Ian A. Wright

Impact of concrete and PVC pipes on urban water chemistry

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.

A new type of water pollution: concrete drainage infrastructure and geochemical contamination of urban waters

Stormwater and other urban runoff is often conveyed by concrete infrastructure and it is plausible that the chemistry of urban streams is modified by the leaching of minerals from this infrastructure. We tested this hypothesis by analysing major anions, cations and other chemical variables from urban and reference freshwater streams in northern Sydney. Urban streams tended towards neutral pH whereas non-urban reference streams were acidic. Bicarbonate levels were more than 10 times higher and calcium concentrations were more than six times higher in urban streams than reference streams. Experimental analysis revealed that the chemistry of rainwater changed when passed through concrete pipes and down concrete gutters, suggesting dissolution of cement products from various concrete materials used for urban drainage. This study concluded that the use of concrete – particularly its application for urban drainage – is responsible for some of the modifications to urban stream geochemistry. Thus, urban geology should be considered as an important factor that contributes to the urban stream syndrome.

Impact of urban development on aquatic macroinvertebrates in south eastern Australia: degradation of in-stream habitats and comparison with non-urban streams

Internationally, waterways within urban areas are subject to broad-scale environmental impairment from urban land uses. In this study, we used in-stream macroinvertebrates as surrogates to measure the aquatic health of urban streams in the established suburbs of northern Sydney, in temperate south eastern Australia. We compared these with samples collected from streams flowing in adjacent naturally vegetated catchments. Macroinvertebrates were collected over a 30-month period from riffle, edge and pool rock habitats and were identified to the family level. Macroinvertebrate assemblages were assessed against the influence of imperviousness and other catchment and water quality variables. The study revealed that urban streams were significantly impaired compared with those that flowed through naturally vegetated non-urban catchments. Urban streams had consistently lower family richness, and sensitive guilds were rare or missing. We found that variation in community assemblages among the in-stream habitats (pool edges, riffles and pool rocks) were more pronounced within streams in naturally vegetated catchments than in urban waterways.

Effects of organic and heavy metal pollution on chironomids within a pristine upland catchment

Several studies, particularly in the Northern Hemisphere, have demonstrated that chironomids are responsive to pollution (e.g., heavy metals, organic). In Australia, there is limited evidence that chironomid species have differential sensitivities to water pollution, with several studies reporting high tolerance of heavy metal pollution. We investigated the impact of both zinc-rich mine waste and organic effluent on chironomids within an effectively pristine background using the Chironomid Pupal Exuviae Technique (CPET). Chironomid species assemblages were strongly influenced by both mine drainage and organic pollution. Community composition differed between unpolluted streams and locations downstream of the pollution sources, and between the two different sources of pollution. Thirty seven of the most abundant species exhibited strong responses to water pollution varying from greatly increased abundance to complete absence. Ten species had higher abundance at one of the polluted sites compared to unpolluted sites; six in the presence of zinc pollution and five in the presence of organic pollution. One species responded positively to both pollution types. Our results indicate that contrary to the mixed reports of Australian chironomids for being insensitive to pollution, we found that they displayed a strong pollution response to both organic and heavy metal contamination.

Impact of mining and industrial pollution on stream macroinvertebrates: importance of taxonomic resolution, water geochemistry and EPT indices for impact detection

This study investigated freshwater macroinvertebrate communities in waterways contaminated by active and abandoned mining and industrial activities in order to ascertain any impact on freshwater ecosystems. We compared macroinvertebrate communities at the species, family and order levels of taxonomic resolution. We also collected water samples to compare ionic composition and metal concentrations from waste-affected and reference (non-affected) sites. In addition to assessing ecological impairment, the study also sought to determine whether the degree of sensitivity in detecting any impairment varied according to the taxonomic level of identification used. We calculated the biotic indices of EPT richness and taxonomic richness at the species, family and order levels, and performed multivariate analyses to measure differences in community structure at all three levels. We found significant differences in both biotic indices and macroinvertebrate community structure at each taxonomic level, indicating ecological impairment at waste-affected sites. We also concluded that the most appropriate taxonomic level for evaluating macroinvertebrates depends on the information required. In this study, the family level provided the clearest assessment of ecological impairment at waterways affected by mining and/or industrial wastes, and order-level data provided only a marginally less sensitive measure of this impairment.

The influence of concrete on the geochemical qualities of urban streams

The geochemical signature of freshwater streams can be used to determine the extent and nature of modification to stream water geochemistry due to urban development. This approach used the Gibbs (1970) diagram as a model for evaluation of changes to ionic composition linked to urban development. In this multi-year study, the geochemistry of 21 waterways in the Georges River catchment, Sydney, were monitored and compared with the level of urban development as measured by sub-catchment imperviousness and directly connected imperviousness. The results reflect a strong relationship between the intensity of sub-catchment urban development and stream geochemistry. All major geochemical attributes increased with escalating levels of urban development. The largest increase was for bicarbonate, which increased 18 times from a mean of 6.4 mg L–1 at non-urban streams to a mean of 118 mg L–1 at urban streams. Similarly, mean concentrations of calcium increased by 14 times (from 2 to 27.9 mg L–1). Mean salinity was enriched in the most urban streams, compared with non-urban streams, by more than 6 times. We attribute this, in part, to the influence of urban geology, notably concrete stormwater infrastructure. Changes in stream geochemistry due to urban development are an important element of the urban stream syndrome.

