Pesticide Residues In Sediments Research Articles

DLLME coupled with HPLC-DAD for enrichment of pesticide residues in environmental sediment and soil samples

Sample pre-treatment during determination of pesticides in sediment and soil is difficult due to matrix effects. For this reason, a low density dispersive liquid-liquid microextraction (ld-dllme) was developed for the determination of carbaryl, cynazine, atrazine, and propazine. The experimental parameters that could potentially influence performances of the developed analytical technique including the extraction solvent type and volume, disperser solvent type and volume, extraction and centrifugation time, centrifugation speed, salt concentration, and pH were optimized. The optimum experimental values were found to be 50 mL 1-octanol, 0.6 mL acetonitrile, 5 min extraction time, centrifugation at 3500 rpm for 3 min, 10% NaCl and pH 5. At the optimum conditions, the methods offer good linearity (R2 = 0.998–0.999) for the concentration ranges of 30-800 µg/kg; the detection limit (lod) ranging from 9-24 µg/kg; precision <5.3% rsd, and reproducibility 0.5-5.2% rsd. The accuracy of the method, determined in terms of recovery was found to vary from 74.5-109.7%. Therefore, the developed analytical method could be used for the determination of trace level of pesticides residues in sediment and agricultural soil samples.

Determination of Pesticide Residues in Sediments of River Ravi

Sediments are socioeconomic, geomorphologic, and an important environmental resource. The purpose of this study was to determine the pesticide residues in the sediments of River Ravi. For analysis 12 sediment samples were collected along with River Ravi, reaching from Ravi Siphon to BS (Balloki Suleiman) link. River Ravi is enlisted as one of the most polluted rivers of Pakistan followed by extreme flow variations, i.e. 10 – 10,000 m3/s. The concentration of pesticide residues in samples was detected by the High-pressure liquid chromatography (HPLC) technique. Noticeable concentrations of pesticides were detected in the majority of the samples which depicted high toxicity levels of pesticides in the sediments of River Ravi. High amounts of pesticides were observed in the right and left banks of Saggian (S4) i.e. 11.37 mg/kg and Khudpur (S6, S7) i.e. 12.116 mg/kg. A significant amount of Imidacloprid and Bifenthrin was detected in the majority of the sediment samples, i.e. 22.78 mg/kg and 15.82 mg/kg. Furthermore the detected concentration of pesticides in the right and left bank of Balloki head works (S10, S11) and Ravi Bridge (S3) was relatively less as compared to other sampling sites. All these sampling points receive irrigational runoff from nearby agricultural lands and urban wastewater, resulting in the accumulation of pesticides in the sediments. The following trend of pesticide contamination was observed in the sediment samples of River Ravi, Bifenthrin > Imidacloprid > Dimethomorph > Glyphosate.

Persistence of organochlorine pesticide residues in sediments derived from an agricultural watershed in Tennessee, USA

Persistence of organochlorine pesticide residues in sediments derived from an agricultural watershed in Tennessee, USA

A reliable LC-MS/MS-based method for trace level determination of 50 medium to highly polar pesticide residues in sediments and ecological risk assessment.

The occurrence of polar pesticides in sediments has not been extensively investigated because of their relatively poor hydrophobicity and apparently less persistence in the environment. However, their continuous release into the aquatic systems calls for the evaluation of their potential accumulation in sediments and the role of this matrix as a potential source of these compounds. Considering this, a method based on pressurized liquid extraction (PLE), extract clean-up by solid phase extraction (SPE), and analyte determination by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was developed and validated to analyze 50 relevant (frequently used and/or regulated or found in water) medium to highly polar pesticides in sediments. The method showed good performance regarding accuracy (relative recoveries between 76 and 124%), precision (relative standard deviation values < 20%), sensitivity (LODs in the low nanogram per gram for most compounds), linearity (coefficients of determination > 0.99), and matrix effects (negligible for all analytes). The use of an isotope dilution approach for quantification ensures result reliability. As a part of the validation process, the method was applied to the analysis of the target pesticides in sediments from the Llobregat River (NE Spain) showing the presence of five of them, namely, terbutryn, dichlorvos, terbuthylazine, diazinon, and irgarol. All 5 pesticides, due to both the concentrations found and their physical-chemical characteristics, demonstrate high potential for bioaccumulation and risk to aquatic organisms. Additional multi-disciplinary studies that investigate pesticide occurrence in different aquatic compartments and evaluate the potential risks for aquatic ecosystems are required to assess the environmental impact and significance of the presence of pesticides in sediments. Graphical Abstract.

