Tittabawassee River Research Articles

Human Impacts on Great Lakes Walleye Sander vitreus Structure, Diversity and Local Adaptation.

Artificial propagation and wild release may influence the genetic integrity of wild populations. This practice has been prevalent in fisheries for centuries and is often termed 'stocking'. In the Laurentian Great Lakes (Great Lakes here-on), walleye populations faced declines from the 1950s to the 1970s, prompting extensive stocking efforts for restoration. By the mid-2010s, walleye populations showed signs of recovery, but the genetic legacy of stocking on population structure at the genomic level remains unclear. Using a dataset of 45,600 genome-aligned SNP loci genotyped in 1075 walleye individuals, we investigated the genetic impacts of over 50 years of stocking across the Great Lakes. Population structure was associated with both natural geographic barriers and stocking from non-native sources. Admixture between Lake Erie walleye and walleye from the re-populated Tittabawassee River indicate that stocking may have re-distributed putatively adaptive alleles around the Great Lakes. Genome scans identified FST outliers and evidence of selective sweeps, indicating local adaptation of spawning populations is likely. Notably, one genomic region showed strong differentiation between Muskegon River and walleye from the Tittabawassee River, which was re-populated by Muskegon strain walleye, suggesting admixture and selection both impact the observed genetic diversity. Overall, our study underscores how artificial propagation and translocations can significantly alter the evolutionary trajectory of populations. The findings highlight the complex interplay between stocking practices and population genetic diversity, emphasising the need for careful management strategies to preserve the genetic integrity of wild populations amidst conservation efforts.

Occurrence of primary aromatic amines and nicotine in sediments collected from the United States

Despite extensive use of primary aromatic amines (AAs) in consumer products, little is known about their occurrence in the environment. In this study, we investigated the occurrence of 14 AAs and nicotine in 75 sediment samples collected from seven estuarine and freshwater ecosystems in the Unites States. Additionally, risk quotients (RQs) were calculated to assess potential risks of these chemicals to aquatic organisms. Of the 14 AAs analyzed, seven of them were found in sediments. The sum concentrations of seven AAs in sediments were in the range of 10.2 to 1810 ng/g, dry wt (mean: 388 ng/g). Aniline was the most abundant compound, accounting for, on average, 53 % of the total concentrations. Nicotine was found in sediments at a concentration range of <LOQ to 1340 ng/g, dry wt (mean: 119 ng/g). Among the seven sampling locations studied, AAs and nicotine concentrations were the highest in sediment from Altavista wastewater lagoon in Virginia (AV, mean: 1700 ng/g) followed in descending order by Chicago Sanitary and Ship Canal (CSSC, mean: 807 ng/g), Indiana Harbor and Ship Canal (IHSC, mean: 698 ng/g) and New Bedford Harbor (NBH, mean: 482 ng/g). Sediments from the upper Mississippi River (MISS, mean: 63.4 ng/g) and Tittabawassee River (TBR, mean: 52.3 ng/g) contained the lowest concentrations. The RQ values for AAs in sediment ranged from 0 to 733 and that for nicotine ranged from 0 to 2060. Among AAs, the highest RQ value was found for 4-chloroaniline. Nicotine exhibited notable RQ values, which suggested risk from this chemical to aquatic organisms. This is the first study to report the occurrence of AAs in sediments and our results suggest the need for further investigations on the sources and ecological impacts of these chemicals in aquatic ecosystems.

Dow recovers from Midland flooding

Dow has begun cleanup and recovery at its chemical complex in Midland, Michigan, following flooding from rain and dam failures. On May 19, heavy rain caused the Tittabawassee River to crest above f...

