Restoration of degraded lands for carbon stock enhancement and climate change mitigation: the case of Rebu watershed, Woliso Woreda, Southwest Shoa, Ethiopia

This study was conducted to estimate carbon stock enhancement and climate change mitigation potential of restoration effort in Rebu Watershed, Woliso Woreda, Ethiopia. Two restored lands of thirteen years old were randomly selected from two kebeles. Biomass and soil data were collected systematically from nested plots. Mensuration of woody species, soil, and grass/litter samples was collected from the subplots of the nested plots. A total of 72 composite soil samples were collected. The results showed the positive impact of restoration activity on enhancing biomass and soil organic carbon stocks. The restored land ecosystem had shown higher carbon stock of (138.51 ± 27.34 t/ha) than the adjacent unrestored land ecosystem (101.43 ± 21.25 t/ha), which confirmed the potential of restoration in enhancing the carbon stock and mitigating climate change. Hence, the restored land use type has been stored about 8.37 t/ha of carbon dioxide equivalent (CO2e) in biomasses. The restored land use type has mitigated climate change (absorb CO2) by 7.7 times than the adjacent unrestored land use type in this study. The significant values in restored land use types were due to the enhanced vegetation and land cover, which contributed to the biomass and soil organic carbon accumulation. Moreover, the lower values in unrestored land use type were due to the continuous degradation and disturbance from livestock and human beings. Therefore, the result of this study showed that protecting the degraded lands from any disturbance could enhance the carbon stocks of the ecosystem and mitigate the carbon emission rate.

Spatial and temporal distribution of estimated surface runoff caused by land use/land cover changes in the upstream Citarum watershed, West Java, Indonesia

In Indonesia, flooding is one of the natural hazards that often occurs during the rainy season. Surface runoff coefficient values are an essential indicator of the supply of regional water resources. The smaller the surface runoff value, the greater the water storage in the ground, and the smaller surface was running water. This study analyses the spatial and temporal distribution of the estimated surface runoff caused by land use/land cover changes in the upstream Citarum watershed. The study area is located in the upstream Citarum watershed, West Java, Indonesia. The site has a long history of flooding and various complex environmental problems. The geographic Information System method was used as a tool in analyzing the spatially and temporally. The research result shows that there has been a change in land cover in several periods of the year in the Citarum upstream watershed. The occurrence of the LULC phenomenon positively affects the surface runoff coefficient. The increasing area of Built land and plantation in the Citarum upstream watershed will further increase the surface runoff coefficient and, in the end, will potentially increase the surface runoff and contribute to flooding in the Bandung basin. This study results can be used to provide input in determining the direction and policies for watershed management, taking into account the varying characteristics of each subwatershed.

Assessing the distribution of total Fe, Cu, and Zn in tropical peat at an oil palm plantation and their relationship with several environmental factors

Extensive utilization of fragile tropical peatlands ecosystem encourages a better understanding of spatiotemporal micronutrients distribution. The distribution of total Fe, Cu, and Zn in peat and their relationship with environmental factors were studied under oil palm plantation, Pangkalan Pisang, Koto Gasib, Riau, Indonesia. Peat samples were taken compositely inside the block using a combination of six factors, including a) the oil palm age (<6, 6-15, >15 years old), b) the peat thickness (< 3 and >3 m), c) season (rainy and dry), d) the distances from the secondary canal (10, 25, 50, 75, 100, and 150 m), e) the distances from an oil palm tree (1, 2, 3, and 4 m), and f) the depth of sample collection (0-20, 20-40, and 40-70 cm from the peat surface). Total Fe, Cu, and Zn were determined by the wet digestion method. These micronutrients observed in this study possessed high variability; however, they were within the expected range in tropical peatland. The entire micronutrients were statistically different by oil palm age, peat thickness, and distance from canal. Meanwhile, total Cu and Zn were also significantly different at each season. The oil palm age, peat thickness, and distance from the canal were the common factors controlling total Fe, Cu, and Zn in peat significantly. Moreover, total Cu and Zn were also dictated by season, distance from the oil palm tree, and depth of sample collection. Based on visual interpretation in PCA (principal component analysis), all micronutrients were categorized into two groups, separated by 2 m distance from the oil palm tree and 20 cm depth from the soil surface. Our study also highlights the dominance of the dilution over the enrichment process in peat, which requires further research to formulate micronutrients fertilization, especially for an extended cultivation time.

