Using bivariate linear mixed models to monitor the change in spatial distribution of heavy metals at the site of a historic landfill.

To improve accuracy and efficiency of monitoring remediated sites, the current study proposed the use of bivariate linear mixed modelling and subsequent hypothesis testing to determine significant change in contaminant concentrations over time. The modelling method integrated soil heavy metal (arsenic-As, lead-Pb and zinc-Zn) concentrations obtained from Bicentennial Park, Sydney, Australia, in the years 1990 (n = 144) and 2015 (n = 60), alongside potential influencing factors as predictor variables. Following variable selection, significant predictors included As (1990)-plan curvature, land cover change; As (2015)-multi-resolution ridge top flatness (MRRTF); Pb (1990)-elevation, MRRTF, type of nearest road; Pb (2015)-land cover change; Zn (1990)-distance to the nearest road and road type; and for Zn (2015)-aspect and land cover change. Model quality statistics (standardised squared prediction error; SSPE) indicated relatively good estimates of the prediction variance (mean ~ 1.0 for all metals, median = 0.512 for As (1990), 0.420 for As (2015), 0.417 for Pb (1990), 0.388 for Pb (2015), 0.342 for Zn (1990) and 0.263 for Zn (2015)), however Lin's concordance correlation coefficient indicated poor prediction of point estimates (LCCC = 0.263 for As (1990), 0.414 for As (2015), 0.250 for Pb (1990), 0.166 for Pb (2015), 0.233 for Zn (1990) and 0.408 for Zn (2015)). Pb in 1990 exceeded the Australian guide value of 600 mg kg-1 in small, isolated areas of the park, and by 2015, these 'hotspots' had significantly diminished (P < 0.05). Concentrations of As were low in both 1990 and 2015, not exceeding the 300 mg kg-1 guide; yet, in 2015, As had significantly increased in the south of the study area (P < 0.2). Zn concentrations in 1990 were elevated but did not exceed the guide value of 30,000 mg kg-1. Overall, the models exhibited good estimation of prediction variance and therefore are suitable for hypothesis testing; however, they exhibited poor prediction quality at times. Despite this, bivariate linear mixed modelling is worth exploring as it provides an advantage over modelling single time points and can assist with tracking potential contaminant sources before they cause harm.

Development of an estuarine assessment scheme for the management of a highly urbanised catchment/estuary system, Sydney estuary, Australia.

As coastal populations increase, considerable pressures are exerted on estuarine environments. Recently, there has been a trend towards the development and use of estuarine assessment schemes as a decision support tool in the management of these environments. These schemes offer a method by which complex environmental data is converted into a readily understandable and communicable format for informed decision making and effective distribution of limited management resources. Reliability and effectiveness of these schemes are often limited due to a complex assessment framework, poor data management and use of ineffective environmental indicators. The current scheme aims to improve reliability in the reporting of estuarine condition by including a concise assessment framework, employing high-value indicators and, in a unique approach, employing fuzzy logic in indicator evaluation. Using Sydney estuary as a case study, each of the 15 sub-catchment/sub-estuary systems were assessed using the current scheme. Results identified that poor sediment quality was a significant issue in Blackwattle/Rozelle Bay, Iron Cove and Hen and Chicken Bay while poor water quality was of particular concern in Duck River, Homebush Bay and the Parramatta River. Overall results of the assessment scheme were used to prioritise the management of each sub-catchment/sub-estuary assessed with Blackwattle/Rozelle Bay, Homebush Bay, Iron Cove and Duck River considered to be in need of a high priority management response. A report card format, using letter grades, was employed to convey the results of the assessment in a readily understood manner to estuarine managers and members of the public. Letter grades also provide benchmarking and performance monitoring ability, allowing estuarine managers to set improvement targets and assesses the effectiveness of management strategies. The current assessment scheme provides an effective, integrated and consistent assessment of estuarine health and provides an effective decision support tool to maximise the efficient distribution of limited management resources.

Historic change in catchment land use and metal loading to Sydney estuary, Australia (1788-2010).

