Volume 19 - 2017

Abundance and availability of unconventional petroleum has led to intensified exploitation and exploration of the bitumen reserves. This has however led to environmental pollution. This study investigated the ability of Providencia stuartii isolated from heavy oil polluted soil to degrade natural bitumen. Temperature, pH and incubation period were independent variables used for optimization of degradation while optical density was used as dependent variable. Optical density was measured using a UV-Vis spectrophotometer. Residual bitumen/degradation products were analyzed using gas chromatography- mass spectrometry (GC-MS). Optical densities obtained ranged from 0.002 to 0.408. Optimum optical density of 0.408 was obtained at 40 oC and pH 7 after 13 days of incubation. There were significant changes in the composition of bitumen after analysis with GC-MS with detection of new compounds due to degradation. The GC-MS results showed the presence of some degradation products such as benzene (1-butylhexyl), benzene (1-propylheptyl) and 23, 28-bisnor-17.β.(h)-hopane. This study revealed the excellent ability of P. stuartii in degrading bitumen contaminated environment.

This study investigates the adsorption kinetics and removal conditions of copper by walnut tree sawdust from synthetic solutions in the batch and fixed bed reactors. The selected experimental parameters for the batch reactor were concentration, solution pH, adsorbent amount and temperature. The optimum batch reactor conditions were applied to the fixed bed reactor. The experimental parameters of the fixed bed reactor were flow rate, bed height, and concentration. The optimum removal conditions for copper removal in the batch reactor were determined as pH (5), temperature (25oC), concentration (25 mg/L), and adsorbent dosage (10 g/L). The kinetic data obtained from the batch reactor were analyzed by the pseudo-first-order and the pseudo-second-order kinetic models and the kinetic data were successfully correlated with the pseudo-second-order model. Activation energy of the process was calculated to be 15.79 kJ/mol. The optimum parameters for the fixed bed reactor were designated as 0.5 mL/min flow rate, 100 mg/L concentration and 15 cm bed height. The kinetic data obtained from the fixed bed reactor were analyzed with the Yoon-Nelson and Thomas kinetic models. The fixed bed kinetics could be described with the Thomas model. Maximum adsorption capacity was calculated as 6.24 mg/g in the fixed bed reactor.

Window length is a very critical tuning parameter in Singular Spectrum Analysis (SSA) technique. For finding the optimal value of window length in SSA application, Periodogram analysis method with SSA for referencing on the selection of window length and confirm that the periodogram analysis can provide a good option for window length selection in the application of SSA. Several potential periods of Florida precipitation data are firstly obtained using periodogram analysis method. The SSA technique is applied to precipitation data with different window length as the period and experiential recommendation to extract the precipitation time series, which determines the leading components for reconstructing the precipitation and forecast respectively. A regressive model linear recurrent formula (LRF) model is used to discover physically evolution with the SSA modes of precipitation variability. Precipitation forecasts are deduced from SSA patterns and compared with observed precipitation. Comparison of forecasting results with observed precipitation indicates that the forecasts with window length of L=60 have the better performance among all. Our findings successfully confirm that the periodogram analysis can provide a good option for window length selection in the application of SSA and presents a detailed physical explanation on the varying conditions of precipitation variables.

Effective eco-environment rehabilitation is an essential policy issue in arid oasis ecosystem. Since 2007, a policy which focuses on environment restoration and protection was implemented in the Shiyang River Basin of Gansu Province, China. Using Minqin oasis as a case, the effectiveness of policy impacts based on farmers’ perception was evaluated. In addition, an ordinal logistic regression model was used to explore the potential factors affecting farmers’ perception of policy effectiveness. Data were collected from household heads or spouses and other adults (age>18) separately in a random sample of 425 households. The results showed that positive outcomes were achieved, however, two policy measures—the water restrictions and the ecological migration project—were rated at a low level of satisfaction by the farmers. Moreover, 11 determinants were extracted by the logistic regression method, and indicating that economic factors including the ownership of the arable land and the availability of household income turned out to be the most significant. The results can help to establish eco-environmental restoration targets, encourage investments, and lead to the development of more applicable methods for assessing policy effects from the perspective of smallholders in ecologically fragile areas all over the world.
Keywords: Environmental policy evaluation; Farmers’ perception; Ordinal logistic regression; Minqin oasis; Northwest China