| Pesticides have become one of the indispensable elements in modern agriculture and have brought great benefits to crop production by controlling weeds or insects. However, pesticides residues have become one of the most frequently occurring organic pollutants in farmland and have detrimental effect on environments and human health. Napropamide is one of pre-emergence herbicides killing many annual monocotyledon grasses and broad leaf weeds. As napropamide is normally soil-applied, relatively soluble in water and half time of degradation70days, it readily accumulates in crops and consequently has caused environmental problems. Hence, it is great important for estimating napropamide behaviors and fate in plant-soil systems.Dissolved organic matter (DOM) is ubiquitous in soil and aqueous environment, and it is the most active component in terrestrial and water ecosystem. It can facilitate the mobility of contaminants in soil and water. Recent studies have shown that dissolved organic matters (DOMs) have multiple capacities of modifying mobility, transformation and binding to organic compounds in soils. Two types of DOM (one is extracted from sludge and the other is from straw) on toxic reactivity of pesticide napropamide in rapeseed was determined in this thesis.We determined the effect of the two types of DOM on the accumulation of napropamide in rape seed. Firstly, a method for determination of napropamide in rape seed root and leaf was developed by HPLC. Residue was extracted with a mixture of V (acetone):V (water)=1:1, followed by cleanup with a LC-18SPE column. The extracted samples were analysed by HPLC-UVD. The recoveries ranged from84.3～100.4%for leaf,83.8～108.3%for root, with the RSD were2.41～4.11%、4.11～11.17%respectively. Then, rape seed seedlings growth under8mg kg-1naprapamide and50mg C kg-1DOM extracted from sludge and straw for10days displayed the accumulation of napropamide in root and leaf. The result indicated that napropamide accumulation in root and leaf of rape seed was decreased with two type of DOM, and the DOM from sludge is more effective than the DOM from straw.Because napropamide-induced oxidative stress in B. napus was linked to the enhanced production of reactive oxygen species and regulation of ROS levels can be achieved by a group of enzymes such as SOD, CAT and APX, it was of interest to valuate the activities of these enzymes which constitute the defense (or antioxidative) systems that plants have evolutionally developed. Our consequence demonstrated that DOM could reduce MDA, CAT, SOD, POD and APX content with the napropamide-induced oxidative stress, suggesting a protective ability of DOM against napropamide-induced oxidative damage. While DOM could increase GST activities, because DOM probably reduce the oxidative injury of H2O2. To get an insight into the effect of napropamide on the enzymes, a non-denaturing polyacrylamide gel electrophoresis (PAGE) for SOD, POD and CAT activities was performed. The results indicate the involvement of all of these enzymes in the similar response to the herbicide.After the element analysis of the two DOMs, we found that DOM (SL) had higher N content than DOM (ST), while DOM (ST) had higher C content than DOM (SL). Spectroscopy technology was used to study DOM and the complex of DOM and napropamide. Three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy indicated that there are two main peaks of DOM and DOM-napropamide complexes. The two peaks related to the aromatic protein-like substances and the tryptophan protein-like substances respectively. FT-IR spectra applied the structure information of DOM and DOM-Napropamide complex. The differences between DOM and DOM-napropamide complexes of EEM and FT-IR demonstrate that some function groups of DOM can combine or react with napropamide. The researches of spectra confirm the consequence of above studies. |
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