This chapter is aimed to study the impact of pollution by the industries in and around Patancheru upon the physical environment of Nakkavagu basin. The physical environment plays an important role in the mobilisation, dispersion, dilution or concentration of the pollutants in the environment. Regarding the physical environment and on relevant themes several people have worked, some of them are (Tank (1973), David (1977), Cooke (1978), Howard (1978) and Leveson (1980)). Physical environment studies help in understanding the present status of pollution and also the carrying capacities of the study area with respect to pollution. The geology, topography, soils, climate, meteorology and air quality are the parameters considered in this chapter for describing the physical environment of Nakkavagu basin.
The geology of the area plays an important role in the mobility and concentration of pollutants released into the environment. The composition and the type of rocks (Igneous or Sedimentary or Metamorphic) and the structures in them such as joints, fractures, fissures, etc. are important in understanding the behaviour of pollutants.
In the Nakkavagu basin and its surrounding areas, the Archaean Peninsular granites and gneisses form the basement, which is overlaid by the Deccan basalt, is the basic geology of the area (Table 2.1).
Table 2.1 The Geological Succession
The grey and pink granite outcrops are seen around Patancheru, on the western and south-western parts, they are overlaid by isolated cappings of basalt and laterite. Granite outcrops in Nakkavagu stream-bed near Bachuguda are shown in Photo 2.1. Dyke outcrops are not seen along the Nakkavagu stream (although dolerite dykes and quartz veins are observed in adjacent areas) because of thick alluvium deposited along the stream. The flood plains of the streams are occupied by recent and older alluvium, mainly consisting of sand, silt and clay in different proportions and thickness varying from 25 to 30 feet. The recent sand and gravel deposited along the banks of Nakkavagu near Bachuguda is shown in Photo 2.2. The lateral extent of alluvium along Nakkavagu is about 250 to 500 meters. Alluvium is mainly found along Nakkavagu near these villages, they are Pocharam, Ganapathigudem, Bachuguda, Arutla, Peddakanjerla and Inole. Black cotton soils derived from the basalt occupy the lower reaches, mainly to the western and north-western parts of Patancheru. The percentage of outcrop exposure is less around Patancheru and at higher contour levels granite outcrops are exposed in the form of kopjes, tors and sheet rocks.
The outcrops are largely exposed to the north-western parts of Patancheru which are studied in detail by Sarvotham and Leelanandam (1987), reveals the nature of Peninsular granite and gneisses and other lithological units. The Peninsular granites and gneisses studied in this region is classified as granodiorite, granite, adamellite (quartz-monzonite), monzodiorite and alkali feldspar granite, which are emplaced as discrete plutons; they form part of a composite batholith and contain inclusions of tonalite quartz-diorite and amphibolite. Alkali feldspar granite intrudes and truncates all the above litho-units, and represents the youngest of the granitic emplacements. A swarm of dolerite and gabbro dykes intruding into the granites and gneisses. At least two sets of dykes are discernable; one set is pre-alkali feldspar granite and the other of post- alkali feldspar granite ages. The older set of dykes are metamorphosed and intruded by alkali feldspar granite veins, while the younger dykes are unaffected (Sarvotham and Leelanandam, 1987). Petrographic and petrochemical studies indicate that the Medak area (along with the adjoining terrain) is dominated by potassic granites, (Bhaskar Rao et al, 1983 and Naqvi et al, 1983).
The structures have a control on the local topography and hydrogeology of the area. Fractures and joints in granites are responsible for the formation of huge boulders and other geomorphic structures such as tors. The width of the joints varies, at places they are 1 to 2 meters wide. The joints filled with weathered material are important, as they are good aquifers. These granitoids show a prominent two to three sets of joints in NNW-SSE, N-S and NE-SW directions. The lineaments of the region are in NNE-SSW, NE-SW and NW-SE directions mainly and very few are in E-W and N-S directions, which are represented by the flow of streams and the dykes and shear zones. The quartz reefs have the trend of NNE-SSW, NE-SW, N-S and a few are in the E-W directions. Dolerite dykes are emplaced in the trend of NW-SE, NE-SW, E-W and N-S.
