Distribution of lead in relation to size of airborne particulate matter in Islamabad, Pakistan

Particle removal in polluted cities: Insights from the wash-off process dynamics for different wetland plants

Particulate matter (PM) in the atmosphere is a threat to human health. Wetland plants were confirmed to accumulate particles on the leaf surface; at the same time, rainfall could wash-off particles and accelerate the whole removal process, however, the dynamic processes occurring during rainfall events on wetland plants remain unclear. In order to provide sustainable strategies for authorities to take measures, we need to figure out how to reduce PM on leave surface by artificial rainfall efficiently. Four wetland species (Scirpus validus, Typha orientalis, Phragmites australis, and Iris wilsonii) were selected to examine for leave surface accumulation and simulate the experiment. We estimated the wash-off ability of rainfalls with three different intensities (15, 30, and 60 mm h^-1) and determined the proportions of different PM size-fractions washed by the rains. The results showed that particles accumulated on the surface could be washed off efficiently (78% ∼ 89%) by the simulated rainfalls. The removal rates were high in the first 30 min and large particles comprised a large proportion of the removed particles. The rainfall with the intensity of 30 mm h^-1 removed the most particles among three different rainfall intensities. When the rainfall intensity increased, fine particles (PM_2.5) could be washed off more easily. Moreover, with a thinner wax layer, fine particles on wetland plants' leaf surfaces might be more easily removed by the rains. While wash off the plants, spraying rains with the intensity of 30 mm h^-1 for about 30 min every time (high intensity with shorter time) may be particle removal efficiency.

Use of statistical and GIS techniques to assess and predict concentrations of heavy metals in soils of Lahore City, Pakistan

Soils from different land use areas in Lahore City, Pakistan, were analyzed for concentrations of heavy metals-cadmium (Cd), chromium (Cr), nickel (Ni), and lead (Pb). One hundred one samples were randomly collected from six land use areas categorized as park, commercial, agricultural, residential, urban, and industrial. Each sample was analyzed in the laboratory with the tri-acid digestion method. Metal concentrations in each sample were obtained with the use of an atomic absorption spectrophotometer. The statistical techniques of analysis of variance, correlation analysis, and cluster analysis were used to analyze all data. In addition, kriging, a geostatistical procedure supported by ArcGIS, was used to model and predict the spatial concentrations of the four heavy metals-Cd, Cr, Ni, and Pb. The results demonstrated significant correlation among the heavy metals in the urban and industrial areas. The dendogram, and the results associated with the cluster analysis, indicated that the agricultural, commercial, and park areas had high concentrations of Cr, Ni, and Pb. High concentrations of Cd and Ni were also observed in the residential and industrial areas, respectively. The maximum concentrations of both Cd and Pb exceeded world toxic limit values. The kriging method demonstrated increasing spatial diffusion of both Cd and Pb concentrations throughout and beyond the Lahore City area.

Pollution status of Pakistan: a retrospective review on heavy metal contamination of water, soil, and vegetables

Trace heavy metals, such as arsenic, cadmium, lead, chromium, nickel, and mercury, are important environmental pollutants, particularly in areas with high anthropogenic pressure. In addition to these metals, copper, manganese, iron, and zinc are also important trace micronutrients. The presence of trace heavy metals in the atmosphere, soil, and water can cause serious problems to all organisms, and the ubiquitous bioavailability of these heavy metal can result in bioaccumulation in the food chain which especially can be highly dangerous to human health. This study reviews the heavy metal contamination in several areas of Pakistan over the past few years, particularly to assess the heavy metal contamination in water (ground water, surface water, and waste water), soil, sediments, particulate matter, and vegetables. The listed contaminations affect the drinking water quality, ecological environment, and food chain. Moreover, the toxicity induced by contaminated water, soil, and vegetables poses serious threat to human health.

Characterization and source apportionment of ambient air particulate matter (PM2.5) in Karachi

Concentrations and source apportionment of PM(2.5) monitored at an urban residential site in Karachi Metropolitan, Pakistan have been reported in this paper. PM(2.5) aerosol samples were collected on alternative days (three times per week) for 24-hrs duration on Zefluor(TM) filter papers using Thermo-Electron Corporation Reference Ambient Air Sampler (RAAS). A total of 402 samples were collected from January 2006 to January 2008. According to results high PM(2.5) loads were observed in post monsoon months that is about 2 times than those observed in the summer and monsoon seasons in the yearlong measurements. The collected samples were analyzed using ICP-MS for trace metal concentration. Source apportionment was performed on PM samples using Positive Matrix Factorization (PMF) model. The results derived from PMF model indicated five (05) major contributors to PM(2.5) in Karachi which were: soil/road dust, industrial emissions, vehicular emissions, sea salt originated from Arabian Sea and secondary aerosols.

