Dissolution Kinetics of Stilbite at Various Temperatures under Alkaline Conditions

Experiments measuring the dissolution rates of stilbite (NaCa [Al Si O ].14H O) in pH-buffered solutions were 2 5 13 36 2 performed in batch reactors at 4, 25, 40 and 60 oC. The pH conditions of the buffer solutions ranged from 8.5 to 12.5. The dissolution rates calculated from silicon concentration of the reacting fluid increased with increasing temperature (4–60 oC) and pH. The dissolution rates ranged from 3.45 x 10-15 (mol cm-2 s-1) at pH 10.7 and 4oC to 1.93 x 10-9 (mol cm-2 s-1) at pH 12 and 60oC and were pH dependent. The rate law was established as R = k (a -)n , where k is OH the rate constant, a is the activity of the OH- species and n the reaction order. The n values obtained were, 0.32 at 4 oC, 0.35 at 25 oC, 0.38 at 40 oC and 0.38 at 60 oC. Activation energy determined using Arrhenius plot was 48.45 kJ/mol at pH 9 and 30.88 kJ/mol at pH 12

Pesticide residues in fish from the Densu River Basin in Ghana

The Densu River is a typical river flowing through agricultural areas in Southern Ghana. Six fish species from different locations in the river were sampled and analyzed for residues of pesticides and metabolites using GC with ECD/FID. The results of the study indicate that all the detected residues and metabolites in fish samples from the Densu River Basin were organochlorines (OCs). Among the pesticides residues analyzed, DDE, α-endosulfan, γ- HCH, δ- HCH, heptachlor and endosulfan sulphate, were predominant in all the samples. About 50% of the samples recorded positive detection of DDE while α-endosulfan was detected in 60% of the samples. γ- HCH, δ- HCH were detected in 75% and 65% of the samples respectively with heptachlor occurring in 80% of the samples. In almost all the fish species analyzed, DDE was the predominant compound having a mean value of 7.99 μgKg-1. Higher concentrations of pesticide residues were detected in fish samples from the Densu River at Nsawam than the other locations. The total concentration of residues in the fish samples ranged between 0.49 μgKg-1 and 8.90 μgKg-1 with the highest level detected in Hepsetue odoe (HO-N). The sequence of pesticide residues detected in fish samples were HO-N > HN-N > CO-N > CG-N > TZ-N > CN-W > TZ-W > CG-W. The high ratio of DDE/DDT in fish samples (0.1 – 6.9 with a mean of 2.51) indicated probably old input of DDT and significant degradation. The γ -HCH isomer (lindane) was the dominant HCH in fish samples suggesting a preferential usage of lindane (purified γ-HCH) in these areas. The δ-HCH/γ-HCH ratios in most fish samples were low indicating the present input of the pesticide lindane from non-point sources.Keywords: Pesticide residues, Fish, Densu River Basin, Ghana, exposur

Water quality assessment of streams draining the Akwapim Ridge of Ghana

Surface water samples from seven streams on the Akwapim Ridge were analysed over a period of 1 year for various water quality parameters following standard methods prescribed in APHA, AWWA, WEF and AOAC. The study was carried out in order to assess the suitability of the streams for drinking and other domestic purposes. Additionally, the effect of land use activities was assessed. The study revealed that, generally, most of the physico-chemical parameters of the streams were below the World Health Organization (WHO) limits recommended for drinking water, with the exception of the levels of sulphate and conductivity in three of the streams (Opiafo: 224 mg/1, 908.5 ìS/cm; Kwati: 221.3 mg/1, 920 ìS/cm; and Ademi: 246 mg/1, 1292 ìS/cm), respectively, which were above the WHO requirements. Nevertheless, taking these factors into consideration (except the sulphate and conductivity), the waters may be regarded as excellent and good for drinking and other domestic uses

Green Supply Chain Management and Environmental Performance: The moderating role of Firm Size

This study examined the impact of internal and external green supply chain practices on environmental performance among construction firms. The study used the quantitative survey research design in its methodology. A total of 217 employees were sampled from fifty (50) construction firms. Structural Equation Modeling was used to analyze the data. The results showed that green design does not have a significant positive relationship with environmental performance. However, green design has a positive impact on external green practices namely green purchasing and green construction. Green purchasing and green construction have direct positive relationships with environmental performance. Green design through external green practices have a significant positive relationship with environmental performance. The study found that firm size moderates the relationship between green design, through external green supply chain practices and environmental performance among construction firms

Additive manufacturing interventions during the covid-19 pandemic: South Africa

Additive manufacturing (AM), also known as 3D printing, is considered a renaissance of the manufacturing industry. Its unique capability of manufacturing 3D objects with intricate geometrical configurations has been used to produce hospital equipment and personal protective equipment (PPE) in an attempt to curb the spread of the COVID-19 pandemic in South Africa. The technology has been used by different research units to produce ventilators, respirator face masks, oscillating respiratory devices, oxygen connectors, oxygen splitters, non-invasive ventilation helmets, reusable clinician PPE, visor frames for face shields, etc. Despite the efforts of the AM community in South Africa, COVID-19 infections have continued to increase in the country. It came to light that technological interventions (including AM) alone cannot prevent the spread of the virus without the corresponding adaptive behavioural changes, such as adhering to COVID-19 prevention protocols (washing of hands, social distancing, etc.). It could be postulated that the spread of COVID-19 can only be prevented by inter-marrying the technological interventions (AM) with adaptive behavioural changes

Sustainable P-enriched biochar-compost production: harnessing the prospects of maize stover and groundnut husk in Ghana’s Guinea Savanna

