Bryan E Chenhall

Identification of historical lead sources in roof dusts and recent lake sediments from an industrialized area: indications from lead isotopes

X-ray fluorescence and stable lead (Pb) isotopic analyses have been undertaken on dusts, known from microscopic investigation to contain significant quantities of industrially- and urban-derived particulate matter, present in the roof cavities of houses in the Illawarra region (N.S.W., Australia), with the objective of examining the historic record of Pb pollution. All investigated houses contained in excess of 250 micrograms g-1 Pb, with dwellings close to a copper smelter, in a large industrial complex including a major steelworks, containing higher (> 2500 micrograms g-1) Pb concentrations. The isotopic composition in the dusts, expressed here as 206Pb/204Pb, is relatively constant at 17.0, irrespective of dwelling age or distance from the industrial complex. Contamination of the dusts by Pb sourced from paint cannot explain the isotopic uniformity of the dust samples. Isotopic modelling indicates that the dusts contain Pb derived from the copper smelter, gasoline-air Pb and a minor contribution from coal-utilising sources. Lead loading was also investigated in the adjacent lagoon, which acts as a natural sink for particulate matter in the Illawarra region. Isotopic data and modelling indicate that one natural and four anthropogenic sources contribute to the Pb burden of this lagoon. The natural source consists of Permian rocks cropping out in the catchment area which have a 206Pb/204Pb of approximately 18.7. The suggested anthropogenic sources are an old disbanded base-metal (Pb) smelter (206Pb/204Pb approximately 16.2-16.3), the copper smelter (206Pb/204Pb approximately 17.9), gasoline-air derived Pb (206Pb/204Pb approximately 16.4-16.5) and industries utilising coal, for example the recently closed thermal coal-fired power station (206Pb/204Pb approximately 18.9). The relative contributions of the base-metal (mainly lead) smelter and gasoline-air Pb in the sediment can only be partly assessed due to the isotopic similarity of these sources. Likewise the natural background and coal source (e.g. power station) contributions can only be estimated from historical data. Age estimations for sediment cores, using 137Cs, provide some control on these assessments. Near surface sediments in the lagoon have a relatively constant 206Pb/204Pb of 17.6-17.7, irrespective of sample location. Isotopic calculations, together with records of particulate matter pollution emissions, indicate a link between the Pb in roof dusts (206Pb/204Pb approximately 17.0) and Pb contamination of the near surface (upper 20 cm) lagoonal sediments via a homogeneous, non-unique source of lead whose isotopic composition closely matches that of the dusts. Over the last 5 decades, atmospheric fallout of Pb-bearing particulate matter appears to have been the dominant pathway for addition of Pb to the lagoon and dwellings in the Illawarra region.

Geochemical comparisons between estuaries with non‐industrialised and industrialised catchments: The Huon and Derwent River estuaries, Tasmania

The adjacent Huon and Derwent estuaries in Tasmania have similar climatic and physical characteristics, and provide a good comparison between relatively uncontaminated and industrially polluted estuaries, respectively. Representative samples were collected from both estuaries and analysed for grainsize and trace‐element content (using X‐ray fluorescence and neutron activation analyses). The Huon estuary drains a predominantly forested and agricultural catchment and contains low (baseline) concentrations of trace elements, including lead, zinc and copper. In contrast, the Derwent estuary has a geologically similar yet larger catchment and it passes through an industrialised area in the midestuarine reach. A zinc refinery has, in the past, been a major source of trace‐element contamination. These contaminants are distributed downstream from the refinery by combined fluvial and tidal activity, while the latter also causes upstream movement of contaminants during non‐flood periods. Significant upstream contamination is limited by fluvial bottom flows remobilising contaminated fine sediment during flood periods. Maximum contamination occurs in the region around the refinery with values in the surface sediments ranging from 40 to 565 times baseline levels and from 2 to 55 times the Australian Interim Sediment Quality Guidelines high‐levels for aquatic sediments (maximum 22593 ppm Zn, 3866 ppm Pb and 1182 ppm Cu). In the lower Derwent estuary, contaminant distribution is inversely related to tidal‐flow velocities and is most prominent in the lower energy muddy substrates. Trace‐metal levels in the more recent surficial aquatic sediments are slightly lower than those recorded in a previous study from the area, possibly reflecting the stricter environmental controls now operating.