The state of ambient air quality in Pakistan--a review

BACKGROUND AND PURPOSE

Pakistan, during the last decade, has seen an extensive escalation in population growth, urbanization, and industrialization, together with a great increase in motorization and energy use. As a result, a substantial rise has taken place in the types and number of emission sources of various air pollutants. However, due to the lack of air quality management capabilities, the country is suffering from deterioration of air quality. Evidence from various governmental organizations and international bodies has indicated that air pollution is a significant risk to the environment, quality of life, and health of the population. The Government has taken positive steps toward air quality management in the form of the Pakistan Clean Air Program and has recently established a small number of continuous monitoring stations. However, ambient air quality standards have not yet been established. This paper reviews the data being available on the criteria air pollutants: particulate matter (PM), sulfur dioxide, ozone, carbon monoxide, nitrogen dioxide, and lead.

METHODS

Air pollution studies in Pakistan published in both scientific journals and by the Government have been reviewed and the reported concentrations of PM, SO(2), O(3), CO, NO(2), and Pb collated. A comparison of the levels of these air pollutants with the World Health Organization air quality guidelines was carried out.

RESULTS

Particulate matter was the most serious air pollutant in the country. NO(2) has emerged as the second high-risk pollutant. The reported levels of PM, SO(2), CO, NO(2), and Pb were many times higher than the World Health Organization air quality guidelines. Only O(3) concentrations were below the guidelines.

CONCLUSIONS

The current state of air quality calls for immediate action to tackle the poor air quality. The establishment of ambient air quality standards, an extension of the continuous monitoring sites, and the development of emission control strategies are essential.

Statistical analysis of atmospheric trace metals and particulate fractions in Islamabad, Pakistan

Airborne suspended particulate matter was collected on glass fibre filters in urban atmosphere of Islamabad, Pakistan, using high volume sampler. The particulate samples were analysed for 10 selected metals (Fe, Na, Zn, K, Pb, Mn, Cr, Ni, Co and Cd) by FAAS method. Maximum mean contribution was noted for Fe (1.761microg/m(3)), followed by Na (1.661microg/m(3)), Zn (1.021microg/m(3)), K (0.488microg/m(3)) and Pb (0.128microg/m(3)). The particle size determination on vol.% basis for nine fractions (PM(<1.0), PM(1.0-2.5), PM(2.5-5), PM(5-10), PM(10-15), PM(15-25), PM(25-50), PM(50-100) and PM(>100)) was carried out using Mastersizer. PM(5.0-10) were found to be most abundant in the local atmosphere followed by PM(2.5-5.0) and PM(15-25) while coarse/giant particles (PM(50-100) and PM(>100)) showed lower contribution. The trace metals were found to be mainly associated with smaller particulate fractions up to PM(10-15). Among the climatic parameters temperature has significant relationship with fine particles and airborne metal levels while relative humidity showed negative correlation. The source identification was carried out by principal component analysis and cluster analysis. Five metal sources were identified: industrial, vehicular emissions, metallurgical operations, garbage incineration and soil derived dust. The metal levels were also compared with those reported for other rural and urban parts around the world.

Characterization, source identification and apportionment of selected metals in TSP in an urban atmosphere