Telemetry reveals limited exchange of walleye between Lake Erie and Lake Huron: Movement of two populations through the Huron-Erie corridor

Immigration and emigration of individuals among populations influence population dynamics and are important considerations for managing exploited populations. Lake Huron and Lake Erie walleye (Sander vitreus) populations are managed separately although the interconnecting Huron-Erie Corridor provides an unimpeded passageway. Acoustic telemetry was used to estimate inter-lake exchange and movement within St.Clair River and Detroit River. Of 492 adult walleyes tagged and released during 2011 and 2012, one fish from Tittabawassee River (Lake Huron; 1 of 259, 0.39%) and one individual from Maumee River (Lake Erie; 1 of 233, 0.43%) exchanged lakes during 2011–2014. However, both fish returned to the lake where tagged prior to the next spawning season. The one walleye from Maumee River that moved to Lake Huron made repeated round-trips between Lake Erie and Lake Huron during three consecutive years. Of twelve fish tagged in the Tittabawassee River detected in the Huron-Erie Corridor, few (n = 3) moved south of Lake St.Clair to the Detroit River. Ten walleye tagged in the Maumee River entered the Huron-Erie Corridor, and five were detected in the St.Clair River. Our hypothesis that walleye spawning in Maumee River, Lake Erie, served as a source population to Lake Huron (“sink population”) was not supported by our results. Emigration of walleye to Lake Huron from other populations than the Maumee River, such as those that spawn on in-lake reefs, or from Lake St.Clair may contribute to Lake Huron walleye populations.

From ash pond to Riverside Wetlands: Making the business case for engineered natural technologies

The 2015 announcement of The Dow Chemical Company's (Dow) Valuing Nature Goal, which aims to identify $1 billion in business value from projects that are better for nature, gives nature a spot at the project design table. To support this goal, Dow and The Nature Conservancy have extended their long-standing collaboration and are now working to develop a defensible methodology to support the implementation of the goal. This paper reviews the nature valuation methodology framework developed by the Collaboration in support of the goal. The nature valuation methodology is a three-step process that engages Dow project managers at multiple stages in the project design and capital allocation processes. The three-step process identifies projects that may have a large impact on nature and then promotes the use of ecosystem service tools, such as the Ecosystem Services Identification and Inventory Tool, to enhance the project design so that it better supports ecosystem health. After reviewing the nature valuation methodology, we describe the results from a case study of redevelopment plans for a 23-acre site adjacent to Dow's Michigan Operations plant along the Tittabawassee River.

Spawning site fidelity and apparent annual survival of walleye (Sander vitreus) differ between a Lake Huron and Lake Erie tributary

AbstractFidelity to spawning habitats can maximise reproductive success of fish by synchronising movements to sites of previous recruitment. To determine the role of reproductive fidelity in structuring walleye Sander vitreus populations in the Laurentian Great Lakes, we used acoustic telemetry combined with Cormack–Jolly–Seber capture–recapture models to estimate spawning site fidelity and apparent annual survival for the Tittabawassee River in Lake Huron and Maumee River in Lake Erie. Walleye in spawning condition were tagged from the Tittabawassee River in Lake Huron and Maumee River in Lake Erie in 2011–2012. Site fidelity and apparent annual survival were estimated from return of individuals to the stream where tagged. Site fidelity estimates were higher in the Tittabawassee River (95%) than the Maumee River (70%) and were not related to sex or fish length at tagging. Apparent annual survival of walleye tagged in the Tittabawassee did not differ among spawning seasons but was higher for female than male walleye and decreased linearly as fish length increased. Apparent annual survival of walleye tagged in the Maumee River did not differ among spawning seasons but was higher for female walleye than male walleye and increased linearly as fish length increased. Greater fidelity of walleye tagged in the Tittabawassee River than walleye tagged in the Maumee River may be related to the close proximity to the Maumee River of other spawning aggregations and multiple spawning sites in Lake Erie. As spawning site fidelity increases, management actions to conserve population structure require an increasing focus on individual stocks.

Contributions of Lake Erie and Lake St. Clair Walleye Populations to the Saginaw Bay, Lake Huron, Recreational Fishery: Evidence from Genetic Stock Identification