Using camera-trap data to model habitat use by bare-nosed wombats (Vombatus ursinus) and cattle (Bos taurus) in a south-eastern Australian agricultural riparian ecosystem

Bare-nosed wombats (Vombatus ursinus) are an often important south-east Australian agricultural riparian species that may improve riparian landscape heterogeneity via their burrowing activity. At the same time they are often accused of causing soil erosion. As populations of wombats in other landscapes are under threat due to habitat disturbance, road mortality and disease, knowledge of the factors determining their use of riparian systems are important for their conservation and management. Since the European colonisation of Australia, riparian areas have been utilised by domestic cattle (Bos taurus), usually resulting in a decline in biodiversity. Camera-trap data was used to investigate the habitat use by wombats and cattle in remnant Eastern Riverine Forests. A total of 664 detections of animals from 13 species were made over the entire riparian-zone survey. Wombats were the most detected species, followed by cattle, then foxes and cats. Wombat and cattle activity varied significantly through the diurnal cycle, with wombats active from 1900 to 0700 hours and cattle active from 0700 to 1900 hours. There were no seasonal effects relating to the detection of either species. Feral species such as foxes, cats and rabbits were more frequently detected at sites highly disturbed by cattle. Results of this study illustrate the potential of camera-trapping for modelling habitat use by wombats and cattle and providing guidelines for the management of feral animals in remnant agricultural riparian habitats.

Environmental impact of coal mining and coal seam gas production on surface water quality in the Sydney basin, Australia

The extraction of coal and coal seam gas (CSG) will generate produced water that, if not adequately treated, will pollute surface and groundwater systems. In Australia, the discharge of produced water from coal mining and related activities is regulated by the state environment agency through a pollution licence. This licence sets the discharge limits for a range of analytes to protect the environment into which the produced water is discharged. This study reports on the impact of produced water from coal mine activities located within or discharging into high conservation environments, such as National Parks, in the outer region of Sydney, Australia. The water samples upstream and downstream from the discharge points from six mines were taken, and 110 parameters were tested. The results were assessed against a water quality index (WQI) which accounts for pH, turbidity, dissolved oxygen, biochemical oxygen demand, total dissolved solids, total phosphorus, nitrate nitrogen and E .coli. The water quality assessment based on the trace metal contents against various national maximum admissible concentration (MAC) and their corresponding environmental impacts was also included in the study which also established a base value of water quality for further study. The study revealed that impacted water downstream of the mine discharge points contained higher metal content than the upstream reference locations. In many cases, the downstream water was above the Australia and New Zealand Environment Conservation Council and international water quality guidelines for freshwater stream. The major outliers to the guidelines were aluminium (Al), iron (Fe), manganese (Mn), nickel (Ni) and zinc (Zn). The WQI of surface water at and downstream of the discharge point was lower when compared to upstream or reference conditions in the majority of cases. Toxicology indices of metals present in industrial discharges were used as an additional tool to assess water quality, and the newly proposed environmental water quality index (EWQI) lead to better trend in the impact of coal and coal seam gas mining activities on surface water quality when compared to the upstream reference water samples. Metal content limits were based on the impact points assigned by the Agency for Toxic Substances and Disease Registry, USA. For environmental and health impact assessment, the approach used in this study can be applied as a model to provide a basis to assess the anthropogenic contribution from the industrial and mining activities on the environment.

Wombats and domestic livestock as potential vectors of Cryptosporidium and Giardia in an agricultural riparian area

Emerging pathogenic diseases are a significant burden on global economies and public health administrators. In Australia, the pathogens Giardia and Cryptosporidium are widespread in riparian areas subject to urban or agricultural contamination. Bare-nosed wombats (Vombatus ursinus) occur at relatively high densities alongside domestic cattle in agricultural riparian areas in south-eastern Australia and may transmit protozoan pathogens. We assessed the distribution of wombat scats and cattle pats on streambanks and screened them for the presence of Giardia and Cryptosporidium. The density of wombat scats declined with increasing distance from water while the cover of cattle pats increased with distance fromwater,butonlyatsitessubjectedtolowcattleusage.Wewereunableto findanyCryptosporidiumspeciesorgenotypes known to infect humans in either wombat or cattle faeces. One cattle sample contained Cryptosporidium bovis, a cattle- specific organism unlikely to be zoonotic. Giardia duodenalis (Assemblage E), a non-zoonotic pathogen, was detected in four cattle samples, but no wombat samples tested positive for Giardia. Our results suggest that while wombats represent a low-pathogenriskthereisaneedforconsistentmonitoringofpotentiallyharmfulwaterborneandchlorine-resistantGiardia and Cryptosporidium pathogens in drinking-water catchments.

Diel variation in chironomid (Diptera: Insecta) exuviae abundance and taxonomic richness in near-pristine upland streams of the Greater Blue Mountains World Heritage Area, South-Eastern Australia

We assessed diurnal variation of Chironomidae exuviae in two small upland streams in temperate Australia, during summer. Understanding the diel periodicity of exuviae can be an important consideration for biomonitoring purposes or to investigate adult emergence patterns. We collected 1,813 floating exuviae, comprising 54 taxa from four subfamilies, from flowing water using a drift net. Unlike many northern hemisphere temperate studies, we observed that peak exuviae abundance (7.3 exuviae per m³) and taxon richness (1.7 taxa per m³) occurred in the dusk and night hours, with the lowest numbers (0.9 exuviae per m³) and taxon richness (0.6 taxa per m³) recorded in the late morning to early afternoon. We suggest that this could be an adaptation to avoid stressful weather during the heat of summer days, or it could be to avoid visual predators. The numerically dominant taxa exhibited peak abundance in the dusk/night samples which indicates predominant crepuscular/nocturnal patterns of adult emergence. This pattern was consistent across both streams surveyed. Our taxon inventory rose steeply during the first 24-h occasion, then at a reduced rate during the second and third days of sampling. For flowing water collections of exuviae that utilise drift-netting, we suggest that sampling at all sites includes at least three 24-h cycles and avoids periods of heavy rainfall and increased stream flow.