Phytotoxicity of weathered petroleum hydrocarbons in soil to boreal plant species.

Canada has extensive petroleum hydrocarbon (PHC) contamination in northern areas and the boreal forest region from historical oil and gas activities. Since the 2013 standardization of boreal forest species for plant toxicity testing in Canada, there has been a need to build the primary literature of the toxicity of weathered PHCs to these species. A series of toxicity experiments were carried out using fine-grained (<0.005-0.425 mm) background (100 total mg/kg total PHCs) and weathered contaminated soil (11,900 mg/kg total PHCs) collected from a contaminated site in northern Ontario, Canada. The PHC mixture in the contaminated site soil was characterized through Canadian Council of Ministers of the Environment Fractions, as indicated by the number equivalent normal straight-chain hydrocarbons (nC). The soil was highly contaminated with Fraction 2 (>nC10 to nC16) at 4790 mg/kg and Fraction 3 (>nC16 to nC34) at 4960 mg/kg. Five plant species (Elymus trachycaulus, Achillea millefolium, Picea mariana, Salix bebbiana, and Alnus viridis) were grown from seed in 0%, 25%, 50%, 75%, and 100% relative contamination mixtures of the PHC-contaminated and background soil from the site over 2-6 weeks. All five species showed significant inhibition in shoot length, shoot weight, root length, and/or root weight (Kruskal-Wallis Tests: p < 0.05, df = 4.0). Measurements of 25% inhibitory concentrations (IC25) following PHC toxicity experiments revealed that S. bebbiana was most significantly impaired by the PHC-contaminated soil (410-990 mg/kg total PHCs), where it showed <35% germination. This study indicates that natural weathering of Fraction 2- and Fraction 3-concentrated soil did not eliminate phytotoxicity to boreal plant species. Furthermore, it builds on the limited existing literature for toxicity of PHCs on boreal plants and supports site remediation to existing Canadian provincial PHC guidelines.

Assessment of the toxicity of weathered petroleum hydrocarbon impacted soils to native plants from a site in the Canadian Subarctic.

Remedial guidelines for petroleum hydrocarbons (PHCs) in soil aid in the mitigation of risks to human health and the environmental. However, some remediation guidelines may overestimate the potential for adverse effects to native plant species, contributing to unnecessary remedial efforts in attempts to meet the guidelines. At sites where PHC-contaminated soils undergo weathering, some PHCs may persist but with decreased bioavailability to organisms. In this study, the toxicity of both coarse and fine-grained subarctic soils, contaminated with weathered PHCs were assessed using five native plant species (Picea mariana, Achillea millefolium, Alnus viridis, Elymus trachycaulus and Salix bebbiana). Soil toxicity tests were conducted in a growth chamber with parameters set to simulate the site's subarctic climate conditions. Reference toxicant tests using boric acid were conducted to provide confidence in the interpretation of the results for the PHC-contaminated soils, and also provide new information on the sensitivities of the four boreal species to boric acid. All plants exhibited reduced growth and germination rates as boric acid concentrations increased. Despite exceeding the Canada-wide standard guidelines for Fraction 3 PHCs, field-collected contaminated soils had no significant negative impacts on the growth (i.e., length, dry weight and emergence) of any of the plant species tested.

The impact of soil chloride concentration and salt type on the excretions of four recretohalophytes with different excretion mechanisms.

Four natives Canadian recretohalophytic species: Atriplex canescens, Armeria maritima, Spartina pectinata, and Distichlis spicata were examined to determine their relative uptake and excretion of chloride in the context of phytoremediation. Adult plants were grown in soils contaminated with either sodium chloride or potassium chloride at various concentrations, then manually washed to collect the excreted salts. Atriplex canescens which has salt bladders, was found to have negligible excretions, suggesting that these structures release minimal amounts of salt onto the leaf's surface. Chloride excretions of S. pectinata and D. spicata increased with higher soil chloride concentrations. A. maritima showed minimal excretion until a threshold soil salinity was reached. This species shifted from a reliance on internal sequestration to secretion at higher soil salinity. The salt used in the media did not impact these trends, but D. spicata excreted significantly more chloride under sodium chloride conditions. While all four species studied were able to translocate significant amount of salt to their shoots, only S. pectinata, D. spicata, and A. maritima are suitable candidates for remediation by haloconduction. Among these, A. maritima showed the greatest potential and significantly reduced the soil chloride concentration by up to 60% in the highest concentration treatment (4 mg/g).HIGHLIGHTSArmeria maritima, Spartina pectinata, and Distichlis spicata are suitable species for remediation via haloconduction.Armeria maritima had the highest total extraction capacity at high soil chloride.Spartina pectinata had the most consistent excretion capacity and is the most suitable for remediation of soils with lower soil chloride.

