Article pubs.acs.org/est
Identification of Marbon in the Indiana Harbor and Ship Canal Jiehong Guo,† Marta Venier,† Kevin Romanak,† Stephen Westenbroek,‡ and Ronald A. Hites*,† †
School of Public and Environmental Affairs, Indiana University, Bloomington, Indiana 47405, United States United States Geological Survey, Wisconsin Water Science Center, Middleton, Wisconsin 53562, United States
‡
S Supporting Information *
ABSTRACT: Marbon is isomeric with Dechlorane Plus (DP). Both are produced by the Diels− Alder condensation of hexachlorocyclopentadiene with cyclic dienes, and both have elemental compositions of C18H12Cl12. Dechlorane Plus is commonly found in the environment throughout the world, but Marbon has, so far, only been detected at low levels in one sediment core collected near the mouth of the Niagara River in Lake Ontario. Here we report on the concentrations of Marbon and anti-DP in 59 water samples from five Lake Michigan tributaries [the Grand, Kalamazoo, St. Joseph, and Lower Fox Rivers, and the Indiana Harbor and Ship Canal (IHSC)], 10 surface sediment samples from the IHSC, and 2 surface sediment samples from the Chicago Sanitary and Ship Canal. Three Marbon diastereomers were detected in the water and sediment samples from the IHSC, which is far from the location of its previous detection in Lake Ontario. The sum of the concentrations of the three Marbons was greater in the water from the IHSC (N = 11, median =150 pg/L) compared to those in water from the other four tributaries (N = 11−13, medians =0.9−2.0 pg/L). Marbon concentrations in sediment samples from the IHSC were up to 450 ng/g dry weight. Anti-DP was also measured for comparison. Its concentrations were not significantly different among the water samples, but its sediment concentrations in the IHSC were significantly correlated with those of Marbon. The source of Marbon contamination in the IHSC is not clear.
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INTRODUCTION Brominated flame retardants are environmentally persistent, bioaccumulative, and toxic,1−3 and many of them have been taken off the market.4 Highly chlorinated flame retardants have not received as much attention, and many of them remain on the market. The most widely studied chlorinated flame retardants are the Dechloranes, the most well-known of which is Mirex (which was also marketed as a pesticide).5,6 The Dechloranes are synthesized by the Diels−Alder condensation of hexachlorocyclopentadiene with various cyclic olefins.7 For example, Dechlorane Plus (DP) is the adduct of 2 mol of hexachlorocyclopentadiene with 1 mol of 1,5-cyclooctadiene, and it has been detected in the environment throughout the world.8,9 Structurally related compounds (for example, Dechlorane 602, 603, and 604) have also been detected in the environment, especially in Great Lakes sediment, water, fish, herring gull eggs, and air.10−17 In 2015, we started measuring halogenated flame retardants (∼75 compounds, some brominated and some chlorinated) in water samples collected from five tributaries that flow into Lake Michigan: the Grand, Kalamazoo, St. Joseph, and the Lower Fox Rivers, and the Indiana Harbor and Ship Canal (IHSC). In the course of these analyses, we noticed a few unusually abundant gas chromatographic peaks with mass spectra similar to those of DP. These peaks were particularly large in samples from the IHSC. We were able to structurally identify these compounds as Marbon diastereomers. To determine potential sources of these compounds, we measured their concentrations in these tributary water samples and in surface sediment samples from the Indiana Harbor and Ship Canal. The © XXXX American Chemical Society
objective of this paper is to present the structures and spatial distributions of these compounds in these samples and to speculate on their source(s).
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MATERIALS AND METHODS Chemicals. The two diastereomers of Dechlorane Plus (DP), syn- and anti-, and the internal standard, BDE-181, were purchased from Wellington Laboratories (Guelph, ON, Canada). Marbon (CAS # 26595-57-3) was purchased from Toronto Research Chemicals (Toronto, ON, Canada). The latter compound was synthesized by a proprietary process, which generally followed patent U.S. 3,859,371.18 The surrogate standard, BDE-166, was purchased from AccuStandard (New Haven, CT). Additional details on the materials are given in the Supporting Information, SI. Sampling and Sample Treatment. Surface water samples, including both the dissolved and particle phases, were collected every two or three weeks between April and December 2015 (sampling dates are given in Table S1) from the Grand River (GR, N = 11), the Kalamazoo River (KR, N = 12), the St. Joseph River (SJR, N = 12), the Lower Fox River (LFR, N = 13), and the Indiana Harbor and Ship Canal (IHSC, N = 11). Samples were collected at USGS gauging stations closest to the river mouth from an 18-foot U.S. Geological Received: September 13, 2016 Revised: November 17, 2016 Accepted: November 19, 2016
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DOI: 10.1021/acs.est.6b04646 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
Article
Environmental Science & Technology
