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In addition to sediments, pesticides can be sorbed to other constituents present in rivers including ash, charcoal, and microplastics. Pesticide sorption by microplastics has been studied for hydrophobic compounds such as the legacy insecticide DDT (dichlorodiphenyltrichloroethane) but not for current-use herbicides. The purpose of this study was to investigate to what extent 2,4-dichlorophenoxyacetic acid (2,4-D) (weak acid), atrazine (weak base), and glyphosate (zwitterion) are sorbed by microplastics (i.e., fiber, polyethylene beads, polyvinyl chloride (PVC), and tire fragments) and other river constituents (i.e., ash, charcoal, suspended and bottom sediments). DDT was included in the study to provide reference data that could be compared to known literature values. Batch equilibrium experiments were conducted following Guidelines 106 of the Organisation for Economic Co-operation and Development. Experiments utilized either a 1:100 solid/solution ratio with 0.1 g of a river constituent as the sorbent or a 1:5 solid/solution ratio with the sorbents consisted of 1.9 g bottom sediments mixed with 0.1 g of a river constituent. Background solutions included 0.01 M CaCl 2 or 0.01 M KCl, deionized water, and river water. Individual microplastics always sorbed >50% of DDT. Current-use herbicides had a weak affinity for microplastics (< 6%) except that a substantial amount of glyphosate was sorbed by PVC (32–36%) in 0.01M KCl and DI water. When river water was used as a background solution, rather than 0.01M KCl or deionized water, there was much less glyphosate sorption by PVC, ash, charcoal, and both sediments. This suggested that ions present in river water competed for sorption sites with glyphosate molecules. Across background solutions, sorption by sediments decreased in the order of DDT (91–95%) > glyphosate (36–88%) >atrazine (5–13%) >2,4-D (2–5%). Sorption of 2,4-D, atrazine, and DDT by ash and charcoal was always > 90% but < 35% for glyphosate. Relative to bottom sediments alone, the presence of ash or charcoal (5% by weight) with sediments significantly increased the sorption of 2,4-D, atrazine, and DDT. Microplastic additions (5% by weight) had no impact on all four pesticides’ sorption by sediments. Microplastics are not a strong sorbent for current-use herbicides, although there are exceptions such as glyphosate by PVC. Ions present in river water competed with glyphosate for sorption sites of river constituents. Hence, the types and concentrations of ions present in rivers might have some influence on the partitioning of glyphosate between the water column and solid phase, including glyphosate fate processes in rivers.

Using a sample of women natural sciences and engineering (NSE) faculty members from 13 Canadian universities, we investigated the impact of women academic leaders on women professors’ perceptions of gender bias. Logistic regression analyses indicated that professors who perceived more workplace gender bias were more likely to feel that they needed to work harder to be seen as legitimate scholars than those who perceived less gender bias. However, professors who perceived that women were better represented amongst their faculty/college and university leadership were significantly less likely to feel that they needed to work harder for legitimacy than those who perceived greater gender bias in leadership. These results suggest that addressing gendered university hierarchies may moderate the impact of gender bias on women in NSE units., Notre étude porte sur l’influence des femmes en position de leadership en milieu universitaire sur la perception des préjugés sexistes chez les professeures. L’échantillon étudié comporte des femmes du corps professoral en sciences naturelles et en génie (SNG) parmi 13 universités canadiennes. Des analyses fondées sur des régressions logistiques montrent que les professeures qui perçoivent davantage de préjugés sexistes en milieu de travail sentent qu’elles doivent travailler plus fort pour se sentir légitimes, comparativement à celles qui perçoivent moins ces mêmes préjugés. Toutefois, si le corps professoral et la direction comptent des femmes, les professeures ressentent beaucoup moins l’obligation de travailler plus fort pour se sentir légitimes, comparativement à celles qui perçoivent plus de préjugés au sein de la direction. Les résultats donnent à penser qu’une réflexion sur la hiérarchie genrée en milieu universitaire pourrait atténuer les effets des préjugés sexistes sur les femmes en SNG.