The topography of an area also influences the drainage system and the groundwater movement. The Nakkavagu basin forms a peneplain surface of the ancient Deccan Peninsula that had undergone several cycles of erosion, deposition and upliftment. Sporadic granitic tors, kopjes and sheets of bedrock are seen in the region. The lands are rolling plains interspersed with stony wastes and open scrubs. Isukavagu, Pamulavagu and Nakkavagu mainly drain the basin. The slope is from east to west up to Nakkavagu and it is south to north and north-west up to Manjira river. The land has a slope of 0.5 percentage. The relief of the basin is about 140 meters. The lowest contour is 500 meters above mean sea level (msl) lies near Gaudcherla at the confluence point with Manjira River. The highest contour passing through the Nakkavagu basin is 640 meters above mean sea level. The highest point 648 meters above mean sea level lies to the North of Gumadidala village, located to the eastern part of Nakkavagu basin.
Nakkavagu basin has rich diverse and fertile soils (Table 2.2 and Figure 2.1).
Table 2.2 The soil of Nakkavagu basin as classified by ICRISAT, Patancheru.
Type of series
(Source: EIA report on the proposed Thermal power plant by National Thermal Power Corporation (NTPC) at Shankarpalli, M/s Kirloskar Consultants Limited, Pune, 1996-97.)
To sum up the black soils comprising of clay loam’s, clays and silty clays are found in the low-lying areas and along the river-banks. Alluvial black cotton soils are found along most stream flood plains (Photo 2.3), while secondary black cotton soils are present in the upland areas in basaltic terrain. The upland areas mainly comprise of red soils, loamy sands and sandy clay loams. The soils in Sangareddy, Patancheru and Ramachandrapuram mandals of Medak mainly comprises of clayey loams, clays and silty clay. They are moderate to well drained and are suitable for cultivation by irrigation.
Black cotton soils are locally known as ‘Regadi matti’. These types of soils develop deep wedge shaped open cracks, helps in tapping the atmospheric nitrogen too. They have the moisture retaining capacity and are best suitable for dry land farming. Black cotton soils are inherently more fertile then red soils. Black soils are slightly saline to alkaline, whereas red soils are neutral. Black cotton soils are suitable for crops like cotton, rice, sugarcane, and other kharif and rabi crops. Red soils are suitable for horticultural crops. Alluvium is mainly suitable for paddy. Salts dissolved and deposited in the valleys will increase soluble salt content in the soils in low-lying areas. Soils are slightly calcareous in areas immediately adjacent to Nakkavagu and more calcareous in the upper reaches of soil profile, forming salt incrustations (Photo 2.4 and 2.5). Saline soils lead to relatively poor germination and leads to physiological drought, thereby effecting the growth of the plants. The industrial effluents caused phyto-toxicity to the crops and also total crop failures. The analysis data of the soils along Nakkavagu are presented in Table 2.3.
Table 2.3 Soil analysis of the fields along Nakkavagu area.
Ranges of soil reaction to Electrical Conductivity (in micromho / cm)
2.5 CLIMATE AND METEOROLOGY
The meteorological data is important in interpreting the air quality and dispersion pattern of pollution. Analysis of recorded historical meteorological data is important in predicting the likely climatic scenario of the region. The climate of the region is broadly divided into four seasons.
· Pre-monsoon season : March to Mid of June
· Monsoon season : Mid of June to end of September
· Post-monsoon season : October to Mid December
· Winter season : Mid of December to end of February
The data is obtained from the Indian Meteorological Department (IMD) – meteorological station located at Begumpet 25 kilometers to the east of Patancheru. It is equipped to observe pressure, temperature, relative humidity, rainfall, evaporation, wind speed and direction, duration of cloud cover, etc. It is in operation since 1891. The synthesised data is pertaining to the period between 1985 and 1994. Rainfall data, for the study area was collected from the local recording stations at Patancheru, Jinnaram and Ramachandrapuram Mandals, rainfall and temperature data of Sangareddy Mandal was also collected.
Temperature conditions of the region has an influence on movement of air, precipitation, formation of fog, evaporation rate, atmospheric pressure, etc., therefore temperature influences directly or indirectly the dispersion, concentration or dilution of pollutants released into the environment.
January is the coldest season with mean daily minimum temperature at 10.3 0 C. Between March and May is the hottest season with increasing day and night temperatures till the onset of Monsoon. The highest pre-monsoon (May) mean maximum temperature is observed at 43.9 0 C and mean minimum temperature observed is 20.3 0 C. Onset of monsoon results in sudden drop in mean maximum temperature, for June it is 39.9 0 C. During post-monsoon season there is a slight increase in mean maximum temperature and it is 36.3 0 C in October. The climate appears enervating during daytime, with relative moisture being high. An appreciable drop in minimum temperatures are observed in nights during the post-monsoon season which is between 10.9 0 C and 14.5 0 C in comparison to the temperatures during monsoon season which is between 19.6 0 C and 20.3 0 C. Average monthly maximum and minimum temperature recordings at Sangareddy (1991-94) are presented in Figure 2.2.