The fate of DDT in soils treated with hydroxypropyl-ß-cyclodextrin (HPßCD).

Point Pelee National Park (PPNP) is highly contaminated with dichlorodiphenyltrichloroethane (DDT) due to the historical use of this persistent organochlorine pesticide. Hydroxypropyl-ß-cyclodextrin (HPßCD) has previously been investigated for its role in the remediation of polyaromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). In the present study, HPßCD's ability to promote DDT microbial degradation, enhance DDT phytoextraction by two native grasses (Schizachyrium scoparium and Panicum virgatum), and increase DDT bioavailability to redworms (Eisenia fetida) was investigated. Using a range of HPßCD concentrations (2.5% to 10%), it was determined that it did not promote DDT microbial degradation in PPNP soils, however, it was able enhance the DDT phytoextraction ability of S. scoparium plants due to the increased water solubility of DDT. Although HPßCD application to PPNP soil did not increase DDT bioavailability to redworms, its enhanced solubility allowed it to move through the soil column, and hence groundwater contamination is a possibility. Due to this important issue, in situ use of HPßCD to remediate DDT contamination is not recommended unless measures are in place to mitigate movement into groundwater.

Geomembrane applications for controlling diffusive migration of petroleum hydrocarbons in cold region environments.

Laboratory permeation tests examine the migration of aromatic hydrocarbons (benzene, toluene, ethylbenzene and xylenes (BTEX)) at 2, 7 and 14 °C through three different types of geomembrane (high density polyethylene (HDPE), linear low density polyethylene (LLDPE) and polyvinyl chloride (PVC)). Tests on both virgin and exhumed field samples provide permeation parameters (partitioning (Sgf), diffusion (Dg), and permeation (Pg) coefficients) for the three geomembranes. These results are combined with published values for the same geomembranes at 23 °C to establish an Arrhenius relationship that can be used to estimate diffusion parameters at temperatures other than those for which tests were conducted. Tests on an HDPE geomembrane sample exhumed after 3 years from a landfill site in the Canadian Arctic showed no significant difference in diffusion characteristics compared to an otherwise similar unaged and unexposed HDPE geomembrane. Contaminant transport modeling for benzene through HDPE, LLPDE and PVC in a simulated landfill cover show that for the conditions examined the presence of any of the three geomembranes below the 2 m thick soil cover substantially reduced the contaminant flux compared to the soils alone for realistic degrees of saturation in the cover soil. For these same realistic cold climate cases, of the three geomembranes examined, the HDPE geomembrane was the most effective at controlling the contaminant flux out of the landfill. An increase in soil cover and liner temperature by 2 °C (from potential climate change effects) above those currently measured at an Arctic landfill showed an increase in contaminant transport through the cover system for all geomembranes due to the increase surface temperature (especially in the summer months). Modeling of the addition of an extra 0.5 m of soil cover, as a mitigation measure for the effects of climate change, indicates that the main benefit of adding this unsaturated soil was to reduce the geomembrane temperature and that this did reduce the magnitude of the increase in contaminant transport.

Phytoextraction of DDT-Contaminated Soil at Point Pelee National Park, Leamington, ON, Using Cultivar Howden and Native Grass Species.

A field investigation was conducted at three dichlorodiphenyltrichloroethane (DDT)-contaminated areas in Point Pelee National Park (PPNP), Leamington, ON. cultivar Howden and three native grass species, (Michx.) Nash (little bluestem), L. (switchgrass), and (Torr.) A. Gray (sand dropseed) were grown at three different sites in the PPNP having low (291 ng/g), moderate (5083 ng/g), and high (10,192 ng/g) soil DDT contamination levels. A threshold soil DDT concentration was identified at ∼5000 ng/g where the DDT uptake into was maximized, resulting in plant shoot and root DDT concentrations of 16,600 and 45,000 ng/g, respectively. Two native grass species ( and ) were identified as potential phytoextractors, with higher shoot extraction capabilities than that of the known phytoextractor when optimal planting density was taken into account.