In addition to her contributions to the field of chemistry, Dr. Margaret-Ann Armour was the foremother of equity, diversity, and inclusion in the natural sciences in Canada and was an exemplary mentor to many women in science, technology, engineering, and mathematics. Dr. Armour emphasized that, to make progress in natural sciences and engineering fields, we also need to make advancements in workplace EDI. Dr. Armour was among the first to recognize the need to fix gender biased systems and not women. Analyses of the 2017–2018 Faculty Workplace Climate Survey, administered to approximately 700 natural sciences and engineering professors from 13 Canadian universities, supports Dr. Armour’s position. We present a synthesis of the key findings from the survey, which speak to some of the gendered challenges that women faculty members in Canada still face; and discuss the implications of these findings in light of women’s continued lack of access to mentors, with an emphasis on gender bias in mentorship within academic chemistry.

Water is considered a major route for transmitting human-associated pathogens. Although microbial water quality indicators are used to test for the presence of waterborne pathogens in drinking water, the two are poorly correlated. The current study investigates the prevalence of thermophilic DNA markers specific for Campylobacter spp. (C. jejuni and C. coli) in source water and throughout the water distribution systems of two First Nations communities in Manitoba, Canada. A total of 220 water samples were collected from various points of the drinking water distribution system (DWDS) between 2016 and 2018. Target Campylobacter spp. were always (100%) detected in a home with a fiberglass (CF) cistern, as well as the community standpipe (SP). The target bacteria were also frequently detected in treated water at the Water Treatment Plant (WTP) (78%), homes with polyethylene (CP) (60%) and concrete (CC) (58%) cisterns, homes with piped (P) water (43%) and water truck (T) samples (20%), with a maximum concentration of 1.9 × 103 cells 100 mL−1 (C. jejuni) and 5.6 × 105 cells 100 mL−1 (C. coli). Similarly, target bacteria were detected in 68% of the source water samples with a maximum concentration of 4.9 × 103 cells 100 mL−1 (C. jejuni) and 8.4 × 105 cells 100 mL−1 (C. coli). Neither target Campylobacter spp. was significantly associated with free and total chlorine concentrations in water. The study results indicate that there is an immediate need to monitor Campylobacter spp. in small communities of Canada and, particularly, to improve the DWDS in First Nations communities to minimize the risk of Campylobacter infection from drinking water sources. Further research is warranted in improving/developing processes and technologies to eliminate microbial contaminants from water.

Sorption to roots is one of several mechanisms by which plant-assisted attenuation of antibiotics can be achieved. The objectives of this study were to (1) evaluate the sorption of sulfamethoxazole (SMX) by cattail and switchgrass roots, (2) determine the kinetics of SMX sorption by cattail and switchgrass roots, and (3) characterize the temperature-dependency of SMX sorption. A batch sorption experiment was conducted to measure SMX sorption by roots of the two plant species using five initial antibiotic concentrations (2.5, 5, 10, 15, and 20 µg L

We tested four proposed dimensions of a Culture Conducive to Women's Academic Success (CCWAS; i.e., supportive leadership, freedom from gender bias, equal access to opportunities, and support for w...

The influent and effluent of two single-cell biobeds (Province of Alberta, Canada) and two dual cell-biobeds (Province of Saskatchewan, Canada) were monitored during a number of growing seasons. A total of 59 unique pesticide active ingredients were detected, with all biobed influent samples (n = 54) and 93% of effluent samples (n = 54) containing pesticide mixtures. About one-half of the effluent samples in both single-cell (56%) and dual-cell (45%) biobeds contained active ingredients that have Groundwater Ubiquity Score (GUS) values2.8 and so were more likely to move through the biomatrix materials into effluent. The Pesticide Toxicity Index (PTI) calculated for aquatic indicator species (i.e., vascular and nonvascular plants, invertebrates, and fish) was always larger for influent samples (e.g., median PTI 500 for invertebrates in dual-cell biobed) than effluent samples (i.e., median PTI 1). As such, this study demonstrates the potential ecosystem benefits of the broad adoption of on-farm biobeds in the Canadian Prairies for recycling tank rinsate as a strategy to accelerate a green economy. Although biobeds were highly effective in reducing the concentrations for pesticides with a wide range of soil organic carbon coefficient and half-life values, the biobed effectiveness was relatively poor for the herbicides clopyralid, diclofop, fluroxypyr, and imazethapyr. Clopyralid (3.02), fluroxypyr (3.70), and imazethapyr (3.90) all have relatively high GUS values (2.8) and are thus more likely to be detected in effluent than active ingredients with smaller GUS values. This suggests that further improvements in biosystem design need to be made for optimizing the recycling of these pesticides.Both single-cell and dual-cell biobeds performed remarkably in colder climates (Canadian Prairies). Pesticides detected in effluents were more likely to be pesticides that have greater GUS values. The Pesticide Toxicity Index (PTI) was drastically smaller for biobed effluent than for influent. The broad adoption of biobeds for recycling tank rinsate will contribute to a green economy. The biobed system design must be refined to broaden its effectiveness to treat all pesticides.

