Air Quality Assessment in the Vicinity of Quarry Site

This study investigated air pollutants associated with quarry activities and the variation of the pollutants with distance from the drilling section. Air pollutants were monitored with the use of automatic air samplers with the exception of ozone (O3) which was determined by iodometric method. All sampling were replicated three times. The data obtained were subjected to descriptive statistics, analysis of variance and correlation. Means were separated using Duncan Multiple Range test. Carbon monoxide and carbon dioxide were detected while sulphur dioxide, nitrogen oxide and O3 were below detection limit. Suspended particulates were the most significant of the air pollutants analyzed. Crushing section had the highest concentrations of PM10 and PM2.5 with 0.231 ± 0.018 mg/m and 0.130 ± 0.010 mg/m respectively followed by the drilling section with 0.074 ± 0.066 mg/m for PM10 and 0.065 ± 0.045 mg/m3 for PM2.5. The mean levels of the total suspended particulate decreased significantly (p < 0.05) with distance from the crushing section to Jagun village. Keyeord: air, quality, quarry site


Introduction
The process of getting useful stone from a quarry is known as quarrying.The methods and equipment used in quarry depend on the purpose for which the stone is extracted.Different quarrying activities have different impacts on air quality (Alaturca, 2012).The process of making holes in rock, limestone or overburden with the aid of a drilling machine (drilling process) may be treated as a point source of pollutant emission.Shattering the drilled limestone or overburden in a bid to loosen the mass in smaller fragments (blasting process) may be treated as an instantaneous point source for suspended particulate.Also, the loading and movement of dumper trucks on haul routes would generate suspended particulates while the crushing of ore and transferring it to a belt conveyor (ore processing) would be a potential source of dust generation.Loading and movement of vehicles may be treated as point and line sources.Mineral exploration, mining and processing have resulted in environmental damages including ecological disturbance, destruction of natural flora, pollution of air, land and water, instability of soil and rock masses, landscape degradation and radiation hazards (Aigbedion & Iyayi, 2007) .Dust is the main source of air pollution in quarry industry.The extent of pollution by dust depends on the local microclimate conditions, the concentration of dust particles in the ambient air, the size of the dust particles and their chemistry (Hsin-Yi, 2012).Dust has effect both on human health and the natural environment.It can lead to chronic health effects for instance decreased lung capacity and lung cancer resulting from long-term exposure to toxic air pollutants (Sunyer, 2001).However, it blocks and damages the internal structure and abrasion of leaves and cuticles (Hsin-Yi, 2012).The number of quarrying industries in Ogun State, Nigeria is kept on increasing.Although it contributes to the internally generated revenue, there is need to look at its effect on the neigbouring communities and the environment in general.Work has been done on the levels of heavy metals in soil and vegetation of a quarry site (Bada & Fagbayibgo, 2009) and on the level of suspended particulates in the ambient air and around selected quarry sites (Oguntoke et al., 2009) but much work has not been done on the effect of quarry activities in relation to the emission of greenhouse gases and suspended particulates.The objectives of this study were to identify the various air pollutants associated with quarry activities and determine the variation in the concentration of the pollutants with respect to the distance from the drilling section.

Location of the Company
This study was carried out in the vicinity of a quarry company, FW SAN HE CONCEPTS LIMITED, along Abeokuta-Ibadan road, Odeda Local Government Area, Ogun State, Nigeria. Figure 1 shows the location of the company in Odeda Local Government Area, Ogun State, Nigeria.The quarry company engages in the production of granite for sale to construction companies and registered agents.The climate of Abeokuta follows a tropical pattern with the rainy season lasting for between seven and eight months between April and October with an interruption in August and the dry season running through November till February.The maximum temperature, minimum temperature, total rainfall, relative humidity, sunshine, wind speed and evaporation for the month of December, 2010 (sampling month) were 31.9ºC, 22.4 ºC, 0.00 mm, 81.1%, 7.2 hours, 0.09 km/hr (2.05 km/day) and 3.0 mm respectively (FUNAAB, Meteorological Station, 2010).

Sample Collection and Analysis
Ambient air samples were taken in the major activities areas of the quarry such as the drilling point, crushing section, loading section, generator house, workshop, administrative section and Jagun village (Table 1).Active sampler was used for all the parameter except ground level ozone where iodometric method was used (Table 2).Active sampling makes use of pump to pull air through filter while iodometric method involves titration.Average time for sampling was 1 hour for active sampler and 72 hours for iodometric method.Sampling was carried out in the afternoon and replicated times.
The parameters measured in the sampled air were sulphur dioxide (SO 2 ), oxides of nitrogen (NO X ), carbon monoxide (CO), carbon dioxide (CO 2 ) and ground level ozone (O 3 ).Total Suspended Particulates (TSP), respirable and inhalable particulates (PM 2.5 and PM 10 ) were also measured.

