Horizontal variation in trace elements and soil characteristics at Siloam and Tshipise geothermal springs, Limpopo Province, South Africa

The Limpopo Province is the location of 31% of South Africa’s geothermal springs. The springs at Siloam and Tshipise are among those springs which fall into the ‘scalding category’ with average temperatures of 67.7°C and 54.6°C, respectively. The aim of this study was to determine the horizontal variation in trace element concentrations and soil indicators in surface soil associated with the geothermal springs at Siloam and Tshipise. Results show that, in general, the trace element concentrations present in the soil decrease with horizontal distance from the springs. Water and soil samples were collected from May to July 2014, with the soil sampled at 0–15 cm depth at 5 m intervals in the horizontal distance from the geothermal spring. The physicochemical parameters of the water were determined as well as the trace elements. The soil samples were digested using microwave digestion and trace elements were determined using an inductively coupled plasmamass spectrometer (ICP-MS). Soil indicators – pH, soil organic matter (SOM) and soil water retention (SWR) – were also determined. The resulting data were subjected to both descriptive and factor analyses. Results showed only one factor determining the variation in geothermal water, attributed to the rock–water interaction in the deep aquifer (geology); two factors were obtained for variation in soil indicators and trace element concentrations, attributed to spring geology and the soil pedogenesis. There was a strong correlation between the trace elements and soil indicators at the 95% confidence level. There is generally a positive correlation between the trace elements and soil indicators if the soil pH, SOM and SWR are high; in these instances most of the trace elements in the soil will also be relatively high. A two-factors-without-replication ANOVA (p ˂ 0.05) showed that there is a significant difference in trace element concentrations at different distances.Keywords: geothermal springs, trace metals, soil indicators, rock-water interactions, soil pedogenesi

Mineral Constituents and Kaolinite Crystallinity of the <2 μm Fraction of Cretaceous-Paleogene/Neogene Kaolins from Eastern Dahomey and Niger Delta Basins, Nigeria

This study examines the mineral composition and kaolinite crystallinity of Cretaceous and Paleogene/Neogene kaolins from Nigeria based on X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy data of the <2 μm fraction. The purpose of this was to assess the minerals present, structural order, and possible industrial applications of the kaolins. A total of twenty-eight (28) samples comprising of fifteen (15) Cretaceous and thirteen (13) Paleogene/Neogene kaolins were analysed. The XRD results showed that both the Cretaceous and Paleogene/Neogene kaolins have kaolinite as the dominant phase followed by quartz with anatase, hematite, and goethite occurring in minor quantities. Based on the mineralogical composition, the Paleogene/Neogene deposits were classified as sandy kaolin and the Cretaceous deposits were classified as pure kaolin. The kaolinite structural order for the Cretaceous pure kaolin was higher than that obtained for the Paleogene/Neogene sandy kaolin with more quartz, iron, and titanium oxides. The economic consideration of the deposits showed that the sandy kaolin type can be used in pigment industrial applications whereas the pure kaolin type can be used in refractory, fiberglass, and ceramic industrial applications

Hydraulic characteristics of a fractured crystalline basement aquifer in Nzhelele area, Limpopo Province, South Africa

Knowledge on hydraulic characteristics of fractured crystalline basement aquifers is limited resulting to lack of reliable information for effective groundwater management. This is crucial as these aquifers provide good sources of potable water in most rural communities. Heterogeneous nature of these aquifers requires detailed understanding and accurate estimation of hydraulic characteristics. This study estimated hydraulic characteristics of a fractured crystalline basement aquifer and inferred their influence on groundwater storage potential and flow. Aquifer Test Solver was used for automatic curve matching to identify appropriate aquifer models and test solutions for estimating hydraulic characteristics. Root-mean-square error (RMSE), mean absolute error (MAE) and correlation coefficient (R) were used to evaluate the performance of the fitted models. Plotted derivative curves were used to identify the presence of fracture dewatering in the aquifer. The R, RMSE and MAE ranged from 0.702 to 0.995, 0.31–3.45 m and 0.23 to 3.06 m, respectively. The fits between measured and estimated drawdowns were good and performance mostly acceptable and comparable to those of related studies. Storativity, transmissivity and hydraulic conductivity ranged from 0.0003 to 0.0680, 0.78 to 12.3 m2/day and 8.56 × 10−7 to 5.32 × 10−6 m/s, respectively. The storage potential of the aquifer varied from low to high, ability to transmit water per unit area was mostly medium though the ability to transmit water through its entire thickness was mostly low. The study area is dominated by leaky aquifer and fracture dewatering. Groundwater use should be monitored and managed effectively to avoid fracture dewatering and its associated risks

Trophic status of Vondo and Albasini Dams; impacts on aquatic ecosystems and drinking water

The presence and levels of major nutrients in the water from Vondo and Albasini Dams and their water treatment plants have been assessed to determine trophic status of the dams and impacts on aquatic ecosystems and drinking water. Water quality parameters particularly phosphates and nitrates are critical in assessing the trophic status. Water quality parameters linked to eutrophication and agrochemicals were analyzed. Phosphate was undetectable in both dams. The nitrate levels in Albasini and Vondo Dams which were from 1.16 to 6.65 mg/L and 0.46 to 4.19 mg/L, respectively, were within and above the South African guideline for aquatic ecosystems of 2 mg/L. The raw water pH for Vondo and Albasini Dams were from 6.20 to 7.46 and 6.35 to 8.70, respectively, and were mostly within acceptable guidelines for aquatic ecosystems. The water transparency for Vondo and Albasini Dams were from 0.5 to 4.2 m and 0.4 to 0.9 m, respectively. The levels of all other water quality parameters investigated in both dams and their WTPs mostly indicate low, rarely high and no water quality problems in aquatic ecosystems and drinking water. The low levels of total suspended solids and water transparency, the pH range, low to high electrical conductivity, low to acceptable dissolved oxygen levels, acceptable to high biological oxygen demand and nitrate levels for both dams indicate oligotrophic to eutrophic states. Though oligotrophic state dominates, the mixture of trophic states has been attributed to increase in urbanization and intensive agriculture