Pollution potential of cemeteries : impact of the 19th century Carter Gate Cemetery, Nottingham

The impact of a 19th century cemetery called "Carter Gate" on groundwater in the underlying Triassic Sandstones aquifer has been determined directly by drilling three boreholes after exhumation of the graves. Pore-water in the unsaturated zone beneath the graves contains high concentrations of Calcium (Ca), Sodium (Na), Magnesium (Mg) and Potassium (K) with Sulphate (SO4) and Chloride (Cl), in ratios which are inconsistent with the known composition of a human body and solutes released from graves. The inorganic solutes are probably derived from contaminated material deposited, or effluents discharged, above the graves. Despite this extraneous contamination, the pore-water profiles are thought to provide evidence of migration of grave derived material. Immediately below the graves a darkcoloured zone (called the “grave cut”) occurs containing elevated concentrations of phosphorous, calcium, copper and zinc. The unsaturated pore-water profiles in one borehole contains peaks of Total Organic Carbon (TOC), Manganese (Mn) and Ammonium (NH4) up to 2–3 m below the grave level. The Mn is thought to result from reductive dissolution of the Triassic Sandstones due to biodegradation of organic material leached from the graves, and is coincident with the TOC peak. The NH4 is reported to be a major solute from graves and is thought to be retarded in its migration relative to conservative species such Na, Cl, SO4. These are also likely to have been released from the graves but probably migrated through the unsaturated zone within a period of 20 years. Anthropogenic organic compounds which were not available industrially when the cemetery was in use, are found in the unsaturated and saturated zones. Coliform bacteria were found at the water table but the associated concentrations of Boron (B) and Phosphorous (P) suggests that they could be from a leaking sewer. Because of time constraints, it was not possible to carry out a detailed microbiological study, but all boreholes contained microbial numbers similar to those in uncontaminated groundwater. The study confirms that this cemetery no longer presents a source of contamination, but suggests that, by comparison with the ammonium peak, the maximum impact of inorganic solutes and volatile fatty acids on groundwater was probably minimal.