The instrumental details are given in the SI. Both the full scan and selected ion monitoring (SIM) modes were used. In the full scan mode, the mass spectrometer was scanned from m/z 35 to m/z 1050. In the SIM mode, syn- and anti-DP and Marbon were monitored with their molecular ions at m/z 652 and 654; the internal and surrogate standards (BDE-181 and BDE-166), were monitored with the bromide ions at m/z 79 and 81. The full scan mass spectra of the authentic standards were also obtained on an Agilent 6890 series GC coupled to an Agilent 5973 MS operating in the electron impact ionization (EI) mode. The same 30 m RTX-OPPesticides2 column as described previously was used, and the mass spectrometer was scanned from m/z 50 to m/z 800. Further instrumental details are given in the SI. Quality Control. Procedural blanks (N = 15 for the surface water and N = 1 for the sediment samples) and field blanks (N = 1 for the surface water samples) were processed along with the environmental samples. Marbon was not detected in any of these blanks. In the 15 surface water procedural blanks, syn-DP was detected at 0.05). The anti-DP concentrations in the tributaries were greater than in water samples collected offshore in Lake Michigan; these concentrations averaged 1.8 ± 0.4 pg/L (average ± standard error).13 With the exception of the IHSC and one sample from the St. Joseph River, the concentrations of anti-DP were significantly greater than those of Marbon-3 in all of these Lake Michigan tributary samples (p < 0.05). Based on these results, the IHSC seems to be a significant source of Marbon to Lake Michigan. Incidentally, this site is already known to be a source of polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons, heavy metals, and other pollutants to Lake Michigan.20,24 To further localize the source(s) of Marbon in the IHSC, concentrations were measured in 10 surface sediment samples collected throughout the IHSC (see Figure S1), and for comparison, in surface sediment samples from the Chicago Ship and Sanitary Canal (CSSC), which we selected as a reference site. We note that these CSSC samples were collected 7 years later than the IHSC samples, and thus, we make this comparison cautiously. All three Marbons were detected in 9 of the 10 sediment samples from the IHSC; the single exception was the sample from site 60. With this exception, the total Marbon concentrations ranged from 0.74 (at site 2) to 448 ng/ g dw (at site 51) (Table 1 and Figure 5). Anti-DP was detected in all of the sediment samples from the IHSC at concentrations ranging from 0.04 (at site 60) to 4.78 ng/g dw (at site 51) (Table 1). The Marbon and anti-DP levels in the sediment
samples of IHSC were correlated with one another (p < 0.001, R2 = 0.76). However, the Marbon and anti-DP levels in the tributary water samples were not correlated with one another. These relatively small amounts of anti-DP in sediment may come from commercial Marbon because 1,5-cyclooctadiene (the starting material for the production of DP) has been found as an impurity in 4-vinylcyclohexene (the starting material of Marbon).25 It is interesting to note that a previous study20 measured relatively high PCB concentrations at site 51, which is located at the junction of Lake George and Calumet River Branches (Figure 5). This previous study20 also reported relatively low PCB concentrations at sites 2 and 60, which are the two sites where we measured the lowest levels of Marbon. Site 2 is located at the outlet of the Indiana Harbor, where the total organic carbon concentrations in the sediment are relatively low.20 We also noticed, during sample pretreatment, that sediment from site 60 was oily. In general, the Marbon concentrations in the sediment samples from the IHSC are not correlated with those of PCB. In all of these sediment samples, the Marbon-3 concentrations exceeded those of the other two Marbons, and the concentrations of Marbon-2 exceeded those of Marbon-1. In the two sediment samples from the Chicago Ship and Sanitary Canal, the Marbons were detected but at relatively low levels compared to those of anti-DP (Table 1). Fractions. We have calculated the fraction of each Marbon diastereomer relative to the total of the three compound’s concentrations using the following equation: ⎛ ⎞ CMarbon ‐ i fMarbon ‐ i = ⎜ ⎟ ⎝ CMarbon ‐ 1 + CMarbon ‐ 2 + CMarbon ‐ 3 ⎠ E
(1)
DOI: 10.1021/acs.est.6b04646 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
Article
Environmental Science & Technology where CMarbon‑i is the concentration of the individual Marbon. These fractions are given in Table 1. The fractions of the three Marbons we measured in the commercial standard from Toronto Research Chemicals are 0.11, 0.35, and 0.54, respectively (see Table 1). In the sediment samples, with the exception of site 60 and the CSSC, these fractions were 0.11 ± 0.02, 0.34 ± 0.03, and 0.55 ± 0.04, respectively (average ± standard deviation). These values are all close to what we observed for the standard. In the tributary water sample from the IHSC, these fractions are 0.11 ± 0.03, 0.33 ± 0.04, and 0.56 ± 0.05, which are also close to those observed for the standard. The fractions for the other sediment and water samples are dominated by Marbon-3, but the absolute concentrations of this GC peak relative to anti-DP at these sites are so low that the correction for syn-DP coelution may not be accurate, and these numbers are discounted. Nevertheless, these values may indicate that there are otheralbeit smallsources of Marbon3 in the other four tributaries or that only Marbon-3 is environmentally persistent. More detailed studies on the presence of Marbon in non-IHSC water, sediment, and air samples is clearly indicated. Source. The source of Marbon in the IHSC is unclear. There is no production or use information available for this chemical. The only other report of Marbon in the environment is by Sverko et al.,10 who reported it in a sediment core taken 16 km off-shore near the mouth of the Niagara River in Lake Ontario. Their reported concentrations were
