Samantha R. Cook

Mineralised organic remains from cesspits at the Roman town of Silchester: processes and preservation.

Mineralised organic remains (including apple pips and cereal grains) collected during the ongoing excavations of Insula IX at the Roman town of Silchester, Hampshire have been analysed by a combination of SEM-EDX, powder XRD and IR spectroscopy. The experiments included mapping experiments using spatially resolved versions of each technique. IR and powder XRD mapping have been carried out utilising the synchrotron source at The Daresbury Laboratory on stations 11.1 and 9.6. It is concluded that these samples are preserved by rapid mineralisation in the carbonate-substituted calcium phosphate mineral, dahllite. The rapid mineralisation leads to excellent preservation of the samples and a small crystal size. The value of IR spectroscopy in studying materials like this where the crystal size is small is demonstrated. A comparison is made between the excellent preservation seen in this context and the much poorer preservation of mineralised remains seen in Context 5276 or Cesspit 5251. Comments on the possible mechanism of mineralisation of these samples are made.

Roman Diet and Trade: Evidence from Organic Residues on Pottery Sherds Recovered at the Roman Town of Calleva Atrebatum (Silchester, Hants.)

The analysis of organic residues from pottery sherds using Gas-Chromatography with mass-spectroscopy (GC-MS) has revealed information about the variety of foods eaten and domestic routine at Silchester between the second and fourth–sixth centuries A.D. Two results are discussed in detail: those of a second-century Gauloise-type amphora and a fourth-century SE Dorset black-burnished ware (BB1) cooking pot, which reveal the use of pine pitch on the inner surface of the amphora and the use of animal fats (ruminant adipose fats) and leafy vegetables in cooking at the Roman town of Silchester, Hants.

MMI partial extraction geochemistry for the resolution of anthropogenic activities across the archaeological Roman town of Calleva Atrebatum

Sixty three soils samples, fourteen samples of previously excavated archaeological material, and five background soil samples taken at the Silchester Roman Town of Calleva Atrebatum in the County of Hampshire, United Kingdom were analysed by the Mobile Metal Ion (MMI) method for a total of fifty three elements. Samples from within the town walls showed considerably higher concentrations than samples outside for many elements; Au, Ag, Cu and Sn were in extremely anomalous concentrations, Bi, Cd, Hg, Mo, P and Pb were anomalous and Sb and Zn in elevated concentrations. The overall pattern of element distribution is one of an annulus of higher elemental concentrations surrounding a centre of generally lower values centred on the previously excavated Forum basilica. The elements Zr, Ti, Th, Ti, Tl, Nb, Sn, Sc, Cr, Co, Sb, Bi, Ce, Nd (and all other REEs), show similar distributions to one another, and their distribution and that of the noble and base metals, as highlighted by various additive indices, is considered to be the result of metallurgical processing on site. The low values for most elements around the Forum basilica are the result of disturbance of the soil geochemical profile in this area by previous archaeological excavation.

Changes to cadmium associations in canal sediments on drying and oxidation

Polycyclic aromatic hydrocarbons (PAHs) are widely distributed in the marine environment. Many PAHs are known to be mutagenic and carcinogenic, so their presence in the environment may constitute a serious threat to the health of humans and ecosystems. Bioremediation has shown promise as a potentially effective and low-cost treatment to eliminate organic pollutants in the environment. However, biodegradation of PAHs in soil or sediment is usually very slow because the bioavailability is limited by a poor mass transfer, since PAHs generally are well known for their low aqueous solubility, high hydrophobicity and tendency to sorb tightly to soil or sediment constituents. Applying surfactants at contaminated site might be one way to facilitate the release of sorbed PAHs from solid matrices and increase the aqueous concentrations of hydrophobic compounds resulting in higher mass transfer rate. Though using chemically produced surfactants has shown promise for significantly reducing time and cost of remediation, the use of these surfactants in environmental treatment processes has been rather limited due to the concerns regarding their toxicity and biodegradation fact. Being biologically synthesized surface-active agents, biosurfactants have the advantages of being readily biodegradable and non-toxic comparable to chemically produced surfactants. This distinct perspective makes them valuable in PAHs bioremediation. In this paper, the effectiveness of anionic rhamnolipid biosurfactant on the desorption and biodegradation of PAHs in sediment slurry was compared with that of synthesized surfactant sodium dodecyl sulfonate (SDS). The artificially fresh-contaminated sediment and aged-contaminated one were used in experiments to determine the effect of aging process on bioremediation. Both biological and chemically synthetic surfactants at high dosages (above effective critical micelle concentration) greatly enhanced desorption of sediment-sorbed phenanthrene, whereas rhamnolipid mixture (Rh-mix) was more efficient than SDS in desorption enhancement. Moreover, Rha-mix showed lower toxicity to the PAH-degrading bacteria. The results of biodegradation experiments showed that the extents of phenanthrene biodegradation were significantly enhanced by both Rha-mix and SDS at the optimal concentrations. When the biodegradation systems amended with rhanmolipid dosages above 400 mg/L and SDS dosages above 5000 mg/L, phenanthrene biodegradation was inhibited because of the mass transfer of phenanthrene from micelle into water. However, Rh-mix at the high concentrations showed lower inhibitory effect on phenanthrene biodegradation than SDS. On the other hand, the lower desorption and biodegradation extent of aged phenanthrene indicated that the aging process could significantly decrease bioavailability of phenanthrene. These results suggested that rhamnolipid may be more effective than SDS in PAH-contaminated sediment remediation processes.