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Integrated Atmospheric Deposition Network (IADN) 

Over the past few decades, the Great Lakes have been the recipient of many different persistent organic pollutants (POPs) from a variety of sources. In an attempt to better understand atmospheric deposition as one of these sources of contamination, the Integrated Atmospheric Deposition Network (IADN) was formed in 1990 through mandates of the Clean Air Act and Great Lakes Water Quality Agreement. The project is a joint venture between Environment Canada, the Ontario Ministry of the Environment, and the United States Environmental Protection Agency’s Great Lakes National Program Office which has provided funding to the Hites’ Laboratory to manage IADN. We operate five sites: the two urban sites  are in Chicago, IL and Cleveland, OH. A rural site is located at Sturgeon Point, NY. The two remote sites are at Sleeping Bear Dunes, MI and Eagle Harbor, MI.  At all the sites, vapor and particle phase air samples are collected every 12 days for 24 hours using a modified Anderson high-volume air sampler.  In addition, precipitation samples are collected using MIC sampler for each calendar month.  We measures 84 polychlorinated biphenyl (PCB) congeners or congener groups, 22 organochlorine pesticides (both banned and in use), 19 polycyclic aromatic hydrocarbons (PAHs), 43 flame retardants (both discontinued PBDEs and alternatives) in each of the phases. Click to view the IADN Field Sampling Procedure, the IADN Sample Preparation Procedure or the IADN GC Analysis Procedure. Long-term monitoring networks like IADN are essential in understanding the behavior of pollutants in the atmosphere and making the link between policy and science. For more information, visit the official IADN website.

Map of the United States IADN Sites.

Legacy POPs
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With almost twenty years of collected data, one of the more interesting aspects of IADN is the analysis of long-term spatial and temporal trends of POP concentrations in the Great Lakes basin.  Our latest approach to the analyses of the temporal trends in POP concentrations includes harmonic multiple regression allowing combining concentrations for a specific compound or group of compounds in all three phases (vapor, particle, and precipitation) at all IADN sites together via calculating partial residuals of actual concentrations.  This allows us to integrate the data from all phases and sites, giving us a better overall depiction of the behavior of these chemicals in the Great Lakes region. This relatively simple approach indicated that the concentrations of PCBs in air around the Great Lakes are decreasing with an overall halving time of 17 ± 2 years, which is slow for a substance that was banned about 35 years ago. Phenanthrene, chrysene, and endosulfan showed halving times on the order of 10 years. The concentrations of several organochlorine pesticides were decreasing more rapidly; for example α- and γ-HCH (lindane) have halving times of about 3.5 years. It is somewhat surprising that, 40 years after it was banned, α-HCH is still present in the environment despite a relatively rapid elimination rate. Clearly, technical-HCH was heavily used in its heyday. The rapid halving times observed for α-HCH and γ-HCH(lindane) are consistent with the relatively high volatilities of these chemicals (for more details go here).

Partial residuals versus sampling date for the three phases combined for (A) PCBs, (B) phenanthrene, (C) chrysene, (D) endosulfans, (E) DDTs, (F) chlordanes, (G) γ-HCH or lindane, and (H) α-HCH.

Brominated Flame Retardants
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Over the last several decades, there has been a rapid growth in flame retardant industry, and there are now more than 175 chemicals classified as flame retardants. These chemicals are used in a variety of consumer products, including electronics, textiles, furniture, and toys.  Of these, at least 75 are brominated flame retardants (BRFs).  Among them, the polybrominated diphenyl ethers (PBDEs) have been widely used and are persistent and accumulate in the environment.  As a result, the use of the Penta-, Octa-, and Deca-BDE commercial mixtures was restricted in the European Union, the production and use of the penta- and octa-mixtures in the United States was voluntarily phased out in 2004, and the production, import, and sale of the deca-BDE mixture in the United States will be discontinued by the end of 2013. These restrictions have led to an increased market demand for non-regulated flame retardants. These include decabromodiphenylethane (DBDPE), 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE),  2-ethylhexyl-2,3,4,5-tetrabromobenzoate (TBB), and bis(2-ethylhexyl)-tetrabromophthalate (TBPH), which have been marketed as alternatives to various PBDE formulations. In addition, “older” chemicals are sometimes being reintroduced to the market. These include hexabromobenzene (HBB) and pentabromoethylbenzene (PBEB), compounds that have apparently been manufactured for several decades.

