Gavin F. Birch

Source of heavy metals in sediments of the Port Jackson estuary, Australia

The Port Jackson estuary has a highly urbanised and industrialised catchment and is central to Sydney, which with a population of approximately 4 million, comprises almost a quarter of Australias population. The estuary has a long history of contamination which has resulted in extensive areas of polluted sediments mainly associated with the most industrialised/commercialised parts of the catchment. The highest concentrations of sedimentary heavy metals occur at the headwaters of embayments and tributaries in the estuary, especially in the central city region where gradients decline rapidly away from canals. High total suspended solids, elevated concentrations of heavy metals in sediment and in particulates in canals draining large catchments are evidence that drainage from these areas is a major source of contaminants to this estuary. Another possible important point source of heavy metals is leachates from reclamation areas, whereas licenced polluters do not impact on a regional scale. Of the diffuse sources, atmospheric contributions may be substantial, but storm water drains with small catchments and sewer overflows have no observable impression on the regional distribution of heavy metals in surficial sediments. Biological effects criteria suggest that heavy metal concentrations in sediments are sufficiently high to adversely affect biota over large areas of Port Jackson. Large volumes of contaminated sediment and a continuing supply of heavy metals to the estuary will make remediation difficult.

The distribution of polycyclic aromatic hydrocarbons in surficial sediments of Sydney Harbour, Australia

Abstract Surface sediment was collected from 124 sites in Sydney Harbour and analysed for the 16 polycyclic aromatic hydrocarbons (PAHs) listed as priority pollutants by the US EPA, as well as 2-methylnaphthalene. PAH concentrations varied widely, from μ g kg−1 of total PAH. The spatial distribution of PAHs suggested that they derive predominantly from urban run-off. However, discrete point sources of PAH appear to exist at several sites. The relative abundance of individual PAH compounds was remarkably consistent throughout the harbour and indicated that high temperature combustion processes are the predominant source of PAH contamination in Sydney Harbour. Comparison with numerical effects-based sediment quality guidelines derived in the US indicated that most of the sites studied in Sydney Harbour (89%) have levels of PAH which are predicted to either occasionally or frequently result in adverse biological effects.

Kinetics of trace element uptake and release by particles in estuarine waters: effects of pH, salinity, and particle loading

The uptake and release of 109Cd, 51Cr, 60Co, 59Fe, 54Mn, and 65Zn were studied using end-member waters and particles from Port Jackson estuary, Australia. The kinetics of adsorption and desorption were studied as a function of suspended particulate matter (SPM) loading and salinity. Batch experiments showed that the position and slope of the pH edges are dependent on the metal and on the salinity of the water (except for Mn). The general effect of salinity was to move the adsorption edge to higher pH values, with the greatest change being found for Cd. Most of the metals showed relatively simple kinetics with an increase in uptake as a function of time and suspended particle concentrations. The time dependence of Cd uptake was more complex, with an initial adsorption phase being followed by strong mobilization from the suspended sediments, explained by chlorocomplexation and competition with seawater major cations. The reversibility of the sorption decreased in the order Co>Mn>Zn>Cd>Fe>Cr. The percentage of adsorbed metal released in desorption experiments was greater in seawater than freshwater for Cd, Zn, and Co. These results are important in understanding the cycling of pollutants in response to pH, salinity, and particle concentrations in estuarine environments. In addition, they give valuable insight into the important mechanisms controlling the partitioning of heavy metals in the Port Jackson estuary.

Dissolved trace metal distributions in Port Jackson estuary (Sydney Harbour), Australia

Concentrations of dissolved metals (Cd, Cu, Ni, Mn and Zn) were determined for summer and winter, under low-flow conditions in Port Jackson, a microtidal, well-mixed estuary in south-east Australia. Mean concentrations of Cd (0.04+/-0.02 microg/l), Ni (0.86+/-0.40 microg/l), Mn (20.0+/-25 microg/l) and Zn (6.47+/-2.0 microg/l) were below water quality guidelines. Concentrations of Cu (1.68+/-0.37 microg/l), however, slightly exceeded recommended values. Dissolved Ni and Mn behaved mostly conservatively, whereas Cd, Cu and Zn showed mid-estuarine maxima. Peaks in Cd, Cu and Zn concentrations were located in the upper estuary, independent of the salinity and suspended particulate matter loading, and were consistent with anthropogenic inputs of metals in the estuary. Concentrations of dissolved Cu were highest in summer, whereas concentrations of Cd, Ni and Mn were significantly lower in summer than winter (P< or =0.05). The increase in temperature and biological activity during summer explained the seasonal variation. The sequence of log K(d) values (20-30 salinity) was Mn>Zn>Cu>Ni. These results give unique information concerning the contemporaneous distribution of dissolved trace metals in the Port Jackson estuary and they provide a data set against which the long-term contamination may be assessed.