AbstractGenetic stock identification analyses were conducted to determine spawning population contributions to the recreational fishery for Walleyes Sander vitreus in Saginaw Bay, Lake Huron. Two spawning population groups were considered: (1) the Tittabawassee River, which has been identified as the largest source of spawning Walleyes for Saginaw Bay; and (2) an aggregate of six spawning populations from Lake Erie and Lake St. Clair that were found to be genetically similar. Overall, the Lake Erie and Lake St. Clair spawning populations were estimated to comprise approximately 26% of the Walleye recreational harvest in Saginaw Bay during 2008–2009. Contribution levels were similar for the 2 years in which genetic samples were collected. Contributions from the Lake Erie and Lake St. Clair spawning populations to the harvest of age‐5 and older Walleyes were greater during summer (31.8%; SE = 6.2%) than during late winter and spring (6.0%; SE = 3.7%). Conversely, contributions from the Lake Erie and Lake St. Clair spawning populations to the harvest of age‐3 and age‐4 fish were fairly similar between seasons (late winter and spring: 31.2%, SE = 6.7%; summer: 41.7%, SE = 5.6%), suggesting that younger Walleyes migrate earlier or reside in Saginaw Bay for extended periods. Our finding that one‐quarter of the Saginaw Bay recreational harvest of Walleyes comprises fish from Lake Erie and Lake St. Clair has important management implications, as policies for one lake may have bearing on the other lake—one of the challenges associated with managing migratory fish species. Fisheries management in the Laurentian Great Lakes has a history of being highly coordinated and cooperative among the states and province bordering the individual lakes. Results from this study suggest that cooperation may need to be expanded to account for fish movement between lakes.Received October 28, 2014; accepted February 11, 2015

Large watershed management and restoration: dioxin sediment remediation case study

This paper reviews continuing, long-term remediation of river sediments containing dioxin and other chemical compounds in a large watershed of the Great Lakes Region. Chlorinated dibenzo-p-dioxins are a ‘family’ of chemically related compounds commonly known as chlorinated dioxins or simply, dioxins. The highest levels are usually found in sediments, soil and animal fats. The most toxic chemical in this group is 2,3,7,8-tetrachlorodibenzo-para-dioxin, the ‘standard’ to which other dioxins are compared and which has been shown to be very toxic in animal studies. The US Environmental Protection Agency (EPA) and Michigan Department of Environmental Quality (MDEQ) have made a lengthy effort to assess and remediate portions of the Saginaw Bay Watershed, including the Tittabawassee River. The paper reviews the EPA-proposed ‘phased approach’ to restoration and remediation of a short segment (Segment 1) of the Tittabawassee River sediments. Sediments are contaminated with a number of chemical pollutants other than dioxins, including arsenic, cholorbenzenes, cholorphenols, ethyl parathion, o-phenylphenol and polycyclic aromatic hydrocarbons. The paper evaluates three proposed ‘cleanup alternatives’, with final action method suggested based on effectiveness, feasibility for implementation and cost.

Multiple lines of evidence risk assessment of american robins exposed to polychlorinated dibenzofurans (PCDFS) and polychlorinated dibenzo‐P‐dioxins (PCDDS) in the tittabawassee river floodplain, Midland, Michigan, Usa

Concentrations of polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzo-p-dioxins (PCDDs) in Tittabawassee River floodplain soils and biota downstream of Midland, Michigan, USA, are greater than regional background concentrations. From 2005 to 2008, a multiple lines of evidence approach was utilized to evaluate the potential for effects of PCDD/DFs on American robins (Turdus migratorius) breeding in the floodplains. A dietary-based assessment indicated there was potential for adverse effects for American robins predicted to have the greatest exposures. Conversely, a tissue-based risk assessment based on site-specific PCDD/DF concentrations in American robin eggs indicated minimal potential for adverse effects. An assessment based on reproductive endpoints indicated that measures of hatch success in study areas were significantly less than those of reference areas. However, there was no dose-response relationship between that endpoint and concentrations of PCDD/DF. Although dietary-based exposure and reproductive endpoint assessments predicted potential for adverse effects to resident American robins, the tissue-based assessment indicates minimal to no potential for adverse effects, which is reinforced by the fact the response was not dose related. It is likely that the dietary assessment is overly conservative given the inherent uncertainties of estimating dietary exposure relative to direct tissue-based assessment measures. Based on the available data, it can be concluded that exposure to PCDD/DFs in the Tittabawassee River floodplain would not likely result in adverse population-level effects to American robins.

