The Remediation Study About Humus On Contaminated Soil By Cu And Zn

The contamination of Cu and Zn are common heavy metal pollution in agricultural production.And the main source of Cu and Zn is the use of pesticides and chemical fertilizer in agriculture.To study The remediation effect about humus on contaminated soil by Cu and Zn,firstly,a field survey was conducted at Dayao Country of Chuxiong Yi Autonomous Prefecture,Yunnan Province,China.We studied the correlation between components of humus and activity of soil enzymes(including urease,alkaline phosphatase,acid phosphatase and catalase).Then,we chose a land use type:cultivated land as research object and set three concentration gradients of exogenous adding HA and FA(organic carbon content:2.076g/kg?4.152g/kg?6.228g/kg)in the first soil culture experiment.After soil culture,four kinds of soil enzymes activity(including urease,alkaline phosphatase,acid phosphatase and catalase)and pH of soil were determined in the experiment and the elemental composition of HA and FA were analyzed with elemental analyzer for the research about the effects and mechanisms of HA and FA on the four kinds of soil enzymes activity.Secondly,the adsorption experiment was carried out.The study was aimed to research the effect of HA and FA on adsorption-desorption behavior of Cu(?)and Zn(?)in the yellow soil and the concentrations of Cu(?)and Zn(?)were determined by atomic absorption spectrometer.Thirdly,the study about the influence of different concentration of exogenous adding Cu and Zn on soil enzymes activity was carried out in the second soil culture experiment.Then,four kinds of soil enzymes activity and pH of soil were determined in the second soil culture experiment.Thus,we chose two suitable concentrations of exogenous adding Cu and Zn,respectively.Finally,we designed the third soil cultUre experiment.The experiment is about the effects and mechanisms of HA and FA on the four kinds of soil enzymes activity under Cu and Zn contamination.In the study,the respective two concentrations of exogenous adding Cu and Zn are(Cu:400mg/kg,800mg/kg)and(Zn:500mg/kg.1000mg/kg)and three concentration gradients of exogenous adding HA and FA are(organic carbon content:2.076g/kg,4.152g/kg and 6.228g/kg).Then,in the third soil culture experiment,four kinds of soil enzymes activity,pH of soil and available content of Cu and Zn were determined and the infrared spectrum analysis of HA and FA are carried out.The results showed that:(1)With the increasing of soil layer depth,the content of soil organic matter and humus components and the activity of four kinds of soil enzymes were all gradually reducing.Besides,correlation analysis showed that the content of soil organic matter and humus components and the activity of four kinds of soil enzymes had significant correlation.HA had the obvious effect in promoting the activity of alkaline phosphatase and acidic phosphatase.FA promoted,obviously,the activity of urease,alkaline phosphatase and catalase increasing;however,FA had the obvious inhibitory effect on acid phosphatase activity.What's more.FA had better effect in promoting the activity of Urease and alkaline phosphatase and catalase than that of HA.Compared with exogenous HA,the content of nutrient element(C,H,O,N,S)in FA is higher.Besides,FA also contained more carbon source of aliphatic carbon and carboxylic acid,which were more likely to be used by microorganisms.Therefore,FA had better effect in promoting the activity of soil enzymes.(2)The results showed that the yellow soil has less adsorption amount of Cu(?)in the presence of HA than that in CK treatment.In addition,at high concentration Zn(?),HA is benefit to the soil adsorption of Zn(?).Furthermore,FA has similar effect on adsorption behavior of the Cu(?)and Zn(?).FA is not conducive to the adsorption of soil for Cu(?)and Zn(?)at low concentrations of Cu(?)and Zn(?.However.FA is benefit to the adsorption at high concentrations of Cu(?)and Zn(?).The adsorbed Zn(?)by soil is hard to be desorbed by the neutral salt solution.There is higher specific adsorption ratio in adsorption of Zn(?),comparing with adsorption of Cu(?).(3)With the increase of the exogenous Cu concentration,the activity of urease,alkaline phosphatase,acidic phosphatase and catalase were gradually reducing in soil.Besides,alkaline phosphatase is most sensitive for soil Cu pollution in four kinds of soil enzymes.The exogenous Zn had the obvious effect in promoting the activity of urease and alkaline phosphatase when the highest concentration of exogenous Zn was not more than 2000 mg/kg.However,Zn had some inhibitory effect on acid phosphatase activity at the concentration of 2000 mg/kg.Furthermore,the activity of catalase was also sensitive for Cu and Zn.With the increase of exogenous Zn concentration.the activity catalase was gradually reducing.Under the low concentration Cu(400 mg/kg)contamination,HA and FA significantly increased the activity of urease and alkaline phosphatase in soil and FA had the better effect than HA.In addition,FA also had the obvious effect on promoting the activity of acid phosphatase.At the highest content(6.228 g/kg)of exogenous FA,catalase activity significantly improved,too.Under the high concentration Cu(800 mg/kg)contamination.FA still significantly promoted the activity of urease,alkaline phosphatase and acidic phosphatase.But HA have a little effect on promoting the activity of urease at high content of exogenous HA.Besides,catalase and related microbes were more sensitive for Cu and HA and FA both had no effect on promoting catalase activity under the high concentration Cu(800 mg/kg)contamination.Under excessive Zn contamination,HA had no obvious effect on the increasing of four kinds of soil enzymes activity.However,FA still increased the activity of urease,alkaline phosphatase and catalase.But,under the low concentration Zn(500mg/kg)contamination.FA had adverse effect on the activity of acid phosphatase.(4)HA and FA could reduce the content of available Cu in soil.But,at the low concentration(400 mg/kg)of exogenous Cu,FA had better effect on decreasing the content of available Cu.Besides,at high concentration(800 mg/kg)of exogenous Cu,HA and FA had similar effect on decreasing the content of available Cu in soil.The possible reason was that HA and FA contained many carboxyl and alcoholic hydroxyls and FA had more the two kinds of functional groups than HA.Therefore,FA could more reduce the content of available Cu.HA had no obvious effect on reducing the content of available Zn in soil.However,FA had the better effect on decreasing the content of available Zn at the low content(2.076 g/kg)of exogenous FA.