Impact of concrete and PVC pipes on urban water chemistry

Abstract

Waterways contain a chemical signature of catchment land use, climate and geology. This is increasingly being influenced by the urban landscape and particularly the composition of materials and activities that occur on impervious surfaces. This paper examines the degree and extent of two types of drainage materials, concrete and PVC, on urban water chemistry. This study found that water collected from a zinc and slate/tile roof and stored in a plastic rain tank (roof water) was acidic (pH 4.79) and had low bicarbonate concentrations (0.5 mg/l), water from an undeveloped catchment (reference creek) was mildly acidic (pH 5.5) with bicarbonate concentrations of 1.7 mg/l while water from a stream draining a residential catchment (urban creek) was mildly alkaline (pH 7.35) with bicarbonate concentrations of 36.3mg/l. The three types of water were then circulated through a concrete pipe or PVC pipe for 100 min and measured for a range of water chemical attributes. Roof water and water from the reference creek reported a significant increase across a range of analytes, most notably bicarbonate and calcium levels when passed through the concrete pipe, while water from the urban creek changed a lesser amount. When passed through the PVC pipe the changes in water chemistry were significantly less for roof water and urban creek water. The data suggests that in-transport processes from concrete drainage systems are having a significant influence on water chemistry, particularly where inflow is acidic. The major factor identified in this study could be attributed to the dissolution of calcium, bicarbonate and potassium ions from the concrete pipe. This could impact on receiving environments that are naturally acidic and low in bicarbonate, such as those in northern Sydney. The implications of this study point towards a need to consider the type of materials used in urban drainage networks if water chemistry and stream ecosystem health is to be protected.

Environmental and landscape factors influencing ant and plant diversity in suburban riparian corridors

“…Urbanisation has been associated with increased alkalinity of riparian soils (Moffatt et al, 2004), thus soil pH may be a proxy for urban development intensity. One potential reason for this is the dissolution of cement products into stormwater conveyed by concrete gutters and pipes (Davies, Wright, Jonasson, & Findlay, 2010). In addition, soil pH is associated intrinsically with the underlying geology.…”

Urban Evolution: The Role of Water

“…Dissolution and degradation of concrete also increases when it is subjected to frequent exposure to road salt [122]. As urban karst weathers and dissolves [10,43], calcium and carbonate are released into urban waters influencing alkalinity, water hardness, and pH [118][119][120]123] (Figure 3). Additionally, decomposition of labile organic matter (e.g., sewage) in urban watersheds can also increase inorganic carbon concentrations and bicarbonate alkalinity in urban watersheds [124].…”

“…The chemistry of streams and rivers draining urban areas can be influenced by the dissolution of concrete and other building materials [116,118,119] (Figure 3). For example, cement can contain limestone, gypsum, and other constituents that weather quickly when exposed to acidic water [120]. Rain water is naturally slightly acidic due to the formation of carbonic acid from atmospheric CO2.…”

Spatio-temporal variation in stream water chemistry in a tropical urban watershed

“…Although there are several possible sources of calcium in the watershed, it is possible that our elevated calcium values are due to the dissolution or chemical weathering of concrete found in the watershed, e.g., structures, other impervious surfaces, and channelized reaches. Several studies have documented the effects of concrete on stream water Table 1. chemistry and its increase in calcium concentrations (Leung and Jiao 2006, Davies et al 2010, Wright et al 2011, Tippler et al 2012. For example, Tippler et al (2012) found that in streams with high imperviousness, calcium concentrations were more than nine times that of less impervious streams (20 mg/L vs. 2.2 mg/ L).…”