Effects Of Modified Biochar On The Physiology Of Rice In Mercury-contaminated Purple Soil

Mercury heavy metal pollution not only causes crop yield reduction,but also threatens the safety of ecological environment and human health.Due to the rapid development of industry,Asia has become the region with the most mercury emissions.China's Mercury reserves are the third in the world.When plants are polluted by mercury,they will cause oxidant damage or even death.During the growing period,rice grows in the flooded environment for most of the time,forming a special wetland BC,which is a potential way for methyl mercury to migrate to the food chain.As a large agricultural country,it is of great significance for the sustainable development of our country to deal with farmland pollutants,especially the heavy metal pollution which is difficult to degrade.Biochar is a kind of soil proverbial which is produced by BC is of biomass under partial or complete nontoxic condition.It is found that biochar can adsorb heavy metals.The modification of the original biochar can optimize the adsorption performance,repair the soil polluted by heavy metals,and realize the reuse of agricultural waste resources.It has a broad research prospect for soil improvement.In view of the mercury pollution of purple soil in Southwest China,this paper compares the changes of rice BC characteristics and the changes of soil crop nutrient content under the condition of applying different kinds of modified biochar to mercury pollution,selects the modified materials with relatively good effect,and analyzes the reasons.Then,the best range of dosage was discussed by setting different mass ratio,which provided the basis for the treatment of mercury pollution in paddy field and the modification of biochar.The main results are as follows:(1)In order to study the effects of different modified biochar on the physiology of mercury contaminated rice,the original biochar and its six kinds modified biochar were used as the test materials to determine the photosynthetic related indexes.The results showed that under the same mercury concentration,with the growth of rice,the net photosynthetic rateincreased first and then decreased,that is,flowering stage >jointing stage >filling stage;transpiration rate decreased with the growth of rice,and the increase of stamina modified biochar treatment was the most significant in flowering stage;stalemate conductance also decreased with the growth of rice,NH at flowering stage was relative to the original biochar The increase of acellular carbon dioxide concentration was the largest at jointing stage and NH at flowering stage.With the increase of the mass ratio of the modified biochar,the photosynthetic BC index first increased and then decreased.In the whole growth period of rice,the net photosynthetic rate,stalemate conductance and transpiration rate increased first and then decreased with the increase of the mass ratio of modified biochar,while the inter cellular carbon dioxide concentration showed the opposite trend,indicating that the first three photosynthetic indexes showed a positive correlation trend,just opposite to the inter cellular carbon dioxide concentration trend.(2)In order to determine the effect of adding different modified biochar on the yield of rice polluted by mercury,the yield of rice was measured at maturity in the experiment of different content of modified biochar.The results showed that under the same mercury concentration,with the increase of the mass ratio,the yield indexes of NH and YYJ(panicky per basin,seed setting rate,yield per basin)first increased and then decreased,and the highest yield was obtained when the mass ratio was 0.20%,while the yield of SH gradually increased higher than that of 0.35%.Therefore,for the yield indexes,the best mass ratio of three kinds of modified biochar was 0.20%-0.35%.(3)In order to explore the effects of adding different modified biochar on the nutrients of mercury polluted purple soil and crops,the nutrient indexes of soil and crops in different growth periods were determined.The results showed that under the condition of mercury pollution,the increment of soil total nitrogen in each growth period was significant in NH treatment,which may be related to the nitrogen content in the stamina modified biochar treatment,and the difference between the other treatments was large with no obvious regularity.In flowering period,YYJ showed an increasing trend with the biochar quality ratio.At jointing stage,the increase of total phosphorus content was the largest in SH at C4,followed by YYJ at C1,NH at C4 and YYJ at C4 at flowering stage,and NH at 0.35%at maturity stage.The total K content of rice leaves increased significantly at NH at 0.35%massratio in flowering stage and maturity stage.In conclusion,the treatment effects of stamina modified biochar(NH),ethology modified biochar(YYJ)and modified biochar(SH)were relatively good in this study.Using these three kinds of modified biochar as test biochar,the best application range is0.20%-0.35%by adding different mass ratio and setting gradient content.