The contents of essential and toxic metals in coffee beans and soil in Dale Woreda, Sidama Regional State, Southern Ethiopia.

Background: For developing countries such as Ethiopia, coffee is a commodity of great economic, social, and environmental importance. No detailed investigations have been performed on the contents of essential and toxic metals in coffee beans and soil in this study area. Methods: The levels of essential metals (Na, K, Ca, Zn, Mn, Cu, Co, Cr, Ni) and toxic elements (Pb and Cd) were investigated in coffee beans (coffee growing farmland and coffee washed plants) and soil samples (from farmland) using flame atomic absorption spectrometry (FAAS) and flame emission atomic spectroscopy. We selected six (20%) administrative units (kebele) with purposive sampling techniques based on their coffee production capacity in Dale Woreda for soil testing. After coffee sample preparation in a microwave system with HNO3and H2O2 reagents, the accuracy of the optimized procedure was evaluated by analysing the digest of the spiked samples. Soil samples were abridged with a slight revision of the EPA 3050B acid digesting method. ANOVA was used to determine the significant differences in the mean concentration of metal within coffee beans from farmland at the various sampled sites at the p < 0.05 significance level. To correlate the effect of one metal concentration on other metals in the coffee bean samples, Pearson correlation matrices were used. Results: Calcium had the highest concentration (1,355 ± 18.02 mg kg-1) of macroelements in soil samples, followed by K (681.43 ± 1.52 mg kg-1). Similarly, Na (111.63 ± 0.35 mg kg-1), Cu (49.96 ± 0.99 mg kg-1), Co (5.43 ± 0.31 mg kg-1), Mn (0.62 ± 0.238 mg kg-1), Ni (0.194 ± 0.01 mg kg-1), and Zn (0.163 ± 0.007 mg kg-1) were detected among the microelements in the soil samples. Pb and Cr were not detected in all soil samples. Potassium (K) was found to have the highest concentration (99.93 ± 0.037 mg kg-1), followed by Ca (17.23 ± 0.36 mg kg-1), among the macroelements in coffee beans from farmers' farms. Similar to coffee beans from farmland, samples from washed plants also contained the highest K (77.93 ± 0.115 mg kg-1), followed by Ca (4.33 ± 0.035 mg kg-1). Metal levels in coffee bean samples from farmland are in the following order: K>Na>Ca >Mn>Cu> Ni>Zn. Metal levels were found to be K>Na>Ca >Mn>Cu> Zn>Ni in coffee beans from the washed plants. Co, Cr, Pb and Cd were no detected in all coffee bean samples. Except for calcium, potassium and manganese, the levels of metals in coffee beans from farmland and washed plants were not significantly different at the 95% confidence level within a kebele. Conclusions: We observed permitted levels of macro- and trace elements in coffee beans from farmlands and washed plants. Only in the soil samples are cadmium concentrations higher than those permitted for agricultural soil recommended by the WHO and FAO. Overall, there is no health danger linked with the use of coffee beans due to detrimental and trace heavy metals.

Treatment Performance Assessment of Natural and Constructed Wetlands on Wastewater From Kege Wet Coffee Processing Plant in Dale Woreda, Sidama Regional State, Ethiopia.

