Abstract:Fractionation of heavy metals helps to determine their binding form, toxicity, and availability in terrestrial environments. Wastewater irrigation may lead to the accumulation of these metals in soil and plants. Wastewater irrigated soils and vegetables were collected from 6 sites in the vicinity of Lahore and analyzed for cadmium, nickel, chromium, zinc, manganese, cobalt, and copper. The quality of wastewater used for growing crops was also determined. In soil, sequential extraction was adopted to demarcate 5 metal fractions: exchangeable, acid-soluble, reducible, oxidizable, and residual, which were quantified by inductively coupled plasma optical emission spectrometry. The accumulations of these metals in vegetables (spinach and bitter gourd) were also assessed and it was found that concentrations of all studied toxic metals in edible parts of the vegetables were above the critical level. The total metal contents in soil were in the order of Mn > Co > Zn > Cr > Ni > Cu > Cd. Correlation analysis between metal concentrations in different fractions of soil and vegetables was performed at 95% and 99% confidence levels. Positive and negative correlations were observed; positive values indicated the bioavailability of these metal fractions to vegetables, while negative values showed that metal concentrations in particular fractions were not bioavailable to plants.
Lahore is a mega city of Pakistan located in South Asia having more than 1.5 million populations. Motor vehicles are the major sources of pollution in this city. This study is focused on the measurement of air pollution levels due to congested traffic in Lahore city. The average results of two-wheeler and four-wheeler vehicles using petrol as fuel showed that the level of CO2 was in the range of 2.20-8.80 %, NO2 from 0.00-83.33 ppm, SO2 99.67-799.33 ppm and hydrocarbons in the range of 77.33-550 ppm. Vehicles using compressed natural gas as fuel showed CO2 was in the range 1.44-9.80 %, NO2, 10.22-25.37 ppm, SO2 zero emissions and hydrocarbons 4.36-13.66 ppm. Vehicle exhaust emission data showed that Lahore city is exposed to high concentration of CO2, NOx and SOx. The overall results of study showed that compressed natural gas is more environment friendly fuel as compared to petrol. However, pollution level can considerably improve by introduction of large-scale compressed natural gas vehicles in Lahore city.
The organic photodetectors (OPDs) with an interdigitated electrodes (IDEs) structure are analyzed to evaluate the optical crosstalk between neighboring pixels for the organic image sensor used in the fingerprint-on-display (FOD) authentication system. The shorter exciton diffusion length of organic semiconductors in the OPD can promote the high resolution of the organic image sensor for full-display sensing applications. We demonstrated the photocurrent diffusion from the exposed area to the hidden electrodes by changing the distance to predict the minimum pixel pitch for the organic image sensor. Unexpectedly, the photocurrent diffusion was observed, even at 10 µm length, as more significant than the expected exciton diffusion length.
The problem of soil and water contamination in many countries has become major issue and thus immediate measures are necessary to avoid further environmental damage. Heavy metals and metalloids, which are toxic and carcinogenic to living organism, mainly enter into the soil and water system due to anthropogenic activities which includes metal processing, mining operations, refinery industries, tannery industries, army activities and landfills 1,2 .Leather industries in Pakistan produce all type of waste that is wastewater, solid waste and air emission. The discharge of untreated wastewater produces number of problems to local community, spoil the civic beauty of area and pollute water sources. The levels of chromium in soil near tannery areas were found beyond the safe limits 3 . Long term wastewater irrigation can cause accumulation of heavy metals in agricultural soil and plants. Heavy metals like zinc, manganese, nickel and copper act as micronutrients at lower concentrations however they become toxic at higher concentrations. Health risk due to heavy metal contamination of soil has been widely reported [4][5][6] .Heavy metals like chromium and lead may be tolerated in lower concentration but are harmful in higher concentration 7 . Plants are non-specific while taking-up metals from soil. Nonessential heavy metals such as arsenic, cadmium, chromium, mercury and lead present in soil would also be accumulated
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