Geogenic contaminants and groundwater quality around Lake Victoria goldfields in northwestern Tanzania.

Geogenic contamination of groundwater is frequently associated with gold mining activities and related to drinking water quality problems worldwide. In Tanzania, elevated levels of trace elements (TEs) have been reported in drinking water sources within the Lake Victoria Basin, posing a serious health risk to communities. The present study aims to assess the groundwater quality with a focus on the concentration levels of geogenic contaminants in groundwater around the Lake Victoria goldfields in Geita and Mara districts. The water samples were collected from community drinking water sources and were analysed for physiochemical parameters (pH, EC, Eh), major ions, and trace elements. The analysed major ions included Na+, K+, Ca2+, Mg2+, SO42-, HCO3- and Cl- whereas the trace elements were As, Al, Li, Ba, B, Ti, V, U, Zr, Sr, Si, Mn Mo, Fe, Ni, Zn, Cr, Pb, Cd, and V. The present study revealed that the concentration levels of the major ions were mostly within the World Health Organization (WHO) drinking water standards in the following order of their relative abundance; for cations, Ca2+∼Na+>Mg2+>K+ and for anions was HCO3- > SO42- > NO3-, Cl- > PO43-. Statistical and geochemical modelling software such as 'R Studio', IBM SPSS, geochemical workbench, visual MINTEQ were used to understand the groundwater chemistry and evaluate its suitability for drinking purpose. The concentration of As in groundwater sources varies between below detection limit (bdl) and 300 µg/L, with highest levels in streams followed by shallow wells and boreholes. In approximately 48% of the analysed samples, As concentration exceeded the WHO drinking water guideline and Tanzania Bureau of Standards (TBS) guideline for drinking water value of 10 µg/L. The concentration of the analyzed TEs and mean values of physicochemical parameters were below the guideline limits based on WHO and TBS standards. The Canadian Council of Ministries of the Environment Water Quality Index (CCME WQI) shows that the overall water quality is acceptable with minimum threats of deviation from natural conditions. We recommend further geochemical exploration and the periodic risk assessment of groundwater in mining areas where high levels of As were recorded.

Long-term phosphorus sorption and leaching in sand filters for onsite treatment systems.

The sorption capacities of sand filters used for onsite wastewater treatment and their associated risks of phosphorus (P) leaching on contact with rainwater were investigated in column experiments and with modelling tool for over 300 days. Columns packed with sand were exposed to real domestic wastewater of different characteristics and hydraulic loading modes. The wastewater fed into the columns was effluent collected from three different treatment units in the field: a septic tank (ST), biofiltration tank (BF) and Polonite® filter bag (PO). The risk of P leaching to groundwater and surface water was also assessed, by exposing the same sand columns to natural rainwater. Overall results indicated that sand soils can exhibit different adsorption and desorption capacities for electrical conductivity (EC), Total-P, phosphate-P and total suspended solids, depending on the characteristics of influent wastewater, loading rate and total operation time. The removal efficiencies of the sand columns increased in the order ST (98.16%) > PO (93.36%) > BF (81.57%) for PO4-P and slightly decreased ST (97.11%) > PO (92.06%) > BF (76.76%) for Total-P columns. All sand columns loaded with actual wastewater solutions from septic tanks and biofiltration tank have demonstrated high risks of phosphorus leaching (>99.99%) to the groundwater. The modelling was successful captured behavior of EC tracer and adsorption of PO4-P with acceptable prediction uncertainty in the PO < 8% columns. The modelling results indicated that the decrease of loading rate from 83.3 mL d-1 to 20.83 mL d-1 led to an average increase of removal efficiency and prolong operational lifetime and mass of adsorbed Total-P in the sand soil. This study concludes that sand is a valuable filter medium at low loading rate for phosphorus removal in full-scale operations of onsite treatment systems, however very vulnerable for leaching P when in contact with rainwater.

Knowledge of cardiovascular risk factors among caretakers of outpatients attending a tertiary cardiovascular center in Tanzania: a cross-sectional survey.

BACKGROUND: Health literacy on cardiovascular diseases (CVDs) plays an effective role in preventing or delaying the disease onset as well as in impacting the efficacy of their management. In view of the projected low health literacy in Tanzania, we conducted this cross-sectional survey to assess for CVD risk knowledge and its associated factors among patient escorts. METHODS: A total of 1063 caretakers were consecutively enrolled in this cross-sectional study. An adopted questionnaire consisting of 22 statements assessing various CVD risk behaviors was utilized for assessment of knowledge. Logistic regression analyses were performed to assess for factors associated with poor knowledge of CVD risks. RESULTS: The mean age was 40.5 years and women predominated (55.7%). Over two-thirds had a body mass index (BMI) ≥25 kg/m2, 18.5% were alcohol drinkers, 3.2% were current smokers, and 47% were physically inactive. The mean score was 78.2 and 80.0% had good knowledge of CVD risks. About 16.3% believed CVDs are diseases of affluence, 17.4% thought CVDs are not preventable, and 56.7% had a perception that CVDs are curable. Low education (OR 2.6, 95%CI 1.9-3.7, p < 0.001), lack of health insurance (OR 1.5, 95%CI 1.1-2.3, p = 0.03), and negative family history of CVD death (OR 2.2, 95%CI 1.4-3.5, p < 0.001), were independently associated with poor CVD knowledge. CONCLUSIONS: In conclusion, despite of a good level of CVD knowledge established in this study, a disparity between individual's knowledge and self-care practices is apparent.