Average Suspended Particulate Matter Concentrations Research Articles

Hydro‐Sedimentary Processes of a Plunging Hyperpycnal River Plume Revealed by Synchronized Remote Imagery and Gridded Current Measurements

AbstractThe present knowledge of plunging hyperpycnal river plumes is mainly based on two‐dimensional (confined) laboratory experiments. Several hypotheses on three‐dimensional (unconfined) flow processes have been made, but not tested in situ. In this field study, the dominant three‐dimensional hydro‐sedimentary processes related to unconfined plunging were elucidated by synchronizing autonomous time‐lapse camera images with boat‐towed acoustic Doppler current profiler measurements. It was found that the flow field complies with two‐dimensional conceptualizations along the plume centerline. Perpendicular to the centerline, the plume slumped laterally due to its density excess and simultaneously converged laterally due to its vertical divergence. This combination led to a narrowing of the plume near the surface, resulting in a sediment‐rich triangle‐shaped pattern on the surface near the inflow, and a rather stable width near the bed. The formation of secondary flow cells transporting riverine water and suspended particulate matter (SPM) away from the plume near the bed, up toward the surface and back toward the plume near the surface, was revealed. An increase of the average SPM concentration and the SPM flux in the main flow direction indicates net sediment erosion under the investigated conditions of high discharge and sediment load. This suggests transient storage of sediment during conditions of lower discharge and sediment load, and high morphological activity in the plunging area. These findings allowed extending a classical conceptual plunging model to laterally unconfined sediment‐laden plunging inflows for conditions of well‐mixed ambient water in the plunging region and inflow densimetric Froude numbers exceeding 1, common in nature.

Biosolar green roofs and ambient air pollution in city centres: Mixed results

Green roofs are known for their ability to reduce ambient air pollution. While the accurate valuation of the air pollution removal services provided by green roofs is rapidly developing, much of this research is still in its infancy, with only a small number of in-situ studies that truly examine the impact of green roofs on city air quality. In this study we present the longest study conducted on an Australian green roof with in-situ air quality monitoring. Field measurements were utilised to calculate the ambient air pollutant removal of an extensive green roof compared to a proximal, near-identical conventional roof over three seasons. The average concentrations of ambient ozone was lower on the green roof compared to that of the conventional roof surface. The theoretical ozone and nitrogen dioxide removal rates on the green roof were higher than the average concentrations calculated from previous research at 3.82 g m-2y-1 and 1.29 g m-2y-1 respectively. There was no significant difference in the average suspended particulate matter concentrations between the two roofs. The particulate matter removal rate was lower than the average previous findings at 0.29 g m-2y-1. The green roof studied was theoretically capable of removing 0.5 kg of PM2.5, 6.9 kg of O3 and 2.3 kg of NO2 per year, values which were significantly higher than the conventional roof. Ambient nitrogen dioxide concentrations were higher on the green roof – largely attributed to local construction activities.

Assessment of suspended particulate matter and heavy metal analysis during Diwali festival at Raipur, Chhattisgarh, India

Diwali is an important festival in India, and a lot of firecracker bursting takes place in every part of the country during festive occasions. The short-term effect of firecrackers on ambient air quality was assessed by monitoring suspended particulate matter (SPM) and heavy metal analysis (iron (Fe), zinc (Zn), lead (Pb), manganese (Mn) and nickel (Ni)) during the Diwali festival at the urban-industrial city of Raipur, India, from 3 to 11 November 2018. The daily average SPM concentrations were found to be about two times higher on 7 November (Diwali; 425.64 µg/m3) and 8 November (next day of Diwali; 417.92 µg/m3) compared with that on 3 November (pre-Diwali day; 247.56 µg/m3). Heavy metal analysis (iron, zinc, lead, manganese and nickel) was carried out using atomic absorption spectroscopy, and the same concentration trend in the order of iron > zinc > lead > manganese > nickel was found during day- and night-time. A significant increment in SPM and heavy metal concentrations was observed post-Diwali. Back-trajectory analysis revealed that the trajectories at surface level (50 and 1000 m above ground level) originated from local sources, showing local anthropogenic activities such as burning of firecrackers and industrial activities as a major pollution source. The wind rose diagram shows a higher SPM concentration when the wind was north-easterly. The present study reveals that pollution levels were considerably increased during Diwali and firecracker bursting played a major role by contributing to air pollution.