Polytopic vector analysis of soil, dust, and serum samples to evaluate exposure sources of PCDD/Fs

As part of the University of Michigan Dioxin Exposure Study, soil, household dust, and serum samples were collected from more than 750 households in five populations around the city of Midland and in Jackson and Calhoun Counties, Michigan, USA. Polytopic vector analysis, a type of receptor model, was applied to better understand the potential sources of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans found in these samples and to quantify the contributions of the sources in each matrix across populations. The results indicated that source signatures found in soil are similar to those found in dust, reflecting various combustion profiles, pentachlorophenol, and graphite electrode sludge. The profiles associated with contamination in the Tittabawassee River, likely related to historical discharges from the Dow Chemical Company facility in Midland, exhibited the largest differences among the regional populations sampled. Differences in serum source contributions among the study populations were consistent with some of the regional differences observed in soil samples. However, the age trends of these differences suggested that they are related to past exposures, rather than ongoing sources.

Maternal and stock effects on egg-size variation among walleye Sander vitreus stocks from the Great Lakes region

Fish egg sizes vary intra-specifically among stocks and individuals, and such variation may reflect a combination of maternal and environmental influences. As egg size variation has important implications for individual and population recruitment success, it is useful to quantify egg-size variation and identify potential factors underlying such variation. We evaluated 1) within-stock maternal influences on egg size and 2) the relative elucidatory power of maternal effects versus stock in explaining inter-individual mean egg size based on eggs collected during 2007–2008 from five walleye Sander vitreus stocks in the North American Laurentian Great Lakes region. We used both linear regression models and classification and regression trees (CART) to describe egg-size variation. Egg size tended to increase with female length and for some stocks was greatest for intermediate maternal ages. However, maternal influences on egg size were relatively low and variable between years. In contrast, stock had a stronger effect; walleye egg-size variation was greater among stocks than within stocks. After controlling for the influence of maternal age and length, we found that egg size was relatively small for fish spawning in Maumee and Sandusky Rivers (western Lake Erie), intermediate in Oneida Lake and Tittabawassee River (Saginaw Bay, Lake Huron), and relatively large in Van Buren Bay (eastern Lake Erie) and Little Bay de Noc (northern Green Bay, Lake Michigan). Such inter-stock differences in maternal influence adjusted egg size appeared to be negatively associated with a system's productivity; suggesting a potential adaptive response of egg size to early life habitat conditions.

Dietary‐ and tissue‐based exposure of belted kingfisher to PCDFs and PCDDs in the Tittabawassee River floodplain, Midland, MI, USA

Concentrations of polychlorinated dibenzofurans (PCDFs) and other dioxin-like compounds in soils and sediments of the Tittabawassee River and associated floodplains downstream of Midland, Michigan, USA, are greater than upstream sites. As a result of these concentrations, which are some of the greatest ever reported, a site-specific exposure assessment of belted kingfisher breeding in the assessment area was conducted. To reduce the uncertainty associated with predicting exposure from abiotic matrices, concentrations of residues were quantified in site-specific prey items and in eggs and nestlings of belted kingfisher. Dietary exposure, expressed as the potential average daily dose, based on site-specific concentrations of PCDFs, polychlorinated dibenzo-p-dioxins (PCDDs), and 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQ(WHO-Avian)) in prey items was consistently greater along the Tittabawassee River than in associated reference areas and further downstream sites in the Saginaw River. Concentrations of PCDD/DFs in eggs and nestlings of belted kingfisher varied among sampling areas, being greater in both eggs and nestlings nesting along the Tittabawassee River compared to those of belted kingfisher from upstream reference areas. Geometric mean concentrations of PCDD/DFs were 130 and 200 ng/kg wet weight in eggs and nestlings of belted kingfisher, respectively. These concentrations are the equivalent of 84 and 95 ng TEQ(WHO-Avian)/kg. Site-specific biomagnification factors for select PCDD/DF congeners ranged from <1.0 to 1.8 in belted kingfisher.

