This study was conducted in the Kilombero Valley Ramsar Site (KVRS), the largest low-altitude freshwater wetland in East Africa to: 1) determine pesticide contamination of soil, water, and sediment at different seasonal weather conditions 2) critically analyze the seasonal and spatial ecological impacts of pesticide contaminations under tropical weather conditions 3) estimate the potential environmental risks from pesticide exposure based on analytical data. Surface sediments, soil and water samples were collected from sugarcane, teak and rice plantations of the KVRS during the dry (January 2012) and the rainy (March–April 2013) seasons. Samples were screened for 97 different types of pesticide residues using and LC–MS and HPLC–MS. Physical-chemical properties of the sediment and soil samples and meteorological data were analyzed. 92% of soil and sediment samples had relatively low OM content (<5%) while 60% of samples had high clay content, indicating high cation exchange capacity that can bind pesticides to the soils. Field soil and air temperature ranging 28–35°C, total sunshine hours-208 h/month, photo radiation −764 MJ/m2, average precipitation 300 mm/month, wind speed >60 km/h, humidity >80% were recorded. Frequency of detection and concentration of pesticides residues depended on seasons. For the dry season sampling, glyphosate/AMPA (0.01–0.55 µg/g), and diuron (0.026–1.7 µg/g) were mostly detected in the sediment and soils. Monuron (1.28–3.9 µg/L) and propoxur (0.05–0.6 µg/L) were mostly detected in the rainy seasons (water and sediments). Glyphosate was above limit of detection in the dry season water samples indicating that its emission into the water system may have been directly through application. Maximum diuron concentrations in water were >30 times higher than the estimated predicted no-effect concentration (PNEC) value (0.054 µg/L) indicating a risk to aquatic community. Calculated pore water concentrations (0.992–0.081 µg/L), exceeded the estimated PNEC values during the dry season, indicating a risk to benthic organisms. Detection of pesticide is influenced by application, environmental factors and the timing of sampling. Further research is recommended to increase our knowledge on soil-water-sediment interactions in the tropics with regard to pesticides.
Introduction: The benefit of wetlands for reducing poverty depends on the effectiveness of governance systems that influence peoples' behaviour in the wise use of wetlands. Objectives: This article critically analyses the current poverty reduction strategies, agrarian policies and economic investments governing wetland usage, especially in Tanzania, with regard to their impact on sustainable Ramsar wetlands management. Methodology: It analyses the management structure, domestic policies and legal framework relating to the protection of wetlands in Tanzania in accordance to the wise use concept of the Ramsar Convention. Outcomes: Tanzanian legal provisions for wetland protection are uncoordinated and too limited in their coverage and scope to sufficiently address the destruction of wetland ecosystems. There is no comprehensive national legal framework to guide sustainable management of Ramsar wetlands in Tanzania as laid out by the Ramsar Convention, which the country ratified in the year 2000. Conclusion: Without a sound legislative and policy-making framework, Tanzanian wetlands and their diverse ecosystem services will continue to degenerate with current strategies of increasing agribusiness and other developmental projects or economic investments. This paper provides critical baseline information to inform decision makers to develop appropriate policy and laws, which promote the wise use of wetlands in Tanzania.
A rapid increase in population and urban development has direct impacts on the natural environment of peri-urban areas of big cities, especially in the developing countries. This study examined land use and land cover changes (LULCC) of peri-urban areas of Kinondoni Municipality in Dar es Salaam city for the period between 1999 and 2019 and predicted future changes by 2039. The specific objectives were to; (i) map the spatial-temporal land use and cover changes (ii) analyze settlements (built-up areas) patterns and factors influencing their changes (iii) predict changes that might happen for the next two decades. LULCC for 1999 to 2019 were detected through Maximum Likelihood (ML) supervised classification techniques while Cellular Automata based on Artificial Neural Network (CA-ANN) model was used to predict future changes. Over the past two decades, 33.7% of vegetation has been lost due to increased settlements, as shown by linear development pattern of built-up areas, which has gained about 30% of other land covers. This study predicts that by 2039, built-up areas will increase drastically to occupy 51.6%, while vegetation and water cover will decrease to occupy 40.4% and 1.4%, respectively. Without good planning strategies and land use policies, the control and management of the magnitude and patterns of peri-urban growth and sustainable management of natural and built environments in Tanzania will remain a challenge. This paper seeks to contribute to the body of knowledge required for evidence-based policy formulation and decision making to attain sustainable urbanization through setting suitable management plans for peri-urban areas of Tanzanian cities. Keywords: Artificial Neural Network, Land use/cover changes, Maximum likelihood, Peri-urban, Remote sensing
This study was conducted in the KVRS to; evaluate the seasonal eco-toxicity of water, soil and sediment samples; establish the suitability of using temperate biotest batteries in tropical systems; classify the toxicity of samples using Fuzzy Rules to estimate potential ecological risks. 143 water, sediment, and soil samples were collected during dry and rainy seasons in plantation areas. Pseudokirchneriella subcapitata, Aliivibrio fischeri and Arthrobacter globiformis bioassays were used to assess the toxicity of the samples. Results were categorized and classified into toxicity classes. Dry season presented a significantly higher mean inhibition of 31% than 5% shown by rainy season samples (p < 0.001) in the bacterial bioassays, indicating a lower concentration of contaminants due to flooding and increased surface runoff. A few sediment samples resulted into 100% inhibition of A. globiformis, implying organisms were physiologically inactive upon exposure to contaminants. Seventy-three percent of samples posed little or no toxic potential risk, 25% posed critical risk and 1% posed elevated critical risk, implying the KVRS ecosystem might be at risk if the extensive usage of pesticides in the area is not well managed and monitored. The temperate micro-biotests can be used in tropical systems, but with further research on suitable organisms and standardized methods. ARTICLE HISTORY
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