Lake extent changes in Basotu,Tanzania: a mixed-methods approach to understanding the impacts of anthropogenic influence and climate variability

Incompatible land use is a major contributor to ecosystem degradation, and is often exacerbated by climate change impacts. We investigate Lake Basotu, Tanzania as a case study where natural lake variability has been affected by agricultural land use. Comparisons between a satellite-derived history of lake surface area, local precipitation records, and corresponding anthropogenic activity show the impacts of agricultural and historical practices. We argue that insufficient consideration to the wider ecological impacts of large agricultural projects has lasting implications. This is particularly true in semi-arid environments where food production demands need to be continuously met. In the future, major conservation strategies should be investigated to maintain the environmental integrity and sustainability of freshwater resources.     

视电阻率测深和音频大地电磁测深在坦桑尼亚某金矿区探测效果的对比分析

隐伏矿产勘查是我国乃至世界现今的主要任务,电阻率测深法和大地电磁测深法是寻找深部矿和隐伏矿的主要工作手段;根据大功率视电阻率测深与音频大地电磁测深在坦桑尼亚某金矿区的实际应用,结合钻孔地质剖面对两者的测量结果反演后进行了对比研究,分析了两种测深方法在构造蚀变岩型金矿上各自的探测效果,研究认为:采用视电阻率测深和音频大地电磁测深可以推测地下构造带电性分布特征、地质结构、构造产状及矿(化)体的赋存空间,音频大地电磁测深对矿区深部构造形态反映效果较好,显示了构造蚀变带的垂向延伸情况;视电阻率测深在反映中、浅部地质体特征方面效果较好,并进一步提高了对大地电磁异常的横向分辨能力,能够为布置钻探工程提供更加充分的依据。     

坦桑尼亚卢帕金矿田中部姆娜兹姆莫加矿区土壤地球化学特征及找矿方向

坦桑尼亚姆娜兹姆莫加矿区位于坦桑尼亚乌本迪造山带东南卢帕金矿田中部,属典型的造山型金矿。为查明该区成矿规律,明确找矿方向,在区内开展了1∶10000土壤地球化学测量工作。通过元素分布、元素相关性、元素异常等特征研究表明,Au为本区主成矿元素;并指出在花岗片麻岩和二长花岗岩等岩性单元中,Au与As、Sb相关性不明显,金成矿作用对岩性单元及围岩无选择。依据成矿地质条件、地球化学异常及查证成果认为金异常浓集区、构造交汇部位、次级断裂及破劈理发育部位和不同岩性单元接触带是勘查重点地段。     

Multiple mycotoxin co-occurrence in maize grown in three agro-ecological zones of Tanzania

In this study, the co-occurrence of multiple mycotoxins in maize kernels collected from 300 households' stores in three agro-ecological zones in Tanzania was evaluated by using ultra high performance liquid chromatography/time-of-flight mass spectrometry (TOFMS) with a QuEChERS-based procedure as sample treatment. This method was validated for the analysis of the main eleven mycotoxins of health concern that can occur in maize: aflatoxin B₁ (AFB₁), aflatoxin B₂ (AFB₂), aflatoxin G₁ (AFG₁), aflatoxin G₂ (AFG₂), ochratoxin A (OTA), deoxynivalenol (DON), fumonisin B₁ (FB₁), fumonisin B₂ (FB₂), HT-2 toxin, T-2 toxin and zearalenone (ZEN). From each zone one major maize producing district for home consumption was chosen and 20 villages for each district were randomly selected for sampling. All mycotoxins of health concern, except for T-2 toxin, were detected in the maize samples. Particularly high levels of AFB₁ (50%; 3–1,081 μg kg⁻¹), FB₁ (73%; 16–18,184 μg kg⁻¹), FB₂ (48%; 178–38,217 μg kg⁻¹) and DON (63%; 68–2,196 μg kg⁻¹) were observed. Some samples exceeded the maximum limits set in Tanzania for aflatoxins or in European regulations for other mycotoxins in unprocessed maize. Eighty seven percent of samples were contaminated with more than one mycotoxin, with 45% of samples co-contaminated by carcinogenic mycotoxins, aflatoxins and fumonisins. Significant differences in contamination pattern were observed among the three agro-ecological zones. The high incidence and at high levels (for some) of these mycotoxins in maize may have serious implications on the health of the consumers since maize constitute the staple food of most Tanzanian population. Effective strategies targeting more than one mycotoxin are encouraged to reduce contamination of maize with mycotoxins.     

Energy consumption and economic growth nexus in Tanzania: An ARDL bounds testing approach

In this paper, we examine the intertemporal causal relationship between energy consumption and economic growth in Tanzania during the period of 1971–2006. Unlike the majority of the previous studies, we employ the newly developed autoregressive distributed lag (ARDL)-bounds testing approach by Pesaran et al. [2001. Bounds testing approaches to the analysis of level relationships. Journal of Applied Econometrics 16, 289–326] to examine this linkage. We also use two proxies of energy consumption, namely total energy consumption per capita and electricity consumption per capita. The results of the bounds test show that there is a stable long-run relationship between each of the proxies of energy consumption and economic growth. The results of the causality test, on the other hand, show that there is a unidirectional causal flow from total energy consumption to economic growth and a prima-facie causal flow from electricity consumption to economic growth. Overall, the study finds that energy consumption spurs economic growth in Tanzania.     

