Reflections about three influential Ambio articles impacting environmental biogeochemistry research and knowledge : This article belongs to Ambio's 50th Anniversary Collection. Theme: Environmental contaminants.

Reflections about three influential environmental contaminants papers published in Ambio are presented. The PCB Story by Jensen in (1972) had a very important influence on environmental chemistry. This is captured by way of comments and personal anecdotes. Wania's and MacKay's (1993) paper highlights the physical chemistry underlying transport of PCBs and organochlorine pesticides from temperate zone ecosystems to Polar Regions. Their paper exemplifies how principles of chemistry and environmental processes informed understanding the biogeochemical cycles of chemicals of environmental concern (CEC). Mergler et al.'s (2007) paper reviews knowledge of methyl mercury exposure and impacts in humans and served as an example of how to approach exposure and human health concerns for all CECs. All great progress. Then, the question: "How we missed for two decades the importance of plastics in the environment identified in a paper published the same year as The PCB Story? Are we missing yet another important environmental contaminant now?

Towards integrated modeling of the long-term impacts of oil spills.

Although great progress has been made to advance the scientific understanding of oil spills, tools for integrated assessment modeling of the long-term impacts on ecosystems, socioeconomics and human health are lacking. The objective of this study was to develop a conceptual framework that could be used to answer stakeholder questions about oil spill impacts and to identify knowledge gaps and future integration priorities. The framework was initially separated into four knowledge domains (ocean environment, biological ecosystems, socioeconomics, and human health) whose interactions were explored by gathering stakeholder questions through public engagement, assimilating expert input about existing models, and consolidating information through a system dynamics approach. This synthesis resulted in a causal loop diagram from which the interconnectivity of the system could be visualized. Results of this analysis indicate that the system naturally separates into two tiers, ocean environment and biological ecosystems versus socioeconomics and human health. As a result, ocean environment and ecosystem models could be used to provide input to explore human health and socioeconomic variables in hypothetical scenarios. At decadal-plus time scales, the analysis emphasized that human domains influence the natural domains through changes in oil-spill related laws and regulations. Although data gaps were identified in all four model domains, the socioeconomics and human health domains are the least established. Considerable future work is needed to address research gaps and to create fully coupled quantitative integrative assessment models that can be used in strategic decision-making that will optimize recoveries from future large oil spills.

Fuel oil hydrocarbons in Mytilus edulis in Buzzards Bay, Massachusetts USA: Comparison of data from two oil spills.

A small No. 2 fuel oil spill contaminated a Mytilus edulis population in the Cape Cod Canal, Massachusetts, USA during a three day period in April 1983. Retention and release of the fuel oil compounds were assessed over several days and months. Compounds analyzed included n-alkanes, pristane, phytane, C2 -, C3 -naphthalenes, flourene, phenanthrene, C1-, C2-, C3 - phenanthrenes. Biological half-lives were calculated for the release of the compounds up to day 29 and ranged from 1.5 days to 9.9 days. Results compared favorably with similar data from a small No. 2 fuel oil spill contaminating the same population of Mytilus edulis at the same time of year, April 1978. Gas chromatography-mass spectrometer analyses of C2-, and C3- phenanthrenes documented changes in relative abundance within the isomer groupings after day 29. This suggests a within isomer grouping molecular structural control on release or enzymatic catalyzed alteration of these compounds.

Need to update human health risk assessment protocols for polycyclic aromatic hydrocarbons in seafood after oil spills.

The need to include alkylated polycyclic aromatic hydrocarbons in human health risks assessments for oil contaminated seafood after crude oil spills is set forth. This is placed within the context of a brief review of the literature for PAHs and human health risk assessments after oil spills. The example of human health risk assessments for oil contaminated seafood after the Deepwater Horizon oil spill is reviewed with the conclusion that PAHs such as alkylated chrysenes/triphenylenes/benzanthracenes should have been included in the human health risk assessment and not dismissed as present in very low concentrations relative to their parent PAHs.

Edward D. Goldberg's proposal of "the Mussel Watch": Reflections after 40years.

We chronicle the extensive influence over the past forty years of Professor Edward D. Goldberg and his call in 1975 for a "Mussel Watch" or bivalve sentinel organism approach to assess geographic status and temporal trends of several chemicals of environmental concern in the coastal ocean. Examples of local, regional, national and international programs are discussed briefly as are examples of interesting useful findings and limitations to the Mussel Watch concept. Mussel Watch continues to provide useful data about status and trends of chemical contamination in coastal ecosystems.

"Unresolved Complex Mixture" (UCM): A brief history of the term and moving beyond it.

The term "Unresolved Complex Mixture" (UCM) has been used extensively for decades to describe a gas chromatographic characteristic indicative of the presence of fossil fuel hydrocarbons (mainly petroleum hydrocarbons) in hydrocarbons isolated from aquatic samples. We chronicle the origin of the term. While it is still a useful characteristic for screening samples, more modern higher resolution two dimensional gas chromatography and gas chromatography coupled with advanced mass spectrometry techniques (Time-of-Flight or Fourier Transform-Ion Cyclotron Resonance) should be employed for analyses of petroleum contaminated samples. This will facilitate advances in understanding of the origins, fates and effects of petroleum compounds in aquatic environments.

Organic micropollutants in marine plastics debris from the open ocean and remote and urban beaches.

To understand the spatial variation in concentrations and compositions of organic micropollutants in marine plastic debris and their sources, we analyzed plastic fragments (∼10 mm) from the open ocean and from remote and urban beaches. Polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), dichloro-diphenyl-trichloroethane and its metabolites (DDTs), polybrominated diphenyl ethers (PBDEs), alkylphenols and bisphenol A were detected in the fragments at concentrations from 1 to 10,000 ng/g. Concentrations showed large piece-to-piece variability. Hydrophobic organic compounds such as PCBs and PAHs were sorbed from seawater to the plastic fragments. PCBs are most probably derived from legacy pollution. PAHs showed a petrogenic signature, suggesting the sorption of PAHs from oil slicks. Nonylphenol, bisphenol A, and PBDEs came mainly from additives and were detected at high concentrations in some fragments both from remote and urban beaches and the open ocean.

The 1974 spill of the Bouchard 65 oil barge: petroleum hydrocarbons persist in Winsor Cove salt marsh sediments.

Petroleum hydrocarbons persist in salt marsh sediments in Winsor Cove (Buzzards Bay, Massachusetts) impacted from the 1974 spill of No. 2 fuel oil by the barge Bouchard 65. Intertidal sediment cores were collected from 2001 to 2005 and analyzed for total petroleum hydrocarbons (TPHs). TPHs content was greatest (as high as 8.7 mg g(-1) dry weight) in the surface sediments and decreased with distance landward. Select samples were analyzed for polycyclic aromatic hydrocarbons (PAHs) with values as high as 16.7 microg g(-1) for total naphthalenes and phenanthrenes/anthracenes. These remaining PAHs are mainly C(4)-naphthalenes and C(1)-, C(2)-, and C(3)-phenanthrenes/anthracenes revealing preferential loss of almost all of the naphthalenes and the parent compound phenanthrene. Inspection of the data indicates that biodegradation, water-washing and evaporation were major removal processes for many of the petroleum hydrocarbons in the marsh sediments. In addition, historical data and photographs combined with their recent counterparts indicate that erosion has physically removed these contaminants from this site.