Effect Of Modified Low-grade Phosphate Rock On Prevention And Control Of Cd Pollution In Rice And Its Mechanism

In recent years,the soil heavy metal pollution threat to food safety has attracted much attention,how to effectively control the economy has become a widespread attention of the world's hot spots.Is rice planting powers in China,rice is a kind of special commodity grain of cadmium strongly the cumulative food crops,rice cadmium residents in our country has become a threat to the major problem of health and social stability.In many soil cadmium repair technology,application of passivator reduces the cadmium is a not affect plant biological validity relatively economic and effective method.However,ordinary passivator general dosage is large,the change of soil physical and chemical properties will lead to crop failures in different level,application difficulty.Studies have shown that hydroxyapatite to lead good passivation effect,rarely make the news and the passive study of cadmium.Phosphorus is a necessary one of the three major elements of crops,our laboratory through activation of low and medium grade phosphate rocks development promote the release of phosphate fertilizer prices are lower and good and slow-release fertilizer effect,for the purpose of soil cadmium passivation,further improvement in and quite ordinary phosphate fertilizer amount if can effective prevention and control under the condition of paddy cadmium pollution,to reduce the phosphorus loss,than ordinary passivation agent has better application prospects.This research adopts the effective phosphorus content of different class 2 each of three developed modified phosphate rock,compared with commercially available passivation agent,through the study of cadmium adsorption characteristics,indoor soil culture of cadmium passivation effect simulation,the rice pot experiment,the research on the effect of cadmium pollution prevention and control of paddy fields,explore the prevention and control mechanism,for the cadmium pollution prevention and control of rice and phosphorus loss provide new technology and scientific basis.The main results were as follows:?1?Cadmium adsorption experimental results show that 6 kinds of modified phosphate rock to cadmium has good adsorption effect,is better than that of biomass carbon.Cadmium adsorption quantity biggest order as:APC3?40.29 g/kg?>APC2?38.74 g/kg?>APC1?37.33 g/kg?>APR1?30.73 g/kg?>APR3?28.98 g/kg?>APR2?28.17 g/kg?>C?17.18g/kg?,Langmuir equation is better than the Freundlich equation can describe the passivator on cadmium adsorption characteristic.SEM and XPS analysis of modified phosphate rock after the adsorption of cadmium,O^2-and OH^-,Si-P,P-O plasma or functional groups and Cd²⁺chemical reactions happened in the solution,proved that the modified phosphate rock mechanism of cadmium adsorption mainly ligand exchange and forming complexes.?2?Indoor soil culture experiment showed that the processing training after 50 days,use of6 kinds of modified phosphate rock soil pH value to different extent,applied APC1,APC2,APC3 processing is 7.4,compared with CK0 increased by 1 unit,and use APR1,APR2,APR3 treatment only for improvement of the 0.5 units.Compared with CK0,all the processing of cadmium content in soil was significantly reduced,in adding 6 kinds of modified phosphate rock processing,add the processing of modified phosphate rock APC1and APC2 of cadmium content in soil was to reduce the sharpest,reduced by 55%and 49%respectively,the effect is better than that of commercially available three passivator;Each processing iron manganese oxide in combination with soil cadmium and cadmium residue state levels were significantly increased,but carbonate combined with the state,the organic combination state has no obvious change,among them,the application of modified phosphate rock APC1,APC2,APC3 processing of iron manganese oxide cadmium content increased by more than 45%,combined with state residue states cadmium content increased by 16.1%to 22.2%.?3?Blame drenchs solution under the condition of the rice pot experiment results show that compared with no use of passivator,the use of 6 kinds of passivator deal with two kinds of rice?Huang Huazhan,Tianyou 3618?cadmium were significantly reduced in brown rice.City of three kinds of modified phosphate rock processing and sale of passivator Y processing Huang Huazhan rice cadmium content in brown rice is more close to between0.2 to 0.24 mg/kg,application of modified phosphate rock APR2 to deal with the best results,compared with CK1 decreased by 66.5%;Tianyou 3618 is still the application of modified phosphate rock APR2 cadmium content in brown rice processing to reduce the effect best,compared with CK1,fell by 66.6%.Rice yield from the determination results,compared with the use of ammonium phosphate treatment?CK1?,three kinds of modified phosphate rock can significantly increase the two kinds of rice production,and three kinds of commercially available passivation agent and CK1 there was no significant difference.Rice post-harvest cadmium content of soil effective state determination results showed that 6 kinds of passivation agent can effectively reduce the soil cadmium,effective state compared with CK1,decline between 19%-39%,effect of the optimal for APR1processing.?4?Under the condition of leaching rice pot experiment results show that compared with no p,the processing of applying superphosphate two rice?Huang Huazhan,Tianyou 3618?cadmium in brown rice were reduced by 19.5%and 11.4%respectively,reached significant level.Application of three kinds of modified phosphate rock processing?Huang Huazhan?between the conventional cadmium content in brown rice,are less than 0.2 mg/kg,66%lower than the use of ordinary superphosphate process,for the hybrid rice?Tianyou 3618?,applying APC1 processing effect is best,than the use of ordinary superphosphate process was reduced by 69%,the rest of the two kinds of modified phosphate rock reduced by 64%and 58%respectivel.Two kinds of phosphate rock modifier showed better than ordinary superphosphate in cadmium resistance control effect,but not as good as modified phosphate rock,the LS is superior to the FU.Determination of phosphorus content in leaching solution results show that the three kinds of modified phosphate rock treatment than ordinary superphosphate by 65.1%,67.1%and 65.1%respectively.From the point of potted rice grain yield determination results,application of three kinds of modified phosphate rock processing and there is no significant difference between calcium superphosphate process.After harvesting the potted soil cadmium determination results showed that the effective application of three kinds of modified phosphate rock processing were significantly lower,compared with the use of calcium superphosphate process fell by45.2%,37%and 45.2%respectively.The above results show that the modified by low grade phosphate rock can be obtained with soil cadmium passivation and reduce the loss of farmland phosphorus function products,this kind of product is not only a significant paddy cadmium pollution and phosphorus loss prevention and control effect,less dosage,and obvious effects to increase production,has a good development prospect.