Method for the Analysis of 7 Indictor Polychlorinated Biphenyls (PCBs) and 13 Organochlorine Pesticide Residues in Sediment by Gas Chromatography (GC)

This study described the development of a multiresidue method based on gas chromatography (GC) for the detection of 7 indictor polychlorinated biphenyls (PCBs) and 13 organochlorine pesticide (OCPs) residues in sediment with electron capture detector (ECD). The samples were extracted by n-hexane/dichloromethane (1/1, v/v) by ultrasonic extraction. The extracts were desulfurization with copper powder and purification with concentrated sulfuric acid. The method was validated by the analysis of spiked Tai lake sediment. Analytical performances were evaluated in terms of linearity, quantification limits, accuracy, and precision. Good linearity responses with coefficients of determination higher than 0.9945 were obtained. Methodological limit of quantitation (LOQ) was 0.5-5.0μg/kg for OCPs and PCBs. The recovery and RSDs of three-level spiked samples were in the ranges of 71.6%-105% and 3.2-11.2%. This method is highly effective to reduce the cost and time for the pretreatment of sample, and offers the ability to detect and quantify the PCBs and OCPs in sediments.

Organochlorine pesticide residues in sediment and water from Nairobi River, Kenya: levels, distribution, and ecological risk assessment.

Production and use of most organochlorine pesticides (OCPs) was banned through the Stockholm Convention on persistent organic pollutants. However, appreciable amounts are still detected in the environment due to their persistence, illegal use, and releases from contaminated soils and obsolete stocks. The present study investigated the levels of OCP residues in Nairobi River. Sediment and water samples were collected from three sites along the river and screened for 17 OCPs using gas chromatography electron capture detector (GC-ECD). Mean pesticide residues ranged from 0.01 to 41.9μgkg-1 in sediment and below detection limit to 39.7ngL-1 in water. In sediment α-HCH, β-HCH, γ-HCH, heptachlor epoxide, and p,p'-DDD were detected in all samples, while α-HCH, γ-HCH, δ-HCH, heptachlor epoxide, endosulfan I, and endrin were detected in all water samples. Levels of OCPs in water were below the WHO maximum allowable limits for surface water. However, values higher than the sediment quality guidelines for sediment samples in Racecourse Road Bridge and Outering Road Bridge were reported, thus confirming the toxicity to aquatic organisms. Consequently, as these compounds are known to bio-accumulate in fatty tissues, continued use of the river water poses a health risk to animals and humans.

Levels of pesticide residues in water, sediment, and fish samples collected from Nile River in Cairo, Egypt

Pesticides constitute one of the major sources of environmental hazards to human and animals as they concentrate in the food chain. Organochlorine, organophosphorus, and carbamate pesticides were investigated using water, sediment, and fish (Clarias gariepinus, Oreochromis niloticus, and Tilapia zillii) muscle samples of the Nile River in Cairo region (Egypt). Pesticide residues were analyzed seasonally using gas chromatography. The results showed that the average total pesticide residue in sediment was higher (63.5 ± 36.2 ppb) than that in water samples (45.1 ± 35.0 ppb). High levels of total pesticide residues in water and sediment samples were detected in autumn (73.57 ± 62.97 and 103.03 ± 16.05 ppb, respectively), which may be attributed to the increase in suspended matter (low flood) and high application of pesticides during that season. Pesticide residue in tissue samples of C. gariepinus amounted to 49.1 ± 17.8 ppb followed by T. zillii (48.3 ± 18.9 ppb) and O. niloticus (45.6 ± 28.7 ppb). The relatively high levels of total pesticide residue on C. gariepinus tissue may be explained by the nature of catfish habits and feeding. The estimated pesticide residual concentrations in fish samples did not exceed the maximum residue limits. Health risk estimation revealed that all tested pesticides in the studied fish species had no potential for systemic toxicity to consumers, but regular monitoring is recommended to control the levels of pesticide residues in the Nile River ecosystem.

Trace analysis of pesticide residues in sediments using liquid chromatography-high-resolution Orbitrap mass spectrometry.