Combining Landsat-8 and Sentinel-2 to investigate seasonal changes of suspended particulate matter off the abandoned distributary mouths of Yellow River Delta

Suspended particulate matter (SPM) is the primary component of coastal waters. The spatiotemporal dynamics of SPM has an important influence on water bio-optical properties, pollutant diffusion, landform evolution, and carbon, oxygen, and nutrient cycles. This study presents the spatial distribution of monthly average SPM concentrations from 2017 to 2020 in the abandoned Diaokouhe and Shenxiangou distributary mouths of the Yellow River Delta (YRD). The SPM concentrations were derived based on 161 Landsat-8 OLI and Sentinel-2A/B MSI satellite images. Accuracy assessment using the synchronous in-situ measurements (R2 = 0.91, root mean square error (RMSE) = 38.79 mg/L, and relative percentage difference (RPD) = 23.45%) and cross comparison between SPM concentrations derived from the two sensors (R2 = 0.97, RPD = 8.77%) showed convincing performances. Our results show that the monthly average SPM is characterized by significant seasonality, with a higher concentration and wider range in dry seasons compared to that in wet seasons. The spatial distributions of SPM are closely associated with coastal water depths. The SPM concentration in the Shenxiangou mouth is always lower than that of the shallower Diaokouhe mouth. The long-term seabed erosion provides a continuous supply of sediment. Wind-wave forces explain the seasonal variations of SPM by inducing the resuspension of bottom sediments. The residual currents control the transportation of SPM to the offshore and to the east. The artificial groins located between the two river mouths show obvious sediment trapping effects. Moreover, the interception capability of impermeable groins is considerably better than that of permeable groins.

COVID-19 and its impact on environment: Improved pollution levels during the lockdown period – A case from Ahmedabad, India

The novel Coronavirus pandemic (COVID-19) hit the world severely in the first half of 2020 which forced several nations to impose severe restrictions on all sorts of activities involving human population. People were mainly advised to remain home quarantined to curb the virus spread. Industrial and vehicular movements were ceased as a result of lockdown, and therefore the rate of pollutants entering the ecosystem was also reduced in many places. Water and air pollution remained a major concern in the last few decades as these were gradually deteriorating in many spheres including the hydrosphere and atmosphere. As the nation-wide lockdown period in India completed more than two months, this study attempted to analyze the impact of lockdown on water and air quality to understand the short-term environmental changes. Using remote sensing data, this study demonstrated the improvements in ambient water quality in terms of decreased turbidity levels for a section of the Sabarmati River in the Ahmedabad region of India. The Suspended Particulate Matter (SPM) concentrations are evaluated to underline the turbidity levels in the study area before and during the lockdown period using the Landsat 8 OLI images. We noticed that the average SPM has significantly decreased by about 36.48% when compared with the pre-lockdown period; and a drop of 16.79% was observed from the previous year's average SPM. Overall, the average SPM concentration during the lockdown period (8.08 mg/l), was the lowest when compared with pre-lockdown average and long-term (2015–2019) April month average. The atmospheric pollution level (NO2, PM2.5, and PM10) data obtained from the Central Pollution Control Board for Ahmedabad city also shows a significant improvement during the study period, implying a positive response of COVID-19 imposed lockdown on the environmental fronts.

