Groundwater bacterioplankton, fluorescent organic matter and nutrient concentration of three major aquifers in England, September-October 2022 and January-February 2023

Groundwater bacterioplankton concentration distribution in drinking water sources are poorly characterised. Therefore we collected groundwater samples form drinking water pumping stations installed in Permo-Triassic sandstone aquifer of English Midlands and East Midlands, Cretaceous Chalk aquifer of South-East England and Jurassic Limestone aquifer of Cotswold, each with distinct aquifer properties. From the intergranular sandstone, dual porosity chalk, and karstic limestone aquifers 29 , 32 , and 8 sites respectively were sampled in the pre-recharge and 34, 33, and 8 sites respectively were sampled in the peak-recharge seasons.
The bacterioplankton total cell concentration (TCC), high nucleic acid cell percentage (%HNA) and intact bacterial cell percentage (%ICC) were measured used Attune Cytpix Flow Cytometer. The data was collected in triplicate, filtered noisy data by manual inspection, and the current data contains average values from the triplicate and standard deviations of the replicated. Fluorescence organic matter (fOM) loading and fluorescence indices were measured using an Aqualog® fluorimeter (Horiba Scientific, Japan). Raw data was processed and PARAFAC analysis was performed using R package staRdom to find the fOM loading values. Dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) concentrations were measured on filtered groundwater samples using an Elementar Vario Cube (Elementar Ananlysensysteme GmbH; Langenselbold, Germany). Borehole depth, perforation depth, were assessed using BGS borehole logs. Confinement and surface water vulnerability interpretations were provided by respective water companies.