Effects on tree swallows exposed to dioxin‐like compounds associated with the Tittabawassee River and floodplain near Midland, Michigan, USA

Concentrations of dioxin-like compounds, primarily polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzo-p-dioxins (PCDDs), in soils and sediments downstream of Midland, Michigan (USA) were greater than upstream sites and prompted a site-specific hazard assessment of tree swallows breeding in the associated floodplains. Potential for adverse population-level effects from site-specific contaminant exposures were evaluated at study areas (SAs) along the Tittabawassee and Saginaw rivers downstream of Midland. The site-specific multiple lines of evidence approach to hazard assessment included endpoints for dietary- and tissue-based exposures, and population productivity measurements for tree swallows ([TS]; Tachycineta bicolor) measured during the 2005, 2006, and 2007 breeding seasons. Exposure to dioxin-like compounds in TS eggs were some of the greatest recorded and were similar among all upstream and downstream study sites. Conversely, concentrations in nestlings from SAs were significantly greater compared to reference areas (RAs). The pattern of relative concentrations of PCDD/DFs in eggs and nestlings at RAs was dominated by dioxin congeners, whereas at SAs it was dominated by furan congeners. No statistically significant differences were noted in exposure to PCDD/DFs or in population-level responses when compared among locations, and total clutch failures were rare. Hatching success and fledging success were weakly negatively correlated with concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQs) in individual eggs and nestlings, respectively. On-site concentrations of TEQs in floodplain soils were some of the greatest ever reported in the environment, and several lines of evidence indicate potential population-level effects on TS overall reproductive productivity.

Multiple Lines of Evidence Risk Assessment of Terrestrial Passerines Exposed to PCDFs and PCDDs in the Tittabawassee River Floodplain, Midland, Michigan, USA

ABSTRACT A site-specific multiple lines of evidence risk assessment was conducted for house wrens (Troglodytes aedon) and eastern bluebirds (Sialia sialis) along the Tittabawassee River downstream of Midland, Michigan, where concentrations of polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzo-p-dioxins (PCDDs) in floodplain soils and sediments are greater compared to upstream areas and some of the greatest anywhere in the world. Lines of evidence supporting the population-level assessment endpoints included site-specific dietary- and tissue-based exposure assessments and population productivity measurements during breeding seasons 2005–2007. While a hazard assessment based on site-specific diets suggested that populations residing in the downstream floodplain had the potential to be affected, concentrations in eggs compared to appropriate toxicity reference values (TRVs) did not predict a potential for population-level effects. There were no significant effects on reproductive success of either species. The most probable cause of the apparent difference between the dietary- and tissue-based exposure assessments was that the dietary-based TRVs were overly conservative based on intraperitoneal injections in the ring-necked pheasant. Agreement between the risk assessment based on concentrations of PCDFs and PCDDs in eggs and reproductive performance in both species supports the conclusion of a small potential for population-level effects at this site.

Distribution of mono- through hexa-chlorobenzenes in floodplain soils and sediments of the Tittabawassee and Saginaw Rivers, Michigan

Chlorobenzenes are used as solvents or as feedstocks in the production of pesticide formulations, dyes, room deodorizers, moth-proofing agents, and de-inking solvents. Chlorobenzenes were produced by the Dow Chemical Company in Midland, Michigan, for several decades. In this study, concentrations of 12 chlorobenzene (CBz) congeners, from mono- to hexachlorobenzenes, were measured in more than 150 floodplain soil (FPS), surface sediment, and sediment core (SC) samples collected during 2002-2004 from the Pine River, Tittabawassee River, Shiawassee River, Saginaw River, and Saginaw Bay, Michigan. Five grams of wet sediment were homogenized with anhydrous sodium sulfate and extracted with 20% dichloromethane/hexane. The extracts were purified by silica gel column chromatography and analyzed by a gas chromatograph interfaced with a mass spectrometer (GC/MS). Mean concentrations of ΣCBz in FPS and surface sediment were seven to 30 times higher in the Tittabawassee River (80 and 60 ng/g dry weight (dw), respectively) than in the Saginaw River (2.4 and 8.1 ng/g dw, respectively) and Saginaw Bay (5.5 and 8.0 ng/g dw, respectively). Concentrations of ΣCBz were low in surface sediment and FPS from locations upstream of Midland, Michigan, on the Tittabawassee River. Concentrations of ΣCBz were higher in FPS than in surface sediment of the Tittabawassee River; on the contrary, surface sediment contained higher concentrations of CBz than FPS from the other rivers studied. High concentrations of hexachlorobenzene were found in FPS of the Tittabawassee River. All CBz congeners, except for dichlorobenzenes (DCBz), showed a trend of spatial decrease with downstream of the Dow Chemical Company in Midland. The CBz congener composition of the samples showed multiple patterns that reflected differences in historical emissions and environmental partitioning, arising from variations in physico-chemical properties of CBz. 1,4-Dichlorobenzene (1,4-DCBz) was found in all of the samples and accounted for a high proportion of total CBz. The relationship between concentrations of CBz and previously reported concentrations of PCDD/Fs for the same set of samples (Kannan et al. 2008) was significant, indicating similarities in sources and depositions of these two classes of compounds in the watershed.

