David O. Yawson

Anthropogenic sources and environmentally relevant concentrations of heavy metals in surface water of a mining district in Ghana: a multivariate statistical approach

The levels of heavy metals in surface water and their potential origin (natural and anthropogenic) were respectively determined and analysed for the Obuasi mining area in Ghana. Using Hawths tool an extension in ArcGIS 9.2 software, a total of 48 water sample points in Obuasi and its environs were randomly selected for study. The magnitude of As, Cu, Mn, Fe, Pb, Hg, Zn and Cd in surface water from the sampling sites were measured by flame Atomic Absorption Spectrophotometry (AAS). Water quality parameters including conductivity, pH, total dissolved solids and turbidity were also evaluated. Principal component analysis and cluster analysis, coupled with correlation coefficient analysis, were used to identify possible sources of these heavy metals. Pearson correlation coefficients among total metal concentrations and selected water properties showed a number of strong associations. The results indicate that apart from tap water, surface water in Obuasi has elevated heavy metal concentrations, especially Hg, Pb, As, Cu and Cd, which are above the Ghana Environmental Protection Agency (GEPA) and World Health Organisation (WHO) permissible levels; clearly demonstrating anthropogenic impact. The mean heavy metal concentrations in surface water divided by the corresponding background values of surface water in Obuasi decrease in the order of Cd > Cu > As > Pb > Hg > Zn > Mn > Fe. The results also showed that Cu, Mn, Cd and Fe are largely responsible for the variations in the data, explaining 72% of total variance; while Pb, As and Hg explain only 18.7% of total variance. Three main sources of these heavy metals were identified. As originates from nature (oxidation of sulphide minerals particularly arsenopyrite-FeAsS). Pb derives from water carrying drainage from towns and mine machinery maintenance yards. Cd, Zn, Fe and Mn mainly emanate from industry sources. Hg mainly originates from artisanal small-scale mining. It cannot be said that the difference in concentration of heavy metals might be attributed to difference in proximity to mining-related activities because this is inconsistent with the cluster analysis. Based on cluster analysis SN32, SN42 and SN43 all belong to group one and are spatially similar. But the maximum Cu concentration was found in SN32 while the minimum Cu concentration was found in SN42 and SN43.

Impact of biomass burning on soil organic carbon and the release of carbon dioxide into the atmosphere in the coastal savanna ecosystem of Ghana

The impact of escalating human activities on greenhouse gas emission, global warming, and changes in global climate patterns is almost certainly the most discussed issue in the first decade of the 21st century. Two-thirds of Africa’s energy consumption consists of various forms of highly inefficient traditional biomass. In rural areas, low energy consumption is both a cause and consequence of poor development and also of the degradation of the natural environment. The burning of biomass or vegetation as a conventional land preparation method has a net negative impact on the soil organic carbon as well as on the environment through the oxidation of carbon into carbon dioxide, an anthropogenic greenhouse gas. This paper reports the findings of an experiment to investigate the impact of the heat due to burning on soil organic carbon at soil depths of 0–5 and 5–10 cm. It was observed that 21% decline in soil organic carbon resulted in the release of 1446 CO2 kg ha−1 into the atmosphere. This underscores the f...

Does incorporation of cowpea-maize residue mixes influence nitrous oxide emission and mineral nitrogen release in a tropical luvisol?

In the face of climate change, quantification of the emission of nitrous oxide from soils in relation to sufficient N availability for crop uptake has assumed much significance. This study used the 15N stable isotope technique, under controlled laboratory conditions, to quantify the interactive effect on and relative contributions of the component species to N2O emission and mineral N dynamics in a tropical luvisol incorporated with different rates of cowpea-maize residue mixtures. The results show that increasing the maize residue proportion in the mixture significantly decreases N2O emission compared to the sole cowpea incorporation but increases mineral N concentration compared to sole maize residue incorporation. It is concluded that mixing low C:N ratio cowpea residue with high C:N ratio maize residue has potential for N management in tropical legume-cereal intercropping systems with the view to minimizing N2O emission while making N available for crop uptake.

