Effects Of Organic Acids And Pig Manure On Cu And Zn Adsorption, Accumulation And Transference In Soil

Some heavy metals like Cu, Zn, etc are added to forage. However, for their low biological potency in the livestock's bodies, most of them are discharged out, so the concentrations of heavy metals in animals'dejecta are high, which increase the risk of environment pollution. Nowadays, researches on soil heavy metal pollution are popular. Most of them focus on heavy metal pollution caused by urban Sludge and waste water applied in agriculture, paying little attention to the soil heavy metal accumulation caused by the dejecta of livestock. Organic acid was the important energy sources for the growth and increasing of microorganism, which could affectted the class and number of soil microorganism directly and would form the steady chelated substance with heavy meral, so organic acid had profount effect to moving action of heavy metai and had been paid attention to some scholars.This paper performed a research on the impact of application of pig manure on the accumulation of heavy metal in soil and ryegrass and the transfer of Cu and Zn, as well as the absorption of Cu and Zn by low molecular weight organic acid, via pot experiment and leaching experiment, which may provide scientific guidelines for proper livestock manure application and pasture ecological environment protection. And the main results are as follows:1, Different organic acids have different impacts on soil absorption of Cu and Zn. Here three organic acids promote soil absorption of Cu and Zn at different levels. In the experimental environment, for Cu, the promotion by tartaric acid is less than citric acid and oxalic acid. The sequence is: citric acid> oxalic acid> tartaric acid. For Zn, the sequence is: oxalic acid> citric acid> tartaric acid. Soil absorption capacity of Cu and Zn increases positively with the concentration of ion outside, however the absorption rate positively with the concentration of cupric ion. There is no or little soil absorption rate increase of Cu and reduce of Zn with the increase of concentration.2, There is not obvious impact of pig manure application on the Germination Rate and plant height of ryegrass. However evident increase of biomass can be seen after the application of pig manure. At the same time, the concentrations of soil Cu and Zn forms were typically chenged with ryegrass planted and the manure application increasing. The changing concentrations of the Cu and Zn forms of the total Cu were, HAC-soluble form, reducible form and oxidisable form were increased, and residual form was decreased. The percentage of soil Cu and Zn forms were typically chenged with the manure application increasing. The changing percentage of the Cu forms of the total Cu were, HAC-soluble form and reducible form were increased, and oxidisable form was chenged little, and residual form was decreased. The changing percentage of the Zn forms of the total Cu were, reducible form were increased, HAC-soluble form was chenged little, and oxidisable form and residual form were decreased.3, Accumulation of Cu and Zn in ryegrass increase along with the increase of concentration of Cu and Zn in soil, and Zn is more easily accumulated in ryegrass than Cu. The Zn concentration in the part of plant above ground excesses the standard set by healthy criteria (20mg/kg, (GB 13106-91)) after the application of pig manure more than 60g/kg, and two reasons may explain this phenomenon: on one hand, the concentration of Zn is high in soil itself, on the other hand, ryegrass has an ability to pool heavy metals.4, Correlation analysis were carried out about the concentration of Cu and Zn in the above ground part of ryegrass and available Cu and available Zn in soil, the results indicate, a good correlation exists between them.5, The concentration of Cu in topsoil is higher than that in deep soil, the deeper of the soil layer, the more approach to background value, and Zn has the similar variation trend. At the beginning, the concentration of Cu and Zn in each treated leaching solution. With the increase of solution volume, soil Cu concentration is higher after leaching with pig manure treated leaching solution than comparison. Different from Cu, the concentration of Zn didn't show phenomena of peak value and decline, increased positively with the volume of leaching solution. The multiply of Cu concentration in leaching solution versus antitheses is less than that of Zn, which indicates a less transfer ability of Cu than Zn.