The Impact of Bouxite Mining On The Semanduk Lake Environment: A Case Study In Tayan Hilir, Sanggau District, West Kalimantan Province, Indonesia Country


 Background: Several mining activities, especially bauxite, have been carried out in several areas in West Kalimantan. The areas most widely carried out bauxite mining are Sanggau and Ketapang districts. Bauxite mining is included in the classification of surface mining or often referred to as open mining. This is characterized by the demolition of the upper layers of soil and taking the results of weathering rocks, namely granite rocks. The demolition of topsoil is done with the clearing of vegetation above. In this condition, the land still has the same morphology when clearing has not been done and the soil has not been much disturbed. But after mining there is a lot of clay, sandstone, topsoil materials, of course, this will have a negative impact on the environment.Result: The results showed that the gradient of the slope has an important role in land conservation. The greater gradient of the slope will automatically increase the surface runoff, so the greater the energy of run-off. The soil depth is shallow on average and has poor deep soil drainage. Soil is easily eroded, so a lot of rocks and gravel are exposed on the surface, plants cannot develop properly. Floods often occur, in areas of alluvial plains with a range of more than 24 hours. The water availability capacity is also very low. Rainwater in the area mostly becomes runoff. The nutrient content in the ex-mining area is also low. Therefore it is necessary to improve efforts by means of reforestation of the former land so that in the future it can be used for certain uses, especially for agriculture, plantations, and forests.Conclusion: Slopes have an important role in land conservation. Slope affects runoff, effective soil depth, erosion rate, plant growth, waterlogging. Nutrient content in ex- Bauxite mining areas is also low.


Introduction
West Kalimantan has very diverse natural resources. Mining potential includes iron, silver, copper, gold, antimony, Mo, lead, bauxite, and so on. The high potential of the mine is due to West Kalimantan is a metalogin track that contains a lot of metal mineral types. The metalogin track or often called metalogin province is an area that contains one or more types of metal mineral traps (Yuniarni R, 2014). The types of metal minerals are widely distributed in various regions in West Kalimantan. Bauxite which is a superior mining resource in West Kalimantan is located in Mempawah, Bengkayang, Sanggau, Landak, Ketapang, Sekadau, Kuburaya, and North Kayong districts.
The large potential of mining materials spread across West Kalimantan has an impact on investment direction. The direction of investment that was initially focused or dominant in the plantation sector has now shifted to the mining sector, especially bauxite re ning. This was carried out until the end of 2016 as many as 640 companies had held mining licenses and 60 percent were engaged in bauxite mining (Jumiadatin, 2015).
Mining activities could be bene cial to the economic growth of countries if managed properly. However, there is always a trade-off between economic growth and environmental sustainability, because of the excessive exploitation of natural resources (Awan, 2013;Bawua & Owusu, 2018).
Several mining activities, especially bauxite, have been carried out in several areas in West Kalimantan. The areas most widely carried out bauxite mining are Sanggau and Ketapang districts. Bauxite mining is included in the classi cation of surface mining or often referred to as open mining. This is characterized by the demolition of the upper layers of soil and taking the results of weathering rocks, namely granite rocks. The demolition of topsoil is done with the clearing of vegetation above. In this condition, the land still has the same morphology when clearing has not been done and the soil has not been much disturbed. But after mining there is a lot of clay, sandstone, topsoil materials, of course, this will have a negative impact on the environment.
Mining impacts can be categorized into three aspects: 1) physical impacts due to mining to the land are Based on a number of mining impacts that might arise above, mitigation of former land mainly to the land, in this case, is the physical and chemical characteristics of the land so it is necessary to make an inventory of conditions that occur after mining. This effort was made so that the land former to bauxite mining does not experience more severe degradation. But land can be used sustainably for the survival of ecosystems in and around it. Though the bene ts are known, its induced consequences are enormous (Adesipo, at al, 2020). Therefore, direct and indirect impacts can be identi ed that have caused them on the environment around the mine ( The method used in this research is the survey and laboratory analysis. The survey method is used to take soil samples and record the physical characteristics of former bauxite mining land, while laboratory analysis is used to determine the chemical nature of the land at the site of the former bauxite mine. The data used in this study are: 1) physical soil data consisting of surface slopes, soil texture, soil permeability, soil depth, soil drainage, erosion hazard, erosion sensitivity, 2) chemical land data consisting of organic soil, Exchange Capacity Cation, pH, KCl, C, total N, N-NH4, phosphorus, P2O5, K2O, Na, K.

