| Phytoremediation is a new novel technique to clean up contaminated soils with some accumulators or hyperaccumulators which can take up heavy metal, and transport and accumulation them in their above ground shoots. The mechanisms of phytoremediation for Cu contaminated soils are not fully understood and the technology is not established yet. Therefore, it is importance to elucidate the characteristics of Cu tolerance and uptake by specialized plants, and the mechanisms of phytoremediation of Cu polluted soils. The major objectives of this study were to identify Cu tolerant and accumulating plant species and characterize their Cu uptake and tolerance, understand their potential of application to phytoremediation of the Cu contaminated agricultural soil, as well as the factors enhancing phytoremediation efficiency. The main results obtained were summarized as follows:1. Investigation and analysis of soils and plants in the heavily polluted agricultural field near a smelting factory showed that the main contaminated heavy metals included As, Cd, Cu, Pb and Zn, among which Cu, Pb and Zn content in soil were very high, reached 1775.6, 1140.1 and 621.3 mg kg"1 respectively. The metal content in the soil decreased with increasing distance from the smelting factory and reached normal level at a distance of about 300 m. Heavy metal concentrations were relatively high at the surface soil layer (15cm), and decreased with increasing soil depth. Soil microbial carbon content in surface soil was closely related to the soil heavy-metal. Some agricultural measures were adopted in a field experiment to remediate the polluted soil, and they effectively reduced available heavy metal content in the soil and increased the crop yield. Yet, the heavy metal concentrations in rice grains still failed to achieve the national sanitary standards. These results indicate that normal chemical amendments can reduced metal toxicity of the crop plants, but can't ensure crop food safety and ecosystem safety.2. Detailed field survey on Cu mining area in Zhuji and Pb/Zn mining area in Sanmeng of Zhejiang province. The results showed that the Cu ore deposit in Zhuji mostly at the altitude of about 630 m and E. splendens was the dominant plants speciesgrowing on Cu ore deposit, and its distribution is along with that of the Cu ore deposit. Chemical analysis indicated that that E. splendens grew prosperously in soil which total Cu and NH4OAc-extracted Cu up to 6050 and 665 mg kg-1 respectively, and in mined tails with both low water and nutrient supply. Copper concentration in root and shoot of E. splendens was 223-613 mg kg-1 and 23-91 mg kg-1. In Sanmeng mining area, E. argyi was the dominant plant species, which grow normally in soil which NH4OAc-extracted Pb and Zn was more than 1000 mg kg-1. Hence, it is concluded that E. splendens and E. argyi belong to Cu tolerant plants in most cases.3. One non-mined ecotype of Elsholtzia argyi was found in Hangzhou suburb. Two contrasting ecotypes of E. argyi were compared with nutrient solution culture for their growth response and the uptake, distribution, and translocation of Cu. The results showed that the ecotype from the old mined area (Sanmen-ecotype) had greater tolerance of Cu than that from the non-mined area (Jiuxi-ecotype) based on their dry matter production. Inhibition of root and leaf growth was noted at the external Cu levels > 50 umol L"1 for the Sanmen-ecotype, and at > 5 umol L"1 Cu for the Jiuxi-ecotype respectively. Root Cu concentrations were higher in Sanmen-ecotype than in Jiuxi-ecotype, by contrast, leafespecially stem Cu concentrations were much lower in the former than in the latter. Furthermore, Jiuxi-ecotype was much more efficient than Sanmeng-ecotype in translocation of Cu from root to shoot, and it had higher ratios of stem/root and leaf/root Cu concentration. These results indicate that the Sanmen-ecotype of E. argyi is a Cu-tolerant ecotype, and its tolerance to high Cu levels was mainly related to its extraordinary capab...
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