Growing trends in industrialization in Ethiopia have raised concerns about pollution of water bodies particularly of lakes. This study was therefore conducted to 1) characterize the chemical contents of major industri...Growing trends in industrialization in Ethiopia have raised concerns about pollution of water bodies particularly of lakes. This study was therefore conducted to 1) characterize the chemical contents of major industrial effluents (namely textile ceramic and soft drink factories) that reached Lake Hawassa and 2) investigate the effects of the above mentioned factory effluents on survival of larvae fish and growth of algae. Effluent samples were collected from the outlet lagoons of each factory in December, 2009. Then, effluent samples were analyzed for total N, NO3-N, NH4-N, S2-, , , COD, total dissolved solids (TDS) and heavy metals at the federal Environmental Protection Agency (EPA) Laboratory, Addis Ababa. The experiments on the impact of effluents on survival of fish larvae and growth of algae were conducted using six concrete paved ponds (with different concentration of effluent). The results of chemical analysis showed that textile effluent had high COD (nearly 3 times higher), TDS (19 times higher) as well as (39 times higher) than the maximum permissible limits (MPL) set by Environmental Protection Authority (EPA). Among heavy metals, Zn and Fe of textile effluent were much higher (41 and 1.5 times higher, respectively) than the MPL set by EPA. Ceramic effluent also contained high concentration of (24.5 times), S2-, (2 times) and Zn (14 times) exceeding the limit of EPA. Regarding soft drink factory, high values of COD, and Zn were found in the effluent than the limit specified by EPA. The biological treatment lagoons of the respective source were not effective since the effluents were taken from the last treatment lagoon (outlet lagoon) and some of the measured parameters were higher than MPL. Results of the pond experiment showed that 5%, 10% and 20% concentration levels of the HTF effluent killed significantly high proportion of the fry (65%, 86.8% and 88.7%, respectively). In contrast, fry mortality in ceramic and soft drink effluent treatments, even at 10 and 20% concentration levels, stayed nearly below 10%, which were not far off from the mortality of the control groups. Algal biomass in the treated ponds varied with the type of effluent treatment and concentration level. Compared with the first day, chlorophyll “a” concentration measured on the 7th day had increased by 51%, 48%, 74%, 27% and 31% at 0%, 1%, 5%, 10% and 20% concentrations, respectively of textile effluent. The 5% treatment level of textile effluent caused the highest rate of algal growth above the growth rate observed in the control pond, but further increased in concentration to 10% and 20% resulted in a lower growth of algae than in the control pond. Therefore, textile effluent may boost up algae growth at lower concentrations (~5%) but at higher concentration levels its toxic effect may become inhibitory. Regarding the effluent of soft drink factory, algal growth progressively diminished with increasing concentration of the effluent. The overall change (between initial and day 7) in chlorophyll “a” concentration was highest in the control pond (36.2%) and decreased with increasing effluent concentration (1% to 20%) from 21.7% to -9.4%. On the other hand, algal growth under ceramic effluent treatment was comparable with that observed in the control pond.展开更多
In the Wondo Genet, Ethiopia, the common agricultural land uses include maize, shade coffee, khat and sugarcane. The objective of this study was to examine the impact of perennial land uses on soil organic carbon (SOC...In the Wondo Genet, Ethiopia, the common agricultural land uses include maize, shade coffee, khat and sugarcane. The objective of this study was to examine the impact of perennial land uses on soil organic carbon (SOC), soil N and base cations. Four sites having maize and one or two of perennial land uses and with similar site characteristics were identified for this study. Soils (0 - 30 cm) were sampled at corners of a plot (20 × 20 m2) placed in each land use at each site. Results indicated that the SOC storage of the shade coffee plantations were 86% and 125% higher compared with adjacent maize land uses with the absolute differences being 50.7 and 54.4 Mg·ha-1, respectively. The soil N stock was 109% and 126% higher for the shade coffee than the maize land use while the absolute differences were 5.7 and 4.7 Mg·ha-1 for the same sites. Among perennials, the higher SOC storage in the shade coffee is attributable to the increased litter input and reduced soil disturbance in the system. While the higher soil N in the shade coffee was attributed to reduction of leaching, N uplift, and the increased litter quality and input. The high relative increase in shade coffee in SOC and soil N at Finance site was ascribed to the finer soil texture and low SOC and soil N at the compared adjacent maize farm. Although not significant, the relative increase in SOC (34%) and soil N (43%) in the sugarcane at the Finance as well as the relative increase in SOC (7%) and soil N (9%) in khat at Gotu as compared to Chaffee site was attributed to mainly the management differences. The shade coffee has the greatest potential for SOC storage and for increasing N stock, while khat and sugarcane have the least potential.展开更多
