دانلود رایگان مقاله ماکروفیتهای آبزی و غلظت عناصر کمیاب آنها

Abstract

Trace elements (TEs) uptake from water and sediments to 10 aquatic macrophytes in the Ethiopia Rift Valley lakes Koka, Ziway and Awassa was investigated to evaluate pollution of these lakes. Concentrations of Cr, Co, Ni, Cu, Zn, As, Se, Cd, Pb and Mn have been determined in leaves of macrophytes, water and sediment, using ICP-MS (Inductively Coupled Plasma–Mass Spectrometry). Principal component analysis showed an existing variation in TEs concentration in leaves of aquatic macrophytes. High concentration of Mn (1.6 × 103 and 1.2 × 103 mg kg−1 dw) was found in Aeschynomene elaphroxylon of Lake Ziway and Eichhornia crassipes of Lake Koka, respectively. Cr concentration in low molecular mass (LMM) fraction of water and total sediment (4.9 g L−1 and 95 ± 4 mg kg−1 dw, respectively) was higher in Lake Koka compared to lakes Ziway and Awassa. Some of the studied macrophytes can accumulate high level of trace elements concentration compared to the surrounding, showing their potential to be utilized as pollution indicators. Most TEs in macrophytes used as animal feed, such as Echinochloa stagnina (Retz.) P. Beauv, were sufficiently low.

5. Conclusion

Growth habits of aquatic macrophytes govern their ability to take up contaminants from lakes water and sediment. Even if most of the trace elements in the leaves of studied aquatic macrophytes were within the normal ranges of plants in uncontaminated environments, trace metal elements such as Mn, Cr, and Ni showed higher than normal concentration in leaves of some of the macrophyte species investigated. This indicates the enrichment of these tracemetal elements inthe aquatic systems.However, comparisons between results of the present work and other published results showed lower concentrations of trace elements in the studied ERV lake macrophytes. This implies that the studied ERV lakes were not heavily impacted due to surrounding natural and anthropogenic factors. Eichhornia crassipes from lake Koka, Potamogeton schweinfurthii from lake Ziway and Potamogeton thunbergii from lake Awassa can accumulate relatively higher concentration of trace elements. These macrophytes can be used as bioindictors of pollution in the respective lakes. PCA applied on trace element data of macrophytes show strong correlation ofAs, Co and Cr with Pb. From the aquatic macrophytes that can be used as feed for animals, the Mn concentration of A. elaphroxylone around Lake Ziway was found higher than the maximum tolerable level of Mn for animal intake. Echinochloa stagnina from lake Koka contains sufficiently low concentration of trace elements that can be used as feed for animals. However, due limited samples and season ofinvestigation,this data cannot be used in making recommendation regarding animal feed intake, rather as preliminary data for undertaking further related studies in the region. With the current increasing socio-economic activity and human pressure in the Ethiopian rift valley, the possibility of trace element pollution is becoming eminent, which prompt effective regular pollution monitoring activities. Therefore, aquatic macrophytes can be included as biomonitor of the aquatic system in the regular pollution monitoring practices in the region