Bradley O. Clarke

Assimilation of Polybrominated Diphenyl Ethers from Microplastics by the Marine Amphipod, Allorchestes Compressa

Microplastic particles (MPPs; <5 mm) are found in skin cleansing soaps and are released into the environment via the sewage system. MPPs in the environment can sorb persistent organic pollutants (POPs) that can potentially be assimilated by organisms mistaking MPPs for food. Amphipods (Allorchestes compressa) exposed to MPPs isolated from a commercial facial cleansing soap ingested ≤45 particles per animal and evacuated them within 36 h. Amphipods were exposed to polybrominated diphenyl ether (PBDEs) congeners (BDE-28, -47, -99, -100, -153, -154, and -183) in the presence or absence of MPPs. This study has demonstrated that PBDEs derived from MPPs can be assimilated into the tissue of a marine amphipod. MPPs reduced PBDE uptake compared to controls, but they caused greater proportional uptake of higher-brominated congeners such as BDE-154 and -153 compared to BDE-28 and -47. While MPPs in the environment may lower PBDE uptake compared to unabsorbed free chemicals, our study has demonstrated they can transfer PBDEs into a marine organism. Therefore, MPPs pose a risk of contaminating aquatic food chains with the potential for increasing public exposure through dietary sources. This study has demonstrated that MPPs can act as a vector for the assimilation of POPs into marine organisms.

Polybrominated diphenyl ethers and polybrominated biphenyls in Australian sewage sludge

This paper presents a brief review of the international scientific literature of polybrominated diphenyl ethers (PBDEs) and polybrominated biphenyls (PBBs) in sewage sludge and a survey of these compounds in sewage sludge from 16 Australian wastewater treatment plants (WWTPs). The SigmaPBDE mean concentration in the Australian study was 1137microgkg(-1) dry weight (d.w.) (s.d. 1116) and ranged between 5 and 4 230microgkg(-1)d.w. The urban mean of 1308microgkg(-1) (s.d. 1320) and the rural mean of 911microgkg(-1) (s.d. 831) are not statistically different and are similar to levels in European sludges. Principal components analysis was performed on the data set and revealed that 76% of the data variation could be explained by two components that corresponded to overall concentration of the pentaBDE and the decaBDE commercial formulations. An analysis of variance was performed comparing PBDEs levels at three WWTPs over the years 2005 and 2006, finding differences between treatment plants (BDE-47) but no significant difference in PBDE levels in the years 2005 and 2006. Low levels of BB-153 were detected in all samples of this survey (n=16); mean 0.6microgkg(-1)d.w. (s.d. 0.5). This compound has rarely been reported in any other study of sewage sludges undertaken outside Australia. This work highlights the need for a risk assessment of PBDEs in sewage sludge when used for land application, taking into account typical levels found in Australian sludges and soils.

Chemical Pollutants Sorbed to Ingested Microbeads from Personal Care Products Accumulate in Fish

The prevalence of microplastics (<5 mm) in natural environments has become a widely recognized global problem. Microplastics have been shown to sorb chemical pollutants from their surrounding environment, thus raising concern as to their role in the movement of these pollutants through the food chain. This experiment investigated whether organic pollutants sorbed to microbeads (MBs) from personal care products were assimilated by fish following particle ingestion. Rainbow fish (Melanotaenia fluviatilis) were exposed to MBs with sorbed polybrominated diphenyl ethers (PBDEs; BDE-28, -47, -100, -99, -153, -154, -183, 200 ng g(-1); BDE-209, 2000 ng g(-1)) and sampled at 0, 21, 42, and 63 days along with two control treatments (food only and food + clean MBs). Exposed fish had significantly higher Σ8PBDE concentrations than both control treatments after just 21 days, and continued exposure resulted in increased accumulation of the pollutants over the experiment (ca. 115 pg g(-1) ww d(-1)). Lower brominated congeners showed the highest assimilation whereas higher brominated congeners did not appear to transfer, indicating they may be too strongly sorbed to the plastic or unable to be assimilated by the fish due to large molecular size or other factors. Seemingly against this trend, however, BDE-99 did not appear to bioaccumulate in the fish, which may be due to partitioning from the MBs or it being metabolized in vivo. This work provides evidence that MBs from personal care products are capable of transferring sorbed pollutants to fish that ingest them.