Suspended particulate matter for sediment accumulation on inundated anthropogenic marshland in the southern North Sea – Potential, thresholds and limitations

Determining the availability of suspension load, i.e. suspended particulate matter (SPM), in shallow marine tidal systems is necessary to estimate whether coastal lowlands may experience vertical accretion rates that keep pace with global sea level rise. In particular anthropogenic marshland areas are affected by limitations of SPM accumulation due to artificial structures such as dikes and revetments that act as transport barriers.With the use of an autonomously operating turbidity measuring network installed at and around the Hallig Langeness in the North Frisian Wadden Sea, we have analyzed eight individual inundations on this island-like marshland during harsh weather conditions. The results reveal that the majority of the available SPM could not accumulate on the marshland due to adjacent coastal protection measures. This reduction in SPM affects especially grain sizes within the very fine to fine sand range between 63 and 200 μm that can account for up to 70% of the sampled SPM during an inundation. Furthermore, we have determined a tidal average SPM concentration threshold of 0.15 g/l should be available on the tidal flat in order to allow sufficient vertical marshland accretion. Although this threshold is exceeded by the determined SPM on the tidal flats around Langeness, the available SPM on the marshland after passing the coastal protection measures is at most 20%. Hence, an optimized coastal management strategy has the potential to increase the sediment accumulation rate on the marshlands by a factor of five, which might allow for keeping pace with local sea level rise.

Long-Term Exposure to Particulate Matter and Mortality from Cardiovascular Diseases in Japan: The Ibaraki Prefectural Health Study (IPHS).

Aim: To examine the association between long-term exposure to suspended particulate matter (SPM) and cardiovascular mortality in Japan after controlling for known major confounding factors among a large middle and elderly cohort study in Ibaraki Prefecture, Japan.Methods: We followed 91,808 residents (men 34%) who undertook a national health check-up at age 40–79 years for 17 years (1993–2010). Two different exposure indices were adopted: baseline SPM concentration (in the year 1990) and average SPM concentration for the first (average of 1990 and 1995) and the second half (average of 2005 to 2009) of the study period. Sex-specific adjusted risk ratios (RRs) for cardiovascular mortality were calculated using general mixed Poisson regression models after adjusting the age, BMI, history of diabetes mellitus and hypertension, creatinine, glutamic pyruvic transaminase, total cholesterol, high-density lipoprotein cholesterol, smoking, alcohol, and temperature. The variation between seven medical administration areas was also taken into account as a random effect.Results: Baseline SPM concentration was associated with an increased risk of mortality from all cardiovascular diseases, coronary artery disease, and stroke. The adjusted RRs (95% confidence interval [CI]) per 10 µg/m3 increase in SPM concentration for all cardiovascular mortality were 1.147 (1.014–1.300) for men and 1.097 (0.985–1.222) for women. The point estimate of RR was highest for non-hemorrhagic stroke in men (1.248 [0.991–1.571]), although CI overlapped the unity. The RRs seemed slightly lower in the second half than in the first half, though the CIs widened in the second half.Conclusion: Our results suggest that long-term exposure to SPM is associated with an increased risk of all cardiovascular mortality for men in Ibaraki, Japan.

Acute effects of summer air pollution on pulmonary function and airway inflammation in healthy young women.

BackgroundExposure to air pollution has been reported to be associated with asthma exacerbation. However, little is known about the effects of air pollutant exposure in healthy people. A panel study was conducted to evaluate the acute effects of air pollutants on pulmonary function and airway inflammation in healthy subjects.MethodsExhaled breath condensate (EBC) pH, fractional concentration of exhaled nitric oxide (FeNO), and pulmonary function were measured in 21 healthy young women repeatedly for two weeks in the summer in Tokyo, Japan. The concentrations of air pollutants were obtained from the monitoring stations in the neighborhoods where the subjects lived. Statistical analyses were performed using generalized estimating equations.ResultsEBC pH decreased significantly with a 10-ppb increase in the 4-day average ozone (O3) concentration and a 10-µg/m3 increase in the 4-day average suspended particulate matter (SPM) concentration (−0.07 [95% confidence interval {CI} −0.11 to −0.03] and −0.08 [95% CI −0.12 to −0.03], respectively). Subjects with a history of rhinitis showed marked decreases in EBC pH associated with increases in O3 and SPM. The changes in forced expiratory volume in 1 second (FEV1) were also significantly associated with a 10-µg/m3 increase in the 3-day average concentration of SPM (−0.09 L [95% CI −0.17 to −0.01]). FeNO increased significantly in relation to the increase in O3 and SPM among only subjects with a history of asthma.ConclusionsOver the course of the study, EBC became significantly acidic with increases in O3 and SPM concentrations. Furthermore, higher SPM concentrations were associated with decreased FEV1. Subjects with a history of rhinitis or asthma are considered to be more susceptible to air pollutants.

