Geochemical signature of urbanisation in Blue Mountains Upland Swamps

Urbanisation leaves a geochemical signature on the environment, as weathering of urban materials such as concrete contributes to elevated levels of major ions including calcium, bicarbonate and potassium. However, there is limited research that addresses the ecological consequences of this signature on the biotic community. Blue Mountains Upland Swamps (BMUS), an endangered ecological community with high conservation values, are vulnerable to urban degradation. Chemical properties of water, sediment and foliage from native and exotic species were assessed within two urbanised and two naturally vegetated swamp catchments. Water in urban swamps exhibited elevated pH and electrical conductivity. Non-urban swamps were sodium and chloride dominated, with higher calcium and bicarbonate in urban swamps. Water from urban swamps also exhibited 32 times higher levels of strontium. Calcium concentrations were elevated by 14 times in urban swamp sediment. Foliage from urban catchments exhibited six times greater potassium, and three times higher calcium and bicarbonate compared to foliage in non-urban catchments. Calcium, bicarbonate, potassium and strontium were key parameters that were enriched in the urbanised swamps. However, the ecological implications of these findings for urban wetland communities, including BMUS, remain unclear. Interestingly, the chemical signature of water did not fully represent the signatures of sediment and foliage, highlighting the need to further explore sources and forms of major ions within these ecosystems, particularly in sediment. In an increasingly urban world, enhancing knowledge of drivers of change in endangered ecosystems such as BMUS is crucial to promote conservation and guide the development of sustainable management practices.