[Dynamics of dissolved organic matter and its effect on copper and cadmium activity in the contaminated wheat soil: field micro-plot trials].

Studies were carried out to investigate effect of application of straw manure, pig manure, and pure fertilizer on dynamics of dissolved organic matter (DOM) as well as copper and cadmium activity in the soil cultivating wheat by field micro-plot trials. Also the distribution of DOM in the different depth of soil was studied. The results showed that the concentration of DOM in three treated soils decreased with wheat growth, especially before the wheat jointing stage. Compared with the control treatment without the addition of organic manures, the concentration of DOM in the orangic manure-treated soils increased drastically. The concentration of DOM was highest in the depth of 0 to 20 cm and decreased with depth. Meanwhile the mainly transference depth of DOM was 40 cm and a little of DOM can transfer to the depth of 60 cm. Before the wheat jointing stage, the concentration of DOM in rhizosphere soil was consistent with that in the bulk soil, and increased drastically after that period. It reached the maximum in heading stage then decreased gradually. The study also observed that the dynamic trend of exchangeable copper in rhizosphere and bulk soil was highly similar to the corresponding DOM. Also there was a significant correlation (r = 0.672, n = 60) between the concentration of DOM and exchangeable copper in three treatments of total 60 samples. The result showed that the activity of soil copper could be accelerated by DOM while cadmium not obviously.