Constructed wetlands are engineered systems built to use natural processes and remove pollutants from contaminated water in a more controlled environment. The research was an experimental research carried out to assess the effectiveness of natural and constructed wetland systems in the treatment of coffee wastewater. The 2 vertical flow constructed wetland was built. The first wetland covered an area of 132 m2. It has 12 m width and 11 m length. Open space is constructed between 2 constructed wetlands with a dimension of 11 m × 3 m × 1 m. The second wetland was constructed and its function is similar to the first one, from this wetland water is discharged to the river. The construction of the wetland is accomplished by constructing 20 cm wide furrows with a spacing of 30 cm. Vetiver grasses have planted with a spacing of 20 cm intervals. The physicochemical data were recorded, organized, and analyzed using R software (version 4.1) and Microsoft Excel. Data were processed using parametric (one-way ANOVA) and nonparametric (Mann-Whitney's U test) statistical tests of homogeneity. One-way analysis of Variance (ANOVA) was used to determine the significance of differences in variations in physicochemical variables within the constructed wetland sites. Tukey's multiple comparisons for differences between means were also assessed. Findings indicated that a natural wetland had a mean influent and effluent of total suspended solids (TSS) of 2190.78 ± 448.46 mg/l and 972.67 ± 234.312 mg/l, respectively. A Mann-Whitney U test revealed that TSS were significantly higher in natural wetland (median = 1551.50) compared to constructed wetland (median = 922.5), U = 676.5, z = -2.435, P = .015, r = .257. Natural wetlands had a mean influent of biological oxygen demand (BOD) was 4277.94 ± 157.02 mg/l, while in the effluent of BOD it was 326.83 ± 112.24 mg/l. While in constructed wetland it was 4192.4 ± 191.3 mg/l, 782.72 ± 507.6 mg/l, and 88.28 ± 20.08 mg/l in influent, middle, and effluent respectively. Average chemical oxygen demand (COD) value at influent in natural wetlands was 8085.61 ± 536.99 mg/l and in the effluent it was 675.33 ± 201.4 mg/l. In constructed wetland, it was found to be 8409.8 ± 592.9, 1372.6 ± 387.94, and 249.0 ± 7.68 for influent, middle, and effluent respectively. Comparatively, the purification efficiency of organic pollutants (TSS, BOD, and COD) of constructed wetlands was better than natural wetlands, whereas natural wetlands had better purification efficiency of nitrogen compounds such as ammonium, nitrite, and nitrate. On average, removal rates for nitrogen compounds were 39.53% and -24.41% for ammonium, 79.44% and 55.4% for nitrite, and 68.90% and 60.6% for nitrate in natural and constructed wetlands respectively, while the phosphate removal rate was 43.17% and 58.7% in natural and constructed wetlands, respectively. A Mann-Whitney U test revealed that there is no significance difference in nitrite, nitrate, ammonium, and phosphate concentration between natural and constructed wetlands(P > .05). Based on these results, both systems of treatment were effective in treating the coffee effluent since most of the values obtained were below the permissible EEPA limits. Even though the constructed wetland treatment plant performed better overall, in comparison, the natural wetlands had better purification efficiency for nitrogen compounds like ammonium, nitrite, and nitrate and the constructed wetlands had better purification efficiency for organic pollutants (TSS, BOD, and COD).

Contamination and ecological risk assessment of toxic metals in Awetu watershed stream waters and sediments, Ethiopia.

The study analyzed the contamination level and ecological risk assessment of toxic metals Awetu watershed streams. A total of 20 water and 20 sediment samples were collected and analyzed for the toxic metals of Arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), manganese (Mn), nickel (Ni), lead (Pb), tin (Sn), and zinc (Zn). Sediment samples showed severe contamination levels based on ranges in sediment quality guidelines (SQGs). Water samples showed high grades of contamination factor and potential ecological risk factor by toxic metals. The synergistic effects of toxic metals in the sampling sites were evaluated by Nemerow pollution index, potential ecological risk index and modified degree of contamination and were found to have similar results. Dololo stream (D1, D2, D3, and D4) and Kito (K1, K2, and K3) were found at 'toxic' contamination and 'severe' ecological risk. Cd, Mn, Ni, Pb, and Sn contributed to the highest ecological risk. Toxic metal contamination in Dololo stream is attributed to institutions carrying out various anthropogenic activities along the stream bank, including traditional metal plating, garages, laboratory effluents, extensive agriculture, carwash, irresponsible waste disposal, and urban population growth. The result shows Awetu watershed streams are seriously contaminated by toxic metals. Therefore, future pollution control and management plans should accentuate the strict regulation of discharge of wastes from these anthropogenic activities.

Sources and level of heavy metal contamination in the water of Awetu watershed streams, southwestern Ethiopia.

The present study aimed to investigate the contamination source, level, and spatial distribution of globally alarming trace metals from Awetu watershed streams, southwestern Ethiopia. Surface water samples were collected from 20 sampling sites in December 2019. Water samples were collected in 500 ml polyethylene bottles previously washed with deionized water and rinsed with the sample to be collected from different stretches and acidified with 5 ml concentrated nitric acid. The samples were digested with open acid digestion and the contents of the metal were analysed using inductively coupled plasma optical emission spectrometry (ICP-OES) ranged from 18 - 351 µg/L for As, 5-19 µg/L for Cd, 232-421 µg/L for Cr, 314-920 µg/L for Pb and 10-16 µg/L for Hg. The highest concentrations of As were detected at K3, Cd at K2, Pb and Cr at D4, and Hg at D5. Analysis of variance results revealed that the Cd concentrations were statistically significant among all the streams except for Boye. Streams found at the center of Jimma city with effluents emanated from Jimma University, garage maintenances, car-wash and agricultural areas had higher values than the streams in the periphery. This study concluded that a higher concentration of trace elements is associated with the type of waste entering the streams. Trace elements concentration in the watershed is to the level that can pose a risk to downstream users. Public awareness creation to establish waste management systems and river quality monitoring should be implemented to minimize the public health risk and deterioration of the aquatic ecosystem.