The Case Study
Administratively the research site is bordered by the village of Kawat in the west, Tebang Benua and Subah in the north, in the east by Subah and Lalang, in the south by Toba sub-district. The results of the author's survey (2020) have been known since PT Mahkota Karya Utama (MKU) engaged in bauxite mining conducted mining, the current condition of the lake experienced silting, the surrounding environment (forest) many were damaged and the community lives increasingly di cult. The source of income is getting smaller and even partially lost, since mining activities began, in 2011.
The results of the author's survey revealed that there had been environmental damage and siltation of the Semanduk lake due to bauxite mining. Land damage was identi ed characteristics: a lot of vegetation was lost, so that many land surfaces were exposed. Land clearing causes rough surface textures, reservoir water bodies to disappear. Land damage is seen in the image even extends to the border of the Kapuas river. There is even soil material which is partly owing and settling in the Kapuas River. Kapuas river water looks turbid and somewhat brownish, this shows that there are materials that are carried by the ow of water into the river and are deposited on the riverbed.

Physical Caracteristic
The slope gradient of the study site ranges from 0-20% with at to hilly topography. The soil texture at the study site is clay to sandy loam. The results of laboratory analysis show that the permeability of the ex-bauxite mine site ranges from 0.059 cm/hour (very slow in the classi cation of permeability) to 15,67 cm/hour (very fast) in the classi cation of permeability. The depth of the soil at the study site ranges 25 -> 90 cm. Based on the survey results it is known that the soil drainage of the study site is bad, poor, and good.
The soil drainage is very bad, shown by the soil in all layers until the soil surface is gray and the subsoil is gray or there are bluish spots, or there is water that has stagnated on the surface of the soil for a long time so that it inhibits plant growth. The drainage poor shown by the soil has good air circulation in the root area. There are no yellow, brown, or gray spots on the top layer and the top of the lower layer (up to about 60 cm and the soil surface). The soil drainage good shown by soil has good air circulation. The entire pro le from top to bottom (soil depth 150 cm) is uniformly light-colored and there are no yellow, brown, or gray spots.
Erosion sensitivity (soil erodibility) in the study area ranges from 0.21 to 0.63 (in the erosion sensitivity include moderate until very high). The form of erosion that occurred at the study site showed the presence of gully erosion. These erosions have a depth of > 40 cm and a width of more than 30 cm.
Rocks and gravels are coarse material that has a diameter of 2.5 cm if they are round, the elongated axis has a size of 15-40 cm if they are at. Rocks that are included in the gravel category have a diameter of more than 12 − 7.5 cm if they are round in shape, an axis that extends 15 cm if they are at. These coarse materials are scattered in the topsoil layer or above the soil surface. A sampling of surface rock or gravel content is done by taking the unit area, which is 25 square meters. Based on the results of the eld survey, it is known that the content of these rocks and gravel ranges from 0.01-90%.
The threat of ooding or inundation is caused by deep drainage and poor surface drainage. The in ltration and percolation processes are hampered by the presence of soil texture or the size of the soft soil grains, while the drying of the surface is also hampered by the at to gentle slope. Based on the research results, it is known that inundation conditions or the threat of ooding only occur in uvial landforms. This landform is in danger of ooding for one month of the year, the land is always inundated by oods for more than 24 hours.
Bauxite mining also affects the water availability capacity of the study site. The results showed that the water availability capacity in the study area ranged from 7.5 to 22.5 cm. The lack of water availability capacity will greatly affect the function and roots in the total volume of soil. These effects are low water density, low soil strength, very low pH values, other chemical and physical properties that can limit root growth and root distribution in soil mass (Sinclair Jr & Dobos,2006; Staff,1999). The physical characteristics mentioned above can be brie y seen in Table1.