Sydney estuary has a long history of environmental degradation and is one of the most modified water ways in Australia due to a highly urbanised catchment (~77 %) and a high population (4.6 million). The objectives of the present study were to map historical land use change from European settlement (1788) to 2010 to determine catchment evolutionary pathways and to estimate catchment loading (total suspended solids, Cu, Pb and Zn) to the estuary over this period. Land use distribution in Sydney catchment, determined for seven time horizons over this period, indicated that a substantial increase in residential land use through subdivision of large estates and an increase in road area resulted in a marked increase in metal loading to Sydney estuary between 1892 and 1936. The decline in industrial activity from a maximum in 1978 (3.9 %) to 1.8 % in 2010 and the introduction of unleaded fuel during this time was accompanied by reduction in metal loading to the estuary. Land use time horizon maps enabled the creation of novel, ternary diagrams to represent temporal evolution in catchment land use. The 15 sub-catchments of Sydney estuary were combined into three major catchment categories, i.e., urban, dense urban and commercial. Present-day annual discharge of stormwater from the Sydney catchment was calculated to be 466,000 ML and annual loadings of total suspended sediment (TSS), Cu, Pb and Zn in tonnes were 49,239, 27, 37 and 57, respectively. Stormwater has superseded industry as the main source of anthropogenic metals to this estuary in recent times.

Growth and decline of shoreline industry in Sydney estuary (Australia) and influence on adjacent estuarine sediments.

Sydney estuary (Australia), like many urbanised waterways, is degraded due to an extended history of anthropogenic activity. Two major sources of contamination to this estuary are discharge by former shoreline industries and historic and contemporary catchment stormwater. The objectives of the present study were to document changes in shoreline land use from European settlement to the present day and determine the influence of this trend on the metal content of adjacent estuarine sediments. Temporal analysis of land use for seven time horizons between 1788 and 2010 showed rapid expansion of industry along much of the Sydney estuary foreshore soon after European settlement due to the benefits of easy and inexpensive access and readily available water for cooling and power. Shoreline industry attained maximum development in 1978 (32-km length) and declined rapidly to the present-day (9-km length) through redevelopment of industrial sites into medium- to high-density, high-value residential housing. Cores taken adjacent to 11 long-term industrial sites showed that past industrial practices contributed significantly to contamination of estuarine sediment. Subsurface metal concentrations were up to 35 times that of present-day surface sediment and over 100 times greater than natural background concentrations. Sedimentation rates for areas adjacent to shoreline industry were between 0.6 and 2.5 cm/year, and relaxation times were estimated at 50 to 100 years. Natural relaxation and non-disturbance of sediments may be the best management practice in most locations.

The magnitude of variability produced by methods used to estimate annual stormwater contaminant loads for highly urbanised catchments.

Stormwater contaminant loading estimates using event mean concentration (EMC), rainfall/runoff relationship calculations and computer modelling (Model of Urban Stormwater Infrastructure Conceptualisation--MUSIC) demonstrated high variability in common methods of water quality assessment. Predictions of metal, nutrient and total suspended solid loadings for three highly urbanised catchments in Sydney estuary, Australia, varied greatly within and amongst methods tested. EMC and rainfall/runoff relationship calculations produced similar estimates (within 1 SD) in a statistically significant number of trials; however, considerable variability within estimates (∼50 and ∼25 % relative standard deviation, respectively) questions the reliability of these methods. Likewise, upper and lower default inputs in a commonly used loading model (MUSIC) produced an extensive range of loading estimates (3.8-8.3 times above and 2.6-4.1 times below typical default inputs, respectively). Default and calibrated MUSIC simulations produced loading estimates that agreed with EMC and rainfall/runoff calculations in some trials (4-10 from 18); however, they were not frequent enough to statistically infer that these methods produced the same results. Great variance within and amongst mean annual loads estimated by common methods of water quality assessment has important ramifications for water quality managers requiring accurate estimates of the quantities and nature of contaminants requiring treatment.