A mixed methods analysis of Canadian natural sciences and engineering faculty’s workplace experiences revealed a gendered care gap with women reporting greater responsibility for students’ personal and mental health problems, including suicidal thoughts and behaviour, and sexual assault. Statistical results demonstrated that women were approached by a significantly greater number of students to discuss serious non-academic issues and experienced more stress as a result. A comparative qualitative analysis found faculty’s responses to students’ problems were informed by gendered cultural care expectations thatrequire women to be more supportive than men. However, female and male faculty’s care burden may also be exacerbated by institutional factors, including senior administrative positions, undergraduate class loads, and teaching courses with mental health-related content. As such, the care gap is relevant to understanding the extent to which gender inequality is embedded within the structure of universities., Une analyse à méthode mixte effectuée auprès du corps professoral canadien en sciences naturelles et en ingénierie signale un écart entre les genres/les sexes quant au soutien fourni auprès de la population étudiante. En effet, les femmes rapportent une responsabilité accrue à l’égard de la santé personnelle et mentale de la population étudiante, y compris la gestion des pensées suicidaires et des cas d’agression sexuelle. Selon les statistiques, les femmes seraient approchées par un plus grand nombre d’étudiants et d’étudiantes pour discuter de sujets non universitaires, ce qui entraînerait pour elles un taux de stress accru. Une analyse comparative de nature qualitative indique que le corps professoral a tendance à gérer les cas d’étudiants et d’étudiantes selon des normes culturelles genrées, en vertu desquelles les femmes seraient plus disposées à offrir du soutien que les hommes. Toutefois, certains facteurs institutionnels contribuent à accroître cette charge émotionnelle, notamment les postes administratifs, la charge d’enseignement et l’enseignement de cours dont le contenu touche les questions de santé mentale, et peuvent exacerber l’écart entre les genres/les sexes. Afin de mieux comprendre comment et pourquoi l’inégalité entre les sexes est structurante dans le contexte universitaire, il ne faut pas négliger le rôle de l’écart quant au soutien offert à la population étudiante.

The university reward structure has traditionally placed greater value on individual research excellence for tenure and promotion, influencing faculty’s allocation of time and definition of worthwhile labour. We find gender differences in Canadian natural sciences and engineering faculty’s opinions of the traditional criteria for measuring academic success that are consistent with an implicit gender bias devaluing service and teamwork. Most women recommend significant changes to the traditional model and its foundation, while a substantial minority of men support the status quo. However, this comparative qualitative analysis finds more cross-gender similarities than differences, as most men also want a more modern definition of success, perceiving the traditional model to be disproportionately supportive of one type of narrow research scholarship that does not align with the realities of most faculty’s efforts. Thus, this study suggests a discrepancy between traditional success criteria and faculty’s understanding of worthwhile labour., Dans un paradigme plus traditionnel, l’évaluation du rendement en milieu universitaire a eu tendance à privilégier la recherche individuelle dans le cadre de la promotion et de l’octroi de la permanence. Cette tendance a eu pour effet dans leur conception d’un travail valorisant. Nous signalons la présence de différences liées au genre dans les opinions du corps professoral en sciences pures et en ingénierie au Canada quant à l’évaluation du rendement qui sont cohérentes avec des préjugés sexistes qui dévalorisent le service à la collectivité et la collaboration. La majorité des femmes revendiquent des changements importants par rapport au paradigme dominant et aux modèles traditionnels, alors qu’une minorité significative des hommes défend le statu quo. Notre analyse comparative qualitative indique toutefois plus de similitudes que de différences entre les sexes : la plupart des hommes souhaitent également une définition actualisée du rendement, car le paradigme traditionnel a tendance à privilégier un seul type de recherche qui ne se fait pas le reflet des activités professionnelles du corps professoral. Cette étude présente donc un écart entre le rendement tel qu’il est défini de manière traditionnelle et les conceptions actuelles du travail dit valorisant au sein du corps professoral.

