Accumulation of metals by aquatic plants in the river wear system

Abstract

A study was made of a range of aquatic plants from various parts of the River Wear system, for 15 metal elements. The heavy metal content of the plants was related to the chemistry of the water using the enrichment ratio. Different chemical environments were studied in an attempt to establish factors affecting the accumulation of heavy metals. Marked Increases were found in Zn, Pb and Cd tn Cladophora glomerata and Fontinalis antipyretioa sampled downstream of the entry of an industrial effluent as compared to a site upstream of this effluent. A clear linear relationship was established for Zn and Pb between the concentration in the plant and that in the water for Cladopkora glomerata, in strictly comparable situations at sites above and. below the effluent. Divided samples of 'Fontinalis antipyretica showed marked increases in many heavy metals in the older material as compared to the younger tips. It is suggested that bryophyte tips could reliably indicate the heavy metal concentration of river water. It is also suggested that leaves of Ramunculus penicillatus var. calcareus might be useful in indicating heavy metals. Plants from a Zn and Pb polluted tributary (Rookhope Burn) showed marked accumulation of Zn and Pb compared to similar plants from waters with low concentrations of these heavy metals. In Brandon Pithouse acid streams enrichment ratios were encountered, at pH <3, several orders of magnitude lower than sites of pH 6-8. It is suggested that pH might have a direct or indirect influence in reducing this ratio. It is also suggested that both physiological and environmental parameters, notably chemical speciation, are important factors affecting enrichment ratios. Importance was attached to defining limits to enrichment ratios so that aquatic plants could be used to' indicate heavy metal concentrations in a wide range of flowing waters.