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The impact of tin mining in the Pompong watershed on vegetation sustainability to maintain environmental quality

Over the past 10 years, the POMPONG watershed has experienced a drastic change in land use, from agricultural to gradually becoming residential and mining area. Mining activities carried out in the Pompong watershed result in changes the characteristics of the watershed and the presence of vegetation that functions as land cover. Therefore, this study aims to investigate the extent of the impact caused by tin mining activities on the survival of vegetation to maintain environmental quality. The data of vegetation type was obtained through field observation. Besides, several maps of the Pompong watersheds, such as.watersheds and river networks, land use, soil types, land slopes, contour, topographic and administrative boundaries were needed. These maps were obtained from several related agencies. Data processing and analysis used ArcGis 10.1. The observation results showed there are four types of vegetation, namely secondary-dryland-forest, dryland-agriculture, dryland-agriculture-mixed-with-shrubs, then bush-and-shrub. The research results indicated there was a change in the function of the land from dryland-agriculture-mixed-with-bush to mining by 0,327%. The existence of these vegetations affect the ability of surface water absorption. Therefore, it is better to use vegetative methods in managing the conservation of land around the Pompong watersheds.


Introduction
Over the past 10 years, the POMPONG watershed has experienced a drastic change in land use, from agricultural to gradually becoming residential and mining area. Mining activities carried out in the Pompong watershed result in changes the characteristics of the watershed and the presence of vegetation that functions as land cover. Therefore, this study aims to investigate the extent of the impact caused by tin mining activities on the survival of vegetation to maintain environmental quality.
The decline in environmental quality that occurs in the Pompong watershed is influenced by changes in land use in the watershed. This is due to the Detailed Spatial Planning (RDTR) of the Sungailiat Urban Area 2010-2030 [1] which converted the areas in the Pompong watershed for residential use, such as the areas in Sungaliat, Kuday, Karya Makmur, Air Ruai and Pemali. In addition, mining activities carried out on the other side of the Pompong watershed (Penyamun Village, Pemali District) also accelerate environmental damage. As a result, the land use change has impacts on vegetation change which affect surface flow velocity [2].

Research Method
This research requires secondary and primary data. Secondary data such as land use, soil types, and land slopes were obtained from BPKH Region XIII Pangkalpinang [3], while primary data like the vegetation types and the impacts due to mining activities in the Pompong watershed were obtained through direct observation in the field.

Data collection
The needed maps needed to the Pompong watershed are the maps from 2000,2003,2006, and from 2009 to 2018. The primary data taken in this study consisted of 2 (two) types of data, namely the type of vegetation (land cover plants) and changes in land use in the Pompong watershed. The identification of vegetation types and the impacts due to mining activities is carried out by observing the condition of the Pompong watershed for one week. The identification is done by manual recordings and taking the vegetation documentation.

Data analysis
Data processing and analysis use ArcGis 10.1. Data analysis uses descriptive methods to determine the impact of mining activities and the needed treatments for the vegetation sustainability so that the environmental quality can be maintained. Primary and secondary data processing use ArcGis 10.1 software. This software is used for determining land use change, land slope, and soil type. Furthermore, the output data from ArcGis 10.1 are analysed to discover information of the sustainability of vegetation to maintain environmental quality. From the research results obtained, recommendations could be given to the parties concerning on the environmental quality improvement in the Pompong watershed.

Research Results
The results of this research were grouped into three categories, namely the characteristics of the Pompong watershed, the impact of mining activities, and the types of vegetation in the Pompong watershed.

Characteristics of the Pompong watershed
The characteristics of a watershed (DAS) are influenced by factors of land use, soil type, and slope [4]. This characteristic also affects the land's ability to retain water. The first factor is land use. The land use in the Pompong watershed is shown in Figure 1.  Land use is divided into six groups, namely: shrubs/shrubs, open land, water bodies, dry land agriculture, dry land mixed with shrubs, and mining. In 2012-2013, there was a change in land use of 0.557 km 2 (0.724%) from shrubs/shrubs to secondary dryland forests. In 2014-2015, there was a change in land use by 5.477 km 2 (7.111%) from open land to dry and mixed shrubland. This is because the open land that is neglected is overgrown by plants with the main function of producing fruit and agricultural products. Among these, the plants are still mixed with shrubs between the distances of the plants. In addition, in 2015-2016 there was a change in land use of 13.497 km 2 (17.525%) from dry land agriculture to residence. Furthermore, the most common land change use found was from dry land farming mixed with shrubs to mining at 0.252 km 2 (0.327%).
The second factor is the type of soil. Soil type is influenced by grain shape, density, and soil water. These properties greatly affect the infiltration rate so that surface runoff is obstructed. The mapping of soil types in the Pompong watershed is shown in Figure 2 below.  The slope of the land is rather steep (> 15-25%) and found in the Pompong watershed, amounting to 12.465%. The type of land slope is very steep (> 40%) which is the least found in the Pompong watershed of 4.404%.

