1. By Maryum Atique M.Phill chemistry University of Agriculture

2.  The term heavy metal refers to any metallic chemical element that has a relatively high density and is toxic or poisonous at low concentrations. They cannot be degraded or destroyed.  Examples of heavy metals include mercury (Hg), cadmium (Cd), arsenic (As), chromium (Cr), thallium (Tl), and lead (Pb).

3. Most air toxics originate from anthropogenic sources like  Mobile sources (e.g., cars, trucks, buses)  Stationary sources (e.g., factories, refineries, power plants), and even released from  Natural sources such as volcanic eruptions and forest fires.

4.  Heavy metals presents in trace concentration play a major role in metabolism. Some metals, such as iron, chromium and copper, are needed in small quantities to keep people and animals healthy.  Further their increased in concentration may have several toxicological effects on human beings.  Heavy metal exposure causes serious health effects, including reduced growth and development, cancer, nervous system damage, and in extreme cases, death.

5.  Sample collection  Sample preparation  Instrumental analysis

6.  Collection of samples from different regions.  Sample is collected from Rural and Urban areas.  Industrial and residential areas.  Collection in polyethylene bags to minimize sample loss.  Protected from light and kept at low temperature.

7.  Air Filter Samples  Sampling pumps  Stopwatch and bubble tube or meter for pump calibration.  De ionized water.

8. Methods Of Preparation 1. Microwave Extraction 2. Hot Acid Extraction

9.  Cutting of filter paper  Extraction in acids  HCl 8 %, HNO 3 3 %  Calibration of Microwave oven  Use of digestion vessel

10.  Take filter strips in a beaker  Refluxing on hot plate  Use 10 ml of 8 % HCl and 3 % of HNO 3 solution  Filtration of digestate

11.  Technologies for metal analysis  Atomic absorption spectroscopy  Flame atomic absorption spectroscopy

12.  For absorption, a hollow cathode lamp or an electrodeless discharge lamp (EDL) is used as the light source.  A double beam spectrophotometer is normally used where the lamp radiation alternately passes through and around a flame into which the sample is being aspirated. The sample is atomized and the metal or metalloid atoms absorb light.

13.  This absorption is proportional to the concentration of the element present in the sample solution. A monochromator isolates the characteristic radiation of the element being analyzed.  A photosensitive device then measures the intensity of the transmitted radiation from the two light paths to determine the amount of absorbance occurring in the flame.

14. For emission, a light source is not used. The sample is introduced into the flame, atomized and excited, and then the light emission from excitation is isolated and measured. The intensity of the light emitted is proportional to the concentration of the element present.  flames used are:  a) Air/Acetylene mixture (Air/C2H2)  b) Nitrous oxide/Acetylene mixture (N2O/C2H2)  c) Air/Hydrogen mixture (Air/H2)  The use of a specific flame is dependent on the respective element's analytical stability

15. Analytical technique differ in terms of 1. Sensitivity 2. Cost of analysis 3. Requirements for sample preparation AAS Sensitivity Selectivity Accuracy Reproducibility Low cost

16.  Atomic absorption spectroscopy Flame atomic absorption spectroscopy Graphite furnace atomic absorption spectroscopy  Inductively coupled plasma emission spectroscopy  Neutron Activation analysis  Electron microscopy

17.  Exposures to airborne metals are known to cause physiological responses in organisms and health effects in humans. Hence determination of metals is important from a toxicological perspective.  Significant positive correlation among metals lead and copper suggests that they originate mostly from a common source.  Air samples of urban and industrial areas showed higher concentrations than residential (Urban) and suburban areas.