A note on in situ estimates of sorption using push-pull tests

A sensitivity analysis reveals that large uncertainty exists in estimates of solute retardation factor R made from sorption push-pull tests. A simplified push-pull data interpretation method for estimating instantaneous linear sorption in confined aquifers is developed. The new method is less restrictive in its application than the conventional method that uses an approximate analytical solution to the push-pull test problem

Capacity for bioreactors and riparian rehabilitation to enhance nitrate attenuation in agricultural streams

© 2019 Elsevier B.V. Globally, small agricultural waterways fed by springs, tile drains, and seeps can disproportionately contribute to downstream nutrient loading, which is associated with declines in water quality and ecosystem functions. Treating nitrate using a multiple tool, multiple-scale approach in small waterways could offer improved management of these sources. We used a before-after-control-impact design to test the suitability of three small (99%, with performance variations due to short residence times and fluctuations in source water chemistry. A single tile drain bioreactor removed 0.41 kg NO 3 -N d −1 , equivalent to ∼10% of the mean daily tile drain nitrate load. Greenhouse gas fluxes from the tile drain bioreactor were similar to the surrounding pasture (CO 2 -C mean: 185–286 mg C m 2 h −1 ; N 2 O-N mean: 49–90 μg N m 2 h −1 ), suggesting no negative impacts from the bioreactor. Overall, our results suggest a multiple-tool, multiple-scale application of rehabilitation tools can reduce downstream N fluxes, but only under certain flow conditions. Thus, local rehabilitation tools, like those trialed here, will need to be scaled appropriately if they are to significantly attenuate nutrient losses from small agricultural waterways. Moreover, these will not replace catchment-scale nutrient plans to address losses from land and legacy groundwater N pollution