In IADN samples, BFRs were found in the gas, particle, and precipitation phases.  In general, the highest BFR concentrations were detected at the two urban sites (Chicago and Cleveland) and the lowest BFR concentrations were measured at the remote Eagle Harbor (EH) site in all three phases. This spatial distribution pattern in BFR concentrations can be explained by the fact that BFRs are used in consumer products, the abundance of which is proportional to population (see Figure). For more details go here.

Figure 1

Concentrations of several brominated flame retardants in the atmosphere around the North American Great Lakes as a function of the number of people living and working within a 25-km radius of the sampling site.  The population metric is the square of the common logarithm of the number of people.  These populations are: Chicago 3,579,651; Cleveland 1,301,787; Sturgeon Point 68,361; Sleeping Bear Dunes 16,097; and Eagle Harbor 481. 

As it was mentioned above, PBDE commercial mixtures have been or will be voluntarily withdrawn from the market because of their tendency to leak from the materials where they has been used and to be-come ubiquitous in the environment.  In 2004, to replace these commercial PBDE mixtures, the flame retardant industry began to use alternative formulations called Firemaster 550, Firemaster BZ-54, and DP-45.  Firemaster 550 consists of about 35% of 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (TBB), about 15% of bis(2-ethylhexyl)-tetrabromophthalate (TBPH), and about 50% of aromatic phosphate es-ters. 5  Firemaster BZ-54 consists of about 70% of TBB and about 30% of TBPH.5  DP-45 contains TBPH only.

Figure 2

In a recent study, TBB and TBPH were identified and quantitated in gas and particle-phase air samples collected from six sites near the shores of the Great Lakes.  TBB and TBPH were detected in more than half of the samples collected from 2008 to 2010.  Urban areas, such as Chicago and Cleveland, showed the highest concentrations (0.36-290 pg/m3), while remote areas, such as Eagle Harbor and Sleeping Bear Dunes, exhibited the lowest levels (0.050-32 pg/m3).  The atmospheric concentrations of TBB and TBPH increased rapidly and significantly over this time period (see figure below), perhaps indicating that these compounds are replacing the polybrominated diphenyl ethers (PBDEs), which have been removed or soon will be removed from the marketplace (for more details go here).

Figure 3

Temporal trends of TBB and TBPH concentrations at urban and rural sites.

Organophosphate Flame Retardants and Plasticizers
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Organophosphate esters (OPs) are widely used as flame retardants in various consumer and industrial products, such as plastics, electronic equipment, furniture, textiles, and building materials.  In addition, some of these chemicals, mainly the non-chlorinated alkyl phosphates, are used as plasticizers, as well as anti-foaming agents in lacquers, hydraulic fluids, and floor polishes.  OPs are high production volume chemicals and because their consumption is expected to increase due to production and use restrictions placed on brominated flame retardants.  For example, the production volumes for tris(1,3-dichloro-2-propyl) phosphate (TDCPP), triphenyl phosphate (TPP), and tris(2-chloro-isopropyl) phosphate (TCPP) in the United States increased from 1-10 million pounds in 1990 to 10-50 million pounds in 2006 [after the so-called pentabrominated diphenyl ether (Penta-BDE) mixture was phased out].   In Western Europe, the consumption of OPs increased 2.5% from 2001 to 2005 and 7.1% from 2005 to 2006.  Data on environmental persistence and toxicity of OPs are limited, but some of these chemicals (especially the halogenated ones) are known to be relatively persistent, mutagenic, carcinogenic, and neurotoxic; they are also developmental and reproductive toxins and skin irritants. OPs were generally more abundant at the urban sites (Chicago and Cleveland) than at the rural and remote sites (Sturgeon Point, Eagle Harbor, and Sleeping Bear Dunes), see Figure.  A one way ANOVA of ΣOP, ΣPBDE (the sum of about 35 congeners), TBB, and TBPH concentrations at each site showed that ΣOP concentrations are consistently higher (P < 0.001) at all five Great Lakes sites compared to the corresponding ΣPBDE, TBB, and TBPH concentrations at the same sites.  In fact, ΣOP concentrations are about 100, 1200, and 600 times higher (on average) than the concentrations of ΣPBDEs, TBB, and TBPH, respectively.  In other words, ΣOP concentrations are on average about 2-3 orders of magnitude higher than the concentrations of brominated flame retardants (PBDEs, TBB, TBPH) in the Great Lakes basin.  For more details go here.

