Mercury concentration and phytotoxicity of biosolids from the Melbourne Water's Western Treatment Plant, Victoria, Australia

摘要

Total mercury concentrations were surveyed in biosolids and vegetation from Melbourne Water's Western Treatment Plant in Victoria, Australia, to investigate a possible reuse of biosolids and to evaluate an eventual mercury phytoremediation study in the area. The results showed that, in some biosolids samples, Hg concentration was above the safety level for land applications (5mg·kg<'-1>), according to the Australian and Victorian State Biosolid Guidelines. Samples of Brassica nigra, Sonchus oleraceus, Chenopodium album, Rumex Crispus, and Phalaris aquatica, were collected and Hg was analyzed in roots and shoots. No significant Hg uptake was revealed by these plants. A germination test with Iceberg lettuce and Scarlet Globe radish seeds was carried out as a preliminary phytoremediation study to assess the phytotoxicity of the biosolids samples. Although the concentrations of mercury and other heavy metals were relatively high, salinity had the most impact on the germination process. A high content of salts in biosolids inhibited and delayed the germination of seeds. This preliminary survey indicates that the biosolids from Melbourne Water's Western Treatment Plant requires Hg remediation prior to re- use in land applications and secondly the choice of plants for the on-going phytoremediation study has been influenced by the high content of salts still present in the biosolids.