Role of black carbon in the distribution of polychlorinated dibenzo- p-dioxins/dibenzofurans in aged field-contaminated soils

Floodplain soils containing elevated levels of polychlorinated dibenzo- p-dioxins/dibenzofurans (PCDD/Fs) were collected from several locations along the Tittabawassee River (Michigan, USA). The PCDD/F profiles of these soils exhibited distinct congener patterns consistent with byproducts from either chloralkali manufacturing or chlorophenols productions. Black carbon (BC) particles were isolated for the first time from floodplain soil impacted by PCDD/Fs. Petrographic analysis showed that BC particles, including coal, oxidized coal, metallurgical coke, depositional carbon, coal tar/pitch, cenosphere, and charcoal, comprised approximately 30% by volume of the organic fraction with size range of 250 μm–2000 μm from a typical floodplain soil. The BC particles with anthropogenic origin such as pitch and coke associated with the chloralkali production process served as both the source and subsequent transporter for the highly hydrophobic PCDD/Fs. These anthropogenic BC particles were enriched with high levels of PCDFs, containing approximately 1000-fold the concentration found in the bulk soil. The strong association of PCDD/Fs with anthropogenic BC directly impacts the physicochemical and biological availability thus the risk associated with these hydrophobic organochlorines in soils and sediments.

Dietary exposure of great blue heron (Ardea herodias) to PCDD/DFs in the Tittabawassee River floodplain, MI, USA

Concentrations of dioxin-like compounds, primarily polychlorinated dibenzofurans (PCDFs), in soils and sediments of the Tittabawassee River (TR) and associated floodplains downstream of Midland, Michigan (USA) were greater than upstream sites and prompted a site-specific risk assessment of great blue herons (GBH). Dietary exposure of GBH to PCDFs and polychlorinated dibenzo-p-dioxins (PCDDs) was evaluated based on site-specific concentrations of residues in prey items. Concentrations of ∑PCDD/DFs and 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQWHO-Avian) in prey items collected from the TR were consistently greater than those collected from associated reference areas (RAs) and further downstream in the Saginaw River (SR). The average daily dose (ADDpot) of ∑PCDD/DFs to GBH was 45- to 54-fold greater along the TR and 12-fold greater along the SR when compared to the RA. ∑PCDD/DFs were normalized to TEQWHO-Avian, and fold differences in the ADDpot increased, being 150- to 190-fold greater along the TR and 36-fold greater along the SR than they were in the RA. Greater fold changes in the ADDpot based on TEQWHO-Avian between the RA and the TR and SR was due to prey items from the latter reaches having a greater relative toxic potency of ∑PCDD/DFs, primarily from greater amounts of 2,3,7,8-tetrachlorodibenzofuran but also 2,3,4,7,8-pentachlorodibenzofuran. Potential for adverse population-level effects from site-specific contaminant exposures were evaluated via comparison to selected toxicity reference values. The prediction of minimal to no risk of adverse population-level effects resultant from the assessment of site-specific dietary exposure of GBH to ∑PCDD/DFs along the TR and SR is consistent with site-specific assessments of tissue-based exposures as well as population condition.

Relationship between polychlorinated dibenzo‐p‐dioxin, polychlorinated dibenzofuran, and dioxin‐like polychlorinated biphenyl concentrations in vegetation and soil on residential properties

