Multivariate Analysis of Soil Salinity in a Semi-Humid Irrigated District of China: Concern about a Recent Water Project

The Chaobai River (CBR) basin in northern China is experiencing an unprecedented continuous inflow of external water via the South–North Water Diversion Project, which has channeled water from the southern part of the country to the north. Consequently, the steady rise of groundwater table in recent years is threatening soil salinity regulation. The purpose of this study was to describe the status of salinity of the surface soil in the CBR basin and to evaluate the impact of environmental factors including groundwater table on the spatial distribution of soil salinity using multivariate analysis (MVA) technique. In this study, 10 chemical variables of soil samples collected in 204 sites along CBR were analyzed, considering their interaction with three environmental factors: the density of irrigation canals, groundwater depth and topography. Statistical analysis mainly consisted of principal component analysis (PCA), redundancy analysis (RDA) and clustering analysis (CA). The results allow defining the surface soil in the CBR basin as a slightly saline and moderately alkaline media. The first two axes of multivariate model approximately explains 51% of the observed variability and allows distinguishing two main domains: the saline and the alkaline. The variability of the saline domain, defined by major cations and anions, is obviously controlled by macro environmental factors, of which the density of irrigation canals and groundwater depth contributes 71% and 28%, respectively, while that of the alkaline domain, related to pH and bicarbonate, mainly manifests as singular behaviors of soil groups like rice cultivation or sewage irrigation. The results suggests that more attention should be paid to the ongoing water table rise to help inform future land management decisions and to prevent a double threat of both groundwater and surface water on soil salinization. Meanwhile, this study shows the enormous potential of MVA technique, specifically the complementary duo of RDA and CA, for integrating both global and local information of soil salinity and environmental factors.

Theoretical and experimental investigation of the function of the wall flow deflecting ring. A mathematical model for the case of a large number of deflecting rings

Solution of the mathematical model has been developed of the distribution of liquid in a random packed bed in the presence of the wall flow deflecting rings. The solution was obtained in the form of a recurrent analytical formula. The formula permits, by repetitive calculation, profiles to be obtained of the densities of irrigation in a bed equipped with an arbitrary number of the wall flow deflecting rings. A comparison of experimental profiles of the density of irrigation with theoretical profiles showed considerable discrepancies between the two profiles. A new optimization of the parameters of the model, taking also the width of the wall flow deflecting ring as an adjustable parameter, showed a good agreement provided that the optimum width of the deflecting ring is about 1·5 times its real physical dimension. This finding can be explained by interaction of the function of the deflecting ring with the packing elements immediately adherring to the ring. This explanation may be partially supported by the visual observation showing the liquid to be deflected by the elements of the packing contacting the deflecting ring instead of the ring alone.

The gas side mass transfer coefficient in the turbulent flow in a packing with a significant dependence of the interfacial area on the density of irrigation

A theoretically derived relationship has been applied for the gas-side mass transfer coefficient to experimental values of kG. The experimental data have been obtained under the two-phase flow of gas and liquid in a plane vertical packing manufactured of the expanded metal sheet. This packing exhibits a significant dependence of the extent of interfacial area, and hence the geometry of the channel available for gas flow, on the density of irrigation.

Measurement of interfacial area and intensity of mass transfer in the gas phase in a packing with significant dependence of the interfacial area on the density of irrigation

The dependence has been measured of the interfacial area and the number of transfer units for gas side resistance controlled absorption on the flow rate of gas and liquid at counter- and cocurrent flow arrangement. The measurements have been carried out for a vertical expanded metal sheet packing exhibiting a strong dependence of the interfacial area on the density of irrigation. The interfacial area has been measured by absorption of carbon dioxide into a solution of sodium hydroxide under the conditions of the pseudo first order reaction. The number of transfer units has been measured by absorption of sulphur dioxide also into a solution of sodium hydroxide. In addition, the pressure drop has been correlated against the flow rate of gas and liquid.