EFFICIENCY OF A CONSTRUCTED WETLAND IN REMOVING CONTAMINANTS FROM STORMWATER

As in most large capital cities, urban stormwater discharging into Port Jackson (Sydney) is highly enriched in a wide range of contaminants, which has resulted in degradation of the receiving basin waters and bottom sediments. The objective of the current investigation was to determine the removal efficiency of contaminants in urban stormwater by a wetland constructed in the Sydney catchment. The wetland (700 m2) drains a residential urban catchment of about 480,000 m2 comprising predominantly houses, streets, gardens, and street parking areas. Samples of stormwater influent and effluent were obtained during rainfall events between April and June 2000. Eight samples were collected at the inlet and outlet to the wetland during each event and analyzed for nutrients, trace metals, total suspended solids (TSS), and organochlorine pesticides and polycyclic aromatic hydrocarbons (PAHs). Water quality parameters (temperature, dissolved oxygen, pH, turbidity, conductivity) were measured concurrently. The average removal efficiency of trace metals Cr, Cu, Pb, Ni, and Zn was 64%, 65%, 65%, 22%, and 52%, respectively for the six events measured, whereas for Fe and Mn, removal efficiencies were negative for most events (mean—84% and—294%, respectively). The average removal efficiency of NOx and TN was 22% and 16%, respectively. The average removal efficiencies of total Kjeldahl nitrogen (TKN) and total phosphorus (TP) were 9% and 12%, respectively. During four high-flow events, the removal efficiency of TSS in stormwater effluent from the wetland was between 9% and 46%; however, substantially higher TSS concentrations were observed in effluent than influent waters during two very high-flow events (removal efficiency—98% and—67%). Fecal coliform counts in the stormwater in this catchment are high (maximum: 620,000 cfu/100 ml), but mean removal efficiency was 76% (range 26% to 98%) during the four high-flow events monitored. Nevertheless, most samples from the outflow exceeded the Public Health criterion for secondary contact (e.g., boating) of 1000 cfu/100 ml. Concentrations of organochlorine pesticides and PAHs in stormwater were below analytical detection. Although highly variable, lower concentrations of Cr, Cu, Ni, Pb, Zn, NOx, TN, and fecal coliform in the stormwater effluent compared to influent waters indicates that the wetland was moderately efficient in removing contaminants from urban stormwater.

Distribution of heavy metals in surficial sediments of Port Jackson, Sydney, New South Wales

The fine fraction (<63 μm) of surficial sediment from Sydneys Port Jackson estuary is markedly enriched in heavy metals (Cr, V, Mn, Fe, Ni, Co, Cu, Zn, Cd and Pb). Highest concentrations are in the two main tributaries (Parramatta and Duck Rivers) and in off‐channel estuarine bays (Homebush, Hen and Chicken, Iron Cove, Blackwattle and Rozelle Bays). Average Cu, Zn and Pb values are enriched by about ten times over background, but maximum enrichment over background is 108 times for Cu, 40 times for Pb, 29 times for Cr, and 48 times for Zn. The distribution of Cu, Pb, Zn, Cr, Ni, Co, Cd and V suggests an association with industrial activity over the past century and metal enrichment in bay ends is probably related to runoff. A marked decrease in metal concentrations down the estuary is probably related to source.

Pollution and health risk of potentially toxic metals in urban road dust in Nanjing, a mega-city of China

Spatial variations in concentrations of a suite of potentially toxic metals (Ba, Cr, Cu, Fe, Mn, Ni, Pb and Zn) and Ca in road dusts (n=99) from urban trunk roads (TR) in Nanjing, a mega-city in China, were established. Metal pollution levels, sources and human health risk (non-carcinogenic) were studied. In contrast to previous studies, we labeled the indicative metals relating to non-exhaust traffic emissions by comparing metal pollution between crossroad and park road dusts, and then anthropogenic sources of metals in TR dusts were assessed combining their spatial pollution patterns, principal component analysis and Pb isotopic compositions. Results showed that the metals were enriched in TR dusts compared to background soil concentrations with mean enrichment factors (EFs) of 2.2-23, indicating considerable anthropogenic influence. The degrees of metal pollution ranged from minimal to extremely high and ranked by Ca>Cu>Pb≈Zn>Cr≈Fe>Ni≈Ba>Mn on average. Pollution of Cr, Cu, Fe, Mn, Ni, Pb and Zn in TR dusts resulted primarily from industrial emissions (e.g., coal combustion and smelting) and high pollution levels were found close to suburb industrial complexes, whereas pollution of Ba and Ca was mainly related to construction/demolition sources and was generally distributed homogeneously. The relatively minor contribution of non-exhaust traffic emissions to metal pollution in TR dusts was considered to be due to overwhelming industrial and construction/demolition contributions, as well as to the dilution effect of natural soil particles. Ingestion appears to be the major route of exposure for road dust for both adults and children, followed by dermal contact. The non-carcinogenic health risk resulting from exposure to the potentially toxic metals in TR dusts was within the safe level based on the Hazard Index (HI), except in pollution hotspots where exposure to Pb, Cr, and Cu may be hazardous to children.

