Evaluation of passive sampling polymers and nonequilibrium adjustment methods in a multiyear surveillance of sediment porewater PCBs.

Polymeric passive sampling devices are increasingly used to measure low-level, freely dissolved concentrations of hydrophobic organic contaminants in environmental waters. A range of polymers have been used for this purpose, and several different methods of accounting for nonequilibrium using performance reference compounds (PRCs) have been proposed. The present study explores the practical impacts of these decisions in an applied context using results from a multiyear passive sampling surveillance of polychlorinated biphenyl concentrations in sediment porewater at a contaminated marsh amended with activated carbon (AC) sorbent materials. In a series of 5 sampling events spanning almost 2 yr, we deployed polyoxymethylene and polyethylene samplers and calculated porewater concentrations with 5 different PRC adjustment methods. The results provide a basis for evaluating amendment performance by showing reductions of 34 to 97% in amended sediment porewater concentrations. They also provide a quantitative underpinning for discussions of the differences between sampling polymers, selection of PRCs, generation of high-resolution vertical profiles of porewater concentrations, and a comparison of PRC adjustment methods. For unamended sediment, older methods based on first-order kinetics agreed well with a recently developed method based on diffusion into and out of sediment beds. However, the sediment diffusion method did not work well for the sediments amended with AC. Environ Toxicol Chem 2018;37:2487-2495. © 2018 SETAC.

Persistent reductions in the bioavailability of PCBs at a tidally inundated Phragmites australis marsh amended with activated carbon.

In situ amendment of sediments with highly sorbent materials like activated carbon (AC) is an increasingly viable strategy to reduce the bioavailability of persistent, sediment-associated contaminants to benthic communities. Because in situ sediment remediation is an emerging strategy, much remains to be learned about the field conditions under which amendments can be effective, the resilience of amendment materials toward extreme weather conditions, and the optimal design of engineered applications. We report the results of a multiyear, pilot-scale field investigation designed to measure the persistence and efficacy of AC amendments to reduce the bioavailability of polychlorinated biphenyls (PCBs) in an intertidal Phragmites marsh. The amendments tested were granular AC (GAC), GAC with a layer of sand, and a pelletized fine AC. Key metrics presented include vertically resolved black carbon concentrations in sediment and PCB concentrations in sediment, porewater, and several invertebrate species. The results demonstrate that all 3 amendments withstood Hurricane Sandy and remained in place for the duration of the study, successfully reducing porewater PCB concentrations by 34 to 97%. Reductions in invertebrate bioaccumulation were observed in all amendment scenarios, with pelletized fine AC producing the most pronounced effect. The present findings support the use of engineered AC amendments in intertidal marshes and can be used to inform amendment design, delivery, and monitoring at other contaminated sediment sites. Environ Toxicol Chem 2018;37:2496-2505. © 2018 SETAC.

Polybrominated diphenyl ethers: Residence time in soils receiving biosolids application.

Polybrominated diphenyl ethers (PBDEs) may enter the environment because of accumulation in biosolids followed by application to agricultural lands. No published dissipation studies are available for PBDEs in agricultural soils after biosolids application. Therefore, we conducted a 3-year study to examine the fate of PBDEs in a small-scale 0.24-ha continuously cropped field after a single biosolids application at 72.3 wet tons/ha and determined dissipation half-lives for BDE-47+BDE-99 and BDE-209. In addition, we conducted a large-scale survey of soils from 26 mostly pasture fields at 10 farms with detailed information on timing and rate of biosolids applications. In the small-scale experiment, maximum soil PBDE concentrations of 43.7 ± 42.7 µg kg-1 d.w. for BDE-209 and 6.05 ± 7.15 µg kg-1 d.w. for BDE-47+BDE-99 were reached 1 year after application. We hypothesized that PBDEs were slowly released from the biosolids matrix into the soil over the first year. After 3 years, median BDE-47+BDE-99 concentrations were approximately equal to preapplication levels, whereas median BDE-209 concentrations remained ∼129% above preapplication levels. The estimated residence time from the small-scale experiment was 342 d for BDE-47+BDE-99 and 861 d for BDE-209. In the large-scale study, a subset of fields that received a single biosolids application was used to generate another estimate of residence time: 704 d for BDE-47+BDE-99 and 1440 d for BDE-209. These longer residence time estimates were used in three different first-order decay dissipation scenarios (continuous, limited, and no dissipation) to predict PBDE concentration in fields with single and multiple biosolids applications. Results indicate that dissipation occurs primarily in the first 2 years after application, but residues remaining in the soil after this period are likely to be much more tightly bound and less available for degradation.

Organic amendments for risk mitigation of organochlorine pesticide residues in old orchard soils.

Performance of compost and biochar amendments for in situ risk mitigation of aged DDT, DDE and dieldrin residues in an old orchard soil was examined. The change in bioavailability of pesticide residues to Lumbricus terrestris L. relative to the unamended control soil was assessed using 4-L soil microcosms with and without plant cover in a 48-day experiment. The use of aged dairy manure compost and biosolids compost was found to be effective, especially in the planted treatments, at lowering the bioavailability factor (BAF) by 18-39%; however, BAF results for DDT in the unplanted soil treatments were unaffected or increased. The pine chip biochar utilized in this experiment was ineffective at lower the BAF of pesticides in the soil. The US EPA Soil Screening Level approach was used with our measured values. Addition of 10% of the aged dairy manure compost reduced the average hazard quotient values to below 1.0 for DDT + DDE and dieldrin. Results indicate this sustainable approach is appropriate to minimize risks to wildlife in areas of marginal organochlorine pesticide contamination. Application of this remediation approach has potential for use internationally in areas where historical pesticide contamination of soils remains a threat to wildlife populations.