Anthropogenic marker evidence for accelerated sedimentation in Lake Illawarra, New South Wales, Australia

The chronology of near-surface sediments in Lake Illawarra has been investigated using radiocarbon dating and anthropogenically derived substances including trace metals, ash, and137Cs. Sediments at depths about 1 m below the water-sediment interface ranged in age from Modern to 786 calendar years bp on the basis of radiocarbon dating ofNotospisula trigonella valves. Multiple marker (for example ash-trace metals) depth-concentration sediment profiles yielded estimates of sedimentation rate ranging from 3 to 5 mm yr−1 at Griffins Bay to more than 16 mm yr−1 at Macquarie Rivulet. Sedimentation rates of approximately 10 mm yr−1 appeared to be typical of the western and southwestern portions of the lagoon. Rates of sediment accretion, prior to catchment clearing, urbanization, and industrialization have been estimated at less than 1 mm yr−1, thus indicating a general tenfold increase in sediment accumulation adjacent to the western foreshore caused by catchment development. Accelerated sedimentation in shallow coastal lagoons constitutes significant environmental impacts including shoaling, degradation of seagrass beds, and increased turbidity with consequent loss of aesthetic appeal. Management policy should be directed at attempts to reduce the amount of sediment input by the construction of strategically placed sediment retention ponds. Siltation within the shallow embayments of Lake Illawarra could be ameliorated by a carefully planned program of dredging.

Heavy metal concentrations in lagoonal saltmarsh species, Illawarra region, southeastern Australia

Abstract The importance of saltmarsh environments and their floral communities lies in their ability to act as a buffer between land and aquatic systems. Runoff from rural and urban areas, the generation of power and heavy industry all contribute pollutants to the Wollongong coastal Zone, where heavy metal contents in saltmarsh substrates are found to be up to 200 times greater than at localities on the south coast of NSW. The saltmarsh species Sarcocornia quinqueflora , Suaeda australis and Triglochin striata show enhanced levels of Cu, Zn, Pb, Cd, Cr and Mn in the Wollongong area relative to sites at Callala Bay and Burrill Lake. This trend reflects, but is much lower than, levels of these metals in the substrate. Cu, Zn and Pb are concentrated in the horizontal stems of Sarcocornia and the leaves of Suaeda , but both are lower than levels in Triglochin . The elevated Cu and Zn levels in plants at Bellambi Lagoon are probably derived from urban runoff as there is no current industrial source of pollution within the catchment. The type of pollutant affects the bioavailability of the heavy metals. Industrial airborne particulate pollutants generally require considerable acidic leaching before the metals become available to the biological community. These processes only occur to a limited extent in a natural ecosystem and hence account for low uptake of heavy metals by plants in the anoxic environment at Griffins Bay. Saltmarshes act as low energy coastal sediment traps and, together with the plants, effectively reduce the amount of bioavailable pollutants being transferred into the aquatic environment. Analysis of saltmarsh species can rapidly provide very important information about the bioavailability of metal pollutants in marginal marine environments and they have considerable potential as monitors of diverse sources of pollution.

The charophyte Lamprothamnium succinctum as an environmental indicator: a Holocene example from Tom Thumbs Lagoon, eastern Australia

The palaeobiota from a middle to late Holocene succession in Tom Thumbs Lagoon, N.S.W., Australia, reflects a range of environmental conditions caused by sea-level changes and active estuarine sedimentation. At the base of the succession (∼ −0.4 m AHD) a thin bed, containing molluscs dated at 6.7 ka B.P. by radiocarbon and amino acid racemisation, and foraminifers is indicative of open estuarine conditions. From +0.35 m AHD towards the top of the sequence the charophyte Lamprothamnium succinctum occurs in subrecent deposits. This species is characterised here by statistical measurements, and new characters are described and illustrated. The charophytes record a drop in sea level and the establishment of a lower salinity artificial wetland. The investigation has also established that decalcification in charophytes can be related to acidification produced by the release of organic acids, aggravated after 1928 by anthropogenic pollution.

Fractionation of sedimentary arsenic from Port Kembla Harbour, NSW, Australia.

