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12/24/2015 by mdc
Graham, Baker and Andersen report that the concentration and flux of organic carbon in aquifers is influenced by recharge and abstraction, and surface and subsurface processing. In this study, groundwater was pumped from a shallow fractured rock aquifer and dissolved organic carbon (DOC) was measured in observation bores at different distances from the pumped bore.

Groundwater production at rates exceeding the aquifers yield resulted in increased DOC concentration up to 3,500% of initial concentrations. Potential sources of this increased DOC were determined using optical fluorescence and absorbance analysis. Groundwater fluorescent dissolved organic material (FDOM) were found to be a combination of terrestrial-derived humic material and microbial or protein sourced material. Relative molecular weight of FDOM within four meters of the produced well increased during the experiment, while the relative molecular weight of FDOM between four and ten meters from the pumped well decreased. When the aquifer is not being pumped, DOC mobilization in the aquifer is low.

We hypothesize that the physical shear stress on aquifer materials caused by intense production significantly increases the temporary release of DOC from sloughing of biofilms and release of otherwise bound colloidal and sedimentary organic carbon (SOC).

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