Heavy metals in road dust, gully pots and parkland soils in a highly urbanised sub-catchment of Port Jackson, Australia

The current temporal and spatial investigation was undertaken to determine the nature and concentration of heavy metals in road dust and to assess whether road dust was a possible source of metals to adjacent soils and gully pots. Three roads were selected in the Iron Cove catchment, Sydney Harbour, to investigate the influence of traffic volume on the heavy metal concentrations and accumulations rates with time. The mass of road dust increased irregularly with time since the last cleaning event and metal concentrations increased with traffic volume, but concentrations did not increase with antecedent time, possible due to variable particle size distributions. The mass of material accumulating on 1 m2 of road surface over 5 days was 72.5, 41.7, and 4.8 g for high (Parramatta Road), medium (Marion Street), and low (National Street) traffic volume roads, respectively. The source area of road surface for the test sites (200–400 m of road) may provide, over the 5-day test period, maximum loads of (g): Cr 2, Cu 7, Ni 2, Pb 29, and Zn 28 for Marion Street; Cr 0.1, Cu 0.3, Ni 0.1, Pb 2, and Zn 3 for National Street; and Cr 2, Cu 8, Ni 1, Pb 26, and Zn 18 for Parramatta Road. To provide better spatial information than the 3 samples sites used in the temporal study, road dust (n = 171) and gully pot (n = 23) samples where taken across the entire Iron Cove catchment. Mean concentrations of road dust were 6, 34, 164, 28 000, 284, 27, 487, and 523 μg/g for Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn, respectively, for all road types, and concentrations in gully pot material were 7, 20, 112, 24 000, 316, 20, 199, and 257 μg/g, respectively. A large proportion of these metals is associated with the mobile, fine fraction (<62.5 μm), and the majority (54–100%) of these elements are extracted with weak leaching agents (EDTA and 1 M hydrochloric acid). However, more information on speciation is required to determine bioavailability. SEM/EDAX analysis suggests that metals in the fine fraction may be adsorbed, whereas particulate metal and inclusion phases are common in the coarser (62.5–125 μm) material. Metal concentrations in parkland soils adjacent to the roads are highly enriched and increase with traffic volume. Concentrations decline markedly with distance from roads, but maximum values are at 30–50 m from the road edge, due to high-velocity wind generated by vehicles in proximity to the road. Metal-rich soils and gully pot deposits may be available for transport to the adjacent stormwater system.

Comparison of heavy metal loads in stormwater runoff from major and minor urban roads using pollutant yield rating curves.

Trace metal export by stormwater runoff from a major road and local street in urban Sydney, Australia, is compared using pollutant yield rating curves derived from intensive sampling data. The event loads of copper, lead and zinc are well approximated by logarithmic relationships with respect to total event discharge owing to the reliable appearance of a first flush in pollutant mass loading from urban roads. Comparisons of the yield rating curves for these three metals show that copper and zinc export rates from the local street are comparable with that of the major road, while lead export from the local street is much higher, despite a 45-fold difference in traffic volume. The yield rating curve approach allows problematic environmental data to be presented in a simple yet meaningful manner with less information loss.

Distribution and possible sources of organochlorine residues in sediments of a large urban estuary, Port Jackson, Sydney

Sydney Harbour is surrounded by a large capital city of about four million people and its highly urbanised (86%) catchment supports a substantial industrial base and an extensive transport infrastructure. Large commercial and naval ports occupy the waterway and the harbour is an important recreational area. Surficial sediment in Sydney Harbour contains high concentrations of PCBs, HCB, total chlordane, total DDT, aldrin, dieldrin, heptachlor and heptachlor‐epoxide, but low concentrations of lindane. PCBs, total chlordane, and to a lesser extent dieldrin, are most elevated in sediment in creeks on the southern shores of the harbour suggesting sources within older, highly urbanised/industrialised catchments of western‐central Sydney. There are high concentrations of total DDT and HCB in sediments of the upper harbour and Homebush Bay suggesting that chemical industries on the shores of the estuary in this area are sources of these contaminants. Although no sediment quality guidelines apply in Australia, empirically derived biological effects criteria suggest that sediment over extensive areas of Sydney Harbour may have an adverse impact on biota. Especially of concern are sediments containing high concentrations of chlordane and DDT.