The binding of arsenic in sediments of the heavily industrialised Port Kembla Harbour, NSW, Australia, has been investigated. Both dredge and core samples have been used to develop a sieving/sequential extraction (SE) procedure. Dredge samples included oxic surficial and deeper anoxic sediment. The main core sample analysed was 18 cm deep, sliced at 2 cm intervals. Sediment was sieved to three size ranges (<63 microm, 63-250 microm, >250 microm) and each of these was then subjected to a four step SE, sequentially solubilizing arsenic as ion exchangeable, 1 M HCl soluble, NH(2)OH.HCl soluble, and strong oxidising acid soluble. Concentrations of 50-500 mg As kg(-1) were found, elevated well above local background values. The core sample showed elevated concentrations of arsenic within the top 6-8 cm (300-500 mg As kg(-1)), relative to the deeper sediment (100-200 mg As kg(-1)). Substantial portions of the total arsenic present in the 0-8 cm sediments of core and dredge samples, were found to be soluble in 1 M pH 5 phosphate buffer or 1 M HCl. Arsenic in the lower 8-18 cm of the core displayed different solubility, the fourth stage SE strong acid digestion being required to solubilize >90% of the deep sediment arsenic. It appears that diagenesis had resulted in remobilisation of weakly bound arsenic with subsequent diffusion and deposition in surficial layers. Strong acid soluble arsenic present in deeper sediments has two possible origins: sedimented as strongly bound remaining untouched by diagenetic events, or subjected to diagenetic reactions such as pyritization, which lead to more stable crystalline forms of minerals.

Skarn development from limestone adjacent to the Glenrock Granodiorite, Marulan Batholith, New South Wales, Australia

Skarns are developed over two temperature‐time intervals in calcite limestone adjacent to the southern extension of the Glenrock Granodiorite, a pluton of the Marulan Batholith, Southern Highlands, New South Wales. The initial volumetrically‐dominant prograde phase of skarn formation produced a suite comprising bimetasomatic skarn, including pyroxene endoskarn, potassic endoskarn and wollastonite‐bearing exoskarn, together with mineralogically‐zoned vein skarn, massive garnet‐pyroxene skarn and calcite‐vesuvianite skarn. Retrograde replacement is manifested by the development of hydrous silicate minerals, carbonate and cross‐cutting sulphide veinlets. A genetic model is proposed to account for the development of bimetasomatic skarn in the deposit. Exoskarn geochemistry indicates addition of many components relative to an essentially pure limestone precursor, including Si, Al, Fe, Zr, Zn, S, Mn and Cu, negligible transfer of K, Na and Rb and loss of CO2. Strontium and Ca loss from the parent limestone is i...

Silurian evaporitic strata from New South Wales, Australia

Abstract During Silurian (Late Wenlockian to Ludlovian) time in the Cudgegong district, New South Wales, a minor regression is represented by local influx of clastic detritus and a brief period of subaerial exposure within a phase of carbonate deposition. Oolitic shoals, formed under shallow warm hypersaline marine conditions, became exposed on supratidal flats where minor dolomitization and gypsum crystallization took place. During diagenesis the gypsum was pseudomorphed by chlorite. Ooids and evaporite minerals have not been previously recorded from Silurian strata in eastern Australia but their occurrence at Cudgegong concurs with a palaeolatitude of approximately 5°N on the basis of geophysical data.

Contact metamorphism of pelitic, psammitic and calcareous sediments in the Southern Highlands of New South Wales

Contact metamorphism has been recognized along a 4 km wide belt adjacent to the shallow‐dipping eastern margin of the Arthursleigh Tonalite, an Early Devonian pluton of the Marulan Batholith, eastern New South Wales. In Ordovician psammitic and pelitic rocks three zones of progressive contact metamorphism range from muscovite + biotite + chlorite assemblages in the outer zone to K‐feldspar + cordierite assemblages adjacent to the pluton and in metasedimentary xenoliths. Retrograde phenomena include extensive replacement of metamorphic minerals by ‘sericite’ and chlorite. Calcareous metasediments adjacent to the tonalite typically contain assemblages of quartz + calcic plagioclase + ferrosalite + sphene, or wollastonite + calcite + diopside with minor grossularite and vesuvianite. Thermal effects in volcanic rocks along the western margin of the pluton are confined to recrystallization of the groundmass. The regional geology indicates confining pressures of approximately 1 kbar at the time of emplacement o...

Chemical variation of almandine and biotite with progressive regional metamorphism of the Willyama complex, broken hill, New South Wales

Abstract Almandines of pelitic schists produced during the Willyama Metamorphism are shown to have enhanced pyrope and diminished spessartite contents with increasing grade. It is suggested that chemical variation of almandine is related to biotite breakdown with increasing temperature of metamorphism and to the partly grade‐dependent partitioning relation Mn almandine >> Mn biotite which is encountered in all the almandine‐biotite pairs studied. Compositions of co‐existing almandine‐pairs are used to estimate Ph2o‐T conditions during metamorphism. These pairs are suggested to reflect a temperature range of about 200° and low water pressures relative to Ptotal. Statistical methods are employed to show that host‐rock chemistry has no apparent control over the chemistry of these almandines. Estimates of oxygen fugacity, derived from host rock ferric/ferrous ratios, suggest that oxygen fugacity is unlikely to exert significant control over almandine composition.