Management of natural resources in a conflicting environment in Ghana: unmasking a messy policy problem

Resource use conflict is an enduring problem for science and policy making. Using in-depth interviews and focus group discussions with resource users, policy makers and key informants, we explored four case examples of resource use conflict within lands and forestry, fisheries, oil and the mining sectors in Ghana. Results indicate that resource use conflict consists of a complex, non-linear system of balancing and reinforcing feedback loops that recur across resource sectors. The conflicts are difficult to clearly define, have many interdependencies and are multi-causal. Specifically, dysfunctional policy, commoditisation of land, infringement on rights of users, shift from communal to private land ownership, renegotiation of rights, and unclear roles and responsibilities of government agencies, exacerbate conflicts among resource users, managers and policy makers in Ghana. In addition, supranational policy such as the protocol of the Economic Community of West African States, which promotes free movement of people and goods within the 16-nation community, is a driver of conflict between native farmers and nomadic Fulani herders. Clear policy directions from government that outlines the specific roles of various departments involved in resource issues together with a holistic community participatory approach is therefore required to comprehensively understand and address such conflicts.

Mapping of noise risk zones derived from religious activities and perceptions in residential neighbourhoods in the Cape Coast metropolis, Ghana

Ambient noise levels emanating from religious activities in residential neighbourhoods are an emerging environmental problem that educes little attention from enforcement agencies and policy makers in Ghana. This paper set out to quantify religious noise exposure in urban residential neighbourhoods in the Cape Coast metropolis of Ghana. Subjective annoyance levels of residents in selected communities were determined. Noise risk zones were mapped using ARCGIS 9.3 software and surface interpolation for the data was carried out using inverse distance weighting. The results show that most (77 and 86 per cent) of the locations recorded noise levels that were above the Ghana Environmental Protection Agency maximum permissible limit for day and night, respectively. Pearsons correlation coefficient for day and night noise exposure shows strong association (0.714) at the 0.01 level. There is variability in the levels of noise for both day and night, which are rather high (standard deviation = 7.59477 and 7.94022, respectively). Generally, levels of noise exposure correlated with levels of annoyance of residents, except that the highest noise exposure was not recorded in the community where the annoyance level of residents was highest. Residential neighbourhoods within the study area largely experienced safe to tolerable levels of religious noise, although 5 per cent were within the high-risk zone. Given that the selected residential areas have high population densities, even when the dispersion of noise risk is spatially limited, it affects a large number of people who belong to different socio-economic classes.

Effects of rooting media on root growth and morphology of Brassica rapa seedlings

Rooting media used in current root phenotyping studies can have substantial effect. In this study, the effects of three different nutrient conducting papers (Black construction paper, Anchor blue germination paper and Kimpak paper) and soil-filled boxes on root growth and root system architecture (RSA) of Brassica rapa (cultivars ‘R500’ and ‘IMB211’) were investigated. Seedlings of the two B. rapa genotypes were supplied with nutrients on the nutrient conducting papers and in the soil-filled boxes. The papers and soil-filled boxes were fixed to flatbed scanners and two-dimensional images of roots were periodically taken and analysed. Root media effects on shoot and root biomass and on topological indices (TI) were observed. For example, root branching was more pronounced on the construction paper. Mean TI of 0.82 and 0.93, recorded for R500 and IMB211, respectively, on the construction paper indicated that substrates affect the herringbone pattern of brassica roots. Whilst it was indicated that different results could be obtained for the same RSA when different germination papers are used, the results showed that Anchor blue germination paper is an ideal proxy for soil in phenotyping seedlings for RSA traits and root growth.

Virtual water and phosphorus gains through rice imports to Ghana: implications for food security policy

This study estimated the gains of virtual water, Phosphorus (P) and Phytic Acid (PA) through rice and wheat import to Ghana for the period 1998– 2005, and assessed the implications of increasing rice import coupled with declining domestic production for food security. The total virtual water of Ghana associated with rice and wheat import for the study period was 5574 Mm3, while the total P and PA was 1,364,097 and 3,825,438 tonnes, respectively. Domestic paddy rice production started declining from 2003, but was exceeded by import from 2001 onwards. Particularly for rice, the combination of factors such as surging demand and per capita consumption, low yield resulting from less land under cultivation and irrigation, and high import bill, necessitates policy actions to remove constraints on domestic production. The paper, therefore, suggests policy actions to increase domestic rice production and to minimise Ghana’s exposure to the risks inherent in rice import.