Statistical Analysis
The data obtained were subjected to descriptive statistics, analysis of variance and correlation.The significance of the treatment means were determined using Duncan Multiple Range (DMR) test.

Results
Sulphur dioxide (SO 2 ), oxides of nitrogen (NO X ) and ozone (O 3 ) concentrations in the ambient air were below detection limit (Table 3).Concentration of carbon monoxide (CO) was highest in the drilling point followed by the crushing section, loading section and workshop place.Generator house had the least concentration of CO.Significantly (p < 0.05) higher carbon dioxide (CO 2 ) was observed at the village and drilling section with mean values of 1.74 ± 0.45% and 1.38 ± 0.50% respectively.
Significantly (p < 0.05) higher PM 10 was observed at the crushing and loading sections (Table 4).The least significant (p < 0.05) values of PM 10 were observed at administrative section and Jagun village.For PM 2.5 , significantly (p < 0.05) higher concentration was observed at the crushing section followed by the drilling section and loading section.Total suspended particulates decreased with distance from the crushing section (Table 4).

Discussion
The levels of carbon dioxide (CO 2 ) in the village and drilling point were significantly (p < 0.05) higher than other locations.The high level experienced at the village might be due to the use of fire wood for cooking and the proximity of the sampling points to the main road in the village.Bada and Akande (2010) stated that vehicular emission contribute to the concentration of CO 2 in the atmosphere.Carbon monoxide (CO) concentration was significantly (p < 0.05) higher at the drilling point and crushing section.This might be due to the incomplete combustion of fuel by heavy duty machineries used in the drilling and crushing activities of quarrying.However, the values were below the Standard of 9 ppm (USEPA, 1996).However, sulphur dioxide (SO 2 ), oxides of nitrogen (NO X ) and Ozone (O 3 ) in the ambient air of the sampling sites were below detection limit.Chaulya (2005) stated that emission of SO 2 and NO X are negligible.This is also in agreement with the prediction of the United State Environmental Protection Agency (USEPA) that Mean levels of PM 10 at both the drilling and the crushing sections were higher than the permissible level of 50 µg/m 3 (WHO, 2005).However, PM 2.5 concentration at the crushing and drilling section were higher than the permissible limit of 35 µg/m 3 (USEPA, 1996) and 25 µg/m 3 (WHO, 2005).These particles may therefore lodge in human lungs, thereby causing lung damages and respiratory problems (Last, 1998).The mean values of Total Suspended Particulates (TSP) in all the sampling locations were higher than the permissible level of 230 µg/m 3 (World Bank, 1998).Particulate matter in the air are transported from the point of generation to areas far removed (UNEP, 1991).
Significant (p < 0.05) positive correlation was observed between carbon monoxide (CO) and particulate matter (PM 2.5 and PM 10 ).This might be an indication that the pollutants were emitted from the same source.PM 2.5 and PM 10 showed significant (p < 0.01) positive correlation.These pollutants were associated and released from the same source (USEPA, 2008).

Conclusion
Quarry activities released air pollutants into the environment.Air pollutants such as Total Suspended Particulates (TSP), particulate matter (PM 2.5 and PM 10 ) and greenhouse gases like CO and CO 2 were detected while SO 2 , NO x and ozone were below the detection limit.Highest levels of PM 2.5 , PM 10 and TSP were generated at the crushing section.
For sustainable quarry activities, quarry site should be located in the interior surrounded by adequate vegetation which would act as sinks and block for various emissions emanating from the quarry.Inhabitant of the area where a quarry is to be sited should be relocated to prevent the impact of the emissions generated by the quarry industries on them.

Figure1.
Figure1.Location of the company in Odeda Local Government Area, Ogun State, Nigeria

Table 1 .
Distance and coordinates of sampling locations with respect to the drilling point

Table 3 .
Mean levels of gaseous pollutants in the vicinity of quarry site

Table 4 .
Mean levels of particulate matters (mg/m 3 ) in the vicinity of quarry site suspended particulate matter is quite outstanding among the pollutants emanating from quarry operations (USEPA, 2008).