The present study describes the optimization and validation of an analytical method based on quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction and purification with dispersive solid-phase extraction(dSPE) before analysis, followed by ultrahigh-performance liquid chromatography-high-resolution linear ion trap/Orbitrap (LTQ Orbitrap) mass spectrometry for the determination of 18 pesticides in sediment. To optimize process efficiency, parameters such as pH, extraction salts, sediment amount, and cleanup sorbents were evaluated. Identification was based on both accurate mass and retention time, and further confirmation was achieved by mass spectrometry fragmentation. The optimized analytical method demonstrated good validation characteristics, such as accuracy (recoveries from 70.8% to 106.2%), method quantification limits (below 10 ng g-1 for 89% of the pesticides selected), linearity (coefficient of determination greater than 0.9921 in all cases), precision (repeatability and reproducibility with standard deviations below 18% and 21%, respectively), and matrix effect (signal suppression was exhibited for almost all analytes). The overall method performance, expressed as process efficiency, ranged from 58.8% to 102.1%. The validated method was successfully applied to real samples collected along two rivers in northwestern Greece, revealing the presence of three selected pesticides but at levels below the method quantification limit.

Human Health Risk Associated with Dietary and Non-Dietary Intake of Organochlorine Pesticide Residues from Rice Fields in Edo State Nigeria

The levels, distribution patterns, ecological risk and human health risk of fourteen organochlorine pesticides in surface water, sediment, and fish (Tilapia zilli and Clarias gariepinus) collected from a massive rice field in Illushi, were monitored. Samples obtained were extracted and analyzed using gas chromatography equipped with electron capture detector while risk assessment was carried out using standard models (risk quotient and Chronic daily intake). Pesticide concentration in water samples ranged from ND to 1.65 µg/l, while the concentration of pesticide residues in sediment, C. gariepinus, and T. zilli ranged from ND to 8.45 µg/kg dw, 0.03 to 1.57 µg/kg/ww, and 0.03 to 0.85 µg/kg/ww, respectively. There was a clear dominance of the organochlorine; Hexachlorocyclohexane (α-HCH, γ-HCH, β-HCH) in all matrices. Risk quotient estimates for heptachlor, heptachlor epoxide, aldrin, dieldrin, DDT, endosulfan I, endosulfan II, and endosulfan aldehyde showed risk to aquatic organisms under extreme conditions. Health risk estimations showed that there is a potential risk to humans exposed to contaminated water, sediment, and fishes through ingestion, inhalation, and dermal routes of exposures. Cumulative hazard quotient estimated for pesticide mixtures in each matrix further confirmed that there was potential risk to human health especially children. Furthermore, the risk of non-carcinogenic effects followed the following sequence; biota > sediment > water. This study presents evidence of the multiple contamination of water, sediment, and biota from the Illushi River Basin which would possibly lead to non-cancer effects in humans especially children when exposed. Therefore, water bodies draining agricultural farmlands should be monitored regularly to prevent the contamination of the aquatic environment by toxic and banned pesticides, while efforts should be intensified to regulate the sales, application, and disposal of pesticide products in Nigeria.

Assessing the distribution and human health risk of organochlorine pesticide residues in sediments from selected rivers.

Sediment samples from major agricultural producing areas in Edo state Nigeria were analysed for α-HCH, γ-HCH, β-HCH and ∑DDT with the aim of elucidating contamination profiles, distribution characteristics, carcinogenic and non-carcinogenic risk of these compounds in these regions. Analysis was done using a gas chromatography (GC) equipped with electron capture detector (ECD), while health risk assessment was carried out using the Incremental Lifetime Cancer Risk (ILCR) and the chronic daily intake (CDI). Results showed varying concentrations of α-HCH, γ-HCH, β-HCH and ∑DDT pesticides in sediment samples with hexachlorocyclohexane (∑HCHs) (4.6 µg/g/dw) being the dominant contaminants as it was widely detected in all samples and stations. Source identification revealed that the current levels of HCHs and DDT in sediments were attributed to both historical use and fresh usage of these pesticides. Risk estimates using ILCR and CDI showed that the risk of cancer and non-cancer effects was highest when exposure route was through ingestion. Furthermore, model projections highlights children as high risk population groups for non-dietary exposure to OCPs. These findings suggests the need for increased monitoring programmes, with a wider scope for both currently used pesticides and legacy/banned pesticides.

