Changes in soil aeration and soil respiration of simulated grave soils after quicklime application

Abstract

The decomposition of buried human remains on cemeteries can be delayed in poorly aerated graves due to high water levels and a low permeable pore system for oxygen and water transport. With aim to improve the soil aeration properties in the burial environment, the addition of quicklime (CaO) to the grave backfill was tested. Quicklime is expected to promote a stronger aggregation and stabilization of the backfilled soil mainly by forcing an immediate dehydration and particle cementation processes. Two different grave simulations (without buried corpses) were prepared: (1) mixing the grave backfill with 20 kg m−3 quicklime (“CaO”) and (2) backfill without CaO (“NIL”) on a cemetery in Northern Germany. The soil type was a Terric Anthrosol (Stagnic) with a loamy sand texture. Undisturbed soil cores were taken from two depths before and after excavation and backfill at regular intervals of 3 months in order to analyze changes in (1) gaseous transport functions expressed by air‐filled porosity, air permeability (air permeameter), gas diffusivity (double chamber method) and related pore continuity indices as well as in (2) soil respiration (alkali trap method) representing microbial activity. Results clearly demonstrated a more conductive pore system in the CaO variant reflected by higher gas diffusivity and air permeability over 1 year compared to the NIL variant. Pore continuity indices also indicated a more connective pore system for the CaO variant. Effects of CaO application on soil respiration rate differed between the quarterly sampling times. Results indicated that microorganism were still active under alkaline soil conditions induced by CaO application, but the quantitative determination of biologically produced CO2 is influenced by chemical reactions when hydrated quicklime [Ca(OH)2] was reformed to limestone under consumption of CO2. The experiments indicate that the application of quicklime is a promising approach to improve aeration properties of grave soils and is therefore proposed as an adequate method to improve the aeration of burials on cemeteries.

Structural stabilization of soil backfill with quicklime

“…Although convective gas fluxes are generally limited to the soil layers close to the surface and gas transport processes in the subsoil are dominated by diffusion, the presence of a well‐connected and rapidly drained pore system in the subsoil is expedient, as gas diffusion is severely limited by water blocked pores ( Hu et al, ). The increase in gas diffusivity in the qlm treatment has already been documented by Mordhorst et al () for the surveyed site.…”

“…Air permeability (k a in µm 2 ) was calculated from k l by factoring air viscosity (η a in Pa s), air density (ρ a in kg m −3 ), and gravitational acceleration (g in m s −2 ), as it is shown in Eq. ( Uteau et al, ; Mordhorst et al, ): …”

“…The application of quicklime as an ameliorative tool for soil structural improvement in earthen graves has already been successfully tested for glacial loam in a Stagnic Luvisol ( Zimmermann et al, ). Furthermore, Mordhorst et al () proved that soil respiration (as a measure for microbial activity) was not hampered by the alkaline soil conditions induced by the quicklime application, which is an important result in the context of the use in earthen graves. In the present study we tested the applicability of the method in a lighter textured cemetery soil and, additionally, monitored subsoil O 2 content directly in the field.…”

Impact of Small-Scaled Differences in Micro-Aggregation on Physico-Chemical Parameters of Macroscopic Biopore Walls

“…This earthworm burrow showed deviations up to several orders of magnitude for the replicates of D s /D O . The minimum value of 6 × 10 −6 indicates a water-filled (Glinski and Stepniewski, 1985) and/or a tortuous or not well-connected pore system while the maximum value of 0.14 is higher than those measured on soil cores by Mordhorst et al (2017).…”

“…This increased PR is possibly caused by calcite, released from specialized esophageal glands of L. terrestris (Lankester, 1865). Calcite can influence PR not only by enhancing the soil development by altering the biological activity in soils (Mordhorst et al, 2017) but also by forming crusts on the aggregate surface and by coagulating primary particles. Biological crusts also may have caused these altered PR (Chamizo et al, 2015).…”