Feasibility of Using Phytoextraction to Remediate a Compost-Based Soil Contaminated with Cadmium.

Greenhouse and in-situ field experiments were used to determine the potential for phytoextraction to remediate soil contaminated with Cd from municipal solid waste (MSW) and sewage sludge (SS) compost application at a Peterborough (Canada) site. For the greenhouse experiment, one native (Chenopodium album) and three naturalized (Poa compressa, Brassica juncea, Helianthus annuus) plant species were planted in soil containing no detectable Cd (<1.0 µg·g(-1)), and soil from the site containing low (5.0 ± 0.3 µg·g(-1) Cd), and high (16.5 ± 1.2 µg⋅g(-1) Cd) Cd concentrations. Plant uptake was low (root BAFs ≤0.5) for all species except P. compressa in the low Cd treatment (BAF 1.0). Only B. juncea accumulated Cd in its shoots, though uptake was low (BAF ≤0.3). For the field experiment, B. juncea was planted in-situ in areas of low and high Cd concentrations. Brassica juncea Cd uptake was low (root and shoot BAFs <0.2) in both treatments. Sequential extraction analysis indicated that Cd is retained primarily by low bioavailability soil fractions, and phytoextraction is therefore not feasible at this site. Though low Cd bioavailability has negative implications for Cd phytoextraction from MSW/SS compost-based soils, it may limit receptor exposure to Cd sufficiently to eliminate the potential for risk at this site.

Non-invasive biomonitoring of polar bear feces can be used to estimate concentrations of metals of concern in traditional food.

The Arctic faces increasing exposure to environmental chemicals such as metals, posing health risks to humans and wildlife. Biomonitoring of polar bears (Ursus maritimus) can be used to quantify chemicals in the environment and in traditional foods consumed by the Inuit. However, typically, these samples are collected through invasive or terminal methods. The biomonitoring of feces could be a useful alternative to the current metal monitoring method within the Arctic. Here, we aim to 1) quantify the relationship between concentrations of metals in the feces and tissues (muscle, liver, and fat) of polar bears using predictive modeling, 2) develop an easy-to-use conversion tool for use in community-based monitoring programs to non-invasively estimate contaminant concentrations in polar bears tissues and 3) demonstrate the application of these models by examining potential exposure risk for humans from consumption of polar bear muscle. Fecal, muscle, liver, and fat samples were harvested from 49 polar bears through a community-based monitoring program. The samples were analyzed for 32 metals. Exploratory analysis indicated that mean metal concentrations generally did not vary by age or sex, and many of the metals measured in feces were positively correlated with the internal tissue concentration. We developed predictive linear regression models between internal (muscle, liver, fat) and external (feces) metal concentrations and further explored the mercury and methylmercury relationships for utility risk screening. Using the cross-validated regression coefficients, we developed a conversion tool that contributes to the One Health approach by understanding the interrelated health of humans, wildlife, and the environment in the Arctic. The findings support using feces as a biomonitoring tool for assessing contaminants in polar bears. Further research is needed to validate the developed models for other regions in the Arctic and assess the impact of environmental weathering on fecal metal concentrations.

Improved methods for quantifying soil invertebrates during ecotoxicological tests: Chill comas and anesthetics.

