Trace Elements Evaluation for some mine ponds in the Tin Mining Areas of Jos amd Environs, Plateau State, Nigeria

ABSTRACT

The study area (“Derelict Land”) in Plateau State fall within Y coordinates 1039185m to 1114995m and X coordinates 452385m to 514845m on the Nigeria’s LANDSAT MSS 2001. The approximate area covered by the project is about 3178.1km22 from the satellite image measurements. Six mining areas were involved ( Jos-Bukuru, Rayfield, Sabongidan kanar, Bisichi, Kuru Ш and Barikin Ladi) in this research. Analysis of land use changes on the confirmed that mining is rapidly claiming most of land. Preliminary application of Remote Sensing and Geographical Information System (GIS) to study satellite image of the mining areas is an attempt to evaluate and characterize the mining areas based on the spectral signatures of mine ponds, inactive abandoned mine dumps and structural pattern of the areas.

The analysis of variance of the average trace element concentration from the six mining localities showed that Iron (Fe) is the only trace element that show universal anomaly in all the mining localities compared to WHO (2002) Standards for drinking (0.30ppm). Iron (Fe) anomaly range from 0.39-2.54ppm. Besides Iron (Fe), each mining locality has its unique trace elements anomaly. The overall analysis of variance between the average trace elements concentration in waters from the six tin mining localities compared to the World Health Organization Standards for consumable water confirmed anomalies of Fe, Pb, Cr, Co, Cu, Ni, Cd in waters collected from the mining localities which portrays environmental degradation as well as a tendency for pollution. The distribution of trace elements anomalies appeared to be consistent with increase in population and industrialization in the order; Jos > Barikin Ladi >Rayfield. The solution calls for intensive utilization of the joint technologies of Remote Sensing and Geographic Information System (GIS) to make effective evaluation of the areas and come up with a cost effective and constructive reclamation and re-utilization scheme which appeals to the environment. The scheme should be flexible enough to accommodate and convert minimum damage to environment as there is no use of land that is completely neutral to the environment

INTRODUCTION

The study area (“derelict land”) on Jos, Plateau tin fields (Fig. 1&2; Plate 1) fall within Y coordinates 1039185m to 1114995m and X coordinates 452385m to 514845m. The approximate area covered by the mine ponds and mine dumps is about 3178.1km2 from the satellite image measurements (area shown by black rectangular lines on Plate 1). The six mining areas are at Jos-Bukuru, Rayfield, Sabongidan kanar, Bisichi, Kuru Ш and Barikin Ladi (Fig. 2; Plate 1).

This study is concerned with assessing the extent of environmental degradation on Jos, Plateau using Remote Sensing and Geographical Information System (GIS) techniques to locate the mine ponds in the mining localities.

Environment is the sum total of all the external condition that may act on organisms of community to influence its development or existence. The external condition of interest are the physical, chemical and biological as they relate to mining, processing, weathering and most importantly the changes imposed by these conditions. Ever since the origin of the earth, it has been subjected to changes. One of such activities that affect the environment and impose some changes in both physical and chemical composition of the environment is mining. Mining according to Adiuki-Brown (1999) is an act, process or work of extracting mineral of economic importance from their natural environments and transporting them to the point of processing and use. A mine is therefore an excavation made into the earth for the purpose of extracting mineral of economic value. It is not a potential Dam (e.g. Mine Pond). Mining has taken place in Plateau State for almost 100 years (1902 – 1982) and this has rendered derelict a land of about 325km2, out of the total of 8,600km2 of the Jos Plateau area (Alexander, 1985). Oxeham (1966) defined “derelict land” as land that has been damaged by extractive on other industrial processes such that in its existing state, it is unsightly and incapable of reasonable beneficial use”. The Land Resource Development Centre in 1976 estimated that some 316km2 of the total 8,600km2 of the Jos, plateau area has been damaged by mining.

The mining on the Plateau has imposed the following structure on the estimated ‘325km2 derelict land’:

a. Inactive and Abandoned Mines (Mine Ponds/Dams)
b. “Lotto” Wells.