Abstract: Gender equality has made its way to the forefront of discussions across various sectors in the Canadian context. Yet the intentional inclusion of gender and other intersectional identity dimensions is just beginning to permeate the realities of performance measurement and evaluation practitioners, particularly those using program theory. There is a vast body of knowledge regarding the measurement of women’s empowerment, gradually declining availability of resources targeting the inclusion of gender in theory, and even less guidance on integrating gender in theory in the context of gendered programming. Similarly, coordinated efforts from multiple sectors have resulted in an abundance of theory regarding girls and women’s representation, recruitment, retention, and promotion within STEM (Science, Technology, Engineering, and Math) but less guidance on the measurement and evaluation in these areas. This article shares recent efforts to bridge the divide using theory knitting to develop a performance measurement framework addressing the decreasing representation of girls and women across the STEM “leaky pipeline” using the COM-B theory of change model.

Here, we report the complete genome sequences of two distinct isolates of Legionella that were obtained from potable water sourced from cistern-bearing homes within a First Nation community in Manitoba, Canada.

Cattail (Typha latifolia L.) and switchgrass (Panicum virgatum L.) can effectively remove inorganic contaminants from soils and biosolids, but their role in the attenuation of organic contaminants, such as antimicrobials, is currently poorly understood. Uptake by plants is one of several mechanisms by which plant-assisted attenuation of antimicrobials can be achieved. The objectives of this growth room study were to evaluate the plant uptake of ciprofloxacin (CIP) and sulfamethoxazole (SMX) and examine their partitioning between plant roots and aboveground biomass (AGB). Plant uptake of the two 14C labeled antimicrobials was studied at two environmentally relevant concentrations (5 and 10 μg L−1). Plants were destructively sampled every 3–4 d during the 21-d growth period. Accumulation of CIP and SMX in both plant species was greater in the roots than in the AGB. The percentage uptake values of the two antimicrobials were significantly greater for cattail (34% for CIP, 20% for SMX) than for switchgrass (10% for both CIP and SMX). Translocation factors of the two antimicrobials were

About one-half of the homes on First Nations (FN) reserves in Manitoba, Canada, receive piped water from a water treatment plant (WTP). Many other homes (31%) are equipped with cisterns that are filled by a water truck, and our objective was to determine how the use of cisterns affects drinking water safety relative to drinking water piped directly to homes from the WTP. The study included belowground concrete cisterns, belowground fiberglass cisterns, and aboveground polyethylene cisterns stored in insulated shelters, and all the data collection methods showed that the tap water in homes with cisterns were relatively more contaminated with coliform bacteria than the tap water in piped homes. The frequency and severity of Escherichia coli and total coliform contamination were numerically greater in drinking water samples from belowground concrete and fiberglass cisterns than in piped water samples in each community, and the contamination of belowground cisterns by coliform bacteria was greatest in late spring. As well, data obtained under the Access to Information Act showed no statistical differences in the percent of satisfactory samples (no detects) between 2014 and 2018, suggesting no clear indication of improved water quality in any of the Tribal Councils in which these three and other communities are a member off. Our results point to the need for additional treatment of drinking water in homes supplied by belowground concrete or fiberglass cisterns and replacement of belowground cisterns with aboveground cisterns or piped water to reduce the risk of water-borne illnesses.

Little is known about the dissipation rate of microcontaminants in biosolids during storage and stabilization in stockpiles (unsaturated) or storage lagoons/tanks (saturated). The objective of this study was to characterize the dissipation in biosolids of two antibiotics, sulfamethoxazole (SMX) and trimethoprim (TMP), in microcosms under saturated and unsaturated conditions that simulate biosolids that are stockpiled on land or deposited in lagoons/tanks, respectively. The laboratory experiment was conducted at 22 °C using biosolids spiked at an initial nominal concentration of 10 mg kg−1 for both antibiotics. Biosolids were sampled in triplicate at seven sampling times over a 42-d period. Concentrations of SMX and TMP in extracts prepared from biosolids were quantified using liquid chromatography with tandem mass spectrometry. Dissipation data fitted to a first-order kinetic model indicated that the time to 50% dissipation (DT50) for SMX was significantly shorter in the unsaturated microcosms (2.8 d) than the saturated microcosms (4.4 d), while the DT50 for TMP was significantly shorter in microcosms under saturated conditions (10 d) relative to unsaturated conditions (116 d). These results indicate that the reducing conditions that develop in biosolids deposited in lagoons or placed in storage tanks might be effective for enhancing the microbial degradation of antibiotics that are otherwise persistent under aerobic conditions (i.e., TMP), while also being effective for removing other antibiotics including those that dissipate relatively readily under aerobic conditions (i.e., SMX).