Soil invertebrate ecotoxicological tests are important when making informed site-management decisions. However, traditional tests are time-consuming and require quantification of high numbers of soil invertebrates burrowed beneath the surface of soil. A commonly used technique to extract invertebrates from the soil is the floatation method. Due to the movement of Collembola, and the presence of small soil particulates and bubbles on the surface of the water, automatic image analysis software may inaccurately quantify the true number of individuals present. Hence, manual counting immediately following extraction, or from images, is still the most effective method utilized for quantifying floated soil invertebrates. This study investigated three novel techniques; the use of an ice-water bath, chest freezer (-12 °C) and ethanol to temporarily immobilize groups of 35 Folsomia candida individuals to increase accuracy during the quantification step. Active thermography to aid automatic image analysis was also investigated. Results show that while thermoimaging did not provide a distinct advantage in differentiating soil invertebrates from soil particles, both an ice-water bath and 4.75% ethanol solution were extremely effective at temporarily immobilizing F. candida with no apparent ill effects. The outcome of this study will assist future soil invertebrate research by increasing the accuracy of invertebrate quantifications. In addition, as the techniques caused no mortality to the invertebrates, the same individuals remain available for continuous monitoring experiments, repeated exposure, and/or multi-generational studies.

Transcriptome analysis of a springtail, Folsomia candida, reveals energy constraint and oxidative stress during petroleum hydrocarbon exposure.

Petroleum hydrocarbon (PHC) contamination in soil is ubiquitous and poses harmful consequences to many organisms. The toxicity of PHC-impacted soil is difficult to predict due to variations in mixture composition and the impacts of natural weathering processes. Hence, high-throughput methods to assess PHC-impacted soils is required to expedite land management decisions. Next-generation sequencing is a robust tool that allows researchers to investigate the effects of contaminants on the transcriptome of organisms and identify molecular biomarkers. In this study, the effects of PHCs on conventional endpoints (i.e., survival and reproduction) and gene expression rates of a model springtail species, Folsomia candida were investigated. Age-synchronized F. candida were exposed to ecologically-relevant concentrations of soils spiked with fresh crude oil to calculate the reproductive EC25 and EC50 values using conventional toxicity testing. Soils spiked to these concentrations were then used to evaluate effects on the F. candida transcriptome over a 7-day exposure period. RNA-seq analysis found 98 and 132 differentially expressed genes when compared to the control for the EC25 and EC50 treatment groups, respectively. The majority of up-regulated genes were related to xenobiotic biotransformation reactions and oxidative stress response, while down-regulated genes coded for carbohydrate and peptide metabolic processes. Promotion of the pentose phosphate pathway was also found. Results suggest that the decreased reproduction rates of F. candida exposed to PHCs is due to energy constraints caused by inhibition of carbohydrate metabolic processes and allocation of remaining energy to detoxify xenobiotics. These findings provide insights into the molecular effects in F. candida following exposure to crude oil for seven days and highlight their potential to be used as a high-throughput screening test for PHC-contaminated sites. Adverse molecular effects can be measured as early as 24 h following exposure, whereas conventional toxicity tests may require a minimum of four weeks.

Contamination of the marine environment by Antarctic research stations: Monitoring marine pollution at Casey station from 1997 to 2015.

The contamination of the marine environment surrounding coastal Antarctic research stations remains insufficiently understood in terms of its extent, persistence, and characteristics. We investigated the presence of contaminants in marine sediments near Casey Station, located in the Windmill Islands of East Antarctica, during the period spanning from 1997 to 2015. Metals, hydrocarbons, PBDEs, PCBs, and nutrients were measured in sediments at anthropogenically disturbed sites, including the wastewater outfall, the wharf area, two former waste disposal sites, and various control locations. Sampling was carried out at three spatial scales: Locations, which were generally kilometres apart and formed the primary scale for comparison; Sites, which were 100 meters apart within each location; and Plots, which were 10 meters apart within each site. Consistently higher concentrations of most contaminants, and in some cases nutrients, were observed at disturbed locations. Some locations also exhibited an increase in contaminant concentrations over time. The spatial distribution of sediment properties (such as grain size and organic matter) and contaminants displayed intricate patterns of variation. Variation in grain size depended on the size category, with fine grains (e.g., <63 µm) showing the greatest variation at the Location scale, while coarse grains exhibited minimal variation at this scale. Contaminant levels demonstrated significant differences between Locations, accounting for approximately 55% of the overall variation for metals, while the variation within the 10-meter scale generally exceeded that within the 100-meter scale. Residual variation among replicate samples was also very high, demonstrating the need for adequate replication in studies of sediments and contaminants around stations. Some contaminants exceeded international guidelines for sediment quality, including metals, hydrocarbons, and PCBs. We conclude that Antarctic research stations such as Casey are likely to pose a moderate level of long-term ecological risk to local marine ecosystems through marine pollution. However, contamination is expected to be confined to areas in close proximity to the stations, although its extent and concentration are anticipated to increase with time. Raising awareness of the contamination risks associated with Antarctic stations and implementing monitoring programs for marine environments adjacent to these stations can contribute to informed decision-making and the improvement of environmental management practices in Antarctica.