Persistent organic pesticide residues in sediments of Vasai Creek near Mumbai: Assessment of sources and potential ecological risk

Thirteen persistent organic pesticides were investigated in the sediments of Vasai Creek near Mumbai to evaluate their pollution levels and potential risks. It was observed that ΣOCPs level was in the range of 597–1538ng/g dw, with an average value of 1115.25ng/g dw. The level of ΣOPPs was in the range of 492–1034ng/g dw, with an average value of 798.15ng/g dw. The values o,p′-DDT/p,p′-DDT ratio gives an indication of use of technical DDT as the prime source of DDT, while the α/γ-BHC ratio indicate that BHCs in study area might have been received from fresh lindane. The results of an ecological risk assessment showed that sediment bound organic pesticides are of more ecotoxicological concern as they might create adverse ecological risk to the marine breeding habitats. These pesticides residues may get remobilize and released to overlying waters creating adverse effects on terrestrial and aquatic organisms.

Persistent Organochlorine Pesticide Residues in Water, Sediments and Fish Samples from Ogbese River

This study considered the levels of 15 organochlorine pesticide (OCPs) residues (α-BHC, β- BHC, ϒ-BHC, lindane, chlorothalonil, heptachlor, aldrin, heptachlor epoxide, endosulfan I, endosulfan II, endrin, dieldrin, p, p'-DDD, p, p'-DDT and endosulfan sulphate in water, sediments and fish species from Ogbese river in Ekiti State, Southwestern Nigeria. Samples were extracted and cleaned-up on silica gel adsorbent. The OCPs concentrations were determined using Gas chromatograph (GC) equipped with Electron Capture Detector. The OCPs concentration in water and sediments ranged from below detection limit (BDL): BDL – 13.6 µg/L and 0.52 –450 µg/kg whilst the mean OCPs in the fish ranged from 2.64 – 66.0 µg/kg, respectively. The results indicated that all the analysed fish samples were contaminated with the studied pesticides. Endosulfan I was found to be above EU and FAO/WHO maximum residue limits (MRL) in Clarias gariepinus fish samples. The sediments and fish samples showed evidence of organochlorine pesticides enrichment and bioaccumulation. Chi-square at α = 0.05 showed there were significant differences in the levels of organochlorine pesticide residues in sediments and fish samples except α-BHC.

Pesticide residues in sediments and aquatic species in Lake Nokoué and Cotonou Lagoon in the Republic of Bénin

Lake Nokoué and Cotonou Lagoon are the most important and most productive continental freshwaters in Bénin, with an estimated fish production of over 2 tonnes per hectare in Lake Nokoué. Organochlorine pesticides are used in agriculture and to repel tsetse flies, malaria mosquitoes and other diseases raised. Sediment, fish, shrimp and oyster species were collected in Lake Nokoué and Cotonou Lagoon for pesticide residues analysis. The main pesticides identified in sediment were pp'-DDT and its metabolites pp-DDE and pp'-DDD, with residue levels between the detection limit and 24.4μg/kg dry weight. Fish species commonly consumed such as Elops lacerta, Podamasys jubelini, Gobbienellus occidentalis, Ethmalosa fimbriata, Mugil cephalus and Hemichromis fasciatus were contaminated with residues of seven to nine pesticides, including pp-DDE, op'-DDD, pp'-DDD, op'-DDT, pp'-DDT, α-endosulfan, aldrin, dieldrin and γ-hexachlorocyclohexane. The levels ranged from detection limit to 289ng/g lipid. The same pesticides were also detected in other aquatic species, such as shrimp and oysters. A summed risk assessment, comparing pesticide intake levels through fish consumption with tolerable daily intake levels proposed by the World Health Organization, showed in all cases a low risk for human health.

Health Risks Associated With Pesticide Residues in Sediments, Fish, and Plants From the Ouémé Valley in the Republic of Bénin

To determine possible human and environmental health risks, organochlorine pesticide residues were determined in vegetables grown in floodplains along the Ouémé River near Lowé in Bénin. Testing of vegetables found 13 pesticides with ΣDDT, α-endosulfan, Σdrin, and lindane being most important. The same pesticides were also detected in plants eaten by bovine cattle, sheep, and herbivorous fish. Human pesticide intake by vegetable consumption was compared with tolerable daily intake (TDI) values reported by the World Health Organization. Pesticide intake by fish consumption was estimated from residue levels in whole fish collected from the Ouémé River in 2004 and reported earlier. Fish consumption does not pose a risk for human health, but consuming vegetables that contain pesticide residues may lead to exceedance of TDI values. Based on these findings, concerns are warranted, and more work is needed to understand the full exposure profile for the local population.

