ALBERT

Description: In arid and semi-arid regions there is usually a shortage of irrigation water; thus, wastewater water, as well as other low-quality water resources, may become an important source of water and nutrients. However, (pre)treated wastewater may contain elements and compounds that can damage the environment. It also has the potential to affect water quality adversely in an aquifer that may be the source of drinking water in the area. In order to assess the impacts of wastewater on the enviromnent, groundwater samples were taken and analysed in typical croplands in the North China Plain, where urban wastewater or groundwater have been used for irrigation for several decades. Concentrations of nitrate (NO3-) in groundwater in the study area varied from 50 to 130 mg 1-1 in the croplands irrigated by wastewater, but in the croplands irrigated by pumping wells, away from the Dongming Canal, NO3- concentrations are less than 35 mg 1-1. It was found that values of δ15N ranged from +5 to +13‰, and dominantly from +7 to +11‰, and the NO3- concentration in most wells with depths of less than 40 m was higher than the drinking water standard set by the WHO. Cluster analysis was used to classify the spatial distribution of nitrates resulting from the wastewater. Identification of chemical patterns is found to be effective for the comprehensive assessment of the spatial distribution of groundwater quality. It is also emphasized that the wastewater in this area controls the NO3- distribution in the groundwater, and should be used carefully to protect both soil and groundwater from NO3- pollution. © 2004 John Wiley and Sons, Ltd.

Description: The lower reaches of the Yellow River are basically a discharge zone with a high salt content, and the study area of Yucheng in Shandong Province became arable only after the water diversion project from the Yellow River was implemented in 1972. The sustainability of agriculture in this area is examined through the redistribution of soil moisture and solutes in the vertical profile based on the measurement of soil moisture, potential and solute content in a maize field at the Yucheng Experimental Station. Diurnal moisture fluctuations appear in the surface layers at 30 and 50 cm depths, and the daily water content at 90 cm depth decreases about a month after planting, due mainly to the effect of root water extraction, even reaching a level lower than that at 70 cm depth. Soil moisture obviously increases for the three layers at 30, 50, 90 cm depth, and the relevant peak-time shifts from the surface 30 cm depth to the deep layer at 120 cm depth with a varied time lag in response to rainfall events, but there is little or no signal for the other layers due to the effects of soil properties, roots, and soil storage. The existence of a convergent zero flux plane may explain to some extent the accumulation of moisture and solutes in the layer at 120 cm. depth. Though the chemical facies along the profile from the unsaturated surface to the deep saturated zone generally evolves in a direction of decreasing SO42- and Cl-, a strong driving force upward and the accumulation of solute at 120 cm may change the redistribution pattern and three groups of this pattern were classified according to the evolution and concentration distribution profiles. The main factors affecting the moisture, solute and their distributions for the three groups are varied: rainfall, irrigation and evapotranspiration for the surface layer till 70 cm depth, root extraction for the accumulation layer of 70-120 cm depth, and the fluctuation of the groundwater table for the deep layer at 120-200 cm depth. The agriculture appears sustainable as long as diverted water from the Yellow River is available, but the high content of solute accumulation in the layer at about 120 cm depth is a potential risk. Copyright 2004 John Wiley and Sons, Ltd.