Earthworm metabolomic responses after exposure to aged PCB contaminated soils.

(1)H NMR metabolomics was used to measure earthworm sub-lethal responses to polychlorinated biphenyls (PCBs) in historically contaminated (>30 years) soils (91-280 mg/kg Aroclor 1254/1260) after two and 14 days of exposure. Although our previous research detected a distinct earthworm metabolic response to PCBs in freshly spiked soil at lower concentrations (0.5-25 mg/kg Aroclor 1254), the results of this study suggest only weak or non-significant relationships between earthworm metabolic profiles and soil PCB concentrations. This concurs with the expectation that decades of contaminant aging have likely decreased PCB bioavailability and toxicity in the field. Instead of being influenced by soil contaminant concentration, earthworm metabolic profiles were more closely correlated to soil properties such as total soil carbon and soil inorganic carbon. Overall, these results suggested that (1)H NMR metabolomics may be capable of detecting both site specific responses and decreased contaminant bioavailability to earthworms after only two days of exposure, whereas traditional toxicity tests require much more time (e.g. 14 days for acute toxicity and >50 days for reproduction tests). Therefore, there is significant opportunity to develop earthworm metabolomics as a sensitive tool for rapid assessment of the toxicity associated with contaminated field soils.

Design and application of surface PRBs for PCB remediation in the Canadian Arctic.

Over the course of three years, several surface permeable reactive barriers were designed and constructed to deal with leftover site contamination at a site located on the summit of Resolution Island, Nunavut, just southeast of Baffin Island at 61° 35'N and 60° 40'W. The site was part of a North American military defense system established in the 1950s that became heavily contaminated with polychlorinated biphenyls (PCBs) during and subsequent to, its operational years. Each of the three barrier designs has a different configuration, to meet the needs of the targeted remediation area, based on their unique contaminant histories. Modifications were made to the barrier designs based on both field observations and laboratory results. The comparison of field and laboratory results indicated that areas with higher concentrations of PCB contamination behaved differently than areas with lower concentrations of PCB contaminated soil. Previous laboratory studies only partially replicated field observations and results. It had previously been hypothesized that particle retention was the most important factor in trapping and capturing PCBs. However, rinsed filter samples from the field indicated that partitioning of PCBs between contaminated soil and granular activated carbon (GAC) filter particles were occurring at levels of 62 ± 11%, suggesting that sequestration of the PCBs from the environment should be a primary focus of the barrier. This sequestration requires both particle retention (within the granular sorptive filters) as well as maintained contact time between particles for sorption processes to proceed. This mechanism--partitioning of PCB to GAC--was more important in areas with higher PCB concentration. These results suggest that it may be possible to tailor future barrier designs to their unique site histories and locations.

The absorption and translocation of polychlorinated biphenyl congeners by Cucurbita pepo ssp pepo.

The mobility of polychlorinated biphenyl (PCB) congeners within Cucurbita pepo ssp pepo cv. Howden (pumpkin), a PCB phytoextracting plant, was investigated through a comparison of field-weathered soil, root, shoot, and xylem sap congener profiles. This is the first study to show the presence of PCBs in xylem sap (range: 0.03-0.18 µg·mL(-1)), confirming that PCB translocation throughout the plant occurs via this medium. A comparison of soil (5.2 ± 2.5 µg·g(-1)), root (27.1 ± 2.1 µg·g(-1)), shoot (range: 1.9 ± 0.5 µg·g(-1) - 8.2 ± 1.4 µg·g(-1)), and xylem sap (0.09 ± 0.04 µg·g(-1)) samples showed significant differences in congener profiles, with lower chlorinated congeners (predominately trichlorinated ones) found within xylem sap in higher amounts than higher chlorinated congeners. The total PCB concentrations of xylem sap samples collected at various lengths along the primary plant shoot were not significantly different from each other, while those of primary shoot tissue samples significantly decreased (two-sample t test, p = 0.01) as the distance from the plant base increased. PCA analysis of individual congeners in the roots, shoots and xylem sap indicated that movement of the PCB congeners in the plant was affected by the number of chlorines in the molecule, and hence possibly log K(ow) and molecular weight, but not by planarity.