Organochlorine Pesticide Residues in Sediments and Waters from Cocoa Producing Areas of Ondo State, Southwestern Nigeria

This study investigated levels of organochlorine pesticide (OCP) residues in water and sediment samples from eleven rivers serving as drinking water sources and receiving runoff from nearby cocoa plantations in Ondo State, Nigeria. Twenty-two composite samples of surface water and sediments (0–3 cm) were collected randomly using grab technique and replicated thrice per season. The efficiency of the two techniques [supercritical fluid extraction (SFE) and liquid/liquid extraction (LLE)] was evaluated with percentage analyte recoveries to for SFE and to 1 for LLE. Determination of OCPs by gas chromatography with electron capture detection gave higher concentrations for sediments compared to the equivalent water samples. The commonly occurring pesticide residues in the sediments were (range, μg g−1) cis-chlordane 0.03–6.99; α-endosulfan 0.03–6.99; p,p′-DDE 0.08–19.04; and dieldrin 0.01–7.62; in the sediments and dieldrin (not detected-1.51 μg L−1) in water samples, during the dry season. OCP levels were significantly higher in dry season than wet season among the rivers. The study concluded that most of the rivers in cocoa growing areas were contaminated with OCPs associated with agricultural activities.

Application of Different Extraction Methods for the Determination of Selected Pesticide Residues in Sediments

Using several extraction methods including the QuEChERS approach, samples of both model and natural sediments were prepared. For the isolation of the target group of pesticides, two variants of two complementary extractions had to be used. Resulting extracts were analysed with LC/MS/MS. Selected methods furnishing the best results were validated in the terms of linearity and repeatability. Their limits of detection ranged from 0.1 to 2ng/g, their limits of quantification from 1 to 6ng/g and their recovery percentage varied between 46% and 102%.

Organochlorine pesticide residues in sediments from the Uganda side of Lake Victoria

Organochlorine (OC) residues were analysed in 117 sediment samples collected from four bays of the Uganda side of Lake Victoria. The sediments were collected with a corer at a depth of 0–20 cm, and extracted for OC residues using a solid dispersion method. The extracts were cleaned using gel permeation chromatography and analysed for pesticide residues using a gas chromatograph (GC) equipped with an electron capture detector. The results were confirmed using a GC equipped with a mass spectrometer (MS). A total of 16 OC residues, most of them persistent organic pollutants (POPs) were identified and quantified. The OC residue levels were expressed on an oven dry weight ( d.w.) basis. Endosulphan sulphate, in the range of 0.82–5.62 μg kg −1 d.w., was the most frequently detected residue. Aldrin and dieldrin were in the ranges of 0.22–15.96 and 0.94–7.18 μg kg −1 d.w., respectively. DDT and its metabolites lay between 0.11–3.59 for p,p′-DDE, 0.38–4.02 for p,p′-DDD, 0.04–1.46 for p,p′-DDT, 0.07–2.72 for o,p′-DDE and 0.01–1.63 μg kg −1 d.w. for o,p′-DDT. The levels of γ-HCH varied from 0.05 to 5.48 μg kg −1 d.w. Heptachlor was detected only once at a level of 0.81 μg kg −1 d.w., while its photo-oxidation product, heptachlor epoxide, ranged between non-detectable (ND) to 3.19 μg kg −1 d.w. Chlordane ranged from ND to 0.76 μg kg −1 d.w. Based on the threshold effect concentration (TEC) for fresh water ecosystems, aldrin and dieldrin were the only OCs that seemed to be a threat to the lake environment.