Effect of meteorological parameters and environmental pollution on thunderstorm and lightning activity over an urban metropolis of India

The purpose of this study is to understand the effect of meteorological parameters and environmental pollution on thunderstorm and lightning activity over Kolkata (22.65° N, 88.45° E), India during the pre monsoon season (April–May). The aerosol optical depth, cloud top temperature and lightning flash rate are analyzed with 2004–2010 observations. The convective available potential energy (CAPE) and convective condensation level (CCL) are utilized to view the role of convective energy and level of cloud base in thunderstorm and lightning activities. The suspended particulate matter (SPM), sulfur oxides (SOx) and nitrogen oxides (NOx) are also considered for a precise understanding of the effects of all these parameters on thunderstorms and lightning activity. High variability in convective energy persists over Kolkata during the pre monsoon season. It is observed that high CAPE and lower CCL leads to maximum wind speed with thunderstorms. Irrespective of CCL heights the average concentration of SPM is observed to be high for increased lightning flash rate. It is revealed that increased surface pollution in a near storm environment can increase the lightning flash rate during thunderstorms. The result also shows that the enhanced lightning activity intensifies the production of tropospheric NO2.

Decreasing trends of suspended particulate matter and PM2.5 concentrations in Tokyo, 1990–2010

In Tokyo, the annual average suspended particulate matter (SPM) and PM2.5 concentrations have decreased in the past two decades. The present study quantitatively evaluated these decreasing trends using data from air-pollution monitoring stations. Annual SPM and PM2.5 levels at 83 monitoring stations and hourly SPM and PM2.5 levels at four monitoring stations in Tokyo, operated by the Tokyo Metropolitan Government, were used for analysis, together with levels of co-pollutants and meteorological conditions. Traffic volume in Tokyo was calculated from the total traveling distance of vehicles as reported by the Ministry of Land, Infrastructure, Transport, and Tourism. High positive correlations between SPM levels and nitrogen oxide levels, sulfur dioxide levels, and traffic volume were determined. The annual average SPM concentration declined by 62.6% from 59.4 µg/m3 in 1994 to 22.2 µg/m3 in 2010, and PM2.5 concentration also declined by 49.8% from 29.3 µg/m3 in 2001 to 14.7 µg/m3 in 2010. Likewise, the frequencies of hourly average SPM and PM2.5 concentrations exceeding the daily guideline values have significantly decreased since 2001 and the hourly average SPM or PM2.5 concentrations per traffic volume for each time period have also significantly decreased since 2001. However, SPM and PM2.5 concentrations increased at some monitoring stations between 2004 and 2006 and from 2009 despite strengthened environmental regulations and improvements in vehicle engine performance. The annual average SPM and PM2.5 concentrations were positively correlated with traffic volumes and in particular with the volume of diesel trucks. These results suggest that the decreasing levels of SPM and PM2.5 in Tokyo may be attributable to decreased traffic volumes, along with the effects of stricter governmental regulation and improvements to vehicle engine performance, including the fitting of devices for exhaust emission reduction. Implications: In Tokyo, the annual average SPM concentration declined by 62.6% from 59.4 μg/m3 in 1994 to 22.2 μg/m3 in 2010, and the concentration of PM2.5 declined by 49.8% from 29.3 μg/m3 in 2001 to 14.7 μg/m3 in 2010. Significant positive correlations were found between traffic volumes and SPM or PM2.5, but the average concentrations of SPM and PM2.5 concentration per traffic volume have also decreased over the decade studied. These results suggest that reductions in traffic volumes as well as improvements in engine design and the installation of exhaust gas treatment systems may have improved air quality.