Investigating the distribution of polybrominated diphenyl ethers through an Australian wastewater treatment plant.

The aim of this study was to quantify the amount of polybrominated diphenyl ethers (PBDEs) released into the environment (biosolids, effluent) from a conventional Australian activated sludge treatment wastewater treatment plant (WWTP). The concentration of PBDE congeners was measured at various treatment stages and included four aqueous samples (raw, primary, secondary and tertiary effluents) and three sludges (primary, secondary and lime stabilized biosolids), collected at three sampling events over the course of the experiment (29 days). Semi-permeable membrane devices (SPMDs) were also installed for the duration of the experiment, the first time that SPMDs have been used to measure PBDEs in a WWTP. Over 99% of the PBDEs entering the WWTP were removed through the treatment processes, principally by sedimentation. The main congeners detected were BDE 47, 99 and 209, which are characteristic of the two major commercial formulations viz penta-BDE and deca-BDE. All the PBDE congeners measured were highly correlated with each other, suggesting a similar origin. In this case, the PBDEs are thought to be from domestic sources since domestic wastewater is the main contribution to the in-flow (approximately 95%). The mean concentration of SigmaPBDEs in chemically stabilized sewage sludge (biosolids) was 300microg kg(-1) dry weight. It is calculated that 2.3+/-0.3kg of PBDEs are disposed of each year with biosolids generated from the WWTP. If all Australian sewage sludge is contaminated to at least this concentration then at least 110kg of PBDEs are associated with Australian sewage sludge annually. Less than 10g are released annually into the environment via ocean outfall and field irrigation; this level of contamination is unlikely to pose risk to humans or the environment. The environmental release of treated effluent and biosolids is not considered a large source of PBDE environmental emissions compared to the quantities used annually in Australia.

A critical review of nitrogen mineralization in biosolids-amended soil, the associated fertilizer value for crop production and potential for emissions to the environment.

International controls for biosolids application to agricultural land ensure the protection of human health and the environment, that it is performed in accordance with good agricultural practice and that nitrogen (N) inputs do not exceed crop requirements. Data from the scientific literature on the total, mineral and mineralizable N contents of biosolids applied to agricultural land under a wide range of climatic and experimental conditions were collated. The mean concentrations of total N (TN) in the dry solids (DS) of different biosolids types ranged from 1.5% (air-dried lime-treated (LT) biosolids) to 7.5% (liquid mesophilic anaerobic digestion (LMAD) biosolids). The overall mean values of mineralizable N, as a proportion of the organic N content, were 47% for aerobic digestion (AeD) biosolids, 40% for thermally dried (TD) biosolids, 34% for LT biosolids, 30% for mesophilic anaerobic digestion (MAD) biosolids, and 7% for composted (Com) biosolids. Biosolids air-dried or stored for extended periods had smaller total and mineralizable N values compared to mechanically dewatered types. For example, for biosolids treated by MAD, the mean TN (% DS) and mineralizable N (% organic N) contents of air-dried materials were 3% and 20%, respectively, compared to 5% and 30% with mechanical dewatering. Thus, mineralizable N declined with the extent of biological stabilization during sewage sludge treatment; nevertheless, overall plant available N (PAN=readily available inorganic N plus mineralizable N) was broadly consistent across several major biosolids categories within climatic regions. However, mineralizable N often varied significantly between climatic regions for similar biosolids types, influencing the overall PAN. This may be partly attributed to the increased rate, and also the greater extent of soil microbial mineralization of more stable, residual organic N fractions in biosolids applied to soil in warmer climatic zones, which also raised the overall PAN, compared to cooler temperate areas. It is also probably influenced by differences in upstream wastewater treatment processes that affect the balance of primary and secondary, biological sludges in the final combined sludge output from wastewater treatment, as well as the relative effectiveness of sludge stabilization treatments at specific sites. Better characterization of biosolids used in N release and mineralization investigations is therefore necessary to improve comparison of system conditions. Furthermore, the review suggested that some international fertilizer recommendations may underestimate mineralizable N in biosolids, and the N fertilizer value. Consequently, greater inputs of supplementary mineral fertilizer N may be supplied than are required for crop production, potentially increasing the risk of fertilizer N emissions to the environment. Thus greater economic and environmental savings in mineral N fertilizer application are potentially possible than are currently realized from biosolids recycling programmes.