A review and critical assessment of sedimentary metal indices used in determining the magnitude of anthropogenic change in coastal environments.

The current critical review examines the application of 11 frequently used sedimentary metal indices in their ability to accurately assess the magnitude of human-induced change (enrichment) in the highly vulnerable and intensely developed coastal environment. The plethora and rapidly increasing number of sedimentary metal indices should, if not derived for special purposes, produce a consistent assessment on the basis that they use the same suite of metals and concentrations. Inconsistent numerical results produced by different index formulations should, when combined with their associated classification scheme, produce a common assessment of environmental condition. However, such a consistent outcome is seldom observed. Significant differences in assessment results are partly due to the historical evolution of indices and to the extraordinary diversity of background and reference values and materials being applied to account for pre-anthropogenic metal levels and confounding due to variable sediment characteristics. Size-normalised sample and background metal data used in the mCd and MEQ indices do not require reference values to account for textural variability and provide a quasi-direct measurement of enrichment with minimal computation (simple division). These priority indices should be combined into a single index (Enrichment Quotient, EQ). Results produced by the EF index were strongly correlated to mCd and MEQ and provide a similar classification and is recommended if normalised data are unavailable. Other indices assessed (MPI, PI, mPI, SEF, Igeo, PLI and Cf, original and current) provided a range of results, which either over- or under-estimated enrichment. The confusion concerning the choice and application of background and reference values in the assessment process is reviewed and their use in local and global assessment is clarified. Single- and combined-metal evaluations are recommended to provide detailed, local and more comprehensive assessments, respectively.

Assessment of future anthropogenic change and associated benthic risk in coastal environments using sedimentary metal indicators.

Indicators of estuarine health are frequently compromised by large, natural temporal and spatial variance, which often mask long-term environmental trends and confound remedial actions. Ecosystem indicators seldom provide information on the pristine condition or the history of anthropogenic change of a water body. The current investigation used sedimentary metals and novel field and analytical techniques to determine the pristine condition and assess the magnitude and history of human-induced temporal and spatial change of an estuarine system. Two vintages of normalised metal concentrations in surficial sediment (1992 and 2007) indicate Cu and Zn concentrations have increased over the period, while Pb concentrations have declined - a change verified by strategically located sedimentary cores. Assuming no change in metals supply and dispersion, Cu and Zn are predicted to increase in concentration and areal extent, whereas Pb concentrations and areal cover will decrease. High concentrations of sedimentary Cu may be having an adverse affect on the health of benthic animals over extensive areas, which are predicted to expand if no remedial strategy is implemented.

Comparison of mangrove (Avicennia marina) metal tissue concentrations to ambient sediment with an extensive range of contaminant levels in a highly-modified estuary (Sydney estuary, Australia).

Statistically distinct 'high', 'moderate' and 'low' metal contamination positions were distinguished across five Sydney estuary embayments for total sedimentary metal concentrations of Ni, Pb and Zn. While statistically distinct total sedimentary As, Cd, Co and Cu concentrations were indicated for the 'low' position samples. Mangrove (Avicennia marina) pneumatophore tissue metal concentrations from 'high' position trees were statistically distinct for Cd, Ni, Pb and Zn, while root tissue samples from 'low' position trees were statistically distinct for As, Cd and Zn. Outcomes from CAP, simple linear regression and DISTLM modelling indicated sedimentary metals were predominantly assimilated into mangrove root tissue, with smaller uptake into pneumatophore tissue. A comparison of floristic tissue metal concentrations indicated mangrove (A. marina) root tissue assimilated higher sedimentary metal concentrations than leaf and root tissue of seagrasses (Zostera capricorni and Halophila ovalis), which had relatively higher metal concentrations than those from pneumatophore and leaf mangrove tissue.

Baseline assessment of anthropogenic change and ecological risk of an estuary bordered by an urbanized catchment and a pristine national park (Port Hacking estuary, Australia).