ASSESSMENT OF AMBIENT AIR QUALITY OF PURULIA TOWN, PURULIA DISTRICT, WEST BENGAL, INDIA

This paper presents data on the concentration of air pollutants at different places of a newly developed industrial estate in a highly growing city of State of West Bengal, India. The ambient air quality assessment was carried out at four different locations with respect to SO2, NOx, Suspended Particulate Matter (SPM) and Respirable Suspended Particulate Matter (RSPM), and monthly air sampling was carried out for a period 24 hours (3 x 8 hours) at each of the site. It is revealed that even the average concentrations of SPM, NOx, and SO2 were in highest level in all sampling sites as observed during winter followed by summer and the rainy season. It is also observed that out of four sampling sites, concentration of all parameters was highest at Bongabari and the minimum value was at South Lake Road, during winter.

Monitoring the levels of toxic air pollutants in the ambient air of Freetown, Sierra Leone

The ambient air quality in Freetown, Sierra Leone was investigated for the first time for toxic air pollutants. We investigated the levels of polycyclic aromatic hydrocarbons (PAHs), suspended particulate matter (SPM) and carbon monoxide (CO) and considered the implication of air quality and health risks. Particulate samples for PM2.5 and PM2.5 to10fractions were collected from four sites, and analyzed by HPLC/FLD. SPM and CO were monitored by realtime monitors. The annual average concentrations of total PAHs for PM2.5and PM2.5 to10 fractions for the various sites were found to be 37.18 and 6.24 ng/m3. The average concentration of SPM was 216.3 count per min (cpm) and the 8-h average concentration of CO was 10 ppm. Higher concentrations of PM2.5 and PM2.5 to 10 PAHs were found in dry season compared with wet season. The annual carcinogenic potential of PAHs was high in PM2.5 fraction while the levels of SPM and CO were high enough to raise concern of health risks. The ambient air quality in Freetown was judged to be poor and in view of human exposure, large portion of urban residents are exposed to high levels of toxic air pollutants which is recognized to be a public health risk. Key words: Air pollution, polycyclic aromatic hydrocarbons, suspended particulate matter, carbon monoxide, African countries

Inorganic ion and nitrogen isotopic compositions of atmospheric aerosols at Yurihonjo, Japan: Implications for nitrogen sources

We studied the suspended particulate matter (SPM) collected in Akita Prefecture, Japan from April 2008 to January 2009 for inorganic ion composition and nitrogen isotopic ratio (δ15N) of NH4+ and NO3−. The results showed an average SPM concentration of 15.6 μg m−3. The seasonal trend for SPM was higher values in the spring, lower in the winter. The major cations were Na+, NH4+, Ca2+ and major anions were SO42−, NO3−, Cl−. The annual correlation coefficient of ions indicates a very high value with NH4+ and SO42− (R = 0.93), NO3− and K+ (R = 0.65), NO3− and Ca2+ (R = 0.62). The high springtime values are the apparent result of the dust stream from Asia. Average δ15N–NH4+ and δ15N–NO3− were 16.1‰ and −0.69‰, respectively. δ15N–NH4+ increased slightly in summer, and δ15N–NO3− increased considerably in winter. The trends indicated conversely. The heavy δ15N–NH4+ in summer appears to be from agricultural sources such as animal waste and fertilizer. In addition, according to the difference in isotopes of NOx sources as the precursor of NO3−, the dominant origin of heavy δ15N–NO3− in winter could be NOx emitted from fossil fuel combustion at low temperature. Moreover, the average δ15N–NO3− seemed to be made to baseline (approximately 0%) by vehicle emissions at high temperature. These results are considered to be very reasonable.