Investigating the levels and trends of organochlorine pesticides and polychlorinated biphenyl in sewage sludge.

A study was completed to investigate temporal trends of organochlorine pesticides (OCPs; aldrin, chlordane, dieldrin, heptachlor, hexachlorbenzene, and DDT) and polychlorinated biphenyls (PCBs) in sewage sludge. Between 2004 and 2006 the concentration of OCPs and PCBs in Australian sewage sludge (n=829) was consistently <1000mugkg(-1) dry solids DS. Dieldrin, chlordane and DDE were detected in 68%, 27% and 13% at maximum concentrations of 770, 290 and 270 microgkg(-1) DS, respectively. Time series analysis (1995-2006) of OCPs and PCBs sewage sludge concentrations (n=2266) taken from six wastewater treatment plants (WWTPs) of the same geographic region found that lindane, aldrin HCB, heptachlor, DDT, DDD and PCBs were infrequently detected (<8%). A correlation between dieldrin and chlordane levels was found (P<0.05) which provides evidence of similar environmental mechanisms facilitating movement of dieldrin and chlordane through environment compartments. It has taken more than 10years for dieldrin and chlordane to reduce to less than detectable concentrations in freshly generated sewage sludge in Australia following government restrictions. Internationally, reported sewage sludge OCP concentrations were consistently low and often less than detection limits. Therefore, OCPs are not considered to be a contaminant of regulatory concern for countries that phased out OCP use several decades ago. Concentrations of PCBs in sewage sludge were also consistently low and rarely exceeded European contaminant limits and therefore, regulatory limits may warrant review. The authors recommend that Australian authorities revise regulatory requirements for OCP and PCBs contaminant levels in sewage sludge destined for beneficial reuse as biosolids.

A review of analytical techniques for quantifying microplastics in sediments

In this review the analytical techniques for measuring microplastics in sediment have been evaluated. Four primary areas of the analytical process have been identified that include (1) sampling, (2) extraction, (3) quantitation and (4) quality assurance/quality control (QAQC). Each of those sections have their own subject specific challenges and require further method development and harmonisation. The most common approach to extracting microplastics from sediments is density separation. Following extraction, visual counting with an optical microscope is the most common technique for quantifying microplastics; a technique that is labour intensive and prone to human error. Spectroscopy (FTIR; Raman) are the most commonly applied techniques for identifying polymers collected through visual sorting. Improvements and harmonisation on size fractions, sampling approaches, extraction protocols and units for reporting plastic abundance would aid comparison of data generated by different research teams. Further, we advocate the development of strong QAQC procedures to be adopted like other fields of analytical chemistry. Finally, inter-laboratory proficiency testing is recommended to give an indication of the variation and reliability in measurements reported in the scientific literature that may be under- or overestimations of environmental burdens.

Critical review of soil contamination by polybrominated diphenyl ethers (PBDEs) and novel brominated flame retardants (NBFRs); concentrations, sources and congener profiles

Polybrominated diphenyl ethers (PBDEs) have been used in a broad array of polymeric materials such as plastics, foams, resins and adhesives to inhibit the spread of fires since the 1970s. The widespread environmental contamination and well documented toxic effects of PBDEs have led to bans and voluntary withdrawals in many jurisdictions. Replacement novel brominated flame retardants (NBFRs) have, however, exhibited many of the same toxic characteristics as PBDEs and appear to share similar environmental fate. This paper presents a critical review of the scientific literature regarding PBDE and NBFR contamination of surface soils internationally, with the secondary objective of identifying probable pollution sources. An evaluation of NBFR distribution in soil was also conducted to assess the suitability of the newer compounds as replacements for PBDEs, with respect to their land contamination potential. Principle production of PBDEs and NBFRs and their consequent use in secondary polymer manufacture appear to be processes with strong potential to contaminate surrounding soils. Evidence suggests that PBDEs and NBFRs are also released from flame retarded products during disposal via landfill, dumping, incineration and recycling. While the land application of sewage sludge represents another major pathway of soil contamination it is not considered in this review as it is extensively covered elsewhere. Both PBDEs and NBFRs were commonly detected at background locations including Antarctica and northern polar regions. PBDE congener profiles in soil were broadly representative of the major constituents in Penta-, Octa- and Deca-BDE commercial mixtures and related to predicted market place demand. BDE-209 dominated soil profiles, followed by BDE-99 and BDE-47. Although further research is required to gain baseline data on NBFRs in soil, the current state of scientific literature suggests that NBFRs pose a similar risk to land contamination as PBDEs.

