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Impact Of Industrial Effluents On Soil Physico-Chemical Characteristics A Case Study Of Ttp Industry In Thiruvananthapuram, South India

Meethu Mohan* and D.S. Jaya

Department of Environmental Sciences, University of Kerala Kariavattom Campus P.O. Thiruvananthapuram 695 581, Kerala, India

*Corresponding Author:
Meethu Mohan
E-mail:
meethuvijayamohan@gmail.com

Received date 27 February, 2015; Accepted date 10 May, 2015

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Abstract

 The present study was conducted to assess the soil physico-chemical characteristics and effect of industrial pollution on soil quality in the surroundings of the industry, Travancore Titanium Products Ltd (TTP), Thiruvananthapuram, in Kerala State, South India. The soil samples were collected from seven stations in the surroundings of TTP during the months of March-April (pre- monsoon season) of the year 2013 and analyzed to find out the soil physical and chemical characteristics. The study showed that the soil pH was acidic to slightly acidic in the surroundings of the industry. The organic matter and nutrient content in majority of the soil samples from the study area recorded low values and therefore soils in the surroundings of TTP industry are of low fertility. The soil heavy metal analysis showed that the concentration of Cd, Pb and Cr were high in the station near the effluent discharge site compared to that in the other stations of the study area. The Soil Quality Index (SQI) values calculated based on the selected soil parameters also revealed that the quality of soil in the surroundings of TTP industry is deteriorated. Recommendations to prevent further degradation of soil in the study area are also mentioned.

Keywords

Effluent, Heavy metal, Physico-chemical, Pollution, Soil Quality Index

Introduction

Soil is a natural body consisting of layers that are primarily composed of minerals mixed with at least some organic matter which differ from their parent materials in their texture, structure, consistency, color, chemical, biological and other characteristics. Soil constitutes an important medium where in numerous animals live. In fact, soil of a nation is its most valuable heritage (Sharma and Kaur, 1996).

Pollution occurs when some part of the environment is made harmful or offensive to organisms and especially to humans. Contamination is the addition of hazardous chemical or organism where no harm has been demonstrated. All chemicals are harmful when their concentrations are high enough even though they are harmless or even beneficial at low concentrations (Alan, 1993). Many toxins added to soils can build up to concentrations that become serious threat to plant and animal health. Materials that are toxic to soil microorganisms further slow recycling. Soil has an intimate and extensive role to maintain a suitable environment and to minimize pollution (Kolay, 2007).

Soil quality is a measure of the condition of soil relative to the requirements of one or more biotic species and or to any human need or purpose. Among different industries, cement industries and mining activities cause dust pollution of agricultural soils. Accumulation of alkaline dusts in the soil can increase soil pH which affects crop growth. Dust deposited on ground may produce changes in soil chemistry, which on the longer term results in changes in plant chemistry (Ajaz et al., 2008). The Travancore Titanium Products Ltd. (TTP) is producing anatase grade titanium dioxide by sulphuric acid extraction method. Literature review show that there are no studies related to soil pollution in this area. The major objective of the present study is to find out the soil physical and chemical attributes, and to assess the soil quality status in the surroundings of Travancore Titanium Products Ltd (TTP), Thiruvananthapuram.

Materials and Methods

Study area and Sampling stations

The area chosen for the present study is the surroundings of Travancore Titanium Products situated in Veli, Thiruvananthapuram district, Kerala. It is a close to beach location in Thiruvananthapuram district of Kerala state. It is identified as one of the pollution hot spots in South West coast of India by the Ministry of Earth Sciences (MoES), Government of India. Thiruvananthapuram, the southern most district of Kerala has a coastline of approximately 29 km dotted with a large number of traditional fishing villages. This coast is also famous for traditional temples and churches. The area is having a south west wind direction with a speed of 4.3 to 5.6 m/sec. The average temperature is 30.4°C with humidity 77.4%. The area selected for the present study is located between North latitudes 08° 29' to 08° 33' and East latitudes 76°52' to 76°54'. The location map of the study area is given in Fig. 1.

icontrolpollution-sampling-stations

Fig. 1 Location map of study area showing different sampling stations.