Impact of tin mining activities
Mining activities carried out by the community in the Pompong watershed area are against the regulations issued by the local government [5]. Observations show that changes in land use in the Pompong watershed due to mining activities have an impact on local natural ecosystems. This phenomenon causes a decrease in the quality of the environment, namely natural resources such as soil and biodiversity as well as changes in the behavior of water systems (hydrological cycle) and biodiversity.
In addition, mining activities could also cause changes in the hydrological cycle. in the form of changes in surface water behavior and function, namely decreased base flow and increased surface runoff. This results in a hydrological imbalance. Changes in land use due to mining activities in the Pompong watershed amounted to 0.327% in Penyamun Village, which contributed to environmental damage due to mining by 30.001% (23.104 km 2 ).

Vegetation types in the Pompong Watershed after mining activities
The results of observations show that the grouping of vegetation types is the same as the information obtained from BPKH Region XIII [3], namely: secondary-dryland-forest, dryland-agriculture, drylandagriculture-mixed-with-shrubs, then bush-and-shrub.
The description regarding to the vegetation group is (a) Secondary Dryland Forest. Land cover in the form of forest that is still natural or free from human intervention is categorized as secondary dryland forest [2]. This forest is located in Bukit Betung, Karya Makmur Village.

Discussion
From the results obtained, there are four things that need to be discussed regarding to the impact of tin mining in the Pompong watershed on the sustainability of vegetation to improve environmental quality, as described below.

The impact of tin mining activities on the sustainability of vegetation in the Pompong watershed
Human activity is very influential on vegetation cover change [6], [7]. Therefore, regulations related to mining activities need to be reviewed in relation to the pollution and urban vegetation and ecosystem services [8]. Another impact that has been generated is a decrease in environmental quality (environmental degradation) in the Pompong watershed, so that land restoration measures to rebalance land functions need to be carried out. Other impacts resulting from mining activities include the disruption of the sustainability of the hydrology and vegetation of the Pompong watershed so that water flow cannot be maintained [9]. Furthermore, disturbed vegetation as a result of mining can lead to reduced rainfall [10] and water drainage [11].

The relation of vegetation to soil quality
Soil type and land slope determine the type of vegetation that can grow [12], [13] in the Pompong watershed, including natural vegetation. Natural vegetation is a plant that grows without human aid and is not disturbed by human activities for the long term. Vegetation growth could be in the form of short plants or tall plants, where grass and shrubs are included in the short plant category. In addition, soil water also affects vegetation characteristics [14]. Furthermore, the type of vegetation affects the availability of mineral phosphorus (P) in the soil system [15], where tree species can have an impact on the amount of P availability in the Pompong watershed.

Countermeasures to maintain the sustainability of vegetation in the Pompong watershed
Countermeasures need to be done to reduce the impact of mining activities in the Pompong watershed: (a) Vegetation restoration. This method has been successfully applied in Wuqi, China, especially in the south-eastern part [16]. The factors that influence this method include natural factors. Vegetation restoration has a very positive impact on environmental improvement [17], [18]. However, the type of soil and its water conservation should be noted. Inaccurate determination of plant types could result in high-risk soil erosion in watershed. Therefore, plant maintenance management needs special attention.
(b) Program for integrating natural vegetation potentials into ecosystem compatibility. This program is to maintain the balance of the ecosystem [19] by taking into account climate change. Natural vegetation is very important to maintain the ecosystem [20] in the watershed, but in this case stakeholders play an important role on the planning, implementation, monitoring, and assessment stages [21] to protect vegetation in the Pompong watershed area. Evaluation of the RDTR [1] also needs to be done to avoid conflicts between policies in different institutions. Furthermore, (c) the Stabilization of acid soils due to waste from tin mining should be undertaken. This stabilization aims to reduce the acidity of the soil using the biochar (BC) and plantation of palmarosa Cymbopogon martini (Roxb.) Wats method [22]. This method is specifically used for highly acidic mine waste to restore the quality of the watershed environment.

Conclusion
The research results indicated there was a change in the function of the land from dryland-agriculturemixed-with-bush to mining by 0,327%. The existence of these vegetations will affect the ability of surface water absorption. Therefore, it is better to use vegetative methods in managing the conservation of land around the Pompong watersheds.