Pertti Vakkilainen

China's 8 challenges to water resources management in the first quarter of the 21st Century

Abstract Northern China has less than half the water per person than the absolutely water-scarce Egypt. This simple comparison helps us to understand that China will face great water-related challenges in the coming decades. Its rapid urbanization, industrialization, growing agricultural demand, environmental degradation, and potential climate-related threats will be the major driving forces that challenge the management and utilization of Chinas water resources over the decades to come. Chinas environmental pressures already exceed the carrying capacity of this densely populated land. This paper surveys Chinas water resource management situation and its challenges for the decades ahead. The Yangtze River basin is a special focus. The waters and hydropower of this vast basin are increasingly being exploited—besides the 400 million people who live in the basin—also those other nearby parts of China. Particularly important is the thirst of the North China Plain—with another 400 million people—seeking the Yangtzes water and power.

Sorption of selenate by Finnish agricultural soils

Abstract The selenium content of Finnish bedrock is low, and the availability of selenium to plants is poor for climatological and geochemical reasons. Therefore all multinutrient fertilizers sold in Finland have been enriched with selenium (selenate) since 1984. Selenate is known to be soluble for at least 3 months after this addition. Soluble selenium can leach into surface and ground waters. The sorption of added selenate in 18 different types of cultivated Finnish soils was studied. In a 7-day incubation trial the sorbed fraction varied from 3.6 to 24.6% from the added amount of 5000 μg Se kg −1 soil. Sorption correlated positively with the clay content, iron content and surface area of the soils and negatively with sulphuric acid-extractable phosphorus. By stepwise multiple linear correlation analysis a model revealed that sulphuric acid-extractable phosphorus explained 63.7% of the variation in sorption, iron content increased the explanation rate to 74.7% and the clay content to 81.5%. The results suggest that in Finnish soils the sorption tendency is higher in fine textured soils and increases with weathering.

Nutrient Load from Two Drainage Systems on Clay Soil

In the southern and the south-western parts of Finland 75% of the arable land has subsurface drainage. The Finnish state subsidizes subsurface drainage on certain conditions including for example different envelope materials, drain depth and total drain length per hectare. The typical drain depth is 1.0-1.2 m and the drain spacing varies mostly between 12 and 26 meters depending on the soil type. Gravel is the most common envelope, but also synthetic and semisynthetic textile, cocos fibre and wood chips are used. The aim of this study is to find out how two different kind of drainage methods affect crop production and nutrient load in both drainage waters and surface runoff. In the method I gravel is used as an envelope and the drain spacing is 8 m. In the method II very thin textile (<1 mm) is used as an envelope and drain spacing is 6 m. The research is carried out on a field at Jokioinen in south-western Finland. The soil is heavy clay and the mean slope is 1%. The existing tile drainage pipes were laid in 1954 using 16 m spacing and an average depth of 1 m. The size of the field is 6 ha and it consists of 3 field sections each with a separate drainage system. In the summer of 2008, the additional drainage systems were built into two of the field sections using the methods I and II . The third one was left as a control plot. Runoff volume and water quality of subsurface and surface waters and crop yield from each field section have been measured. Concentrations of total phosphorus, dissolved orthophosphate, total nitrogen, ammonium nitrate, nitrate nitrogen and solid substances have been determined from the samples. In the paper runoff, nutrient load and crop yield from the calibration and testing periods are presented. The feasibility of the two drainage methods is evaluated from the point of view of crop production and nutrient loading to surface waters.