Chemis caracteristic
The chemical elements in this study included soil organic, CEC, pH, KCl, C, total N, N-NH4, P, P2O5, K2O, Na, K and salinity. These chemical properties, namely: location is quite high, so that the plants will not be able to grow and even die quickly.

d. Alkalinity (xn)
Alkalinity is determined by the sodium (Na) content. Alkalinity describes the amount of base contained in water.
The Na content in the soil is between 0.24 and 0.36 cmol. Alkalinity or exchangeable Na content in this soil form is very low.

Discussion
The slope of gradient has an important role in land conservation and land suitability. The composition of the developed soil, structure, biomass, density of the plant community is strongly in uenced by the slope (Albaba, 2014). For the threat of ooding to occur during one month of the year, the land is always inundated by oods for more than 24 hours. The threat of ooding or inundation is caused by deep drainage and poor surface drainage. The in ltration and percolation processes are hampered due to the presence of soil texture or the size of the soft soil grains, meanwhile, the surface grinding is also hampered due to the at to gentle slope.
Water availability capacity has a very important role. High water availability capacity is very bene cial for soil density, soil permeability, and soil strength and structure. High soil density, high soil strength, low permeability, massive non-granular soil structures, and blocks reduce water capacity thereby limiting plant roots (Uhland, 1951) and root distribution over the entire soil mass. The ability of soil to provide water is needed by plants. In general, in a lot of open land conditions in ex-mining areas, the ability of the soil to store water is greatly reduced. However, an assessment of the capacity of water availability is necessary to determine the capacity of the land.
In areas where it rains frequently and supplying the land with more water, available water capacity is not very important. However, the condition of the former mining area which is wide open where the falling water becomes runoff and with high heat causes high evaporation, the falling rain is not su cient to supply groundwater. However, in areas where crops emit more water than the amount provided by rainfall, the amount of available water that the soil can provide is very important. Water is needed to support the needs of plants.
Soil properties that affect water are soil texture and organic matter. Soil that has a ne soil texture has a high to very high water storage capacity and vice versa. Rock fragments reduce the capacity of available water in direct proportion to their volume unless the rock is porous. Soil that has a ne texture can bind more water. This is because soils with ne textures have a larger surface area than coarse-textured soils. Bulk density plays a role by controlling the pore spaces that hold the available water. In areas where it rains every day and supplies the soil with as much or more water than the plants remove, the available water capacity is not that important.
However, the condition of the former mining area which is widely open, where the water that falls a lot becomes runoff and with high heat causing high evaporation, the rain that falls is not enough if it is only used as a supply factor for groundwater availability.
In areas where plants emit more water than the amount supplied by rainfall, the amount of available water that the soil can provide may be very important. This water is needed to sustain crops between rainfall events or irrigation periods. Soil effectively supports the root environment of the plant against periods of water de cit.
Soil properties that affect water are soil texture and organic matter. Soil that has a ne soil texture has a high to very high water storage capacity and vice versa. Rock fragments reduce the capacity of available water in direct proportion to their volume unless the rock is porous. Soil that has a ne texture can bind more water. This is because soils with ne textures have a larger surface area than coarse-textured soils. Bulk density plays a role by controlling the pore spaces that hold the available water.

Conclusion
The results showed that the slope of the gradient has an important role in land conservation and land suitability. The greater the slope of the slope will automatically increase the surface runoff, so the greater the energy of surface water (run-off), which will interfere with plant growth and productivity. The effective soil depth is shallow on average and has poor deep soil drainage. Soil is easily eroded, so a lot of rocks and gravel are exposed on the surface, plants cannot develop properly. Floods often occur, especially in areas located on alluvial plains with a range of more than 24 hours. The water availability capacity is also very low. Rainwater in the area mostly becomes runoff. The nutrient content in the ex-mining area is also low. Therefore it is necessary to improve efforts by means of reforestation of the former land so that in the future it can be used for certain uses, especially for agriculture, plantations, and forests. Gully Erosion