Effects of Land Application of Municipal Sewage Sludge on Growth, Physiology and Accumulation of Heavy Metals in Wheat (Triticum aestivum L.)

The application of sewage sludge on agricultural soils is a promising technical solution. Pot experiments were performed to study the effect of sewage sludge application on growth, physiology and accumulation of heavy metals in three kinds of wheat. The experimental results showed soil pH decreased significantly with the increase of the application of sewage sludge. The contents of Cu, Zn and Pb in the mixed soil did not exceed the Environmental quality standards for soils in China for Grade II (GB-1518-1995). Wheat obtained good growth activities after the application of sewage sludge, however, high land application of sewage sludge (the ratio of sludge in the mixed soil of dry weight was 20% and 25%) inhibited seed emergence and root length. The content of total chlorophyll in wheat increased with the increase of sewage sludge application first and reached a maximum, and then decreased with a further increase of sewage sludge. Compared with the control, the a/b value in chlorophyll showed trace change. The content of proline in wheat increased with the increase of sewage sludge in low doses of sewage sludge (5%, 10% and 15%), while there was no significant increase in the content in high land application of sewage sludge. The physiological metabolism of wheat will exhibit abnormality as the stress of pollutants from sludge exceeded the tolerance of wheat. The content of three kinds of heavy metals in wheat grain increased obviously with sludge application increasing, indicating an increasing trend, and had the phenomenon of exceeded the safety qualification of non-environmental pollution food in china at high doses of sewage sludge. Taking account of the effects of sewage sludge application on growth, physiology and accumulation of heavy metals in wheat, the doses of sludge in the mixed soil of dry weight should be lower than 15%.