The concentration of the pollutants in the effluents increases with increase in evaporation rate. The concentrated effluents are more toxic then diluted effluents. In the tropical areas one of the extensively used methods of treatment of effluents is by letting of effluents into solar – evaporation ponds, where the water gets evaporated under intense tropical sunlight, leaving behind sludge which is dried and disposed in the secure landfill sites. Such a treatment process is effective where evaporation rates are high. The evaporation rate also depends on the solar radiation, cloud cover, wind, etc.
Evaporation rate increases from February through June. A steep fall in evaporation rate is observed during the first half of south-west monsoon season. Maximum evaporation rate is observed in May at 16.2 mm with minimum occurring in November at 7.6 mm. Evaporation rate does not change much in all other seasons.
The total solar radiation levels direct and diffuse are between 15.2 MJm-2 day-1 and 24.3 MJm-2 day-1. Minimum radiation levels are recorded in the month of July and Maximum levels recorded in the month of May.
During winter season clear bright weather prevails with clear to lightly clouded skies. During the onset of south-west monsoon sky appears moderately to heavily clouded.
Dilution is an important factor in lessening the adverse impacts of pollution. Precipitation is one of the natural diluting factors of the polluted waters. The problems of salt incrustations in the soils would not exist in areas with heavy rainfall. The residence time of the pollutants in a basin would be less with heavy rainfall.
The average annual rainfall for the 10years period is 802.8 mm as recorded at IMD, Hyderabad. About 85 % of the rainfall is received during south-west monsoon season. Maximum rainy days occur in the month of July. District average rainfall from 1981-82 to 1993-94 is presented in Figure 2.3.
2.5.4 Wind Speed and Direction
Wind speed and direction are very much important in case of air pollution studies and its impact on the residential population around the industrial areas. High-speed winds disperse suspended particulate matter and other pollutants to far off places, thereby lessening the pollution in the immediate surroundings.
Light to moderate winds prevail through out the year, during early monsoon slightly stronger winds are observed. Pre-monsoon winds travel north-west in the mornings, reversal of the wind takes place in the evenings and they travel in the south-east direction (Figure 2.4). These winds in the peak of summer carrying dust and polluted gases are threat to the residents of Hyderabad, which is located to the south-east of Patancheru. Monsoon winds are predominantly in the west and west-north-west direction at 0830 and 1730 hours (Figure 2.5). The post-monsoon winds travel between north and east directions (Figure 2.6). Winter winds mainly move in the eastern and south-eastern directions and in the northern direction for few days especially in the mornings (Figure 2.7). The annual wind patterns at 0830 hours recordings are in between west and north-west direction and also in the northern direction, 1730 hours recordings are in eastern, western and northern directions (Figure 2.8). The winds in the southern and south-western directions are rare. Wind speeds are presented in Table 2.4.
To the south-east quadrant of Patancheru Hyderabad is located. The other three quadrants have rural population. Overall the people residing in the south-western quadrant of Patancheru are safe from air pollution.
Table 2.4 Most probable wind speed class.
(Source: IMD, Hyderabad).
2.6 AMBIENT AIR QUALITY
As man consumes more air in a day then the quantity of water and food, and unlike water and food he has little choice regarding the quality of air he breaths. The quality of air is important to all the living things on earth.
The air quality data of various locations in and around Patancheru town and Bonthapally areas are presented in Table 2.5 and average air quality data recorded for three months period recorded at Patancheru and Lakdaram are presented in Table 2.6. The Suspended Particulate Matter (SPM) is high in Patancheru beyond the permissible limit of CPCB; this could be the resultant effect of industries and the movement of vehicles on the busiest National Highway-9. SO2 and NOX values are well within the limits at all locations prescribed by CPCB. Patancheru is showing relatively higher concentration of all the parameters. Carbondioxide and other gases released by the vehicular movement and the industrial activity may contribute for acid rains and smog in the area.
Table 2.5 Ambient air quality (random)
Near NH9 bridge over Nakkavagu, Patancheru Mandal
Date: 18-11-97 Time: 12pm to 6pm
Near Pocharam Junction at NH-9
Date: 11-11-97 Day time 6 hours
(Source: Yegna Envirochem Pvt. Ltd, Hyderabad (1997-98)).
Table 2.6 Ambient air quality (December 1994 to February 1995)
(Source: EPTRI, Hyderabad (1995).