The Promulgation of the Mine Lands Act of 1946 paved way for the reclamation of mined areas on the Jos Plateau. Active reclamation began in 1964 by the Mine Land Reclamation Unit (MLRU) and the Forestry Department of the Ministry of Agriculture and Nation Resources (ATMN, 1969). Other bodies involved in the reclamation activity included the mining companies and the Joint Consultancy Committee (JCC) on Mine Land Reclamation. The reclamation involved essentially the bulldozing of mound and filling in the ditches and flooded Paddocks and thereafter, planting the affected areas with eucalyptus tree seedlings in order to stabilize the soil and produce a good tilt. This is the so called “Level and Fill” method. Only 12.37km2 of land was reclamed before the reclamation came to more or less a stand still due to the fact the “Level and Fill”: method later proved extremely expensive to shoulder by the mining companies. By implication while the reclamation stopped, the mining continued and this annulled the initial impact of the reclamation. Alexander (1990) summarized the problems of reclamation as legislative, adverse economy and political influences. Hence the need to adopt a new reclamation strategy involving minimal cost with guaranteed immediate economic benefits. A key to this approach involves an understanding of the soil of the mined lands, existing land uses and soil- crop relationships.

Commercial tin mining started in Jos, Plateau about the year 1902 and in 1909, and the Niger Company was the only operating company, producing over 5,000 tonnes of cassiterite (Calvert, 1977). Tin mining expanded slowly due to poor transport facilities at the beginning. The construction of the Bauchi light railway in 1914 and an increase in the demand and the price of tin in the World market and due to the high requirement of tin for military use between 1914 and 1919, the production of tin increased (De kun, 1965). The production of tin further expanded with the arrival of a branch railway line at Kafanchan in 1927. This trend continues until the economic depression of the 1930s which caused a drop in the price of tin. Production however declined again after the war as a result of stiff competition faced by mining companies in the World market.

As the tin mining continued to grow, so did the mining settlements which are closer to the mining sites. At least about 50 of them were established over four decades (1902 – 1942). Some of the smaller labour camps are Sabongida kanar, Bisichi, Doruwa Babuje, Gana Ropp, Naraguta and Rayfield. The larger centers include, Barikin Ladi, Bukuru and Jos. By 1943, when Tin mining peaked with the production of 15,843 tons of Cassiterite, there were up to 7500 miners’ employees. The population of Jos had then grown to about 18,000 people. Between 1942 and 1945 production reached 17,000 tonnes during the Second World War due to manufactures of armaments.

By mid 1985 large scale mining has visually collapsed, and small scale mining continued. Small scale mining is a continuous processes on the Plateau with even some of the reclaimed mine lands in most of the former mining areas being reworked using Lotto mining techniques (Eziashi, 1998). The abandoned Lotto mines are now posing even greater environmental hazards

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Fig. 1 Location of the Study Area in Nigeria

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Fig. 2 Areas Affected by Tin Mining showing the sampling points on the Jos Plateau

(modified after Eziashi 1998)

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Geology of the Area

Jos Plateau is an isolated upland with an elevation of about 1219.20m above sea level and several satellite hill masses which rise from the surrounding plains (Macleod et al. 1971). The scenery varies from level plain and Plateau surface almost devoid of exposed rocks to rugged, deeply dissected massifs developed on the more resistant rock types (Macleod et al. 1971). The main rock types that exists on the Plateau are; the Basement Complex rocks including the Older-Granite and Metamorphic rocks (Gneisses and Migmatites), the Younger Granite from which Tin-ore (Cassiterite) originated and the Older and Newer Basalts (Fig. 3). The Biotite Granite of the Jurassic Younger Granite suites is the host for the Tin mineralization. The Tin mineralization is usually disseminated in the roof zone of the Biotite Granite Plutons and is related to post emplacement of hydrothermal greissenization, quartz veins and albitization (Macleod et al. 1971). The mineralized roof zone was weathered to form tin placer deposit along ancient river channels. Cretaceous basaltic flow (both Older and Newer basalt invaded the ancient river channels covering the tin placer deposits at their different periods of crystallization) and also the tin-bearing Biotite Granite were widely distributed in the surrounding drainage system (Macleod et al, 1970) (Fig. 3).

The research areas fall within the weathered basalts zone where the former and present legal and illegal mining took place (Fig. 2&3, Plate 1).

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