Shang-Yu Gao

Short-term dynamics of wind erosion of three newly cultivated grassland soils in Northern China

This study examined the dynamic nature of short-term wind erosion processes of three grassland soils under simulated cultivation. In a laboratory wind tunnel, soil loss on a sandy loam, a loamy sand, and a sand soil was measured in six successive 10-, 3-, and 1-min exposures at the speeds of 10, 18, and 26 m s 1 , respectively. Erodible soil particle sizes of each interval were determined through direct dry sieving. It was observed that increasing blowing duration generally led to rapid decrease of soil loss, decrease of the erodible soil particle size from a definitely restricted area by any definite speed of wind, and the non-erodible particles remaining on the soil surface increased. From the first to the last blowing interval, soil loss decreased by 86.4–94.8% at 10 m s 1 in 60 min, 90.0–95.4% at 18 m s 1 in 18 min, and 71.5–97.8% at 26 m s 1 in 6 min. The results indicate that wind erosion on the newly cultivated soils is most intense during the initial blowing. The decrease of soil loss with time is presumed due to modification of soil surface by blowing wind, i.e. the concentration of non-erodible aggregates with the deflation of the erodible particles on the soil surfaces.

137Cs dating of lacustrine sediments and human impacts on Dalian Lake, Qinghai Province, China

Cs-137 and grain-size analyses indicate the total amounts of Cs-137 deposited by wind and water in the Dalian Lake of Gonghe Basin, Qinghai Province. The vertical profile of Cs-137 in the lacustrine sediments shows three Cs-137 activity peaks and one trough: the main peak corresponds to the global Cs-137 fallout in 1963: the two secondary peaks correspond to the leakage of the Chernobyl reactor in 1986 and complete desiccation of the lake in 1994. The trough corresponds to aeolian deposition caused by extensive reclamation of farmland in late 1980s and early 1990s. The Cs-137 dating was used to evaluate sedimentation rates in Dalian Lake since 1963. They are divided into three periods: two with slow deposition (1963-1986 and 1994-1998), and one with rapid deposition (19861994). Cs-137 seems to have the same potential for indicating environmental changes and human interference in the and and semiarid regions as in humid regions