The University of Michigan Dioxin Exposure Study was undertaken to address concerns that the industrial discharge of dioxin-like compounds in the Midland, Michigan, USA area had resulted in the contamination of soil and vegetation in the Tittabawassee River floodplain and downwind of the incinerator in the City of Midland. The study included the analysis of 597 vegetation samples, predominantly grass and weeds, from residential properties selected through a multistage probabilistic sample design in the Midland area, and in Jackson and Calhoun Counties (Michigan), as a background comparison, for 29 polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs). The mean toxic equivalent (TEQ) of the house perimeter vegetation samples ranged from 4.2 to 377 pg/g. The ratio of TEQs (vegetation to soil) was about 0.3, with a maximum of 3.5. Based on a calculation of the similarity of the congener patterns between the soil and the vegetation, it appeared that the source of the contamination on the vegetation was the surrounding soil. This conclusion was supported by linear regression analysis, which showed that the largest contributor to the R(2) for the outcome variable of log(10) of the vegetation concentration was log(10) of the surrounding soil concentration. Models of vegetation contamination usually focus on atmospheric deposition and partitioning. The results obtained here suggest that the deposition of soil particles onto vegetation is a significant route of contamination for residential herbage. Thus, the inclusion of deposition of soil particles onto vegetation is critical to the accurate modeling of contamination residential herbage in communities impacted by historic industrial discharges of persistent organic compounds.

Tissue‐based risk assessment of great blue heron (Ardea herodias) exposed to PCDD/DF in the Tittabawassee River floodplain, Michigan, USA

Concentrations of dioxin-like compounds, primarily polychlorinated dibenzofurans (PCDFs), in soils and sediments of the Tittabawassee River (TR) and associated floodplains downstream of Midland, Michigan, USA, were greater than upstream sites and prompted a site-specific risk assessment of great blue herons (GBH). Tissue exposure of PCDF and polychlorinated dibenzo-p-dioxins (PCDDs) was assessed in multiple GBH tissue types, including blood plasma of adults and eggs, as well as blood plasma, adipose, liver, and muscle of nestlings. Adult GBH exposure was associated with foraging area and age class, with concentrations of PCDD/DF being greater in blood plasma of adult GBH foraging in the TR compared with those foraging in upstream reference areas and in older birds as compared with their younger cohorts. Concentrations of PCDD/DFs and dioxin-like polychlorinated biphenyls (PCBs) in eggs and nestling tissues of GBH collected from rookeries within the TR floodplain were generally similar among rookeries. Mean concentrations of PCDD/DFs in eggs of GBH ranged from 45 to 67 ng/kg, wet weight for the rookeries studied, with a maximum concentration of 210 ng/kg, wet weight observed. Adipose consistently had the greatest concentration of PCDD/DFs of all tissues collected from nestlings of GBH, ranging from 98 to 430 ng/kg, wet weight. Potential for adverse population-level effects from site-specific contaminant exposures were evaluated by comparison with selected toxicity reference values (TRVs). Minimal risk of adverse population-level effects were predicted when exposures measured in tissues of GBH collected from rookeries within the TR were compared with appropriate TRVs. This prediction is consistent with site-specific measures of population condition, which included clutch size and number of nestlings per successful nest.

Great horned owl (Bubo virginianus) dietary exposure to PCDD/DF in the Tittabawassee River floodplain in Midland, Michigan, USA

Soils and sediments in the floodplain of the Tittabawassee River downstream of Midland, Michigan, USA contain elevated concentrations of polychlorinated dibenzofurans (PCDF) and polychlorinated dibenzo-p-dioxins (PCDD). As a long-lived, resident top predator, the great horned owl (Bubo virginianus; GHO) has the potential to be exposed to bioaccumulative compounds such as PCDD/DF. Site-specific components of the GHO diet were collected along 115 km of the Tittabawassee, Pine, Chippewa, and Saginaw Rivers during 2005 and 2006. The site-specific GHO biomass-based diet was dominated by cottontail rabbits (Sylvilagus floridanus) and muskrats (Ondatra zibethicus). Incidental soil ingestion and cottontail rabbits were the primary contributors of PCDD/DF to the GHO diet. The great horned owl daily dietary exposure estimates were greater in the study area (SA) (3.3 to 5.0 ng 2,3,7,8-TCDD equivalents (TEQ(WHO-avian))/kg body wt/d) than the reference area (RA) (0.07 ng TEQ(WHO-Avian)/kg body wt/d). Hazard quotients (HQs) based on central tendency estimates of the average daily dose and no-observable-adverse effect level (NOAEL) for the screech owl and uncertainty factors were <1.0 for both the RA and the SA. Hazard quotients based on upper end estimates of the average daily dose and NOAEL were <1.0 in the RA and up to 3.4 in the SA.