Darryl William Hawker

Metal Accumulation in Aquatic Macrophytes from Southeast Queensland, Australia

To determine the extent of metal accumulation in some aquatic macrophytes from contaminated urban streams in southeast Queensland, plants were sampled from six sites, along with contiguous sediments. In all, 15 different species were collected, the most common genera being Typha (Cattails or Bulrushes) and Persicaria (Knotweeds). Before heavy metal analysis, plants were further separated into various morphological tissues, and five selected samples were separated into various physiological tissues. The cadmium, copper, lead and zinc content of the plants were analysed using flames AAS. In general, plant roots exhibited higher metal concentrations than the contiguous sediments. Of the metals of interest, only for zinc was there a relatively clear pattern of increasing accumulation in aquatic macrophytes with increasing sediment metal concentrations. Comparison between morphological tissues of the sampled plants found that roots consistently presented higher metal concentrations than either the stems or leaves, however unlike previous studies, this investigation revealed no consistent trend of stems accumulating more metals than the leaves. For Typha spp., metal concentrations followed the order of roots > rhizomes > leaves, while for Persicaria spp. the order was roots > leaves > stems. The submerged species Myriophyllum aquaticum accumulated the highest levels of metals overall (e.g. Zn 4300 micrograms g-1 dry weight and Cd 6.5 micrograms g-1), and the emergent macrophytes also exhibited relatively high metal contents in their roots. The leaves of the submerged and floating-leafed species collected contained relatively high quantities of the four metals of interest, compared with the leaves of emergent aquatic macrophytes. In the Typha rhizome and Persicaria stem samples analysed for internal variation in metal content, there was a pattern of increasing metal concentrations towards the external sections of the stem, both for subterranean stems (rhizomes) and above-substrate stems. For Persicaria stems, no clear pattern was observed for cadmium and lead, the two metals investigated that are not required by plants for survival.

Use of polynomial expressions to describe the bioconcentration of hydrophobic chemicals by fish

For the bioconcentration of hydrophobic chemicals by fish, relationships have been previously established between uptake rate constants (k1) and the octanol/water partition coefficient (Kow), and also between the clearance rate constant (k2) and Kow. These have been refined and extended on the basis of data for chlorinated hydrocarbons, and closely related compounds including polychlorinated dibenzodioxins, that covered a wider range of hydrophobicity (2.5 less than log Kow less than 9.5). This has allowed the development of new relationships between log Kow and various factors, including the bioconcentration factor (as log KB), equilibrium time (as log teq), and maximum biotic concentration (as log CB), which include extremely hydrophobic compounds previously not taken into account. The shape of the curves generated by these equations are in qualitative agreement with theoretical prediction and are described by polynomial expressions which are generally approximately linear over the more limited range of log Kow values used to develop previous relationships. The influences of factors such as hydrophobicity, aqueous solubility, molecular weight, lipid solubility, and also exposure time were considered. Decreasing lipid solubilities of extremely hydrophobic chemicals were found to result in increasing clearance rate constants, as well decreasing equilibrium times and bioconcentration factors.

Polycyclic aromatic hydrocarbons in air, soil and vegetation in the vicinity of an urban roadway

The polycyclic aromatic hydrocarbon (PAH) content of air particulate matter, surface soil and grass in the vicinity of an urban roadway was measured using gas chromatography. All fourteen PAHs analyzed for were found in soil and, except for dibenz[a,h]anthracene, were also detected in air particulate matter. Only phenanthrene, anthracene, fluoranthene and pyrene were detected in grass. Motor vehicle exhaust was the dominant source of PAHs in air particulate matter and soil. The soil concentrations of PAHs decrease with increasing distance from the road, although significant concentrations were present at a distanc of 15m. PAHs with three or four rings existed in both particulate and vapour forms in the atmosphere, which probably contributed to their relatively wide distribution. On the other hand, the PAHs with more than four rings were deposited close to the roadway due to their predominant particulate form.

Bioconcentration of lipophilic compounds by some aquatic organisms.

With nondegradable, lipophilic compounds having log P values ranging from 2 to 6, direct linear relationships have been found between the logarithms of the equilibrium bioconcentration factors, and also reciprocal clearance rate constants, with log P for daphnids and molluscs. These relationships permit calculation of the times required for equilibrium and significant bioconcentration of lipophilic chemicals. Compared with fish, these time periods are successively shorter for molluscs, then daphnids. The equilibrium biotic concentration was found to decrease with increasing chemical hydrophobicity for both molluscs and daphnids. Also, new linear relationships between the logarithm of the bioconcentration factor and log P were found for compounds not attaining equilibrium within finite exposure times.

Relationships between partition coefficient, uptake rate constant, clearance rate constant and time to equilibrium for bioaccumulation

Abstract Theoretical derivations together with published experimental data on bioaccumulation of lipophilic compounds by certain groups of fish indicates that the uptake and clearance rate constants have a fixed relationship to the octanol to water partition coefficient over the partition coefficient range 10 2.5 to 10 6 . This allows the calculation of times to establish effective equilibrium, and significant bioaccumulation of compounds in relation to the partition coefficient. By extrapolation superlipophilic compounds (partition coefficients > 10 6 ) have been shown to require a minimum period of 0.5 years increasing to 10 years when P = 10 8 to establish effective equilibrium and compounds with partition coefficients >10 13 are not bioaccumulated to any significant extent. In practice then, a direct relationship between the bioaccumulation factor and the partition coefficient will not result with superlipophilic componds.

