| The Three Gorges Project is the largest artificial water-control and hydropower Project, and also is a world class hydraulic engineering, which has formed into a gigantic integrated business pattern for water controlling, hydropower generation, navigation facilitation, and so on. After the construction of the Three Gorges Project, the flow rate of major Yangtze River has slowed greatly. The capability of recovering clean also has dropped in water condition. The negatively environmental effect of the Three Gorges Reservoir gradually is showing up. Especially, there are a lot of serious problems in water condition. The total efficiency is influenced by the water safety and ecological environment healthy of the Three Gorges Reservoir. The Three Gorges Project adopts the scheme of storing fresh water and excluding the muddy water, that is, the lowest water level of145meters in summer and the highest water level of175meters in winter, which will form water level fluctuating zones with a drop of30meters in maximum water level in the areas along the river. The water level fluctuating zone influences the diffusion, migration and transformation of pollutants in water-soil-sediment system. The various kinds of pollutants are greater active in this zone. The water level fluctuating zones is not only the source of pollutants, but also the combination of pollutants.The TGRA is intensively impacted by human activities, such as industry and towns along the bank of the TGRA. Besides, farming takes large possession of land exploitation mode in TGRA. The widely use of pesticide will influnence water quality and ecological system in TGRA. The total usage and dropout of pesticides reached hundreds of ton, and are increasing year by year in TGRA. The organophosphorus pesticide and organonitrogen pesticide are the most typically in the total usage and dropout of the pesticides in the TGRA. For example, the use of organophosphorus pesticide and organonitrogen pesticide is more than74.5%in the total. And the dropout is more than80.1%. The organophosphorus pesticide have the characteristics of broad spectrum, high performance and acute high noxious. The organonitrogen pesticides have the characteristic of stomach toxicity, thouch kill internal absorption and fumigation action. Besides, they are all nerve agent.There are some reports about pollutants in TGRA, mainly focused on the study of organic contaminant such as polycyclic aromatic hydrocarbon(PAHs), polychlorinated biphenyl(PCB) and environmental hormone contaminant. The organophosphorus pesticides and organonitrogen pesticides are seldom paid attention. Therefore, dichlorvos and trichforphon belonged to organophosphorus pesticides, and monosultap and dimehypo belonged to organonitrogen pesticides were researched. Especially, through selected dissovled organic matter (DOM) as major environmental medium, and united multiple molecular spectroscopic technologies, which contained FTIR, FT-Raman, Surface Enhanced Raman Scattering (SERS), Excitation Emission Matrix (EEM) and Polarized Excitation Emission Matrix (PEEM), to study the interaction of two kides of4pesticides with the environmental medium. These could be an index and reference for the study of pollutants’migration and transformation in water level fluctuating zone. The results are as follows:1. Fluorescence excitation emission matrix (EEM) was applied to characterize the dissolved organic matter (DOM) from waters in the water level fluctuating zone of the Three Gorges Reservoir. The composition, distribution of the DOM are investigated by combination of pH values, dissolved oxygen(DO), dissolved organic carbon(DOC), oxidation reduction potential (ORP), A254nm etc., with impacted by30m water levels fluctuation, and the correlations between each fluorophore’s intensity and environmental factors mentioned above were fitted. From the results, all the DOM’s EEM from main streams in the Three Gorges Reservoir had four fluorescence peaks, attributed to protein-like(P1,225-236nm/330-155nm; P2,271-285nm/330-355nm), humic-like(H,296-315nm/395-410nm) and fulvic-like(F,230-245nm/390-410nm) respectively. During175m dry season, fluorescence intensities in EEMs increased from upstream to downstream, with the Dam section having the strongest intensity; comparatively, during145m wet season, the fluorescence intensities was obviously higher than those in dry season, impacted by terrestrial confluence along the bank of the Three Gorges Reservoir, and the strongest intensity occurred in the middle and upper reaches. A good correlation between environmental parameters and EEM Peaks was observed in dry season. On the contrary, only Peak A and DO has positive linear correlation during wet season. The present article revealed the water quality in the Three Gorges Reservoir is mainly affected from the terrestrial confluence, with less impact by the30m water level fluctuation in reverse way to the Yangtze River’s natural water level fluctuating law.2. The typical parts of three kinds of soils (brown soil, yellow soil and purple soil) along the bank of the TGRA were collected, and the humic substance isolated from the parts of the soils according to different water condition. Using FTIR, FT-Raman, SERS, EEM and PEEM, the formulation of DOM and the influnce by changed water are researched. (1) The typical vibration structure of DOM with IR and Raman are as follows:1789-1732cm"1assigned