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General Introduction

NBE at Oasis is located in the city center of the Patan at the close vicinity of the Patan Gate. This area can commonly be considered as the commercial cum residential area of the Patan city. Various commercial and technical enterprises are in housed with in this location. The production of electronic components here was hypothetically considered to be one of the major contributor of air pollution for this location. Similarly the operation of hot water generator and diesel generator also releases considerable quantity of the air pollutants into the ambient atmosphere. Emission of the pollutants into the ambient atmosphere, if high, could severely affect the ambient atmosphere of the vicinity which is against the established legal provision. Therefore it was imperative to know the levels of pollution discharge cumulatively by the various activities prevailing inside the Oasis and to adopt appropriate mitigation measures, if the emission level found high, to prevent the high levels of emission of the pollutants into the ambient atmosphere. Such investigation requires the monitoring of the air quality at emission point of the complex.

Objective of the Study

The main objective of this study is to find out the pollution emission levels of NBE and to assess the obtained air quality data in relation to the human health effects and prevailing background air quality levels. However following are the specific objectives of this study:

  •  Monitoring of the air quality at the emission point of NBE.
  •  Assessment of the obtained air quality data with respect to the human health and background urban air quality levels.


To execute the above mentioned tasks following methodologies have been adopted:

  • Selection of the sampling point: As the main objective is to find out the air quality emission levels of NBE and its implication on the local environment, the monitoring point was selected: very close to the exhaust where pollutants generated at different parts of the industry is drawn and ultimately discharged.

  •  Selection of the air quality parameters: The various activities prevailing inside the industry may generate particulate matters and discharge through the exhaust outlet. Likewise the electronic works carried out in the component production unit may emit high levels of metals and use of the different types of fuels at various sections of NBE may increase particulate matters along with other gaseous pollutants such as SO2 & NO2. Therefore the air quality parameters TSP, PM10, SO2, NO2 and heavy metals specifically chromium, copper and lead were selected for the monitoring of the exhaust air quality of this complex.

  •  Collection of the air samples: The air samples for the TSP and PM10 were collected by the use of High Volume Air Sampler (HVAS). The HVAS was operated for the period of the nine hours at the suction rate of 1 m3/minute and the sampling height was adjusted at the emission level of the exhaust. The PM10 were collected in the tarred glass filter whereas the coarse particles were collected into the cup of the instrument. Trace metals lead; copper and chromium were also determined in the collected PM10. As far as the collection of the SO2 & NO2 is concerned they were collected by active absorption method using gaseous collection unit attached with the HVAS. The air at controlled flow was passed through the impingners filled with absorbents tetrachloromercurate and sodium arsenite for SO2 and NO2 respectively.

  •  Determination: Particulate matters present in the exhaust air was determined by gravimetric method. The samples for both TSP and PM10 were conditioned for 48 hours inside the silica gel desiccators and weighted. From the increased weight of the cup and filter paper, concentration of both TSP and PM10 were calculated. The collected sample of SO2 was treated with formaldehyde and pararosaline whereas the intensity of the developed color was measured by spectrophotometer to estimate SO2 concentration. Similarly collected sample of the NO2 was treated with NEDA and sulfanilamide solution to develop pink color. The intensity of the developed color is then measured by spectrophotometric method. Collected PM10 sample was digested with nitric acid to leach out the metals. After digestion it was filtered and the residue was washed with warm diluted solution of the acid to wash down all the metals. Then the filtrate was heated over the hot plate to reduce the volume at required extent. After that fixed volume of the solution was prepared and determination of the lead, copper and chromium was carried out by AAS.

Result and Discussion

The obtained monitoring data of all air quality parameters are given in the table below:

Air Quality Data

Observed value (µg/m3) NAAQS Guideline Value (µg/m3)

Field Observation Data:

Weather :   
Initial flow-meter reading
Final flow-meter reading
NOx initial flow (litre/min)
NOx final flow (litre/min)
SOx initial flow (litre/min)
28 oC
SOx final flow (litre/min)
Initial temperature
Final temperature
Initial rotameter reading
Final rotameter reading
9:10 AM / 27 May 2005
Running hours
18:10 PM / 27 May 2005
Start time
9:00 AM - 17:00 PM
End time
Office hours

The obtained air quality data at the emission point reveals that no significant levels of air pollutants have been discharged by NBE / Oasis into the local atmosphere. Though the levels of both TSP and PM10 were found slightly above the recommended NAAQS guideline values, observed levels of the TSP and PM10 may not be the consequences of the complex activities and its emission because high concentrations of TSP and PM10 usually prevail on the ambient atmosphere of the Katmandu valley. Likewise the concentration of the gaseous pollutants particularly SO2 and NO2 seems very low or below the detection, which proves that, NBE / Oasis does not generate and emit any gaseous pollutants into the local environment. As far as the observed concentration of the heavy metals is concerned, the observed data indicates that trace levels of chromium, copper, manganese and except iron were detected from the exhausted air of NBE / Oasis. However their concentrations are at low risk levels.

Conclusion and Recommendations:

From the observed air quality data, it can be concluded that NBE has not discharged significant levels of air pollutants that can cause deterioration of the local atmosphere and cause serious ill effects to the local residents. However the observed level of the chromium seems above the average ambient air concentration of the urban centers. Based on the observed air quality data following recommendation are made:

  • This result reflects the exhaust air quality of NBE only of the particular day and time. To understand the status of the average emission levels it is recommended to carry out air quality monitoring on regular and systematic manner.
  • During the monitoring, there was no operation of the boiler. Boiler and generator operation could be significant potential source of the air pollution for this complex. Therefore it is recommended to carry out the air quality monitoring during the operation of the boiler / generator also.

Dr. Narayan Pd. Upadhyaya
Director, Chief, Water Quality & Laboratory Division
Water Engg and Training Center ( P ) Ltd,
Ga 1/262, Dillibazar,
P.O.Box# 8975, EPC 5205
Kathmandu, Nepal
22 June 200