Assessment of ambient background concentrations of elements in soil using combined survey and open-source data

Understanding ambient background concentrations in soil, at a local scale, is an essential part of environmental risk assessment. Where high resolution geochemical soil surveys have not been undertaken, soil data from alternative sources, such as environmental site assessment reports, can be used to support an understanding of ambient background conditions. Concentrations of metals/metalloids (As, Mn, Ni, Pb and Zn) were extracted from open-source environmental site assessment reports, for soils derived from the Newer Volcanics basalt, of Melbourne, Victoria, Australia. A manual screening method was applied to remove samples that were indicated to be contaminated by point sources and hence not representative of ambient background conditions. The manual screening approach was validated by comparison to data from a targeted background soil survey. Statistical methods for exclusion of contaminated samples from background soil datasets were compared to the manual screening method. The statistical methods tested included the Median plus Two Median Absolute Deviations, the upper whisker of a normal and log transformed Tukey boxplot, the point of inflection on a cumulative frequency plot and the 95th percentile. We have demonstrated that where anomalous sample results cannot be screened using site information, the Median plus Two Median Absolute Deviations is a conservative method for derivation of ambient background upper concentration limits (i.e. expected maximums). The upper whisker of a boxplot and the point of inflection on a cumulative frequency plot, were also considered adequate methods for deriving ambient background upper concentration limits, where the percentage of contaminated samples is <25%. Median ambient background concentrations of metals/metalloids in the Newer Volcanic soils of Melbourne were comparable to ambient background concentrations in Europe and the United States, except for Ni, which was naturally enriched in the basalt-derived soils of Melbourne.

Selective pressurized liquid extraction of replacement and legacy brominated flame retardants from soil.

Polybrominated diphenyl ethers (PBDEs) are a class of flame retardant registered as UN POPs due to their persistence in the environment, bioaccumulation potential and toxicity. Replacement novel brominated flame retardants (NBFRs) have exhibited similar health hazards and environmental distribution, becoming recognized as significant contaminants. This work describes the development and validation of a sensitive and reliable method for the simultaneous quantitation of PBDEs and NBFRs in environmental soil samples using selective pressurized liquid extraction (S-PLE) and gas chromatography coupled to triple quadrupole mass spectrometry (GC-(EI)-MS/MS). Under optimal conditions, extraction of eight PBDEs (-28, -47, -99, -100, -153, -154, -183 and -209) and five NBFRs; pentabromotoluene (PBT), pentabromoethylbenzene (PBEB), hexabromobenzene (HBB), 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (EH-TBB) and bis(2,4,6-tribromophenoxy)ethane (BTBPE) was performed at 100°C and 1500psi using a 1:1 mixture of hexane and dichloromethane. The method utilized 33mL capacity PLE cells containing, from bottom to top, a single cellulose filter, 3g activated Florisil, 6g acid silica (10% w/w), 3g Na2SO4, another cellulose filter, 2g activated copper powder and 3g soil sample dispersed in 2g Na2SO4 and 1g of Hydromatrix. The method was evaluated by repeated extraction and analysis of all analytes from 3g soil at three spike concentrations. Good recoveries were observed for most analytes at each of the spiking levels with RSD values generally below 20%. MDLs ranged from 0.01 to 4.8ng/g dw for PBDEs and 0.01-0.55ng/g dw for NBFRs. The described one-step combined extraction and cleanup method reduces sample processing times compared with traditional procedures, while delivering comparable analytical performance. The method was successfully applied to environmental soil samples (n=5), detecting PBDEs in each sample and providing the first account of NBFR contamination in Australian soils.