The study of agricultural non-point source pollution control policy system

As the agricultural non-point source pollution(ANPSP) has become the most significant threat for water environmental deterioration and lake eutrophication in China, more and more scientists and technologists are focusing on the control countermeasure and pollution mechanism of agricultural non-point source pollution. The unreasonable rural production structure and limited scientific management measures are the main reasons for acute ANSPS problems in China. At present, the problem for pollution control is a lack of specific regulations, which affects the government's management efficiency. According to these characteristics and problems, this paper puts forward some corresponding policies. The status of the agricultural non-point source pollution of China is analyzed, and ANSPS prevention and control model is provided based on governance policy, environmental legislation, technical system and subsidy policy. At last, the case analysis of Qiandao Lake is given, and an economic policy is adopted based on its situation.

Optimization of ethanol production by yeasts from lignocellulosic feedstocks

Ethanol from lignocellulosic feedstocks is not currently competitive with corn-based ethanol in terms of yields and commercial feasibility. Through optimization of the pretreatment and fermentation steps this could change. The overall goal of this study was to evaluate, characterize, and optimize ethanol production from lignocellulosic feedstocks by the yeasts Saccharomyces cerevisiae (strain Ethanol Red, ER) and Pichia stipitis CBS 6054. Through a series of fermentations and growth studies, P. stipitis CBS 6054 and S. cerevisiae (ER) were evaluated on their ability to produce ethanol from both single substrate (xylose and glucose) and mixed substrate (five sugars present in hemicellulose) fermentations. The yeasts were also evaluated on their ability to produce ethanol from dilute acid pretreated hydrolysate and enzymatic hydrolysate. Hardwood (aspen), softwood (balsam), and herbaceous (switchgrass) hydrolysates were also tested to determine the effect of the source of the feedstock. P. stipitis produced ethanol from 66-98% of the theoretical yield throughout the fermentation studies completed over the course of this work. S. cerevisiae (ER) was determined to not be ideal for dilute acid pretreated lignocellulose because it was not able to utilize all the sugars found in hemicellulose. S. cerevisiae (ER) was instead used to optimize enzymatic pretreated lignocellulose that contained only glucose monomers. It was able to produce ethanol from enzymatically pretreated hydrolysate but the sugar level was so low (>3 g/L) that it would not be commercially feasible. Two lignocellulosic degradation products, furfural and acetic acid, were evaluated for whether or not they had an inhibitory effect on biomass production, substrate utilization, and ethanol production by P. stipitis and S. cerevisiae (ER). It was determined that inhibition is directly related to the concentration of the inhibitor and the organism. The final phase for this thesis focused on adapting P. stipitis CBS 6054 to toxic compounds present in dilute acid pretreated hydrolysate through directed evolution. Cultures were transferred to increasing concentrations of dilute acid pretreated hydrolysate in the fermentation media. The adapted strains’ fermentation capabilities were tested against the unadapted parent strain at each hydrolysate concentration. The fermentation capabilities of the adapted strain were significantly improved over the unadapted parentstrain. On media containing 60% hydrolysate the adapted strain yielded 0.30 g_ethanol/g_sugar ± 0.033 (g/g) and the unadapted parent strain yielded 0.11 g/g ±0.028. The culture has been successfully adapted to growth on media containing 65%, 70%, 75%, and 80% hydrolysate but with below optimal ethanol yields (0.14-0.19 g/g). Cell recycle could be a viable option for improving ethanol yields in these cases. A study was conducted to determine the optimal media for production of ethanol from xylose and mixed substrate fermentations by P. stipitis. Growth, substrate utilization, and ethanol production were the three factors used to evaluate the media. The three media tested were Yeast Peptone (YP), Yeast Nitrogen Base (YNB), and Corn Steep Liquor (CSL). The ethanol yields (g/g) for each medium are as follows: YP - 0.40-0.42, YNB -0.28-.030, and CSL - 0.44-.051. The results show that media containing CSL result in slightly higher ethanol yields then other fermentation media. P. stipitis was successfully adapted to dilute acid pretreated aspen hydrolysate in increasing concentrations in order to produce higher ethanol yields compared to the unadapted parent strain. S. cerevisiae (ER) produced ethanol from enzymatic pretreated cellulose containing low concentrations of glucose (1-3g/L). These results show that fermentations of lignocellulosic feedstocks can be optimized based on the substrate and organism for increased ethanol yields.

COORDINATION CHEMISTRY OF BIS(BENZYL)PHOSPHINATE

The work presented in this dissertation deals with the coordination chemistry of the bis(benzyl)phosphinate ligand with vanadium, tungsten and cobalt. The long term goal of this project was to produce and physically characterize high oxidation state transition metal oxide phosphinate compounds with potential catalytic applications. The reaction of bis(benzyl)phosphinic acid with VO(acac)2 in the presence of water or pyridine leads to the synthesis of trimeric vanadium(IV) clusters (V3(µ3-O)O2)(µ2-O2P(CH2C6H5)2)6(H2O) and (V3(µ3-O)O2)(µ2-O2P(CH2C6H5)2)6(py). In contrast, when diphenylphosphinic acid or 2-hydroxyisophosphindoline-2-oxide were reacted with VO(acac)2, insoluble polymeric compounds were produced. The trimeric clusters were characterized using FTIR, elemental analysis, single crystal diffraction, room temperature magnetic susceptibility, thermogravimetric analysis and differential scanning calorimetry. The variable-temperature, solid-state magnetic susceptibility was measured on (V3(µ3-O)O2)(µ2-O2P(CH2C6H5)2)6(py). The polymeric compounds were characterized using FTIR, powder diffraction and elemental analysis. Two different cubane clusters made of tungsten(V) and vanadium(V) were stabilized using bis(benzyl)phosphinate. The oxidation of (V3(µ3-O)O2)(µ2-O2P(CH2C6H5)2)6(H2O) with tBuOOH led to the formation of V4(µ3-O)4(µ2-O2P(Bn)2)4(O4). W4(µ3-O)4(µ2-O2P(Bn)2)4(O4) was produced by heating W(CO)6 in a 1:1 mixture of EtOH/THF at 120 ˚C. Both compounds were characterized using single crystal diffraction, FTIR, 31P-NMR, 1H-NMR and elemental analysis. W4(µ3-O)4(µ2-O2P(Bn)2)4(O4) was also characterized using UV-vis. Cobalt(II) reacted with bis(benzyl)phosphinate to produce three different dinuclear complexes. [(py)3Co(µ2-O2P(Bn)2)3Co(py)][ClO4], (py)3Co(µ2-O2P(Bn)2)3Co(Cl) and (py)(µ2-NO3)Co(µ2-O2P(Bn)2)3Co(py) were all characterized using single crystal diffraction, elemental analysis and FTIR. Room temperature magnetic susceptibility measurements were performed on [(py)3Co(µ2-O2P(Bn)2)3Co(py)][ClO4] and (py)3Co(µ2-O2P(Bn)2)3Co(Cl). The variable-temperature, solid-state magnetic susceptibility was also measured on [(py)3Co(µ2-O2P(Bn)2)3Co(py)][ClO4].