Dissertation > Excellent graduate degree dissertation topics show

Study on Arsenic Behaviors in Rhizosphere of Rice and Influence Factors

Author: WangYing
Tutor: LiuWenJu
School: Agricultural University of Hebei
Course: Soil
Keywords: Rice Arsenic Iron oxide film Arsenic - Iron Rhizosphere pH Exogenous silicon and organic matter
CLC: S511
Type: Master's thesis
Year: 2011
Downloads: 143
Quote: 1
Read: Download Dissertation

Abstract

Natural and anthropogenic factors caused by rice paddies arsenic contamination phenomenon in recent years, becoming more serious, as the main food crops in the world, rice, rice growth environment, making it easier than other upland field crop accumulation of arsenic in the edible parts, through the food chain pose a threat to human health. Therefore, the regulation of the behavior of arsenic in the soil - rice system can reduce its accumulation in the edible parts, in order to effectively improve food security. Based on this, the first heavy metal pollution phenomenon Tailing the surrounding rice fields were investigated and rice in arsenic contamination evaluation. For the paddy fields arsenic pollution conducted rhizosphere and arsenic behavior regulation mechanism related research: using nutrient solution culture method, dynamic process and its impact mechanism Rice dynamic adsorption and absorption of arsenic Rice Seedling root surface iron oxide formed ; using the compartment soil cultivation method of alternating wet and dry moisture management mode rice root soil interface liquid phase and solid phase arsenic, iron daily dynamic changes of the law as well as the different arsenic-contaminated soil pH value after flooding rice rhizosphere pH and arsenic content of the dynamic changes; finally add exogenous silicon and organic matter in the rhizosphere of rice and edible arsenic cumulative effect of regulation. The main findings are as follows: (1) lead and zinc the tail mines surrounding each sampling point average soil As content of 328 mg / kg, more than the background value of soil environment, the performance of each sampling point for contaminated rice fields and woodland soil arsenic pollution index greater than 3 severe arsenic contamination; ordinary rice arsenic pollution index 2.74, belongs to the moderate arsenic contamination. The contaminated rice paddies and Rice in edible parts of arsenic pollution evaluation results show that the rice grains are slightly polluted polluted rice paddies and rice paddies. (2) the number of the iron oxide is formed by the low concentration of Fe2 treatment induced are lower than the corresponding time point induced by high concentrations of Fe2 processing and increase the number of the root iron oxide along with the extension of the induction time. Enrichment of root surface iron oxide induces the formation of arsenic (0.53 g / kg -0.99 g / kg) were higher than that of the control (0.41 g / kg, P lt; 0.05), and the number of iron plaque and its rich set arsenic concentrations positively correlated; significantly inhibited root absorption of arsenic in root the table iron oxide formation, when the quantity of the iron film in the range of 5-20 g / kg, and this inhibition is not with the number of iron plaque changes significantly changed, but when the number of iron oxide gt; 20 g / kg, the rice absorb arsenic inhibition weaken with the increase in the number of iron plaque; in arsenic treatment within 24 hours, the root Table of iron oxide obvious inhibition of arsenic in rice shoot cumulative control shoot arsenic concentrations: 6.79 mg / kg, the iron film formed rice shoot arsenic concentration range :2.55-4 .96 mg / kg. (3) alternate wetting and drying cycle, from wet to dry soil solution total arsenic content showed a reduced gradually, little change in the total iron content, changes in pH and Eh values ??were in the range of 7.5-8.3, and 150 -200 mV. Alternate wetting and drying cycle and during the week, the iron content of arsenic in the root soil interface changed little, but the two phases cycle showed a significant correlation, the correlation coefficient of 0.650 and 0.764, respectively. Was a significant positive correlation between total arsenic in iron rice root alternate wetting and drying cycle. (4) the various points of the low pH of arsenic-contaminated soil planting rice in soil solution pH value higher than rice cultivation, the higher the pH range of 0.06-0.21 units; while high pH of arsenic-contaminated soil planting rice 9 days after its soil solution pH lower than rice cultivation, the biggest difference of 0.38 units. For the low pH of arsenic-contaminated soil, rhizosphere soil pH changes rhizosphere there is no correlation between the arsenic content in the soil arsenic content and root; while high pH of arsenic-contaminated soil and rhizosphere pH changes rhizosphere soil arsenic concentration was a significant positive correlation with the concentration of arsenic in the roots was a significant negative correlation. (5) plus silicon rice shoots mature biomass was significantly higher than the control; adding organic matter, aboveground and belowground biomass than the control did not change significantly; adding silicon and organic matter processing tillering and maturity ground and below-ground biomass is less than the control. At tillering and maturity, plus silicon reduce rice underground arsenic concentration, decreased 22.8% and 60.9%, respectively, aboveground arsenic concentration lower than that of the control in the two growth stages, and arsenic transfer coefficient significantly reduced the; Canadian organic matter significantly reduce the the underground arsenic concentration, tillering stage decreased 69.5%, 53.8% maturity shoot arsenic concentrations, tillering reduced 44.5%, a 40.8% reduction in mature; adding silicon and organic matter processing highly significant reduce rice arsenic concentration underground, tillering reduced 68.2%, a 82.0% reduction in mature shoot arsenic concentrations were reduced by 75.4% and 94.1%.

Study on Arsenic Behaviors in Rhizosphere of Rice and Influence Factors

Abstract

Related Dissertations