| Due to the rapid advance of China’s industrialization, the sludge production is also increasing. How to dispose of sludge is the focus research topic in the world. Sludge contains abundant organic matter and nutrients required by plants, therefore, sludge land application is the most promising utilization way. But how to achieve scientific and reasonable land resource utilization of city sludge is the urgent problem need to solve by finding out the effects of heavy metals absorption in plant uptake by utilization of sludge. In view of the loess-wheat in arid areas system, formulate scientific and reasonable pot experiment and research on the effect to plant growth by different cadmium pollution levels and different proportions (1.5%&3%) of composted sludge application to Loess. This research provides a reference for future sludge soil fertilization and helps to understand the interaction between soil heavy metal pollution and the accumulation of heavy metals in plants, providing the basis for soil heavy metal repair. The main research results are as follows:(1) The pH value of soil decreased with the percentage of composted sludge increased, while, the conductivity, organic matter and cadmium content gradually increased. Stable adsorption capacity increased with the concentration of composted sludge in soil samples increased. The organic matter in soil samples had the greatest contribution to the stable ability of cadmium.(2) Cd stress promoted the effective state of the distribution coefficient of Cd in soil, so as to promote the absorption of plants. But with the concentration of composted sludge in soil samples increased, the distribution coefficient of bioavailability Cd decreased, so Cd in soil could be more stable. The main reason was the composted sludge rich in organic matter and easy to form organic Cd, but there was still risky because organic matter would be microbial decomposition and slow released into the soil under certain conditions.(3) Application of composted sludge could effectively promote the growth of wheat, and sludge applied 3% was more conducive than sludge applied 1.5% to promoting the growth of wheat, the promotion degree of the parts of wheat:leaf> seed. In the condition of S6 (Cd=6.8mg/kg)and 3% composted sludge, the largest increase in wheat plant height reached 117%.In the Loess added 3% sludge and S8 (Cd=12mg/kg) level, the dry weight of the wheat stem and leaf was 9.757+0.353g and the maximum growth rate was about 336.75% compared with that added no sludge and the seeds dry weight of wheatwasl3.433±0.13g and the maximum growth rate was about 2329.11% compared with that added no sludge.(4) In low Cd concentration level (0-10mg/kg), application of composted sludge inhibited the absorption of each part of wheat Cd. The degree of inhibition:seed> root>stem and leaf, while Cd concentration exceeded lOmg/kg, composted sludge addition would bring threaten to wheat because of heavy metal pollution.(5) The accumulation ability of wheat tissues of Cd was:root>stem and leaf>seed, indicating that Cd was easier to enter the plant from the soil system and enriched in wheat roots, but enriched lest in seeds. The application of sewage sludge to a certain extent inhibited the accumulation of Cd in various parts of wheat, but the effect was not significant. At the same time, the application of sewage sludge greatly promoted the migration of Cd from stem and leaf to grain, and the effect of migration of Cd from root to stem and leaf was not significant. |
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