Do natural landscapes contribute to reducing Land Surface Temperature (LST)? A case study from Muthurajawela wetland, Sri Lanka

Microclimate regulation is one of the most significant ecosystem services provided by wetlands. The present study attempted to investigate the cooling effect provided by Muthurajawela, a coastal Ramsar wetland using Remote Sensing and GIS. The variation of Land Surface Temperatures (LST) over different land use categories of natural (water bodies, marsh, thick vegetation, grassland) and anthropogenic (built-up areas, coconut cultivations and bare lands) areas in 2015 and 2020. Parameters including Satellite Brightness Temperature, Normalized Difference Vegetation Index, Proportion of Vegetation and Land Surface Emissivity were calculated along eight transects starting from the center of the water body and extending up to 5 km from the boundary of the wetland. The results revealed that LST over areas under natural land cover (2015 - mean 25.040C, 2020 - mean 23.360C) were significantly lower than that of areas under anthropogenic influence (2015 - mean 26.520C and 2020 - mean 26.220C). The lowest increase of LST was over the water body and the highest was over the built-up areas indicating the buffering capacity of wetlands. As air temperatures are highly linked to LST, our findings suggest that wetlands contribute to lower atmospheric temperature and offer cooling effects during dry months. Acknowledging the importance of wetlands in reducing temperature, at least in a local scale, justifies the need of conserving these ecosystems, as seeking mitigatory measures for climate change driven frequent heating effects is challenging.

Nitrogen released from sago pulp waste and Gliricidia sepium pruning mixtures on a Dystrudept of Central Moluccas and its effect on the growth of maize

The agricultural sector is the mainstay of the economy in Central Moluccas. However, most agricultural soils on the island have low soil fertility. One of the efforts that farmers can make to improve soil fertility is to apply organic matter, which is widely found in Central Moluccas. This study aimed at elucidating the effect of mixing high-quality organic material (Glicidia sepium pruning) with low-quality organic material (sago pulp waste) on the improvement of available nitrogen in an acid soil (Dystrudept) and growth of maize. Two experiments were carried out in a laboratory and a greenhouse. The compositions of the mixtures of sago pulp waste (A) and pruning of Gliricidia sepium (G) were A0 G100; A20G80; A40G60; A60G40; A80G20, and A100G0. Six treatments and one control (no application of residues) were arranged in a completely randomized design. The results showed that the application of the mixture of 20% and 80% of Gliricidia sepium pruning (A20G80) increased the cumulative amount of mineral N in the soil higher than that of the other organic material mixtures, which in turn improved maize growth.

Evaluation of copper tailings from the abandoned Messina Mine for possible reuse in recreational projects, South Africa

Historic mining of copper around Musina Town left behind a sizeable unrehabilitated tailing dump. This article reports on the study conducted to investigate the suitability of using copper tailings as sand replacement in recreational projects. The methodology used involved analyzing the particle size distribution and plasticity index (PI) of the tailings and determining their particle density, bulk density, particle shape, total porosity, and permeability coefficient. The pH of the tailings, major element oxides, and heavy metals composition were all analyzed. The tailings were classified as poorly graded sand with silt (SP-SM). Low fines (9.6%) and PI (1.4) values revealed that the copper tailings were texturally suitable for application in rootzones of sports fields, courts for beach volleyball, and bunkers of the golf courses. Their particle density (2.90 g/cm³), bulk density (1.53-1.89 g/cm³), porosity (34.62-47.04%), and permeability (1.42 x 10-3 cm/sec) were all within the recommended range for application in rootzones. The angular particles of the tailings supported their uses in the bunkers. However, their pH (7.9) and high quartz content (69% SiO2) confirmed their suitability for rootzones. However, the high concentration of Cu (1872.0 mg/kg) and Cr (159.5 mg/kg) was identified as a potential risk of using the copper tailings in rootzones. This and the relatively high Al2O3 (11%) and Fe2O3 (8%) suggested that the copper tailings should be first washed or processed before being used in any recreational projects. Developing a suitable technique for processing the studied copper tailings to enhance their properties for different recreational projects was recommended.

Effect of application compost and vermicompost from market waste on soil chemical properties and plant growth

This study was conducted to determine the effect of compost and vermicompost from market organic waste on the soil chemical properties and the growth of maize. The treatments tested were three doses of compost (2.5, 5, and 10 t/ha), three doses of vermicompost (2.5, 5, and 10 t/ha), and one control (without compost or vermicompost). At the time of harvest (10 weeks after planting), maize shoot dry weight, root dry weight, cob length, cob diameter, cob with husk, and cob dry weight, as well as the soil chemical properties organic carbon (C), total nitrogen (N), total phosphorus (P), available P, total potassium (K), and pH were observed. Maize plant height, leaf number, and stem diameter were observed at 2, 4, 6, and 8 weeks after planting. The results showed that the application of compost and vermicompost significantly affected soil chemical properties and the yield of maize. The application of 10 t vermicompost/ha resulted in the highest yield of maize and highest increase of soil organic carbon, total phosphorus available phosphorus, total potassium, and pH by 7.21%, 112.41%, 287.44%, 85.44% and 17.58%, respectively. The application of 10 t compost/ha resulted in the highest increase of soil total N by 44%.

