| It is a pleasant thing if a fertilizer can not only overcome heavy metal pollution t but also make vegetables safe and high quality.However,the special fertilizer is not yet available at present.The main problem is that in-situ passivation technology is difficult to achieve the expected objective at low concentrations heavy metal pollution at present.Based on the above reason,the study found a new in-situ passivation material-hoof horn.The animal hoof horn contains about 80%proteins in which there are a large number of sulfhydryls,and the sulfhydryls can bind low concentrations of heavy metal ions as previous reported.Therefore,the fertilizer effect,in-situ passivation and fertilizer effect combined experiment with in-situ passivation of the hoof horn powder and its hydrolyzed polypeptide were studied respectively.The results showed the hoof horn powder and its hydrolyzed polypeptide had both good fertilizer effect and passivation functions,and the study idea was effective and feasible and it provided a basis of theoretic and research.The concrete results are as following:(1)Growth effects of hoof horn powder and its hydrolyzed polypeptide on brassica campestris L.in normal soil were studied.The results showed that both hoof horn powder and its hydrolyzed polypeptide could promote plant growth when fertilization amount was consistent with conventional method(based on nitrogen content).The single plant biomass of both hoof horn powder and its hydrolyzed polypeptide reached more than 15.07 g(normal 40-days harvest),which were at least 9.8%higher than the single plant biomass of the compound fertilizer(CF)and 59%higher than that of the blank control(CK).In double-fertilization(two-times normal fertilization amount)studies,the single plant biomass of both hoof horn powder and its hydrolyzed polypeptide reached more than 17.72 g,which were at least 13.8%higher than the single plant biomass of CF and 67,2%higher than that of CK.The above results indicated that both hoof horn powder and its hydrolyzed polypeptide were good organic fertilizers and were more effective than commercial compound fertilizers to brassica campestris L.(2)According to the biochemical characteristics of the hoof horn powder and its hydrolyzed polypeptide,both materials might bind or absorb heavy metal ions.Therefore,the adsorption or binding of both the hoof horn powder and its hydrolyzed polypeptide to copper ions in the aqueous solution state was studied.The results showed that both materials had strong adsorption or binding effect at the three copper ions concentrations of 80 mg/L,100 mg/L,and 300 mg/L respectively.After a certain time of treatment,the adsorbed or bound amounts of hoof horn powder reached 81.09%,78.03%,74.01%at the three copper ions concentrations respectively,and that of hydrolyzed polypeptide of hoof horn reached 66.69%,64.88%,54.35%,both materials were better than that of the control activated carbon.This conclusion indicates that the hoof horn powder and its hydrolyzed polypeptide have the potential ability to passivate heavy metals in soil.(3)Effects of hoof horn powder and its hydrolyzed polypeptide on passivation of manually formulated single copper polluted soil and compound polluted soil,which was brought from copper mining area,were studied.The results showed that both horn powder and its hydrolyzed polypeptide had passivation ability in the three manually formulated single copper polluted soil,which contained copper ion concentrations of 80 mg/kg,100 mg/kg,and 300 mg/kg respectively.The passivation effect of hoof horn powder was better than that of hydrolyzed polypeptide,and the maximum passivation effect reached 47.65%.To compound polluted soil,which was brought from copper mining area,the passivation effect of hoof horn powder was more obvious than that of hydrolyzed polypeptide.The activated copper ion content of three different copper concentration polluted soil for hoof horn powder were decreased to 50.20%,47.21%,42.30%compared with that of CK respectively,and that for hydrolyzed polypeptide were decreased to 24.61%,23.23%,22.61%,while that for CF was increased.(4)Effects of hoof horn powder and its hydrolyzed polypeptide on promoting brassica campestris L growth and copper ion content of plants in compound polluted soil,which was brought from copper mining area,were studied.Based on copper ion content of 100 mg/kg was minimum pollution index for alkaline soil,copper ion content of 80 mg/kg(slight pollution,acid soil)and 300 mg/kg(severe pollution)were selected as the reasrch objects.The results showed that the hoof horn powder and its hydrolyzed polypeptide could promote the plant growth in the total copper ion content of 80 mg/kg polluted soil.After 40 days growth,the biomass of single plant with both hoof horn powder and its hydrolyzed polypeptide were more than 12.36 g,which were 60.4%higher than that of CK and 12.9%higher than that of CF.The relative chlorophyll contents with both materials were also more than 48.24,which were 22.2%higher than that of CK and 16.3%higher than that of CF.In high copper content(300 mg/kg)polluted soil,the results were similar with that of the total copper content of 80 mg/kg polluted soil.During different periods,a serial of the copper contents of brassica campestris L.were studied.The results showed that the copper content(40 days)was 0.97 mg/kg with hoof horn powder in the 80 mg/kg copper-polluted soil,which was 75.7%and 69.4%lower than that of CK and CF respectively,while the content of copper with hydrolyzed polypeptide was 2.03 mg/kg,which was decreased by 49.1%and 39.4%compared with CK and CF respectively.At the same time,the copper contents(40 days)was 1.63 mg/kg with hoof horn powder in the 300 mg/kg copper polluted soil,which was 73.9%and 68.9%lower than that of CK and CF respectively,while the content of copper with hydrolyzed polypeptide was 2.31 mg/kg,which was decreased by 63%and 55.9%compared with CK and CF respectively.At brassica campestris L.florescence period,the total copper content of cultivated crops was up to far lower than the national standard value.In the 300 mg/kg copper-polluted soil,the maximum copper content of the brassica campestris L.in experiment groups was 8.674 mg/kg,which also reached the national safety standard,while the copper content of the control group was 15.078 mg/kg and was higher than the national standard value.Therefore,hoof horn powder and its hydrolyzed polypeptide have potential application value as special fertilizers for copper mining areas. |
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