Comparative studies of chemical composition of particulate matter between sea and remote location of eastern part of India

Suspended particulate matter (SPM) was collected by using high volume samplers (HVS) from two different locations: Bay of Bengal (BoB) and State Botanical Garden (SBG) situated in the eastern part of India. The SPM samples were collected on Whatman No.41 filter papers. The samples were simultaneously collected daily from both the locations during March 17–April 1, 2006. The average SPM concentration over BoB and SBG was found to be 39.05 and 78.14 μg/m 3 respectively. Na + and SO 4 2− were the most dominant water-soluble constituents over BoB and SBG respectively. The ratio of SO 4 2−/NO 3 − concentrations in both the cases was observed to be > 1 indicating that the contribution of atmospheric acidity was more due to SO 4 2− than NO 3 −. From intra-correlation analysis it is found that at both the locations, Na + and Cl − were well correlated while SO 4 2−-Ca 2+ and SO 4 2−-NH 4 + were poorly correlated indicating the later ion pairs to be derived from different sources. The Windrose diagrams for wind speed and direction show that for SBG, the wind blew from the SE and SW directions and brought in pollutants from soil and anthropogenic sources. In case of BoB, the wind parcels mostly were blown from the land mass (EES direction) showing the influence of anthropogenic pollutants on the marine aerosols. All the variables can be classified into three factors using principal component analyses technique. It explained 85% of total variance.

Impact of rice crop residue burning on levels of SPM, SO2 and NO2 in the ambient air of Patiala (India)

Ground-based ambient air monitoring was conducted at five different locations in and around Patiala city (29°49′–30°47′N Latitude, 75°58′–76°54′E Longitude) in Northern India in order to determine the impact of open burning of rice (Oriza sativa) crop residues on concentration levels of suspended particulate matter (SPM), sulphur dioxide (SO2) and nitrogen dioxide (NO2). Covering sensitive, residential, agricultural, commercial and urban areas, sampling of these pollutants was organised during August 2006 to January 2007 and August 2007 to January 2008 casing two rice crop residue burning periods (October–November) using a high volume sampling technique combined with gaseous sampling systems. Gravimetric analysis was used in the estimation of total suspended particulate matter (TSPM) whereas SO2 and NO2 concentration was determined using spectrophotometer (Specord205, Analytikjena). Monthly average concentrations of SPM, SO2 and NO2 have shown significant up and down features at all the selected sampling sites during the study period. Monthly average concentrations (24 hour) of SPM, SO2 and NO2 varied from 100 ± 11 µg m−3 to 547 ± 152 µg m−3, 5 ± 4 µg m−3 to 55 ± 34 µg m−3 and 9 ± 5 µg m−3 to 91 ± 39 µg m−3. Substantially higher concentrations were recorded at the commercial area site as compared to the other sampling sites for all the targeted air pollutants. Levels of SPM, SO2 and NO2 showed clear increase during the burning months (October–November) incorporated with the effect of meteorological parameters especially wind direction, precipitation and atmospheric temperature.

Wind-driven estuarine turbidity maxima in Mandovi Estuary, central west coast of India

Systematic studies on the suspended particulate matter (SPM) measured on a seasonal cycle in the Mandovi Estuary, Goa indicate that the average concentrations of SPM at the regular station are ∼20mg/l, 5mg/l, 19mg/l and 5mg/l for June–September, October–January, February–April and May, respectively. SPM exhibits low-to-moderate correlation with rainfall indicating that SPM is also influenced by other processes. Transect stations reveal that the SPM at sea-end stations of the estuary are at least two orders of magnitude greater than those at the river-end during the monsoon. Estuarine turbidity maximum (ETM) of nearly similar magnitude occurs at the same location in two periods, interrupted by a period with very low SPM concentrations. The ETM occurring in June–September is associated with low salinities; its formation is attributed to the interactions between strong southwesterly winds (5.1–5.6ms−1) and wind-induced waves and tidal currents and, dominant easterly river flow at the mouth of the estuary. The ETM occurring in February–April is associated with high salinity and is conspicuous. The strong NW and SW winds (3.2–3.7ms−1) and wind-driven waves and currents seem to have acted effectively at the mouth of the estuary in developing turbidity maximum. The impact of sea breeze appears nearly same as that of trade winds and cannot be underestimated in sediment resuspension and deposition

