Tripti Agarwal

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.

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.

Concentration level, pattern and toxic potential of PAHs in traffic soil of Delhi, India

Present study was envisaged to examine the impact of vehicular traffic on the contamination status of urban traffic sites in Delhi with respect to Polycyclic Aromatic Hydrocarbon (PAH). Surface soil (0-5 cm) from three traffic sites and one rural site was analyzed and the content of 16 priority PAHs was determined. Total PAH concentration at traffic sites ranged from 1062 microg kg(-1) to 9652 microg kg(-1) with an average value of 4694+/-3028 microg kg(-1). At the rural site average concentration of total PAHs was found to be 886+/-303 microg kg(-1). Carcinogenic potency of PAH load in traffic soil was nearly 21 times higher as compared to the rural soil. PAH pattern was dominated by five- and six-ring PAHs (contributing >50% to the total PAHs) at all the three traffic sites. On the other hand, rural soil showed a predominance of low molecular weight two- and three-ring PAHs (contributing >50% to the total PAHs). A lack of correlation was observed between total PAH and total organic carbon (TOC) content in traffic soils but in rural soil both were positively correlated (r=0.76). In rural soil naphthalene (r=0.88, P=<0.05) displayed strongest correlation with TOC. Indeno[123-cd]pyrene/benz[ghi]perylene (IP/BgP) ratio indicated that PAH load at the traffic sites is predominated by the gasoline-driven vehicles. Principal Component Analysis (PCA) provided the fingerprints of vehicular traffic emission and coal combustion 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.

Has the Burden and Distribution of PCBs and PBDEs Changed in European Background Soils between 1998 and 2008? Implications for Sources and Processes

Background soils were collected from 70 locations on a latitudinal transect in the United Kingdom and Norway in 2008, ten years after they had first been sampled in 1998. The soils were analyzed for polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and organochlorine pesticides (OCs), to see whether there had been any change in the loadings or distributions of these persistent organic pollutants (POPs). The same transect has also been used to sample air between the mid-1990s and the present, so the air and soil spatial and temporal trends provide information on air-soil transfers, source-receptor relationships, long-range atmospheric transport (LRAT), and recycling phenomena. Comparisons of the 2008 and 1998 data sets show a general decline for PBDEs in surface soil, and a smaller averaged net decline of PCBs. Changes between the years were observed for total POP concentrations in soil and also for correlations with site and sample characteristics assumed to affect those concentrations. POP concentrations were correlated to distance and strength of possible sources, a relationship that became weaker in the 2008 data. Fractionation, a commonly discussed process for the global cycling of POPs was also lost in the 2008 data. As in 1998, soil organic matter content continues to have a strong influence on the loadings of POPs in surface soils, but changes in the PCB loads were noted. These factors indicate an approach to air-surface soil equilibrium and a lessening of the influence of primary sources on POP concentrations in soil between 1998 and 2008.

Is black carbon a better predictor of polycyclic aromatic hydrocarbon distribution in soils than total organic carbon

Black carbon (BC) and total organic carbon (TOC) were quantified in the surface soils of Switzerland (N=105) and Delhi (N=36), India, to examine their relationships with contents of polycyclic aromatic hydrocarbons (PAH). BC content in Swiss (background) soils (N=104) varied from 0.41 to 4.75 mg/g (median: 1.13 mg/g) and constituted 1-9% (median: 3%) of TOC. Indian (urban) soils had similar BC concentrations (0.37-2.05 mg/g, median: 1.19 mg/g), with relatively higher BC/TOC (6-23%, median: 13%). Similar to TOC, BC showed significant positive correlation with lighter PAH, but no correlation with heavier PAH in Swiss soils. In contrast, heavier PAH were significantly correlated only with BC in Delhi soils. It seems that TOC governs the distribution of PAH in organic matter rich background soils, while the proximity to emission sources is reflected by BC-PAH association in urban soils.

Polycyclic aromatic hydrocarbons' formation and occurrence in processed food.

Polycyclic aromatic hydrocarbons (PAHs) emerged as an important contaminant group in a gamut of processed food groups like dairy, nuts, herbs, beverages, meat products etc. Different cooking processes and processing techniques like roasting, barbecuing, grilling, smoking, heating, drying, baking, ohmic-infrared cooking etc. contribute towards its formation. The level of PAHs depends on factors like distance from heat source, fuel used, level of processing, cooking durations and methods, whereas processes like reuse, conching, concentration, crushing and storage enhance the amount of PAHs in some food items. This review paper provides insight into the impact of dietary intake of PAHs, its levels and formation mechanism in processed food items and possible interventions for prevention and reduction of the PAHs contamination. The gaps and future prospects have also been assessed.

Adaptation, validation and application of the chemo-thermal oxidation method to quantify black carbon in soils

The chemo-thermal oxidation method at 375°C (CTO-375) has been widely used to quantify black carbon (BC) in sediments. In the present study, CTO-375 was tested and adapted for application to soil, accounting for some matrix specific properties like high organic carbon (≤ 39%) and carbonate (≤ 37%) content. Average recoveries of standard reference material SRM-2975 ranged from 25 to 86% for nine representative Swiss and Indian samples, which is similar to literature data for sediments. The adapted method was applied to selected samples of the Swiss soil monitoring network (NABO). BC content exhibited different patterns in three soil profiles while contribution of BC to TOC was found maximum below the topsoil at all three sites, however at different depths (60-130 cm). Six different NABO sites exhibited largely constant BC concentrations over the last 25 years, with short-term (6 months) prevailing over long-term (5 years) temporal fluctuations.

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.

PAHs in Indian diet: Assessing the cancer risk

Food products such as bread, biscuits, tea, coffee, oils, chocolates, grapes, pepper and fishes belonging to different categories represent a significant part of everyday diet in India and other countries having variable cooking techniques. In this study, we evaluated cancer risks of long term exposure to polycyclic aromatic hydrocarbons (PAHs) through consumption of these products for eight societal groups in India. Total concentrations of PAHs in these products from India ranged from 0.18 to 61967 μg kg-1 and the cancer risk values for the eight sections of Indian population ranged between 7.63E-10 to 5.05E+00, indicating product specific distribution of risk from non-significant to significant levels. Cereals, vegetables and decoctions contributed majorly to cancer risk and the most susceptible group identified was children. The spread of risk estimates followed Burr and Exponential distributions. To the best of our knowledge, this is the first study to develop information on the health risk faced by Indian population through dietary PAHs.