Studying nitrogen surplus (1960-2010), transfer time and impact of the change in agricultural practices

Studying transfer time of nitrogen surplus from agro-systems to continental shores. The method we have in mind consists of a calculation of the amounts in nitrogen surplus in watersheds, coupled with a comparison between the logs on nitrogen pressure and the logs on nitrogen concentration in surface continental waters. The variation between both logs will enable us to provide an estimation of the transfer time for nitrogen from agricultural system to watershed.