Zhang Guang-xin

Sustainable agriculture development in saline-alkali soil area of Songnen Plain, Northeast China

There is great potential for agriculture in saline-alkali soil area in Songnen Plain, Northeast China. But the sustainable crop production in this area has been restricted by a few of main factors, such as less precipitation, higher evaporation and frequent drought, high salinity and alkalinity, high exchangeable sodium content and poor infiltration of the soil, and insufficiency and low availability in nutrition. It is also considered that there are a few of favorable conditions for agricultural development in this region, such as sufficient light and heat resources, rich ground water resources, plenty of manure produced by livestock, and so on. At the same time, scientific management and measurements have been employed; rational irrigation and drainage system has been established; reclamation, amendment and fertilization of soil, and suitable strategies of cropping practices have been made for the sustainable development of agriculture. Great progress has been made during 1996 – 2000.

Simulation and evaluation of the water purification function of Zhalong Wetland based on a combined water quantity-quality model

The water purification function of natural wetland systems is widely recognized, but rarely studied or scientifically evaluated. Extensive studies have been carried out by various international wetland research communities to quantify the water quality improvement ability of the natural wetlands, in order to maintain such ability and wetland ecological health. This study aims to evaluate the purification function of Zhalong Wetland in China for removing total nitrogen (TN) and phosphorus (TP), based on ex-situ experiments and the development of a combined water quantity-quality model. Experiments and model predictions were carried out with different input TP and TN concentrations. Statistical analyses demonstrated that the relative errors between model simulations and experimental observations for TN and TP were 8.6% and 12.4%, respectively. With water retention time being maintained at 90 d, the removal rate of these pollutants could not reach the required Grade V standards, if the inflow TN concentration was over 42 mg L−1, or the input TP concentration was over 14 mg L−1. The simulation results also demonstrated that, even with Grade V quality standard compliance, when the water inflow from surrounding industries and agriculture lands into Zhalong Wetland reaches 0.3×108 m3 a−1, the maximum TN and TP loads that the reserve can cope with are 1.26×103 t a−1 and 0.42×103 t a−1, respectively. Overall, this study has produced a significant amount of information that can be used for the protection of water quality and ecological health of Zhalong Wetland.

The Chemical Kinetics in Migration of Organophosphorus in Clay with Different pH

: In order to study the characters of chemical kinetics for organophosphorus migration in clay with different pH, waste of organophosphorus was put under pressure to leakage permeating the cohesive soil, and simulate the process of organophosphorus leakage permeating the Aquitard, searching the characters of chemical kinetics for organophosphorus migration in clay with different pH. It is shown that the ability of migration of organophosphorus leakage permeating the cohesive soil fall with increase of pH; the penetration rate of organophosphorus is about 1.25% when pH is 7.5, organophosphorus has not penetrated the cohesive soil when pH is equal or greater than 8.5. The effect of retardarce is obvious. Concentration of PO43− that comes from the mineralization of organophosphorus is lowered slightly with increases of pH of clay, and rise with extension of time. The Chemical Kinetics equation is log c=−0.1pH+0.2172k1t+S.