Soil samples were collected from seven selected stations during the months March to April (pre monsoon season) of the year 2013. The description of sampling stations is given in Table 1. Soil was collected from the study area to the depth of about 0 to 15 cm from the surface, using a showel by Cone and Quarter method (Head, 1982). Soil samples collected were put in thick quality polythene bags and immediately brought to the laboratory for the analysis of physical and chemical parameters.

icontrolpollution-Description-sampling-stations

Table 1. Description of sampling stations in the study area

The physical parameters (moisture, bulk density and specific gravity) and chemical parameters (chlorides, conductivity, organic matter, organic carbon, total nitrogen, sulphates, phosphates, nitrates, sodium, potassium, calcium and magnesium) of soil were determined following the standard procedures described by Trivedy and Goel (1986) and by Saxena (1998). For the estimation of heavy metals, 0.5g of fine soil powder was weighed in a Teflon crucible, and added 4 mL perchloric acid and 15 mL hydrofluoric acid to it. The contents in the hot plate were digested until it becomes a yellow cake. Then it was allowed to cool after adding 3-5 mL nitric acid. The solution was made up to 100 mL in a standard flask. The solution was filtered in Whatmann No. 41 filter paper. The final solution was collected in a clean polythene container. From the digested sample, heavy metals were determined using an Atomic Absorption Spectro- photometer (Perkin Elmer PINAACLE 900 H).

Soil Quality Index (SQI) is a function determining the quality of soil with respect to selected parameters. Based on the selected physical and chemical parameters, SQI was computed to determine the soil quality and categorized into good, average and poor. According to Brejda and Moormann (2011), the soil quality index can be calculated by the formula using the values of pH, organic matter, phosphorous, potassium and electrical conductivity. If SQI is less than 1, the soil is of poor quality. If SQI is of values between 1 and 2, the soil is of average quality and if the SQI is of values >1, the soil is of high quality.

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Results and Discusion

Physical and Chemical characteristics of Soil

The results of physical and chemical analysis of soil samples collected from the different study stations during the pre-monsoon season is given in Table 2 and 3. They have shown an increase in the moisture content in the soils at the effluent discharge point of TTP industry. In the study stations the moisture content varies from 1.6% to 4.48% in the pre monsoon season. There is an increase in moisture content in the soils (4.48%) at effluent discharge point of the TTP industry during pre-monsoon season. The bulk density of the soil is defined as the dry weight of a unit volume of it and is expressed in g/cm3. Normally, the soils with high bulk density are inhibitive to root penetration and have low permeability and infiltration (Saxena, 1998). In the study stations the soil bulk density varies from 1.47 g/cm3. The highest value of bulk density was observed at the soil taken from effluent discharge point (S1). Specific gravity of soil is directly related to its bulk density and may be used as an index of soil quality. High specific gravity is observed in Station 1 (S1) and low at Station 2 (S2).

icontrolpollution-Physical-characteristics-soils

Table 2. Physical characteristics of soils in the study area

icontrolpollution-Chemical-characteristics-soils

Table 3. Chemical characteristics of soils in the study area

The pH of study station soils range from 3.05 to 6.3 with lowest pH value at Station 1 (S1) and it is highly acidic. Conductivity of the stations ranges from 0.097 to 0.211mS with highest value recorded at Station 1 (S1) and lowest value at Station 4 (S4). The highest concentration of chlorides (49.7mg/L) was estimated in the soils of effluent discharge point. Nitrogen in the soil is present in the form of organic nitrogenous substances such as ammonia, nitrate and nitrite (Sharma and Kaur, 1996). The concentration of nitrates ranges from 0.0003 to 0.0061mg/g dry wt. The highest concentration of sulphates was recorded at the effluent discharge point (S1). This shows the highest concentration of sulphates in TTP effluents due to by- products formed in the TTP production process. The high sodium content was observed in Station 1 (S1), the effluent discharge point and it adversely affects the growth of plants and is considered unfertile. The highest concentration of calcium (26.05 mg/100g) was recorded at Station 2 (S2). Soil magnesium concentra tion was found always less than the calcium concentration in all the stations studied. The estimation of total nitrogen in the soil is essential to evaluate the fertility of soil. Station 1 (S1), the effluent discharge point has lower concentration of nitrogen (0.28 mg/g dry soil).