Activated carbon immobilizes residual polychlorinated biphenyls in weathered contaminated soil.

Activated carbon (AC) has recently been shown to be effective in sequestering persistent organic pollutants (POPs) from aquatic sediments. Most studies have demonstrated significant reductions of POP concentrations in water and in aquatic organisms; however, limited data exist on the possibility of using AC to immobilize remaining POPs at terrestrial contaminated sites. Under greenhouse conditions, pumpkin ssp cv. Howden) were grown, and red wiggler worms () were exposed to an industrial contaminated soil containing a mixture of polychlorinated biphenyls (PCBs), i.e., Aroclors 1254 and 1260) treated with one of four concentrations of AC (0.2, 0.8, 3.1, and 12.5%) for 2 mo. The addition of AC to contaminated soils virtually eliminated the bioavailability of PCBs to the plant and invertebrate species. There were reductions in PCB concentrations of more than 67% in ssp and 95% in . These data suggest that AC could be included as part of comprehensive site closure strategy at PCB-contaminated sites.

Phytoextraction and uptake patterns of weathered polychlorinated biphenyl-contaminated soils using three perennial weed species.

Three promising phytoextracting perennial weed species [ L. (ox-eye daisy), L. (curly dock), and L. (Canada goldenrod)] were planted in monoculture plots at two polychlorinated biphenyl (PCB)-contaminated sites in southern Ontario and followed over 2 yr to investigate the effects of plant age, contaminant characteristics, and species-specific properties on PCB uptake and accumulation patterns in plant tissues. Results from this study indicate that, for each of these weed species, shoot contaminant concentrations and total biomass are dependent on plant age and life cycle (vegetative and reproductive stages), which affects the total amount of PCBs phytoextracted on a per-plant basis. Even at suboptimal planting densities of 3 to 5 plants m, all three weed species extracted a greater quantity of PCBs per unit area (4800-10,000 µg m) than the known PCB-accumulator L. ssp (cv Howden pumpkins) (1500-2100 µg m) at one of the two sites. Calculated PCB extractions based on theoretical optimal planting densities were significantly higher at both sites and illustrate the potential of these weeds for site remediation. This study also demonstrates that plants may accumulate PCBs along the stem length in a similar manner as plants.

Evaluating mercury concentrations in edible plant and fungi species in the Canadian Arctic environment.

Levels of environmental mercury (Hg) within the Canadian Arctic are a current area of concern. Although efforts have been made to reduce Hg released into the environment, levels remain elevated in flora and fauna. This study examined the concentrations of Hg in soil and naturally occurring edible plant and fungi species, identified by local Inuit residents, from eight locations in Iqaluit, Nunavut, and the surrounding area during the summers of 2018 and 2019. Total Hg concentrations were obtained in 24 soil samples, 112 flora samples from 23 plant and five lichen species, and 157 fungal samples from eight species. Median Hg concentrations in plant species ranged from 0.005 µg g-1 Hg dry weight (dw) in Saxifraga cernua to 0.19 µg g-1 Hg dw in Oxytropis maydelliana. Median concentrations in edible fungi species ranged from 0.084 µg g-1 Hg dw in the Cortinarius croceus (non-puffball species) to 1.6 µg g-1 Hg dw in Lycoperdon perlatum (a puffball mushroom). Additionally, median Hg concentration in puffball species (1.4 µg g-1 ) were higher than non-puffball species (0.12 µg g-1 ). Three puffball species were assessed for methylmercury (MeHg), with mean concentrations ranging from 0.013 to 0.085 µg g-1 MeHg dw. Limited research has been conducted on Hg uptake in naturally occurring edible plant and fungi species of the Canadian Arctic. This study contributes important information on Hg accumulation and processes in edible plant and fungi Arctic species, is the first to focus on plants used by the local Indigenous community, and demonstrates a need for further studies to assess Hg in Arctic environments.

