Effect of Land Cultivation on Soil Nutrient Sedimentation in Water at Southern China

Soil erosion associated with land cultivation exerts a great impact on ecological environment.Such an impact is specific of land,crop,tillage,management and so on.This study aimed to investigate the effects of crop cultivation on water quality by comparing nutrient distribution in the sediment at Southern China.Two sedimentation sites adjacent to the uncultivated(S1)and cultivated upland(S2)were selected and samples were analyzed.Results showed that soil pH decreased with the increasing depth above 20 cm and then kept relatively stable of the both sediments.Soil organic matter,nitrogen and phosphorus contents decreased with the increasing depth.There was no significant difference between two sediments in organic matter and nitrogen contents,but the total phosphorus and extractable phosphorus contents in S2 were much higher than that in S1.The data indicated that soil eroded from S2 could possess much high potential to deteriorate water quality.Nutrient sedimentation can reflect the history of soil erosion and provide useful information for sustainable soil management and water conservation through improving cultivation and tillage measures.

Saturated absorption spectroscopy of buffergas-cooled Barium monofluoride molecules

We report an experimental investigation on the Doppler-free saturated absorption spectroscopy of buffer-gas-cooled Barium monofluoride(BaF)molecules in a 4 K cryogenic cell.The obtained spectra with a resolution of 19 MHz,much smaller than previously observed in absorption spectroscopy,clearly resolve the hyperfine transitions.Moreover,we use these high-resolution spectra to fit the hyperfine splittings of excited A(v=0)state and find the hyperfine splitting of the laser-cooling-relevant A^(2)Π_(1/2)(v=0,J=1/2,+)state is about 18 MHz,much higher than the previous theoretically predicted value.This provides important missing information for laser cooling of BaF molecules.