This paper highlights the levels of anions (nitrate, nitrite, sulfate, bromide, chloride, and fluoride) and cations (potassium, sodium, magnesium, and calcium) in selected springs and groundwater sources in the urban-west region of Zanzibar Island. The levels of total dissolved solids (TDS) and sodium adsorption ratio (SAR) were also studied. Thirty water samples were collected in December 2012 from various types of water sources, which included closed hand-dug wells (CHDW), open hand-dug wells (OHDW), springwater (SW), public bore wells (PBW), and bore wells owned by private individuals (BWP), and analyzed after filtration and sometimes dilution. The cations were analyzed using inductively coupled plasma-optical emission spectrometry (ICP-OES). The anions were analyzed by chemically suppressed ion chromatography (IC). The ranges of the levels of the investigated parameters were as follows: Na 13.68-3,656 mg L(-1), K 2.66-583 mg L(-1), Mg 0.63-131.10 mg L(-1), Ca 16.79-189.9 mg L(-1), Cl(-) 8.61-4,340.97 mg L(-1), F(-) 0-1.02 mg L(-1), Br(-) 0-10.88 mg L(-1), NO₃(-) 0.18-342.4 mg L(-1), NO₂(-) 0-1.39, SO₄(2-) 4.43-534.02 mg L(-1), TDS 7-6,380 mg L(-1), and SAR 0.63-50. Except fluoride, most of the studied parameters in the water samples had concentrations beyond the permissible limits of the World Health Organization (WHO). The elevated concentrations are a result of seepage of contaminated water from on-site septic tanks, pit latrines, landfill leachates, fertilizer applications, and domestic effluents. These results should alert domestic water stakeholders in Zanzibar to the urgent task of initiating a quick mitigation response to control these alarming water risks.

The South Region of Pemba is one of the two Regions in Pemba Island. Residents within the region depend on groundwater as the main water source for the domestic and other social purposes. This study was conducted to assess the quality of drinking water in different areas of South region of Pemba. In order to evaluate the quality of groundwater in the study area, 17 groundwater samples were collected and analyzed for different physico-chemical parameters. In each water sample, four physicochemical parameters were analyzed, namely, electrical conductivity (EC), total dissolved solids (TDS), pH, and turbidity. For the case of metals, eleven metals, namely, Cd, Co, Cu, Cr (III), Li, Fe, Mg, Ni, Pb, Sr, and Zn were analyzed using standard procedures. The dataobtained were then compared with the available WHO and or USEPA drinking water standards. All the samples had EC and TDS within the recommended limits, while 53% and 29% of the samples had higher turbidity levels and lower pH, respectively than the WHO recommended guidelines. All the samples contained Co, Cu, Fe, Mg, Ni, Pb, and Zn within the maximum admissible limits. According to heavy metal pollution index (HPI), degree of contamination (Cd), and heavy metal evaluation index (HEI), only one area (Mgonanje-1) showed alarming risks. In most water samples, the ratio of concentrations of Li to Ni was greater than 1, while all Sr to Mg ratios were less than 1. Generally, the values of the analyzed physico-chemical parameters were within the recommended maximum admissible limits. However, the study recommends the stakeholders and other responsible authorities to take appropriate and corrective measures for the water sources located at the Mgonanje area.

At the present time, there is continuous increase of heavy metal burden in our environment, which has become one of the most serious problems globally. Heavy metals cause threat on land and in aquatic life. The problem of metals is significantly attributed by increase of activities from industrial, agricultural, hospital sectors etc. Heavy metals are not degradable, but they are persistent in environments. The aim of this study is to prepare adsorbent from powder of Ajwaa date seeds (PADS). The adsorbent was applied in removing heavy metal ion such as cadmium, lead, copper, chromium, cobalt and manganese from aqueous solution. The study also examined the removal efficiency of PADS. Constant mass of 0.1gram of PADS which was added in a volume of 50 mL of ultra-pure water reached maximum removal efficiency of 93.34%, 71.06%, 92.06%, 96.96%, 95.91% and 36.13% for Cd 2+ ions, Cr 3+ ions, Co 2+ ions, Cu 2+ ions, Pb 2+ ions and Mn 2+ ions respectively. The findings of the present study can be taken as a best solution and baseline information of heavy metal removal in different areas. The PADS treatment is efficient, simple, low cost and green alternative for heavy metal treatments methods to overcome the problems of heavy metals discharged in aqueous solution.

Aim of the study was to assess the physicochemical characteristics of rainwater at urban and rural (north B) Unguja. Twenty four (24) rainwater samples were analyzed for pH, electrical conductivity (EC) and total dissolved solids (TDS) and cations: calcium (Ca2+), copper (Cu2+), iron (Fe2+), chromium (Cr VI) , and anions: fluoride (F-), nitrite and sulfate (SO42-). The investigated physicochemical parameters in the rainwater samples were within the permissible limits of the World Health Organization (WHO) drinking water quality guidelines. The ranges of concentration for the physical parameters analyzed were; pH: (5.8 – 7.7), EC: (5.08 – 35.6 µS/cm),  TDS: (1.68 – 20.16 mg/L, Ca: (0.163 – 24.331 mg/L), Cr: (VI) : (BDL – 0.029 mg/L), Cu: (BDL - 0.085 mg/L); Fe: (BDL – 0.068), anions were SO42- : (BDL – 5.00 mg/L) and F- : (BDL – 0.5 mg/L). Nevertheless, there was no significant difference for the measured parameters between urban and rural areas. This is a good indication that the air quality in Zanzibar is remarkably not polluted with respect to the parameters studied.

Ambient concentration of ground-level ozone was quantified from 14 petroleum filling stations in Urban and West districts allocated in urban west region Zanzibar between August and November 2019. In situ measurement was conducted for two separate sessions that involved before noon and afternoon in each day in the field using BH-4S Portable multi-gas detector. The analyzed data revealed both temporary and spatial variations of measured parameters. During phase1, the range of ozone was 4.8- 0.6 ppm. During phase2, the range of ozone was 14.2 - 4.5 ppm. The mean values recorded for ozone ranged from 0.6 ppm to 4.8 ppm for phase1, and from 4.5 ppm to 14.2 ppm for phase2. This study revealed that, ground-level ozone is at a point that calls attention tothe environment and health sectors.