To understand the metal distribution characteristics in the atmosphere of urban Islamabad, total suspended particulate (TSP) samples were collected on daily 12 h basis, at Quaid-i-Azam University campus, using high volume sampler. The TSP samples were treated with HNO(3)/HClO(4) based wet digestion method for the quantification of eight selected metals; Fe, Zn, Pb, Mn, Cr, Co, Ni and Cd by FAAS method. The monitoring period ran from June 2001 to January 2002, with a total of 194 samples collected on cellulose filters. Effects of different meteorological conditions such as temperature, relative humidity, wind speed and wind direction on selected metal levels were interpreted by means of multivariate statistical approach. Enhanced metal levels for Fe (930 ng/m(3)), Zn (542 ng/m(3)) and Pb (210 ng/m(3)) were found on the mean scale while Mn, Cr, Co and Ni emerged as minor contributors. Statistical correlation study was also conducted and a strong correlation was observed between Pb-Cr (r=0.611). The relative humidity showed some significant influence on atmospheric metal distribution while other meteorological parameters showed weak relationship with TSP metal levels. Regarding the origin of sources of heavy metals in TSP, the statistical procedure identified three source profiles; automobile emissions, industrial/metallurgical units, and natural soil dust. The metal levels were also compared with those reported for other parts of the world which showed that the metal levels in urban atmosphere of Islamabad are in exceedence than those of European industrial and urban sites while comparable with some Asian sites.

Comparative metal distribution in hair of Pakistani and Libyan population and source identification by multivariate analysis

Using nitric acid-perchloric acid wet digestion based FAAS method ten selected metals (Cd, Co, Cr, Fe, K, Mn, Na, Ni, Pb and Zn) were determined in the scalp hair of male Pakistani and Libyan donors (n = 62), between 3-54 years age and residing in typical urban areas. The study was taken up to identify sources of metal distribution in two diverse population segments exposed to different environments. Sodium emerged with the highest mean hair concentration of 511.0 microg/g and 496.9 mug/g for Libyan and Pakistani donors respectively, followed by K, at 266.2 microg/g and 242.4 microg/g for the two donor categories. Cadmium showed the lowest mean hair concentration for both Pakistani (0.380 microg/g) and Libyan (0.530 microg/g) donors. Levels of Na, K, Pb, Cr and Cd were higher in hair of Libyan donors compared with Pakistani counterparts which showed higher comparative levels of Zn, Fe, Co, Ni and Mn. Strong metal-to-metal correlations were found between Na-K (r = 0.638) and Cd-Co (r = 0.574) for Pakistani donors, while for Libyan donors, Na-K (r = 0.680) and Fe-Mn (r = 0.624) correlations emerged as strongly significant. Only K was found to have a strong positive correlation (r = 0.611) with age for Pakistani donors while this correlation was significantly negative (r = -0.500) for Libyan donors, probably arising from individual food habits. Other metals showed no viable relationship with age. Principal Component Analysis (PCA) and Cluster Analysis (CA) of the data evidenced food, industrial emissions and automobile emissions as possible sources of metal distribution. The results of the present study are compared with those reported for subjects from other regions of the world.

Spatial variations in selected metal contents and particle size distribution in an urban and rural atmosphere of Islamabad, Pakistan

Spatial variations in total suspended particulate matter (TSP) were investigated for distribution of metals and particle size fractions in the urban and rural atmosphere of Islamabad, Pakistan. The metals Na, K, Fe, Mn, Pb, Cd, Cr, Zn, Ni and Co, and the particle fractions <2.5, 2.5-10, 10-100 and >100 microm were included in the study. TSP samples were trapped on glass fibre filters using high volume samplers and quantification of metals was done using Atomic Absorption Spectrometry employing HNO(3) based wet digestion. At the urban site, Na was dominant at 2.384 microg/m(3) followed by K, Fe and Zn with 0.778, 0.667 and 0.567 microg/m(3) as mean concentrations, respectively. The metal levels for the rural site ranged from 0.002 microg/m(3) for Cd to 1.077 microg/m(3) for Na. However, compared with the urban site, mean Pb concentration showed an almost two-fold enhancement, i.e., 0.163 Vs. 0.327 microg/m(3). Metals and particle size source identification was done using Principal Component Analysis and Cluster Analysis. Five sources were traced out for the urban site: industrial, soil, automobile emissions, metallurgical industries and excavation activities. For the rural site, four sources were recorded: agricultural, automotive emissions, excavation activities and metallurgical units. Collectively, for both the sites, PM(10-100) emerged as a major contributor to TSP, followed by PM(2.5-10), PM(<2.5) and PM(>100) in that order. The metals showed in general positive relationship with fine particulate fractions (PM(2.5-10), PM(<2.5)), and negative correlation with coarse fractions (PM(10-100), PM(>100)). Comparison with the corresponding data from various Asian sites revealed that the levels of Na, K, Fe, Mn, Co and Ni for the present study were lower than those reported for grossly polluted cities of the world.