The effect of waste disposal on soils in and around historic small towns

Abstract

Soils in the urban environment are distinctive in that they are modified through waste amendments. Consideration has been given to how urban soil properties reflect current human influence; however, recent studies highlight their potential as historical archives. The impact of waste disposal on the nature, properties and formation of urban soils is significant, especially in historic small towns where the extent and complexity of refuse management practices is only just emerging. This study uses a multi-method approach to characterise and understand modes of urban anthrosol formation in three Scottish burghs; Lauder, Pittenweem and Wigtown. The objectives of this study are threefold; to establish the nature and diversity of urban anthrosols in and near to historic small towns, to characterise and account for the multiplicity of urban anthrosols in and near to historic small towns, and to elucidate the processes associated with waste management and disposal in historic small towns.

Physical, chemical and micromorphological analysis of topsoil deposits indicate sustained addition of past waste materials to soils within and near to historic small towns. Soil characteristics were heterogeneous across burghs; however, distinct patterns according to past functional zones were identified. The burgh core and burgh acres are important areas of interest at all three burghs. Soil modification was most pronounced within burgh cores resulting in the formation of hortic horizons. Soils within burgh cores are characterised by neutral pH, increased organic matter content, enhanced magnetic susceptibility and elevated elemental concentrations such as calcium, phosphorus and potassium. In comparison the nature and extent of soil modification within burgh acres is more varied. At Lauder hortic soils were identified in the burgh acres suggesting pronounced soil modification through cultivation. Deepened topsoil in the burgh acres at Pittenweem provided evidence for application of mineral rich waste materials in the past. Moreover, magnetic and elemental enhancement (barium, phosphorus, lead, zinc) within the burgh acres south of Wigtown revealed historic soils based anthropogenic signal.

It is argued that changes in soil characteristics at Lauder, Pittenweem and Wigtown can be explained through processes of waste management and disposal in the past. Evidence from micromorphological analyses suggests that waste in burgh cores typically comprised domestic waste, animal waste, building materials and fuel residues. These materials were also identified within burgh acres, although it is noted that their abundances were significantly lower. Variation in urban anthrosol characteristics between burghs is attributed to differing industries and patterns of resource exploitation, for example marine waste associated with fishing was only identified in coastal burghs.

The sustained addition of waste materials to soils within and near to historic small towns was an effective waste management strategy. Waste disposal in burgh cores was likely to be a combination of direct application and midden spreading in back gardens. This led to enhanced soil fertility which was important in the development of urban horticulture; particularly for poorer inhabitants who did not have access to arable farm land adjacent to the burgh. Dunghills acted as temporary stores of waste in the main thoroughfares of Lauder, Pittenweem and Wigtown. These dunghills were systematically transported to the burgh acres for further use as a fertiliser; hence, an early form of urban composting. Processes of waste disposal could not be deduced from soil characteristics alone; however, likely methods include direct waste deposition, storage and redistribution of midden waste, and storage and redistribution of dunghills.

The limitations of soil classification systems and mapping are highlighted, for example urban soils are either omitted from soil maps or are misclassified. It is recommended that urban soils in historic towns should be incorporated into future regional soil maps. Urban soils represent a complex archive of past human behaviour not necessarily reflected in archaeological excavation or documentary analysis. It is argued that soil and artefacts are equally important, hence soil should be a consideration in urban heritage and conservation strategies.