The total phosphorous is the phosphorous available to plants which can be correlated with the response of crops to phosphate fertilizers. In the present study, the concentration of total phosphorous in soil samples ranges from 0.61 to 2.08mg/g dry soil during the pre-monsoon season with high concentration at Station 3 (2.08mg/g dry soil) and low concentration at Station 2 (0.616 mg/g dry soil). The high potassium concentration was observed in S4 whereas low potassium concentrations at Station 1 (S1) and Station (S2). The present study shows the concentration of phosphates ranging from 0.005 to 0.53 mg/ g dry soil during pre- monsoon season. Station 4 and Station 5 recorded maximum concentration of phosphates (0.053 mg/g dry soil) and Station 1(S1) shows minimum concentration (0.005 mg/g dry soil) indicating less nutrient content in the soil near the TTP effluent discharge point. The organic carbon content is a measure of fertility. The source of all the fixed carbon in living organisms as well as in fossils deposit is carbon dioxide found in the atmosphere and dissolved in the waters of earth (Sharma and Kaur, 1996). The organic carbon content recorded low values in the study station soils and ranges from 0.025 to 0.82%.

Concentration of Heavy metals in Soils

Heavy metals are conventionally defined as elements with metallic properties and are non-biodegradable rather has long residence time in soils. In the present study, the concentration of three heavy metals Cd, Pb, and Cr were estimated in soils of study stations. The changes in the concentration of heavy metals in the soil of study stations are given in Fig. 2. It was found that the concentration of cadmium ranges from 1.6 to 4 mg/kg dry soil with maximum at Station 1 (S1), near the effluent discharge point of TTP. The increase in concentrations of lead and chromium were estimated in the Station 1 (S1) soils, near the TTP effluent discharge point which indicate the presence of Pb and Cr in the TTP effluent. Studies by Sukumaran (2013) also showed the presence of heavy metals in the effluent discharged from Travancore Titanium Products (TTP) industry, Kerala.

icontrolpollution-Concentration-heavy-metals

Fig. 2 Concentration of heavy metals in the soils of study area.

Soil Quality Index

Based on the selected physical and chemical parameters (pH, organic matter, phosphorous, potassium and electrical conductivity), Soil Quality Index (SQI) was computed to determine the soil quality and is categorized into good, average and poor. The SQI values and quality status of soil samples taken from different stations of the study area are shown in Table 4. The Soil Quality Index (SQI) was found as 0.2 in all the stations studied. In all the study stations the SQI was less than 1and the soil is of poor quality.

icontrolpollution-Soil-Quality-Index

Table 4. Soil Quality Index (SQI)

The water in the soil is not only important as a solvent and transporting agent, but it maintains texture and compactness of soil. The moisture in the soil is mainly gained from infiltration of precipitated water. The bulk density of soil is defined as the dry weight of unit volume of it and is expressed in g/cm3. Normally, the soils with high bulk density are inhibitive of root penetration and have low permeability and infiltration. Soil pH in the study stations are in acidic to slightly acidic range. It is a good measure of acidity and alkalinity of soil-water suspension and provides a good identification of the soil chemical nature. The pH at a given time is the reflection of the status of bio-geochemical processes because the temporal changes in pH are presumably due to change in primary production, respiration, mineralization and decomposition of organic matter in the soil (Behera, 2006). The chlorides present in the soil are mostly soluble in water (Trivedy and Goel, 1986). The soil chloride and conductivity in the study stations recorded high values. Soil electrical conductivity is an important indicator of soil health. It affects crop yields, crop suitability, plant nutrient availability and activity of soil microorganisms. Excessively high salinity can affect the plants adversely. Nitrogen in the soil is present in the form of organic nitrogenous substances and organic nitrogenous substances such as ammonia, nitrite and nitrate. Calcium is necessary for the normal growth of plants. The higher concentration of calcium in soil indicates its fertility. Nitrogen in the soil and sediments are present mostly in the organic form together with small quantities of ammonium and nitrate.