Organochlorine pesticide residues in sediments from coastal environment of Cantabria (northern Spain) and evaluation of the Atlantic Ocean

This paper documents levels of organochlorine pesticides (OCs) in coastal surface sediments from selected reference sites on the northern Atlantic Spanish coast. One hundred eight samples covering three estuaries in the Cantabrian Coast were sampled in 2006 and analyzed in the finer fraction (<63 μm) for 19 OCs by gas chromatography with electron capture detector after confirmation by mass spectrometry. Detected organochlorine pesticides were endosulfan α, endosulfan β, endosulfan sulfate, hexachlorobenzene (HCB), aldrin, dieldrin, methoxychlor, 1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene (4,4'-DDE) and 1,1-dichloro-2,2-bis(4-chlorophenyl)ethane (4,4'-DDD). Total OCs concentrations ranged from 1.8 ng g(-1) dry weight (dw) to 3.9 ng g(-1) dw, showing a uniform distribution along the studied area, and being consistent with recorded levels in the literature for coastal sediments in other reference sites with low levels of pollution by OCs along the Atlantic Ocean. Endosulfan, 4,4'-DDD, HCB, aldrin, and dieldrin seemed to be ubiquitous as the legacy of past uses and deposition. OCs concentrations were significantly correlated to organic matter content and particle size distribution. No adverse biological effects derived from these pollutants are expected to take place as it can be concluded from the comparison with the existent marine sediment quality guidelines.

Occurrence of endocrine‐disrupting pesticide residues in wetland sediments from beijing, china

Wetlands are important habitats and spawning grounds to a diverse wildlife population and are particularly vulnerable to adverse effects of endocrine disruptors. Many pesticides possess hormonal activity and have thus been classified as endocrine disruptors. A new analytical method based on ultrasonic-assisted extraction, solid-phase extraction, and gas chromatography technologies was developed for analysis of selected potential endocrine-disrupting pesticide residues in wetland sediment samples from northern Beijing, China. The newly developed method was a less time-consuming and less solvent-consuming way of analyzing residues without an air-drying process prior to extraction. The selected pesticides included the compounds hexachlorocyclohexane, cyclodiene, DDTs, chlordane, hexachlorobenzene, heptachlor, endrin aldehyde, heptachlor epoxide, dicofol, acetochlor, alachlor, metolachlor, chlorpyrifos, nitrofen, trifluralin, cypermethrin, fenvalerate, and deltamethrin. Characterization and identification of the selected endocrine-disrupting pesticide residues in sediments may help to assess current pollution status of endocrine-disrupting pesticides in the area. Total concentrations of pesticides ranged from 15.4 to 38.1 ng/g (dry weight) with a mean concentration of 23.7 ng/g (dry weight) for sediment samples. Although levels of all detected pesticides were below the New York State Department of Environmental Conservation, USA, sediment quality criteria, considering the potential health effects of endocrine disruptors even in a trace level, the use of the pesticides in the agricultural system should be minimized and regular monitoring is needed in the area.

A River-wide Survey of Polychlorinated Biphenyls (PCBs), Polycylic Aromatic Hydrocarbons (PAHs), and Selected Organochlorine Pesticide Residues in Sediments of the Detroit River—1999

The spatial distribution of hydrophobic organic contaminants, including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and octachlorostyrene (OCS) in sediments of the Detroit River was established using data from a 1999 river-wide survey. The survey employed a stratified random sampling design that divided the river into six geostatistical zones consisting of upper, middle, and lower U.S. and equivalent Canadian river reaches. Organic carbon normalized OCS sediment concentrations demonstrated no significant differences between U.S. or Canadian sediments or upstream/downstream gradients suggesting that OCS is derived primarily from sources upstream of the Detroit River. In contrast, sum PCBs and sum PAHs were significantly elevated at U.S. as compared to Canadian stations and demonstrated significant increasing upstream/downstream gradients in organic carbon normalized sediment contamination. The upper and middle U.S. river reaches contained a number of near-shore stations with high localized PCB and PAH sediment concentrations suggesting multiple inputs along the upper U.S. portion of the river. Consistent with past surveys, wide-spread sediment contamination of PCBs and PAHs continues to be observed in the highly industrialized Trenton Channel and downstream of Grosse Isle. Threshold effect level (TEL) sediment quality guidelines for PAHs and PCBs were exceeded in 92.6 and 77.8%, respectively, of stations in Trenton Channel and downstream of Grosse Isle. This large reservoir of degraded sediments in the lower U.S. river reach has the potential to enter Lake Erie during sediment disturbance events and likely contributes to gentoxic stress and increased bioaccumulation of PCBs in resident benthos, fish, and wildlife.