Farmers in resource-poor areas of the Guinea Savanna zone of Ghana often face declining soil fertility due to the continuous removal of nutrient-rich harvested produce from their fields. This study focuses on the Lawra Municipality in the Guinea Savanna zone of Ghana, where low soil fertility, specifically, limits phosphorus (P) bioavailability and hinders crop production. The objective of this research is to formulate P-enhanced biochar-compost from maize stover (MS) and groundnut husk, which abound in the area, to close the nutrient loop. MS was co-composted with groundnut husk biochar at varying rates of 0, 10, 20, 30, and 40% by volume. To facilitate decomposition using the windrow system, the composting heaps were inoculated with decomposing cow dung, and the moisture content was kept at 60% throughout the monitoring period. The addition of biochar shortened the lag phase of composting. However, rates above 20% resulted in reduced degradation of MS. Biochar incorporation enriched the available phosphorus content in the final compost from 286.7 mg kg−1 in the non-biochar-compost to 320, 370, 546, and 840.0 mg kg−1 in the 10, 20, 30, and 40% biochar-compost, respectively

Artificial and Natural Radioactivity Measurements and Radiation Dose Assessment in the Vicinity of Ghana Nuclear Research Reactor-1 (GHARR-1)

Radioactivity concentrations of <sup>226</sup>Ra, <sup>232</sup>Th, <sup>40</sup>K and <sup>137</sup>Cs in soil samples and water sources around the Ghana Research Reactor-1 (GHARR-1) and the immediate surroundings have been measured using gamma spectrometry. The primary aim of the study was to establish baseline radioactivity levels in the environs of GHARR-1. The average activity concentration of <sup>226</sup>Ra, <sup>232</sup>Th, <sup>40</sup>K and <sup>137</sup>Cs were 22.3 ± 1.12 Bq kg<sup>-1</sup>, 49.8 ± 1.60Bq kg-1, 99.60 ± 5.81 Bq kg<sup>-1</sup> and 1.48 ± 0.25 Bq kg<sup>-1</sup> for soil and 0.60 ± 0.11 Bq l<sup>-1</sup>, 2.13 ± 0.21 Bq l<sup>-1</sup>, 10.75 ± 0.84 Bq l<sup>-1</sup> and 0.47 ± 0.05 Bq l<sup>-1</sup>for the water, respectively. The <sup>226</sup>Ra and <sup>232</sup>Th concentrations compare quite well with world averages, whilst the <sup>40</sup>K concentration was lower than the world average. The levels of <sup>137</sup>Cs observed in the samples are within the range of ‘background’  concentrations. The estimated average annual effective doses from external exposure to soil and ingestion of water samples were calculated to be 0.06 mSv and 0.53 mSv, respectively. The estimated outdoor  external gamma dose rate measured in air ranged from 20-430 nGy h<sup>-1</sup> with an average value of 100 nGy h<sup>-1</sup>, which is higher than the world average value of 59 nGy h<sup>-1</sup>. In the case of water samples, the average value was higher than the guidance level of 0.1 mSv y<sup>-1</sup>, as recommended by the European Union and the World Health Organization

Determination of Trace Elements in the Sakumo Wetland Sediments

Abstract: The objective of this research was to determine the current pollution status of the Sakumo wetland with the aim of identifying factors affecting the long-term integrity of the wetland ecosystem. Sediment samples from the Sakumo wetland were analysed for Cd, Co, Cr, Cu, Fe, Ni, Mn and Zn using Instrumental Neutron Activation Analysis (INAA) coupled with the conventional counting system. The sediment materials exhibited higher concentrations of trace elements Cd (maximum; 0.041 mg/kg), Co (maximum; 0.64 mg/kg), Cr (maximum; 30.73 mg/kg), Cu (maximum; 22.89 mg/kg), Ni (maximum; 11.69 mg/kg) and Zn (maximum; 6.52 mg/kg). In some of the lagoon sediments compared with their levels in world average soils, the average concentrations of the trace elements in general are below or within levels in world average soils/uncontaminated soils. Concentrations of Ni showed positive correlation with Cr whilst Co correlated positively with Cr and Zn. However, lack of correlation between Fe and Cd, suggests that the influence of these parameters on the distribution of trace metals is not important

Global patterns of nitrate isotope composition in rivers and adjacent aquifers reveal reactive nitrogen cascading

Remediation of nitrate pollution of Earth’s rivers and aquifers is hampered by cumulative biogeochemical processes and nitrogen sources. Isotopes (δ15N, δ18O) help unravel spatiotemporal nitrogen(N)-cycling of aquatic nitrate (NO3−). We synthesized nitrate isotope data (n = ~5200) for global rivers and shallow aquifers for common patterns and processes. Rivers had lower median NO3− (0.3 ± 0.2 mg L−1, n = 2902) compared to aquifers (5.5 ± 5.1 mg L−1, n = 2291) and slightly lower δ15N values (+7.1 ± 3.8‰, n = 2902 vs +7.7 ± 4.5‰, n = 2291), but were indistinguishable in δ18O (+2.3 ± 6.2‰, n = 2790 vs +2.3 ± 5.4‰, n = 2235). The isotope composition of NO3− was correlated with water temperature revealing enhanced N-cascading in warmer climates. Seasonal analyses revealed higher δ15N and δ18O values in wintertime, suggesting waste-related N-source signals are better preserved in the cold seasons. Isotopic assays of nitrate biogeochemical transformations are key to understanding nitrate pollution and to inform beneficial agricultural and land management strategies