Carbon being a basic constituent of all organic compounds and a major element involved in the fixation of energy by the process of photosynthesis is so closely tied to energy flow that two are difficult to be separated. The source of all the fixed carbon in living organisms as well as in fossil deposits is carbon dioxide found in the atmosphere and dissolved in the waters of earth (Sharma and Kaur, 1996). Organic matter represents the remains of roots, plant materials and soil organisms in various stages of decomposition. The amount of organic material in the soil depends on climatic conditions, the type of inorganic constituents present and topography (Charanjit and Syed, 2011). The study area soils in the surroundings of TTP industry in Thiruvananthapuram were contaminated with heavy metals cadmium, chromium and lead. Heavy metals are harmful in nature because of their non-biodegradable nature, long half lives and their potential to accumulate in body parts when they enter into a human system. Waste water contains substantial amount of toxic heavy metals which create a series of problems studied by Chen (2005). The increasing amount of heavy metals inhibit enzymatic activities, especially dehydrogenase activity seems to be sensitive indicator of soil pollution (Smejkalova et al., 2003). Lead is neither an essential nor a beneficial element in soils and plants and is a toxic metal which interferes with the availability of one of the essential micronutrient copper. Increase in lead levels in soil may adversely affect plant growth and the agro-ecological environment (Kalavrouziotis et al., 2009).

Conclusion

Soils have a major role in maintaining the environmental quality. It improves the environment by acting as a physical, chemical or biological filter to remove the substances from water and to decompose organic pollutants. The present study carried out around the Travancore Titanium Products Ltd. factory in Thiruvananthapuram, South India during the premonsoon season reveals the changes in the soil physical and chemical characteristics. The percolation of highly acidic effluents discharged from TTP industry altered the physical and chemical characteristics of the soil in nearby area and degraded the soil quality. The heavy metals lead, chromium and cadmium were detected in the soils of study area and recorded highest values in the effluent discharge station. The SQI values also showed the poor quality of soils in the surroundings of the Travancore Titanium Products Ltd. The waste waters or effluents discharged from the factory without proper treatment may cause ground water contamination; direct public health hazards and also alter the ambient air quality in the surrounding areas. Therefore the present study concluded that the industrial activities in Travancore Titanium Products Ltd. producing anatase grade titanium dioxide by sulphuric acid extraction method have significant negative impacts on environmental quality in surrounding areas.

Recommendations

The recommendations to improve the soil quality in the surroundings of Travancore Titanium Products industry are given below:

• Maintenance and upgradation of the existing waste water treatment plant with sophisticated pollution control equipments.

• Proper methods should be adopted to reduce the acidity of soils by suitable liming and adjust the pH to a neutral value.

• Creation of awareness among the people in that area around the Travancore Titanium Products industry in collaboration with government authorities which is essential for the proper management of soil quality in Veli industrial area.

• Suitable eco-friendly waste management practices should be adopted in order to avoid contamination such as growing pollution tolerant plants such as Polyalthia longifolia, Alstonia scholaris etc. in the surroundings of the industry.

Acnowledgements

Gratefully acknowledge the financial assistance extended by the Kerala State Council for Science, Technology and Environment (KSCSTE) for this study. The authors are thankful to the Director, Cashew Export Promotion Council, Kollam, South India for providing the facilities to carry out heavy metal analysis.

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