Port Hacking is a tide-dominated, drowned river valley at the southern edge of the Sydney conurbation (Australia) and is bordered by intense urbanization to the north and native bushland in the south. The current work provides a first-time, baseline evaluation of the magnitude of human-induced change and risk posed by sedimentary metals in Port Hacking and catchment. The estuary separates fluvial and estuarine sediment enriched in metals exhibiting moderate ecological risk from sediments with minimal anthropogenic change and no biological risk. A full set of baseline data is provided in support of new monitoring of recent and future anthropogenic impacts on the system.

Unusually high sedimentary metal concentrations in intermittently closed and open lakes and lagoons (ICOLLs) in the northern lagoons of Sydney (Australia).

The environmental status of three Intermittently Closed and Open Lakes and Lagoons (ICOLLs) (Manly, Curl Curl and Dee Why Lagoons) in northern Sydney (Australia) were assessed using sedimentary metals. Results identified the highest sedimentary metal enrichment in the Australian central east coast estuaries, with only a moderate ecological risk. A comparison with surficial sediment concentrations from 1996 to 2008 indicated declining metal concentrations, which is largely supported by subsurface metals data. Extensive low-lying areas of the catchments were historically reclaimed by infilling wetlands, which may have resulted in contaminated groundwater influx to the lagoons. An analysis of the sedimentary metals mix in lagoons surrounded by extensive infilling and estuaries with minor reclamation were statistically distinct. ICOLLs are environmentally sensitive due to large catchment/estuary ratios and restricted access to the ocean. A full set of baseline data is provided to support future monitoring of anthropogenic impacts on the system.

An assessment of aluminum and iron in normalisation and enrichment procedures for environmental assessment of marine sediment.

An increasing use of Al and Fe as normalising elements in assessment of anthropogenic change (metal enrichment) in marine environments has prompted the current study. This investigation was facilitated by a unique, large data set comprising total- and size-normalised sedimentary metals data from 41 estuaries (n = 3494) in central New South Wales, Australia. Total sediment Al and Fe concentrations varied substantially in these estuaries, even for samples comprising 100% fine fraction (ff), due to changes in the clay mineral mix and variable clay mineral chemistry. Normalising sedimentary metals to 100% ff produced variable results, however this approach improved markedly when samples with <10% ff was removed. The technique of normalising sedimentary metals by adjusting total Al to 50,000 µg/g considered to represent 100% ff was critically assessed. Results showed that total Al for 100% ff varied between estuaries and the most appropriate Al concentration for normalisation was the intercept value of the trend line in total Al vs ff bivariate plots and the 100% ff axis. It is recommended that, in the absence of size-normalised metals data, this intercept value be used as the normalising Al concentration, which should be determined locally for 100% ff. Iron was also assessed as a normalising element using the same approach and provided similar results, but was less attractive due to diagenetic alteration. The post-extraction normalisation (PEN) method provided valid, normalised metals data capable of estimating enrichment (magnitude of anthropogenic change) in marine environments.

Sediment metal enrichment and ecological risk assessment of ten ports and estuaries in the World Harbours Project.

Ten global harbours were assessed for sediment quality by quantifying the magnitude of anthropogenic change and ecological risk. Anthropogenic change (enrichment) was high for Derwent River and Sydney estuary, moderate for Santander Harbour, Rio de Janeiro and Dublin Port, slight for Hong Kong, minimal for Darwin. All 10 enrichment indices used showed similar results. Derwent River sediment was rated at high ecological risk, followed by Sydney and Santander estuaries with moderate risk. Auckland and Darwin sediments exhibited minimal ecological risk and sediment in the remaining harbours (Dublin, Hong Kong, Ravenna, Ria de Vigo and Rio de Janeiro) were assessed at slight ecological risk. The extraordinary variety of environments and types/quantities/qualities of data investigated resulted in as much a critique and development of methodology, as an assessment of human impact, including unique techniques for elemental normalisation and contaminant classification. Recommendations for an improved technical framework for sediment quality assessment are provided.

Catchment condition as a major control on the quality of receiving basin sediments (Sydney Harbour, Australia).