坦桑尼亚芒果金矿成矿地质特征及金赋存状态研究

太古宙卡哈马(Kahama)绿岩带为坦桑尼亚环维多利亚湖区域八大绿岩带之一,长约100 km,是坦桑尼亚重要的成矿带之一,带上分布有盖塔(Geita)、布鲁杨葫芦(Bulyanuhulu)、高登瑞德(Golden Ridge)、朱比利里夫(Jubilee Reef)等大型、特大型金矿床和众多金矿(化)点,具有很大的找矿前景。芒果(Manangu)金矿体分别赋存于矿区北西部条带状含铁建造(磁铁石英岩)与酸性火山沉积岩(凝灰岩)的上下接触带部位,矿体形态简单,具不规则层状、似层状,金属矿物自然金呈他形粒状,亮金黄色,高反射率,均质性,多属于粒间金。     

Weathering the storm: disaster risk and vulnerability assessment of informal settlements in Mwanza city,Tanzania

This study employs participatory disaster risk and vulnerability assessment to analyse vulnerability to disasters in informal settlements in Mwanza city, Tanzania. The results show that a plethora of factors – human, physical, social, economic and natural – interact in complex non-linear ways to shape vulnerability to disaster in informal settlements in Mwanza city. The study shows that coping strategies of some individuals in informal settlements reinforce their risks to disaster. For example, the stones that are positioned on weak roof structures for protection may become projectiles in the event of storm: a kind of disaster by design. This quick-fix coping strategy is unlikely to be sustainable.     

Oviposition and Behavioral Responses of Culex quinquefasciatus to Skatole and Synthetic Oviposition Pheromone in Tanzania

Studies on the behavioral and oviposition responses of Culex quinquefasciatus to 3-methylindole or skatole (an oviposition site cue) and (5R,6S)-6-acetoxy-5-hexadecanolide (the synthetic oviposition pheromone, SOP) were conducted in Muheza, northeast Tanzania. Cx. quinquefasciatus displayed a bimodal pattern of oviposition. The highest peak (64.8%) was between 18:00 and 20:00 hr, while the second peak (18.9%) was between 06:00 and 08:00 hr. The mean number of egg rafts oviposited per day between the two peaks was different (P < 0.05). Oviposition responses of gravid Cx. quinquefasciatus differed across the range of concentrations of skatole. Larger numbers of egg rafts were deposited in bowls treated with 10^–6 g or 10^–5 g skatole than in bowls with tap water (P < 0.05). The number of egg rafts deposited in bowls treated with 10^–4 or 10^–1 g skatole was not different from that laid in tap water (P > 0.05). Under field conditions skatole was found to be effective for a period of seven days, after which its biological activity decreased significantly. It was further found that more egg rafts of Cx. quinquefasciatus were deposited in water treated with SOP than in water treated with skatole (P = 0.0002). An additive effect was observed when the SOP + skatole combination was used to attract gravid Cx. quinquefasciatus to oviposition sites. It is concluded that skatole and SOP mediate oviposition site selection of Cx. quinquefasciatus under field conditions.     

坦桑尼亚太古宙绿岩带中BIF型金矿床的勘查标志——以Maheiga金矿床为例

Maheiga金矿产于坦桑尼亚克拉通的太古宙Kahama绿岩带尼安萨(Nyanzian)群上下段接触带附近,是受层间剪切破碎带控制的隐伏条带状含铁建造型金矿床。区内褶皱发育,岩浆活动强烈。硅化、绿泥石化、黄铁矿化和褐铁矿化与金矿关系密切。矿床可分为3期5个成矿阶段,自然金―石英―多金属硫化物阶段为主要的成矿阶段。赋矿的磁铁石英岩和金矿石的磁化率(达342×10-3~1 477×10-3SI)与背景岩石变凝灰质砂岩、变质凝灰岩及绿泥石化千枚岩(仅0.16×10-3~1.26×10-3SI)差异明显;条带状含铁建造、含铁建造金矿石和变凝灰质砂岩的视极化率分别为8.66×10-2、2.18×10-2和0.48×10-2,视电阻率分别为220、280和380Ω·m,前者具明显的相对"低阻、高极化"物性特征。化探异常元素组合为Au、As、Sb、Ag、Hg、Pb和Ba。矿石中各元素的浓集克拉克值由大到小依次为Au-As-Sb-W-Pb-B-Ag-Zn-Sn-Mo-Bi-Cu-Cr-Hg,其中,Au、As和Sb在条带状磁铁石英岩中富集明显,与成矿有利层位为条带状磁铁石英岩的特征相一致,是深部寻找金盲矿体的主要指示元素。根据上述特征,确定了该类型金矿床的勘查标志。     

Evaluation of iron oxide impregnated filter paper method as an index of phosphorus availability in paddy soils of Tanzania

Phosphorus is a major yield limiting nutrient in rice production and yet most soil test methods for predicting P availability to plants have a number of shortcomings especially under flooded conditions. The objective of this study was to evaluate the iron oxide impregnated filter paper (Pi) method for assessing changes in P availability in soils subsequent to flooding and to determine the suitability of the method in assessing P status in paddy soils. The results indicated that available P increases considerably (between 34% and 256%) subsequent to flooding and this affected responsiveness of the soils to P application. Two versions of the Pi method namely; the Pi method used under flooded conditions (Pi-P_f) and Pi strips embedded directly in flooded soils (Pi-P_fe) were effective in assessing P availability in paddy soils. The two Pi methods were better correlated with rice dry matter yield than the traditional soil tests and are hence recommended for use in soil testing under flooded conditions. The tentative critical levels of P for the two procedures under pot conditions were 22 mg/kg for Pi-P_f and 15 mg/strip for Pi-P_ef.