to v (-C=O) and δ (CH), τ(NH),δ (COO-), γ (C-O) are the typical vibration of DOM. The differents between DOM of three kinds soil in IR is that there is or not δ(CH2) at1454-1435cm-1and group or skeletal vibration at1300-900cm-1and800cm-1. Among these, the most different structure is DOM in yellow soil and brown soil. In Raman,1668cm is assigned to v (C-H) of alicyclic,732cm-1and185cm-1is assigned to carbon chain skeletal vibration of DOM. Besides, the strong peak at1067cm-1and1385cm-1is v (-C=O) and v (-C-C), v (-C-O) of carbohydrate is at1011cm-1. All of the vibrational peaks reveal that DOM which in soil and sediment is complicated combination macromolecule with multifunctional structure. And the numbers of vibration active functional group in DOM from upstream with brown soil and purple soil significantly more than downstream with yellow soil. Yellow soil surface, especially in the dam section, the vibration of DOM is very strong.(2)Among SERS of DOM from red soil, the vibration of v (C-C), τ(CH),δ(CH2) is obviously different from those in brown soil and purple soil. The SERS of DOM is scarcely different in upstream soil and the peak is the same. The SERS of DOM from downstream in sediment is stronger than in soil, especially the vibration of v (O-H...O), vs (NH), v (COO). The change of DOM’s SERS with the factors that contain the change of water in water level fluctuating, the type of soil and exploitation mode is discussed.(3) The fluorescence peak which is in EEM of DOM from soil and sediment in TGRA is very strong. There is one fluorescence peak in361-372nm/441-457nm from purple and yellow soil. And there are two fluorescence peaks in260-27lnm/417-126nm and331-345nm/411-419nm from brown soil. Among PEEM of DOM, there is scarcely fluorescence peak from some yellow and purple soil. Fluorescence peak position of PEEM from part of purple soil is the same as that from brown soil, but the intensity is much weaker. Fluorescence peak position of PEEM from brown soil is the same as that of EEM, but the intensity is much weaker too. The change of DOM’s structure with the factors that contain the change of water in water level fluctuating, the type of soil and exploitation mode is discussed.3. The vibration peaks of dichlorvos, trichforphon, monosultap, dimehypo by IR and Raman are obtained and sssigned.(1) Among vibrational spectrum of dichlorvos and trichforphon, v (P=O) is separately at1240cm-1and1278cm-1, the others of v (C-C), v (C-Cl), v (P-O-C) are very different. Then the peaks of2858cm-1assigned to vas (CH3) and2960cm-1assigned to v (O-CH3) are the same.(2) Among vibrational spectrum of monosultap and dimehypo, there is only same peak at1465cm-1assigned to δ (CH3). The others of vas (CH3), v (C-N), v (C-N-C), v (S-O), v (S-C) are different. The most difference is v (C-N) and v (S-C).4. SERS of dichlorvos, trichforphon, monosultap, dimehypo adsorbed on core-shell Au/Ag nanoparticles are obtained and assigned.(1) Among SERS of dichlorvos, the structure at2960cm-1assiged to v (O-CH3),783cm-1assiged to v (C-C),415cm-1assiged to v (C-Cl) and skeleton are enhanced on core-shell Au/Ag nanoparticles. But there is no signal of trichforphon.(2) Monosultap and dimehypo on core-shell Au/Ag nanoparticles are enhanced. Among SERS of them, the SERS peak at3034cm-1assiged to v (C-N),835cm-1assiged to v (C-N-C) and low wave numbers are correspondence. There are less different of v (CH3) and vas (CH3). The interaction of v (C-C), v (C-S), v (C-H) and basement are more different.5. The interactions of DOM and two kinds of pesticides, dichlorvos, trichforphon, monosultap, dimehypo, are discussed by SERS, EEM and PEEM. The migration and transformation mechanism of four pesticides in water level fluctuating zones of the TGRA are researched at the molecular level.(1) When the reactions of DOM, which is from siols and sediments in water level fluctuating zones of the TGRA and dichlorvos/trichforphon, monosultap/imehypo are in balance, the compound of DOM-dichlorvos/richforphon and DOM-monosultap/dimehypo is formed separately. Because of the different enviroment, molecular structure of DOM, the compounds show the corresponding difference. But there are some typical peaks at395cm-1,950cm-1,1020cm-1,3030cm-1among every SERS of DOM-monosultap/imehypo. There are some typical peaks at730cm-1,606cm-1among every SERS of DOM-dichlorvos/richforphon.(2) Dichlorvos, trichforphon, monosultap, dimehypo can not be excited by the fluorescence directly, but DOM has the strong fluorescence properties. DOM and monosultap/dimehypo, dichlorvos/richforphon composite of changes in the molecular structure and size information are further characterized with EEM and PEEM. Before DOM and four kinds of organic pesticide are compounded or after that, there are no significant changes in EEM. DOM from yellow soil of TGRA downtream water level fluctuating zone has no PEEM. After DOM and four kinds of organic pesticide are compounded, the compound have PEEM. In addition, DOM from brown and purple soil with two types of organic pesticides have some changes with flurescence peak posotion and intensity in PEEM. These indicating that, when four types of organic pesticides and DOM effects, the molecular structure and size of environmental media DOM are changed. Thus it is an important factor which affected environmental behavior of organic pesticides in the TGRA. |
PDF Full Text Request