The current work aimed to compile existing information to better understand the source, fate and effects of metallic contaminants in one catchment-receiving basin system (Iron Cove) in Sydney Harbour (Australia). Copper, Pb and Zn concentrations of potential source materials, i.e. soils (mean 62, 410 and 340 microg g(-1), respectively) and road dust (mean 160, 490 and 520 microg g(-1), respectively) and in materials being transported to the estuary, i.e. in gully pots (mean 110, 200 and 260 microg g(-1) for Cu, Pb, and Zn, respectively), in bedload (mean 210, 880 and 1700 microg g(-1), respectively) and particulates in canals draining the catchment (mean 325, 290 and 1865 microg g(-1), respectively) were highly enriched. Estuarine sediments in the receiving basin are enriched 20 times over pre-anthropogenic concentrations and are toxic to benthic animals at the canal mouths. Stormwater remediation is required to reduce metal loads to the adjacent estuary.

Deepwater ocean outfalls: A sustainable solution for sewage discharge for mega-coastal cities (Sydney, Australia): A synthesis.

In 1990-91 three deepwater ocean outfalls replaced three cliff-face outfalls discharging approximately 940 ML/day, or 80% of sewage generated by the City of Sydney (Australia) (population 3.3 million). Operation of these outfalls was assessed for the first two years and performed well, mitigating most of the environmental problems previously experienced from shoreline discharge. However, a concern remained for the unknown long-term effects on the marine environment. The current series of articles examine over 20 years of monitoring, for possible accumulative effects. Oceanographic modelling provided an understanding of particle settling, dispersion and distribution of discharged wastewater and monitoring assessed potential impact of offshore discharges on beach bathing water quality, sediment chemistry and benthic infauna. These four articles demonstrate that properly designed ocean outfalls are a viable, sustainable solution to sewage disposal for mega-coastal cities, however, continued monitoring is required to assess possible long-term environmental degradation.

Deepwater ocean outfalls: A sustainable solution for sewage discharge for mega-coastal cities (Sydney, Australia): Influence of deepwater ocean outfalls on shelf benthic infauna.

In the early 1990s, a cliff-face disposal-system discharging approximately 940 ML/day, or 80% of sewage generated by the City of Sydney (Australia) (population 3.3 million) was replaced by three deepwater ocean outfalls. An 18-year benthic infauna monitoring study was undertaken to address earlier concerns of long-term accumulation from sewage discharges and potential adverse effects on the marine environment. Assessment of outfall community structure indicated organic input from discharges has not resulted in sediment anoxia. The current post-commissioning investigation detected a gradual change in community structure from north to south in the study area, which was also displayed in taxonomic turnover south of the Malabar outfall. Temporal fluctuation in community structure detected at the three outfall and three reference locations in the current study was also noted in the pre-commissioning study at these locations. Evidence provided by this study indicated the Sydney deepwater ocean outfalls do not cause significant ecological impact.

Deepwater ocean outfalls: A sustainable solution for sewage discharge for mega-coastal cities (Sydney, Australia): Influence of deepwater ocean outfalls on shelf sediment chemistry.

A cliff-face disposal system discharging approximately 940 ML/day, or 80% of sewage generated by the City of Sydney (Australia) (population 3.3 million) was replaced by three deepwater ocean outfalls in the early 1990s. Enrichment of anthropogenic chemicals from cliff-face discharges raised concerns regarding long-term accumulation of sewage particulates and associated contaminants in offshore sediments and for reduced beach water quality. The current post-commissioning investigation detected a southward gradient of sediment fining and increased total organic carbon in the study region. Deepwater ocean discharges have not contributed to an accumulation of fines, or to increased metallic/nonmetallic chemicals of concern with no elevated risk of adverse biological effects beyond pre-commissioning conditions. Instead, the best modelled relationship was recorded between benthic infauna and sedimentary fines and not to contaminants. Historic sea dumping prior to 1932 in the north of the study area has resulted in enrichment of some non-bioavailable sedimentary metals.