Weekend Weekday differences in near-surface ozone concentrations in Chennai, South India

The paper describes the weekend?weekday differences in near-surface ozone (O3) concentration in Chennai, South India. The O3 data measured during 18 January 2006 to 28 February 2006 has been analysed. The result indicated no major difference between the weekdays and weekend profiles for the O3 concentrations. Further, oxides of nitrogen (NOx), carbon monoxide (CO), Suspended Particulate Matter (SPM), wind speed and direction data has also been analysed for the same period. It has been observed that the 24-hour average SPM concentrations exceeded the National Ambient Air Quality Standards (NAAQS) on 26 January 2006 (Thursday), which is a national holiday.

Heavy Metal Content of Suspended Particulate Matter at World’s Largest Ship-Breaking Yard, Alang-Sosiya, India

This study vividly presents results from a seasonal particulate matter measurement campaign conducted at world’s largest ship-breaking yard i.e., Alang-Sosiya (Gujarat, India) at six locations and a reference station at Gopnath which is 30 km south of this ship-breaking yard. The collected suspended particulate matter (SPM) 24-h samples were critically analyzed for heavy metals (Pb, Cd, Co, Ni, Cr, Mn, Fe, Cu, Zn). The average concentration of SPM within the ship-breaking yard during the investigation was 287.5 ± 20.4 μg m−3 and at reference station it was 111.13 ± 5.81 μg m−3. These values are found to be in excess of the permitted national standards. The levels of heavy metals at Alang-Sosiya are very high as compared to US EPA and WHO guidelines. The mean concentrations of all metals are in the order: Fe >>Zn >Cu > Mn > Cd >Pb > Co >Ni >Cr. The results on enrichment factors (EF) suggest that most of the metals in the ship-breaking yard exhibit EF values of near or above 100 which must have been comprehensively affected by ship-breaking activities. Metal data was used to evaluate the role of spatial factors on their distribution characteristics. Thereafter, factor analysis was carried out to identify the main components liable for the variance of the data set.

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 four different 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 microg 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 microg m(-3).

Present scenario of air quality in Delhi: a case study of CNG implementation

The present study discusses the ambient air quality of Delhi from the point of view of change of diesel by Compressed Natural Gas (CNG) in transportation in Delhi. Several initiatives were taken to reduce extremely high levels of pollutants present in the ambient air of urban city. One of the initiatives was to move public transport to CNG, which has been implemented in Delhi since April 2001. Delhi boasted CNG in nearly 2200 buses, 25,000 three wheelers, 6000 taxis and 10,000 cars. However, more than half of the vehicles are yet to be changed to CNG. A relative comparison of ambient air concentration of pollutants, e.g. carbon monoxide (CO), sulphur dioxide (SO2), suspended particulate matter (SPM) and oxides of nitrogen (NOX), emitted from transport sector, during the years 1995–2000 (without CNG) and the year 2001 (with CNG) has been made in order to assess the impact of CNG vehicles on ambient air quality in Delhi. It has been found that concentration contribution of above pollutants has been reduced considerably. The annual average concentration of SPM came down to 347 from 405 μg m−3, which is still beyond the permissible limits. The concentration of annual averages of CO, SO2 and NOX decreased to 4197 from 4681 μg m−3, 14 from 18 μg m−3 and 34 from 36 μg m−3, respectively, and are well within the permissible limits. An analysis of SO2/NOX and CO/NOX concentrations, whose correlation coefficient r2 has the values 0.7613 and 0.7903, respectively, indicates that point sources are contributing to SO2 and mobile sources are contributing to NOX concentrations.