Heavy metal contamination in agricultural soils and water in Dar es Salaam city, Tanzania

Heavy metals in soil and water were determined at four points along Msimbazi River valley in Dar es Salaam city, which is popular for vegetable farming. Results indicated that the concentration of chromium in water ranged from (1.414±0.922) to 0.01 mg/L. Maximum and minimum lead concentrations of 0.113 and 0.083 mg/L were detected. The concentration of copper was generally low at all sites, ranging from (0.013±0.005) to (0.016±0.005) mg/L. The concentration of lead in water throughout the river exceeds the WHO (2004) drinking water limit of 0.01 mg/L, ranging from (0.113±0.104) to (0.083±0.059) mg/L. Cadmium concentration at all sampling points was below detection limit of 0.01 mg/L. Soil analysis indicated that the concentrations of heavy metals are highest at the top soil and decreased with depth. Lead had the highest concentration of (22.85±1.502) mg/kg; which did not exceed the TZS (2003) maximum limit of 200 mg/kg for soils. Chromium had maximum and minimum concentrations of (502.33±150.991) and (174.707±168.278) mg/kg, respectively, with most of samples exceeding the TZS (2003) permissible limit of 200 mg/kg. The maximum and minimum concentrations of copper were (21.073±2.881) and (4.513±1.713) mg/kg, respectively, lower than the TZS (2003) permissible limit of 100 mg/kg. Cadmium concentrations at all sampling points were lower than the permissible concentration of 100 mg/kg in soils (TZS, 2003). The presence of heavy metals in soil and water indicates the potential for pollution transfer from these media to the food chain, especially since this valley is popular for vegetable cultivation.Key words: Heavy metal, soil, water, pH, dissolved oxygen, Msimbazi River

Residues of Organochlorinated Pesticides in Soil from Tomato Fields, Ngarenanyuki, Tanzania

This work presents the concentrations of five pesticide residues, lindane, chlorpyrifos, endosulfan, p, p'-DDE and p, p'-DDD in soil samples collected from tomato fields in Ngarenanyuki, Tanzania. Endosulfan sulphate was detected in 100 % of the sample analysed with mean concentration of 0.2407 mg/kg dw. Chlorpyrifos was detected in 87 % of the samples with mean concentration of 0.1253 mg/kg dw. p, p'-DDE and p, p'-DDD were detected in 46 and 40 % of the samples analysed with mean concentrations of 0.1482 and 0.154 mg/kg dw, respectively. Lindane was the least detected pesticide. It was detected in 5 (33 %) of soil samples analysed with mean concentration of 0.2126 mg/kg dw. Low concentrations detected indicate the past usage of the pesticides

Antimosquito Phenylpropenoids from the Stem and Root Barks of Uvariodendron pycnophyllum (Diels) R.E.Fr

The phenylpropenoids O-methyleugenol, O-methylisoeugenol and 2,3-dimethoxycinnamaldehyde, have been isolated as the antimosquitocidal principles of the stem and root bark extracts of Uvariodendron pycnophyllum (Diels) R.E. Fr. The extracts and compounds exhibited activity with LC50 values in the range 17-59 ppm against the Anopheles gambiae s.s Giles mosquito larvae, while the constituent phenylpropenoids showed long term mortality effects to adult An. gambiae mosquito on impregnated bednets, and mosquito repellency that was stronger than the activity of the standard repellent DEET

Performance of Solanum incunum Linnaeus as natural coagulant and disinfectant for drinking water

The paper reports the performance of Solanum incunum Linnaeus as coagulant and disinfectant for water purification. The coagulation-flocculation experiment was carried out using a Phipps and Bird PB-700™ Jar Tester. Results show that coagulation depends on Fe(II) content and disinfectant on bioactive natural product compounds from the plant. Turbidity removals were 96, 97 and 75% for raw water with turbidity of 450, 300 and 105 NTU, respectively. Fecal coliform removal increased with coagulant concentration, displayed a maximum removal of 99% at 2.2 × 10-4 g/ml. LD50 ranged from 0.62-2.6 × 10-5 g/ml, which were within the range of optimum coagulation concentration of 2.2 × 10-5 g/ml. Turbidity and SO42- concentrations for the treated water conforms to the Tanzanian Standards and WHO guidelines for drinking water, while fecal coliform counts exceeded the recommended values. The results suggest that S. incunum is promising as coagulant and disinfectant product for water purification.Key words: Coagulant, disinfection, fecal coliform, Solanum, turbidity, water

Heavy Metal Pollution And Urban Agriculture In Msimbazi River Valley: Health Risk And Public Awareness. Ijpaes.