文摘Growing trends in industrialization in Ethiopia have raised concerns about pollution of water bodies particularly of lakes. This study was therefore conducted to 1) characterize the chemical contents of major industrial effluents (namely textile ceramic and soft drink factories) that reached Lake Hawassa and 2) investigate the effects of the above mentioned factory effluents on survival of larvae fish and growth of algae. Effluent samples were collected from the outlet lagoons of each factory in December, 2009. Then, effluent samples were analyzed for total N, NO3-N, NH4-N, S2-, , , COD, total dissolved solids (TDS) and heavy metals at the federal Environmental Protection Agency (EPA) Laboratory, Addis Ababa. The experiments on the impact of effluents on survival of fish larvae and growth of algae were conducted using six concrete paved ponds (with different concentration of effluent). The results of chemical analysis showed that textile effluent had high COD (nearly 3 times higher), TDS (19 times higher) as well as (39 times higher) than the maximum permissible limits (MPL) set by Environmental Protection Authority (EPA). Among heavy metals, Zn and Fe of textile effluent were much higher (41 and 1.5 times higher, respectively) than the MPL set by EPA. Ceramic effluent also contained high concentration of (24.5 times), S2-, (2 times) and Zn (14 times) exceeding the limit of EPA. Regarding soft drink factory, high values of COD, and Zn were found in the effluent than the limit specified by EPA. The biological treatment lagoons of the respective source were not effective since the effluents were taken from the last treatment lagoon (outlet lagoon) and some of the measured parameters were higher than MPL. Results of the pond experiment showed that 5%, 10% and 20% concentration levels of the HTF effluent killed significantly high proportion of the fry (65%, 86.8% and 88.7%, respectively). In contrast, fry mortality in ceramic and soft drink effluent treatments, even at 10 and 20% concentration levels, stayed nearly below 10%, which were not far off from the mortality of the control groups. Algal biomass in the treated ponds varied with the type of effluent treatment and concentration level. Compared with the first day, chlorophyll “a” concentration measured on the 7th day had increased by 51%, 48%, 74%, 27% and 31% at 0%, 1%, 5%, 10% and 20% concentrations, respectively of textile effluent. The 5% treatment level of textile effluent caused the highest rate of algal growth above the growth rate observed in the control pond, but further increased in concentration to 10% and 20% resulted in a lower growth of algae than in the control pond. Therefore, textile effluent may boost up algae growth at lower concentrations (~5%) but at higher concentration levels its toxic effect may become inhibitory. Regarding the effluent of soft drink factory, algal growth progressively diminished with increasing concentration of the effluent. The overall change (between initial and day 7) in chlorophyll “a” concentration was highest in the control pond (36.2%) and decreased with increasing effluent concentration (1% to 20%) from 21.7% to -9.4%. On the other hand, algal growth under ceramic effluent treatment was comparable with that observed in the control pond.
文摘In the Wondo Genet, Ethiopia, the common agricultural land uses include maize, shade coffee, khat and sugarcane. The objective of this study was to examine the impact of perennial land uses on soil organic carbon (SOC), soil N and base cations. Four sites having maize and one or two of perennial land uses and with similar site characteristics were identified for this study. Soils (0 - 30 cm) were sampled at corners of a plot (20 × 20 m2) placed in each land use at each site. Results indicated that the SOC storage of the shade coffee plantations were 86% and 125% higher compared with adjacent maize land uses with the absolute differences being 50.7 and 54.4 Mg·ha-1, respectively. The soil N stock was 109% and 126% higher for the shade coffee than the maize land use while the absolute differences were 5.7 and 4.7 Mg·ha-1 for the same sites. Among perennials, the higher SOC storage in the shade coffee is attributable to the increased litter input and reduced soil disturbance in the system. While the higher soil N in the shade coffee was attributed to reduction of leaching, N uplift, and the increased litter quality and input. The high relative increase in shade coffee in SOC and soil N at Finance site was ascribed to the finer soil texture and low SOC and soil N at the compared adjacent maize farm. Although not significant, the relative increase in SOC (34%) and soil N (43%) in the sugarcane at the Finance as well as the relative increase in SOC (7%) and soil N (9%) in khat at Gotu as compared to Chaffee site was attributed to mainly the management differences. The shade coffee has the greatest potential for SOC storage and for increasing N stock, while khat and sugarcane have the least potential.