Metal concentrations in Sydney Cockle (Anadara trapezia) tissue and ambient sediment in a highly-modified estuary (Sydney estuary, Australia).

The influence of sedimentary metals on the cockle A. trapezia tissue was examined using a strong difference in sedimentary metal concentrations in an embayment (Hen and Chicken Bay) highly contaminated in Cu and an adjacent cove (Iron Cove), strongly enriched in Cd, Cu, Pb and Zn within the heavily-urbanised Sydney estuary catchment (Australia). Statistically significant differences were recorded for cockle tissue metal concentrations between the study locations reflecting differences in surficial sediment metal concentrations. Low metal uptake was apparent in A. trapezia tissue, which were considerably less than background sedimentary concentrations and was of low-risk for human consumption. Dissimilar bioconcentration of Cd, Cu, Pb and Zn was apparent in tissue of cockles (A. trapezia), prawns (Metapenaeus bennettae), mussels (Mytilus galloprovincialis) and oysters (Saccostrea glomerata), due possibly to different feeding patterns and biogeochemical conditions in bottom sediments.

Deepwater ocean outfalls: A sustainable solution for sewage discharge for mega-coastal cities (Sydney, Australia): Influences on beach water quality.

Shoreline discharge representing approximately 80% of sewage generated by Sydney (Australia) was replaced with three deepwater ocean outfalls between 1990 and 1991. Beachwatch bacterial monitoring data collected between 1989 and 2016 were analysed to assess the impact of commissioning on bathing water quality along 32 km of coastline. Bacterial contamination was reduced by 26-99% during the first 32 months post-commissioning and in the longer post-commissioning period, 1993 to 2016, bathing water quality improved for 31 beaches. Relatively stable bathing water quality was observed for five other beaches after the 2001 upgrade of another shoreline wastewater treatment plant. Bacterial contamination of bathing water in this 24-year post-commissioning period was most influenced by rainfall in the 24-h to 9 am on the day of sampling. Bacterial contamination from surfacing shore-blown wastewater plumes was not evident, whereas stormwater-delivered bacterial contamination was apparent and varied between beaches.

A review of chemical-based sediment quality assessment methodologies for the marine environment.

This review of 19 chemical approaches used in assessing sediment quality are classified into empirical, mechanistic and sediment quality indices (SQI) groups. Empirical sediment quality guidelines (SQGs), based on matching chemical and biological-effects data and the mechanistic techniques, founded on equilibrium partitioning principals (EqP), are well established and most used. Empirical SQGs provide a useful screening tool to initially identify locations and chemicals of most concern, but are not regulatory criteria. The EqP approach is causally linked however, the scheme assumes porewater chemistry largely controls sediment toxicity. SQIs are not based on matching chemical-biological data and combine schemes with multiple narrative intents. The 41 SQGs reviewed show a considerable range in upper and lower guideline values. Grain size and organic content should be included into SQGs, however inclusion of suspended sediment into SQGs raises concerns. SQGs are built into decision-tree schemes with other lines-of-evidence and evaluated in a weight-of-evidence framework.

Baseline physio-chemical characteristics of Sydney estuary water under quiescent conditions.

The current study establishes baseline water quality properties for Sydney estuary, Australia for long periods of quiescence, which characterize the region. The study was undertaken in response to numerous requests for such data by researchers, government agencies and contractors. During quiescent periods, the range in Secchi depth transparency, turbidity, salinity and total suspended solid (TSS) values was 0.3-5.3 m, 18.6-0.1 NTU, 26.4-35.3 PSU and 8.3-1.0 mg/L in the upper and lower estuary, respectively. Baseline particulate metal concentrations were high, however TSS metal mass was greater during high rainfall. Tables and GIS-based maps allow baseline physio-chemical values to be extracted from the database for any location in Sydney estuary for quiescent conditions. Strong inter-parameter baseline relationships enable interpolation between water quality data. Baseline physio-chemical values were used to assess the impact of a high-precipitation event to demonstrate the utility of the new database.