DISTRIBUTION OF VEHICULAR LEAD IN ROADSIDE SOILS OF MAJOR ROADS OF BRISBANE, AUSTRALIA

Collections were made from three sites in the urbanarea of Brisbane, Australia. At each site, soilsamples were collected from transects parallel andperpendicular to the roadway, as well as a depthprofile. Total lead was determined by refluxing thesamples with concentrated nitric acid (1 h) andorganic lead by shaking with cold ammoniacal methanol(Flameless AAS). Both chloride and bromide anionswere obtained from an aqueous extract (HPLC). Resultsshowed that vehicular emissions were the major sourceof lead in the roadside soils of this study. At siteslocated in relatively enclosed areas of higheratmospheric stability, both lead and bromide contentsdecreased markedly with increasing distance from theroadway. However, in the absence of such atmosphericstability, the distribution of both lead and bromidecontents revealed different patterns which wasattributed mainly to the effect of meteorologicalfactors such as wind direction and speed. The depthprofile of roadside soils generally showed leadaccumulation within the uppermost 5 cm, whereaselevated concentrations of bromide were observed at greater depth.

Accumulation of oxytetracycline and norfloxacin from saline soil by soybeans

Soil of former shrimp aquaculture facilities in Thailand may be contaminated by antibiotics (e.g. oxytetracycline and norfloxacin) and have elevated salinity. Therefore, reuse of this land can be problematic. The utility of soybean (Glycine max (L.) Merr.) for phytoremediation was investigated. The rate of germination and seedling emergence in prepared contaminated soil (conductivity 17.7 dS m(-1) from adding 70 mg sodium chloride g(-1) dry weight, 105 mg kg(-1) dry weight oxytetracycline and 55 mg kg(-1) dry weight norfloxacin) in sunlight was approximately 80% that of uncontaminated soil. This reduction was largely due to the high salinity. The antibiotics of interest degraded relatively rapidly in soil (half-life <10h for both) but loss was slower in deionised water. Accumulation of the antibiotics from deionised water by soybean resulted in little effect on growth rate and maximum levels in plants were observed after two days exposure, followed by declining concentrations. For soybean plants grown in saline soil, 90% removal of NaCl from soil adjacent to plant roots was observed, most within two days. Wilting and defoliation occurred, but plants recovered after 10 days and maximum salt levels in plants exceeded 20,000 mg g(-1) dry weight with translocation from root to shoot tissue noted. Soybean plants also accumulated the antibiotics from prepared contaminated saline soil, but translocation from the roots was not observed. The results showed that soybean can be valuable for phytoremediation in these situations.

Polycyclic aromatic hydrocarbons in the atmospheric environment of Brisbane, Australia

Atmospheric concentrations of PAHs were determined in air samples collected at various sites in Brisbane, Australia. Results for a given air sample are presented as the sum of the vapour and particle associated fraction of the compounds. PAH concentrations were highest at sites located in the vicinity of major roads. At a site located adjacent to a major road with a high frequency of heavy vehicle traffic, levels of B(a)P exceeded 1 ng m−3 air. Overall, traffic was found to be the dominant source for PAHs in Brisbane air. The results further indicated the existence of seasonal variations with highest levels in winter. The use of PAH profiles and ratios for identifying sources and processes is discussed.

Influence of solubility in lipid on bioconcentration of hydrophobic compounds

Superhydrophobic compounds (log K(ow) greater than 6) do not bioconcentrate as much as predicted from the extrapolation of linear relationships between the logarithms of the bioconcentration factor (KB) and the octan-1-ol/water partition coefficient (K(ow)) developed for compounds with log K(ow) from 2 to 6. Statistical analysis of the literature data on solubility in lipid for 79 hydrophobic compounds demonstrated a decrease in lipid solubility with increasing K(ow) values for superhydrophobic compounds. A similar, but more significant, relationship was obtained for the chlorinated hydrocarbons which closely corresponded with effectively the same relationship derived from fish bioconcentration data. As a result it is suggested that an important factor contributing to the lower than expected bioconcentration exhibited by superhydrophobic compounds is their relatively low solubility in lipid not reflected by the K(ow) value. It is suggested that lipid/water partition coefficients would provide more accurate descriptors of the bioconcentration process.

Factors Controlling the Geochemical Partitioning of Trace Metals in Estuarine Sediments

The geochemical partitioning of trace metals in sediments is of great importance in risk assessment and remedial investigation. Selected factors that may control the partitioning behavior of Cu, Pb and Zn in non-sulfidic, estuarine sediments were examined with the use of combined sorption curve—sequential extraction analysis. This approach, which has not been previously used to examine estuarine sediments, allowed determination of sorption parameters for Cu, Pb and Zn partitioning to individual geochemical fractions. Partitioning behavior in sulfidic sediments was also determined by sequentially extracting Cu, Pb, and Zn from synthetic sulfide minerals and from natural sediment and pure quartz sand after spiking with acid-volatile sulfide (AVS). Trace metal sorption to the “carbonate” fraction (pH 5, NaOAc extraction) increased with metal loading due to saturation of sorption sites associated with the “Fe-oxide” (NH2OH·HCl extraction) and “organic” (H2O2 extraction) fractions in non-sulfidic sediments. Freundlich parameters describing sorption to the “Fe-oxide” and “organic” fractions were controlled by the sediment Fe-oxide and organic carbon content, respectively. Sequential extraction of Cu from pure CuS, AVS-spiked sediment and AVS-spiked quartz sand showed that AVS-bound Cu was quantitatively recovered in association with the “organic” fraction. However, some AVS-bound Pb and Zn were recovered by the NH2OH·HCl step (which has been previously interpreted as “Fe-oxide” bound metals) in the sequential extraction procedure used in this study. This indicates that the sequential extraction of Pb and Zn in sulfidic sediments may lead to AVS-bound metals being mistaken as Fe-oxide bound species. Caution should therefore be exercised when interpreting sequential extraction results for Pb and Zn in anoxic sediments.