Long-term trends of PBDEs, triclosan, and triclocarban in biosolids from a wastewater treatment plant in the Mid-Atlantic region of the US.

In the US, land application of biosolids has been utilized in government-regulated programs to recycle valuable nutrients and organic carbon that would otherwise be incinerated or buried in landfills. While many benefits have been reported, there are concerns that these practices represent a source of organic micropollutants to the environment. In this study, biosolids samples from a wastewater treatment plant in the Mid-Atlantic region of the US were collected approximately every 2 months over a 7-year period and analyzed for brominated diphenyl ethers (BDE-47, BDE-99, and BDE-209), triclosan, and triclocarban. During the collection period of 2005-2011, concentrations of the brominated diphenyl ethers BDE-47+BDE-99 decreased by 42%, triclocarban decreased by 47%, but BDE-209 and triclosan remained fairly constant. Observed reductions in contaminant concentrations could not be explained by different seasons or by volumetric changes of wastewaters arriving at the treatment plant and instead may be the result of the recent phaseout of BDE-47 and BDE-99 as well as potential reductions in the use of triclocarban.

Fate of microconstituents in biosolids composted in an aerated silage bag.

Although most composting studies report pathogen concentrations, little is known about the fate of Endocrine Disruptor Chemicals (EDCs) during composting. In this study, a positively aerated polyethylene bag composting system was filled with a mixture of woodchips and limed biosolids from a large Waste Water Treatment Plant (WWTP) to study the removal efficiency of two different groups of EDCs. Two antibacterial compounds, Triclocarban (TCC) and Triclosan (TCS), and a TCS byproduct, Methyltriclosan (MeTCS), as well as seven congeners of flame retardants known as PBDEs (Polybrominated Diphenyl Ethers) were studied during two phases of composting: 1) a thermophilic phase, in which positive mechanical aeration, pushing air into and through the materials matrix, was conducted for 2 months; and 2) a curing and stabilization phase in which no mechanical aeration was provided and the bag was opened to ambient passive aeration to simulate storage conditions for seven months. Our results showed that while TCC concentrations remained constant, TCS degradation took place during both phases. The degradation of TCS was corroborated by the formation of MeTCS in both phases. The TCS concentrations decreased from 18409 ± 1,877 to 11955 ± 288 ng g(-1) dry wt. during the thermophilic phase and declined from 11,955 ± 288 to 7,244 ± 909. ng g(-1) dry wt. by the end of the curing phase. Thus, slightly greater TCS transformation occurred during the second than during the first (35.1 vs. 39.4%). MeTCS concentrations increased from 189.3 ± 8.6 to 364.6 ± 72.5 ng g(-1) dry wt. during the first phase and reached 589.0 ± 94.9 ng g(-1) dry wt. at the end of the second phase. PBDEs concentrations were below quantification limits for all but two of the congeners analyzed (BDE-47 and BDE-99). PBDE concentrations were measured at the end of the first phase only and were comparable to initial concentrations.

Utilizing thin-film solid-phase extraction to assess the effect of organic carbon amendments on the bioavailability of DDT and dieldrin to earthworms.

Improved approaches are needed to assess bioavailability of hydrophobic organic compounds in contaminated soils. Performance of thin-film solid-phase extraction (TF-SPE) using vials coated with ethylene vinyl acetate was compared to earthworm bioassay (Lumbricus terrestris). A DDT and dieldrin contaminated soil was amended with four organic carbon materials to assess the change in bioavailability. Addition of organic carbon significantly lowered bioavailability for all compounds except for 4,4'-DDT. Equilibrium concentrations of compounds in the polymer were correlated with uptake by earthworms after 48d exposure (R(2) = 0.97; p < 0.001), indicating TF-SPE provided an accurate uptake simulation. Bioavailability of residues in soil was compared with a spiked soil aged for 90d in laboratory. Dieldrin and DDX were respectively 18% and 11% less bioavailable in contaminated soil relative to spiked soil despite >40yr of aging. Results show that TF-SPE can be useful in examining potential risks associated with contaminated soils and to test effectiveness of remediation efforts.

Persistence of polybrominated diphenyl ethers in agricultural soils after biosolids applications.

This study examines polybrominated diphenyl ethers (PBDE) levels, trends in biosolids from a wastewater treatment plant, and evaluates potential factors governing PBDE concentrations and the fate in agricultural soils fertilized by biosolids. The mean concentration of the most abundant PBDE congeners in biosolids ( summation operatorBDE-47, BDE-99, and BDE-209) generated by one wastewater treatment plant was 1250 +/- 134 microg/kg d.w. with no significant change in concentration over 32 months (n = 15). In surface soil samples from the Mid-Atlantic region, average PBDE concentrations in soil from fields receiving no biosolids (5.01 +/- 3.01 microg/kg d.w.) were 3 times lower than fields receiving one application (15.2 +/- 10.2 microg/kg d.w.) and 10 times lower than fields that had received multiple applications (53.0 +/- 41.7 microg/kg d.w.). The cumulative biosolids application rate and soil organic carbon were correlated with concentrations and persistence of PBDEs in soil. A model to predict PBDE concentrations in soil after single or multiple biosolids applications provides estimates which fall within a factor of 2 of observed values.