the background site. Higher abundances of coal tracer PAHs such as Phen, Anth, Flan, Pyr and Chry in power plant vegetables suggested possible impacts of coal combustion emissions. Higher ratios of polluted sample-to-background sample of vegetables were found especially for Cr, Cd, Ni and Zn. Spinach and radish showed greater accumulation of PAHs and metals on a mass basis at the power plant sites while vegetables belonging to the gourd family showed highest relative enrichment. Power plant samples showed 184-475% greater metal pollution index (MPI) values as compared to the background location while health risk indices (HRI) for Cd and Ni exceeded the safe limit for most vegetables. Incremental lifetime cancer risk (ILCR) assessment showed that up to 58 excess cancer cases are likely in Delhi for lifetime ingestion exposure to PAHs at their observed concentrations.

Occurrence of acid rain over Delhi.

Precipitation samples were collected as wet-fall only andprimarily on event basis in Delhi during the monsoon period of1995. Concentrations of major anions (SO42-,NO3- and Cl-) andcations (Ca2+, Mg2+,Na+ and K+) were determined. The pH of the rain waterwas found to be more than 5.6, showing alkalinity during theearly phase of monsoon, but during the late phase of monsoon pHtendency was towards acidity due to lack of proper neutralizationof acidic ions. Neutralization is not only due to the localprocess but also due to the pre-monsoon ‘Andhi’ which bringsSuspended Particulate Matter (SPM) containing Ca2+,Mg2+, Na+ and K+ as well as the local emission ofNH3. In the late monsoon the concentration of cations getsreduced because of heavy rainfall and relatively unfavourablecondition for their transport from the adjoining areas, whereasthe anion concentrations remain unchanged owing to theircontinuous emission.

Impact of CNG implementation on PAHs concentration in the ambient air of Delhi: A comparative assessment of pre- and post-CNG scenario

The use of alternative fuel is considered to be an effective measure to improve the urban air quality. Concerned over deteriorating air quality in Delhi, the Delhi government initiated different measures including stringent emission norms, improved fuel quality and above all introduction of cleaner fuel-CNG in public transport system. The entire city bus fleet was converted to CNG mode by 2002. The present study reports the comparative assessment of the status of air quality with respect to PM10 and PAH before and after the introduction of CNG in public transport system in Delhi. The study has been carried out for two different time periods: first in the year 1998 and second in the year 2004. Following the total conversion of public transport system to CNG in 2002, Post-CNG data indicate a sharp reduction of 51–74% in the PM10 concentration and 58–68% in the TPAH concentration as compared to the Pre-CNG data.

Characterisation of Indoor PM10 in Residential Areas of Delhi

The relationship between indoor and outdoor concentrations of fine and coarse fractions of PM10 with respect to their chemical composition was investigated simultaneously at two different localities in Delhi. Indoor and outdoor aerosol samples for the fine fraction (with an aerodynamic diameter less than 2.1 μm) and coarse fraction (with an aerodynamic diameter between 2.1–10 μm) were collected simultaneously from inside and outside of two different houses in two different types of localities for the period of January to June 2000. The average contribution of the fine fraction indoors for Sites I and II respectively was 51 and 53% of the total PM10 and outdoors was 43 and 41%. The highest outdoor concentration of PM10 was recorded in the month of May/June at both sites. The reason for the higher values in the months of May/June could be the frequent pre-monsoon dust storm events commonly called ‘‘Andhi’’ in India, which generally carry loads of fine dust from the neighbouring Thar Desert to Northern India before the onset of the monsoon.

Persistent Pesticides in Fluvial Sediment and Their Relationship with Black Carbon

The persistence of Organochlorine pesticides (OCPs) and Black Carbon (BC) was studied in sediment samples from river Yamuna, a major tributary of the Ganges (one of the largest, most populated and intensively used rivers in Asia). High levels (21.41 to 139.95 ng g-1) of sum of 20 OCPs (∑20OCPs) have been detected with β-HCH as the predominant component. ∑HCH and ∑DDT constituted ~86% of ∑20OCPs. Lindane, DDT and technical grade HCH were recently used. Toxicological studies with reference to fresh water sediment quality guidelines showed alarming levels of γ-HCH and DDT. DDD, DDE, β-HCH, α-HCH, Endrin, Heptachlor epoxide and Chlordane exceeded some of the guideline levels. High levels of BC (0.46 ± 0.23 mg g-1) constituted 1.25 to 10.56% of TOC. BC was correlated with isomers of HCH, p,p’-DDT and Methoxychlor; while TOC with ∑20OCPs, γ-HCH, Endosulfan Sulfate and Methoxychlor. PCA enabled better understanding of the relationship between various OCPs, BC and TOC. The association of BC with various OCPs indicated its importance in retention of some OCPs into fluvial sediments; exhibiting the potential to reduce their bioavailability. The study is unique to report the role of BC in persistence of OCPs in fluvial sediments.