Groundwater quality mapping for drinking and irrigation purposes using statistical, hydrochemical facies, and water quality indices in Tercha District, Dawuro Zone, Southern Ethiopia

When groundwater quality is good, it may be a substantial water supply for various applications. However, no systematic research on hydrogeochemistry and water quality features for drinking and irrigation has been undertaken in the present study area. As a result, the current study looked at hydrogeochemical variables and groundwater quality for drinking and irrigation in Tercha district, Dawuro Zone, Southern Ethiopia. Forty-seven groundwater samples were collected and tested to satisfy the required target for various physicochemical properties. The hydrogeochemical features of the groundwater in the study region were assessed using in-situ testing and laboratory analysis of physicochemical parameters. Groundwater samples from the research region were slightly acidic to slightly basic, with the principal cations and anions decreasing in sequence: Na+ > Ca2+ > Mg2+ > K+ and HCO3-> Cl-> SO42-. The hadrochemical facies of the studied region evolved from mildly mineralized dominant highland Ca-HCO3 water types to moderately mineralized mixed Ca-Na-HCO3 water types to highly mineralized deep rift floor Na-HCO3 water types. Additionally, the World Health Organization and the Ethiopian Standard Agency were utilized to compare the drinking water quality. Except for NO3- (4.25 %), Fe (8.51 %), and F- (2.12%), all groundwater samples from the research region were determined to be within permitted limits and appropriate for drinking. According to the Water Quality Index, about 80.86% of groundwater samples are excellent, and 19.14% are good drinking water. Sodium absorption ratio (SAR), sodium (Na) percentage, residual sodium carbonate RSC, permeability index (PI), and magnesium hazard were among the irrigation water quality indicators calculated (MH). The great majority of groundwater samples are suitable for agricultural use.

Identification of subsidence hazard zone by integrating engineering geological mapping and electrical resistivity tomography in Gunung Kidul karst area, Indonesia

The presence of natural cavities in karst morphology may cause severe civil engineering and environmental management problems. Karst formations will limit the expansion of urbanization, especially infrastructure development in limestone areas. Geophysical methods, especially electrical resistivity tomography (ERT) techniques, are effective and efficient solutions to detect voids below the surface. This study aimed to develop a subsidence hazard map as basic information for infrastructure development. The identification was made by measuring electrical resistivity tomography on eight profiles in the infrastructure development plan. In addition, it was also supported by geological mapping, particularly the structural geology and types of rocks around the site. The research area consists of massive limestone, bedded limestone, and cavity limestone with generally north-south joints. The analysis of geological mapping data and electrical resistivity tomography measurements showed that the cavity limestone was identified with a north-south elongated pattern in line with the fracture pattern found on the surface at the research area. The surface lithology type, the geological structures density, and the subsurface lithology were used to develop a subsidence hazard map. This information is beneficial in determining the safe location of infrastructure development based on disaster risk mitigation.

Determination of heavy metal elements concentration in soils and tailing sediments from lateritic nickel post-mining areas in Motui District, Southeast Sulawesi

Heavy metal elements concentration study has been determined from soils and tailing sediments in laterite nickel post-mining area in Motui District Southeast Sulawesi. This study aimed to determine the concentration of some heavy metal elements, especially Fe, Co, Mn and Cr, from surface soils sediments in waste dump sites and tailing sediments in settling ponds from lateritic nickel post-mining areas. A total of 20 samples consisting of 18 soil samples and 2 tailing sediments samples were systematically collected for the study. The soil samples from the waste dump site profile were collected from 3 layers which were divided based on the colour of the soils from top to bottom, namely Layer C, Layer D and Layer E. Six soil samples were taken from each layer with space between each sample in one layer was about 50 – 60 cm. The samples were sent to the laboratory and analysed using Atomic Absorption Spectrometer (AAS) method to determine the concentration of heavy elements. Metal-bearing minerals detected from the bedrock consists of chromite, manganese, magnetite and limonite which are responsible for the Cr, Mn and Co, and Fe content, respectively. The result showed that Fe content is significantly higher in soil samples from Layer C and tailing sediments with dark red to brown in colour, suggesting the strong relation between Fe content and colour index. The general element mobility trend showed that Mn and Co are positively correlated in soil sampling from all layers and tailing samples, whereas Fe and Cr show a negative correlation trend in Layer C, D and tailing sediments but positively correlated in Layer E.