Characterising shoot and root system trait variability and contribution to genotypic variability in juvenile cassava (Manihot esculenta Crantz) plants

The development of cassava genotypes with root system traits that increase soil resource acquisition could increase yields on infertile soils but there are relatively few work that has quantified cassava root system architecture (RSA). We used an easily adaptable and inexpensive protocol to: (i) measure genotypic variation for RSA and shoot traits of a range of cassava genotypes; and (ii) identify candidate variables that contribute the largest share of variance. Cassava genotypes were grown in soil-filled pots, maintained at 70% field capacity. Shoot and RSA traits were measured on plants grown up to 30, 45 and 60 days. Multivariate analysis was used to determine major traits contributing to variation. The study showed that cassava roots are adventitious in origin consisting of a main root axis and orders of lateral roots, and therefore the historically used term “fibrous roots” are redundant currently not contributing to clarity. There were significant differences (P < 0.05) for traits evaluated. The highest relative root growth rate occurred over the first 30 days and ranged from 0.39 to 0.48 cm day−1. Root fresh weight was significantly correlated with other traits, including root length (r = 0.79), leaf area (r = 0.72), number of lower nodal roots (r = 0.60), indicating that direct selection based on these traits might be sufficient to improve root biomass. Up to the first six principal components explained over 80% of the total variation among the genotypes for the traits measured at 30, 45 and 60 days. Leaf area, root diameter and branching density-related traits were the most important traits contributing to variation. Selection of cassava genotypes based on shoot and root biomass, root diameter and branching density at juvenile growth stage could be successful predictors of nutrient and water-use efficiency in the field. Further studies are required to relate studied juvenile cassava root traits with the performance of field-grown-mature plant with regard to drought, nutrient-use efficiency and yield.

Ghanaians Might Be at Risk of Inadequate Dietary Intake of Potassium.

Adequate dietary intake of potassium (K) helps fight noncommunicable diseases (NCDs), mainly hypertension and cardiovascular diseases. This paper (i) estimated the K intake of Ghanaian population using food supply and food composition data and (ii) compared this estimate with the WHO recommended requirement for K in order to assess if there is a risk of inadequate K intake. Food supply data (1961–2011) was obtained from the FAO Food Balance Sheet (FBS) to derive trends in food and K supply. The average food supply in the FBS for 2010 and 2011 was used in assessing the risk of inadequate dietary intake of K. The K contents of the food items were obtained from food composition databases. The mean K supply per capita per day was approximately 856 mg. The assessment suggests a potentially large risk of inadequate dietary K supply at both individual and population levels. The results suggest the need for assessing options for managing K deficiency, including assessment of K supplying power of soils and K fertilizer management in food crop production systems, as well as empirical estimates of K content of food items (including those underreported in the FBS) and mixed diets in Ghana.

Systematic review of the effects of agricultural interventions on food security in northern Ghana

Background Food insecurity and poverty rates in Ghana are highest in the districts from latitude 8° N upwards. These have motivated several interventions aimed at addressing the food insecurity via promoting agricultural growth. An assessment of the overall impact of these interventions on food security is necessary to guide policy design and future interventions. Methods and findings A systematic review was used to assess the cumulative evidence of the effect of development interventions, implemented from 2006 to 2016 on food security, especially in Northern Ghana. Information were retrieved from over 20 Government and non-Governmental organisations through online search and actual visits. The number of studies included in systematic review was 22. The study showed that a large number of interventions have been implemented in Northern Ghana over the study period. Access to quality extension services, training and capacity building was a major intervention strategy. About 82% of studies considered increasing production but only 14% of the studies reported on changes in yield. About 42% of the included studies used market access as a strategy but about 44% reported increase in incomes of beneficiaries (with only seven studies providing numerical evidence for this claim). The ranking of frequency of intervention strategies was in the order extension and capacity building > production > postharvest value addition > water and irrigation facilities > storage facilities > input supply. A substantial number of the studies had no counterfactuals, weakening confidence in attributing impacts on food security for even the beneficiaries. Conclusions It is concluded that evidence for impacts of the interventions on food security was weak, or largely assumed. A logical recommendation is the need for development partners to synchronise their measurement and indicators of food security outcomes. It is also recommended that some food security indicators are explicitly incorporated into intervention design while bearing in mind the potential need for counterfactuals.