ABSTRACT : Awareness of the urban population on the potential environmental and human health risks resulting from and consuming vegetables polluted with heavy metals from Msimbazi river, Dar es Salaam city, Tanzania was investigated. Results show that more than 71% of the 35 respondents use Msimbazi river as a major source of water for vegetable irrigation. High levels of chromium, lead and copper have been observed in four most popular vegetables namely Amaranthus blitum, Amaranthus gangeticus, Cucurbita maxima, Ipomea batata and Brasica oleracea. The survey indicated further that about 69% of respondents are not aware on industrial pollution in the Msimbazi River. 63% of respondents do not know the potential human health effects attributed to the current irrigation practice. Vegetables grown along the Msimbazi river valley feeds most of markets in the City. The study also established the risk value as well as population at risk through oral exposure to vegetables grown in Msimbazi River valley. Results on vegetable consumption shows that 95.6% of adults, 30.7% of children aged 6-12 years and 12.5% of children aged 2-6 years are at risk of getting lead carcinogenic effects. Additionally, children aged 2-6 years (5%) followed by children aged 6-12 years (2.8%) and adults (1.2%) are at risk from carcinogenic cadmium effects. For non carcinogenic effects, 0.7% adults, 1.18% children aged 6-12 years, and 0.122% children aged 2-6 years are dermal exposed to copper in vegetables

Assessment of the potential effectiveness of poultry egg shells in the removal of lead ions from contaminated water

The influence of pH, initial concentration of Pb2+ ions, sorbent (poultry egg shells) dose, and contact time on the adsorption of Pb2+ from contaminated water to egg shells was studied. Results indicate that adsorption capacity increases with the increase of Pb2+ ion concentration and dose of egg shells, and varied with change of pH. Egg shell was mainly composed of CaCO3 and other few elements as, S, Al, Mg, Si, Cl, K and Zn. The optimum pH for lead removal was at pH 7 with highest efficiency of 96.65 %, this was also revealed by Freundlich adsorption isotherm that displayed the highest value of K of 3.18419 for wastewater of concentration 0.884 mg/l Pb. The optimum dose of egg shells was 25g with contact time of 90 min and residue lead of 0.027 mg/l which is lower than the Limits for Municipal and Industrial Wastewater discharge (0.1 mg/l). The adsorption isotherms also showed that the lead removal efficiency was descending from pH 7, 12.3 to 3.4. These results suggest that poultry egg shells can be a potential candidate adsorbent material for removal of lead ions from contaminated water.Keywords: Adsorption, Lead, Egg shells, Sorbent, Poultry, Wate

Distribution of pesticide residues in soil due to point source pollution at old Korogwe, Tanzania

This paper summarizes the findings of a study carried out to assess the levels of pesticide residues in soil along the old obsolete pesticides storage site at Old Korogwe. Gas chromatography spectrophotometryequipped with electron capture detector was used in the identification and quantification of the residues. DDT and its metabolites, DDD and DDE, were detected at different distances from the point source. p,p’-DDT wasthe predominant residue in all the samples analysed, detected in 92% of samples at a mean concentration of 425.76 + 4.75 μg/g. o,p’–DDT was detected in 33% with a mean concentration of 55.83 + 2.65 μg/g, metabolites p, p’–DDD and p,p’–DDE were detected in 50% and 58% at mean concentrations of 92.5 + 3.50 and 20.84 + 1.72 μg/g, respectively. The detection of higher level of p,p’–DDT than o,p’–DDT in the samples implies contamination was due to technical-grade DDT.Keywords: DDT, DDD and DDE, Obsolete pesticides, Soil Contamination, Old Korogwe

Heavy metals accumulation in vegetables grown along the Msimbazi River in Dar es Salaam, Tanzania

Concentrations of cadmium, copper, chromium and lead was determined in four different edible vegetables namely Amaranthus blitum, A. gangeticus, Ipomea batata and Cucurbita maxima grown at four different sites along the contaminated Msimbazi River, Dar es Salaam, Tanzania. Analyses of these heavy metals were conducted using Atomic Absorption Spectrophotometry. Results obtained indicate that the concentrations of heavy metals range from below detection limit to 0.53, 0.14 to 29.08, 0.76 to 17.69, and below detection limit to 39.69 mg/100 g for cadmium, chromium, copper and lead, respectively. With exception to Ipomea batata, other vegetables contained at least two types of heavy metals with high concentrations beyond the permissible values recommended by FAO and WHO for human consumption. Concentrations of cadmium were within the acceptable limits for human consumption in all the vegetables investigated. This work, thus, seeks to provide information on levels of toxic heavy metals in leaves of edible vegetables irrigated with water contaminated by industrial and other anthropogenic effluents, and grown in contaminated soils along the Msimbazi River. The information can be used for monitoring processes to prevent excessive build-up in the food chain