Average atmospheric concentrations (pg/m3) of individual OPs (and their standard errors) in the particle phase at the five IADN sampling sites around the Great Lakes. 

Dechlorane Plus
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Dechlorane Plus (DP) is a highly chlorinated flame retardant (see Figure 1). It is a substitute for Dechlorane, which was also marketed under the name Mirex as a pesticide and was banned in 1970s. Although DP is a high production volume chemical and has been in use for decades, it was found in the environment for the first time in IADN samples (for more details go here). In fact, DP was detected in samples from all IADN sampling sites, with relatively high levels in samples from Sturgeon Point. This observation suggests that the manufacturing facility of DP, OxyChem in Niagara Falls, New York, might be the main source of DP to the Great Lakes.

Description: anti siomer of DP

Description: syn isomer of DP



Molecular structures of the two Dechlorane Plus stereoisomers.


Concentrations of syn-DP, anti-DP, and ΣDP in the atmospheric vapor phase, particle phase, and precipitation. The thin black lines represent the median, and the thick red lines represent the mean; the boxes represent the 25th and 75th percentiles; the whiskers represent the 5th and 95th percentiles. Site abbreviations: EH EagleHarbor, CH Chicago, SB Sleeping Bear Dunes, CL Cleveland, SP Sturgeon Point.

The analysis of the temporal trends of the anti-DP concentrations shows that the concentrations of this compound are increasing in the atmosphere with the doubling time of ~10 years (for more details go here).


Chicago as a Source of Air Toxics to Lake Michigan
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Description: K:\Zach Rodenburg\Chicago EPA Project\Chicago Fieldwork September 2010\Cruise Photos\DSC_4669.jpg

This study investigates the Chicago region as a source of air toxics to Lake Michigan.  The long-term outcome is the reduction of potentially toxic organic compounds in the lake.  Sites will be established on water intake cribs to augment existing monitoring sites in the city.  Over the four-year study, about 650 air samples will be collected and analyzed for a suite of over 250 organic pollutants.  The data will be interpreted to find the Chicago contribution of the pollutants entering Lake Michigan (in kilograms per year).  This project is located at the University of Iowa and at Indiana University.  Field work is conducted in Chicago, Illinois and Lake Michigan.  This study investigates the importance of the Chicago region as a source of persistent organic pollutants (POPs) to Lake Michigan.  The overall goal of the project is to better understand the relationship between the observed concentrations of persistent organic pollutants in Chicago’s air and their subsequent deposition into Lake Michigan.  Our overall objectives are to quantify the spatial variability of POPs in the City of Chicago; to quantify the annual deposition of Chicago POPs into Lake Michigan; and to determine the variability and major forcing functions that control deposition of urban airborne POPs to Lake Michigan.  The overall hypothesis is that the entire Chicago metro area is a major source of airborne POPs to Lake Michigan.  This work will further address a corollary hypothesis that the effectiveness of remediation efforts is dependent on the successful identification and quantitative characterization of emission sources (hot spots) in Chicago.   We will address these hypotheses through field studies, laboratory measurements, and modeling.


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