Transplacental benzene exposure increases tumor incidence in mouse offspring: possible role of fetal benzene metabolism.

Childhood cancer is the leading cause of disease-related death in children aged 1-14 years in Canada and the USA and it has been hypothesized that transplacental exposure to environmental carcinogens such as benzene may contribute to the etiology of these cancers. Our objectives were to determine if transplacental benzene exposure increased tumor incidence in mouse offspring and assess fetal benzene metabolism capability. Pregnant CD-1 and C57Bl/6N mice were given intraperitoneal injections of corn oil, 200 mg/kg, or 400 mg/kg benzene on gestational days 8, 10, 12 and 14. A significant increase in tumor incidence was observed in CD-1, but not C57BL/6N, 1-year-old offspring exposed transplacentally to 200 mg/kg benzene. Hepatic and hematopoietic tumors were predominantly observed in male and female CD-1 offspring, respectively. Female CD-1 offspring exposed transplacentally to 200 mg/kg benzene had significantly suppressed bone marrow CD11b(+) cells 1 year after birth, correlating with reduced colony-forming unit granulocyte/macrophage numbers in 2-day-old pups. CD-1 and C57Bl/6N maternal blood benzene levels and fetal liver benzene, t, t-muconic acid, hydroquinone and catechol levels were analyzed by gas chromatography/mass spectrometry. Significant strain-, gender- and dose-related differences were observed. Male CD-1 fetuses had high hydroquinone levels, whereas females had high catechol levels after maternal exposure to 200 mg/kg benzene. This is the first demonstration that transplacental benzene exposure can induce hepatic and hematopoietic tumors in mice, which may be dependent on fetal benzene metabolism capability.

Effect of plant age on PCB accumulation by Cucurbita pepo ssp. pepo.

A greenhouse experiment was conducted to investigate polychlorinated biphenyl (PCB) uptake and translocation from soil over time in pumpkin plants (Cucurbita pepo ssp. pepo cv. Howden). Plants were grown in weathered soil collected from a former industrial site contaminated with Aroclor 1248 (mean [PCB](soil) = 6.5 mg kg(-1)). Plants were harvested five times over 42 d and analyzed for total PCB concentration in the root and shoot tissues. The concentration of PCBs in the root was not significantly different between harvests (mean [PCB](root) = 21.5 mg kg(-1)). The concentration of PCBs in the shoots was also relatively stable over time (mean [PCB](shoot) = 3.5 mg kg(-1)) despite increases in shoot biomass (fresh weight of 4.3 g at Day 12 to 59 g at Day 42). This suggests that PCBs were continuously accumulated throughout the growth period. The trends found in this study indicate the optimal time to harvest C. pepo ssp pepo plants to maximize PCB phytoextraction is when the plant shoot has reached its maximum biomass.

Evaluating the efficacy of Atriplex spp. in the phytoextraction of road salt (NaCl) from contaminated soil.

Soil and freshwater salinization are growing issues worldwide. Road salt, primarily sodium chloride (NaCl), is a significant contributor to this issue in North America. In this study, the ability of three native Canadian halophytes (Atriplex patula, Atriplex hortensis, and Atriplex canescans) to remove Na+ and Cl- from contaminated soil was investigated. Field and greenhouse studies determined plant survivability in roadside areas, as well as Na+ and Cl- extraction levels. The Atriplex spp. accumulated 18-55 mg Na+ g-1 dry weight (DW) and 41-64 mg Cl- g-1 DW when grown for a two-month period in soil spiked with NaCl to simulate a very highly contaminated roadside. Using A. patula, it would theoretically take 6 growing seasons to remove all salt from an area contaminated with 1540 µg Cl- g-1, while A. hortensis and A. canescens would take 19 and 9 years, respectively. Salt content in shoot components (seeds, stem, leaves) was determined to provide further insight on phytoextraction processes. In all three Atriplex species, the leaves had the highest Cl- concentration, followed by the seeds (bracteoles included), with the lowest concentrations found in the stem. These novel findings provide important information for road salt remediation and indicate that using Atriplex spp. may be a viable way in which to reduce the environmental impact of road salting.