Groundwater samples were collected from piezometers and water table wells in both dryland and irrigated agricultural regions of Alberta, Canada, to examine the occurrence of pesticide mixtures. Fourteen current-use pesticides and two historical compounds were detected over a 3-yr sampling period. Pesticide mixtures were detected in ∼3% of the groundwater samples, and the frequency of detection increased from spring (1.5%) to summer (3.8%) and fall (4.8%). Pesticide mixtures always consisted of at least one of two auxin herbicides: 2,4-dichlorophenoxyacetic acid (2,4-D) or 2-methyl-4-chlorophenoxyacetic acid (MCPA). 19% of all samples contained a single pesticide, with auxin herbicides 2,4-D (7.3%), MCPA (4.4%), and clopyralid (3.9%) being most prevalent. We detected 2,4-D predominantly in the fall (72% of 2,4-D detections) and less in spring and summer (28%). We detected MCPA mostly in summer (85% of MCPA detections) and less in spring and fall (15%). Clopyralid was more evenly detected across spring (30%), summer (25%), and fall (45%). Since the auxin herbicides above are typically applied in summer, results suggest that each herbicide may have different mobility and persistence characteristics in prairie soils. Guidelines for Canadian Drinking Water Quality have been set for a range of individual pesticides, but not for pesticide mixtures. If Canada is to establish such guidelines, this study demonstrates that auxin herbicides should be prioritized. In addition, only 7 of the 16 compounds detected in this study have established maximum acceptable concentrations (MACs), excluding clopyralid, which was detected in all three sampling years.

Phosphate and glyphosate molecules compete for sorption sites in soil. The objective of this study was to quantify the impact of Olsen P concentrations in two contrasting soils on phosphate and glyphosate sorption. Soils were a sandy clay loam soil rich in iron oxides (SCL-Fe2O3) and a clay loam soil rich in calcium carbonates (CL-CaCO3). The phosphate Freundlich sorption coefficient (Kf) ranged from 3 to 68 L1/n mg1–1/n kg− 1 in the SCL-Fe2O3 and from 21 to 76 L1/n mg1–1/n kg− 1 in the CL-CaCO3. Glyphosate sorption coefficient (Kd) ranged from 293 to 1173 L kg− 1 in the SCL-Fe2O3 but only 99 to 141 L kg− 1 in the CL-CaCO3. Glyphosate Kd and phosphate Kf values decreased significantly with increasing Olsen P concentrations in both soils. Glyphosate Kd values were further significantly reduced when phosphate was added to the slurry solutions, but phosphate Kf values were not impacted by the presence of glyphosate in solutions. We conclude that annual phosphate fertilizer applications leave phosphate concentrations in Prairie soils to the extent that soils have a lesser capacity to retain glyphosate and phosphate that are subsequently applied, but glyphosate residues will not influence phosphate sorption.

Solid-state 13C Nuclear Magnetic Resonance (NMR) and synchrotron-based X-ray Absorption Near-Edge Structure (XANES) have applications for determining the relative proportions of organic C functional groups in materials. Spectral data obtained by NMR is typically processed using integration (INTEG) whereas XANES spectral data is typically processed using deconvolution (DECONV). The objective of this study was to examine the impact of spectral data collection and processing on the estimated relative proportions of organic C functional groups in biochars. Biochars showed large variations in aromatic C (45–97%), alkyl C (0–23%), O-alkyl C (1–41%), phenolic C (0–20%) and carboxylic C (0–20%). NMR had a better ability than XANES to differentiate % aromatic C across biochars, and the mean % aromatic C was always greater for NMR-INTEG and NMR-DECONV than for XANES-INTEG or XANES-DECONV. NMR-INTEG showed significant associations with NMR-DECONV and XANES-INTEG for % aromatic C and alkyl C, but there were no significant associations between NMR and XANES for % O-alkyl C, phenolic C and carboxylic C. As well, there was no association between NMR-INTEG and XANES-DECONV for any organic C functional group, and in some cases, spectral data collection and processing influenced the quantification of organic C functional groups in a given biochar to the extent that the differences observed were as large as differences observed between biochars when analyzed using the same spectral data collection and processing technique. We conclude that great caution must be taken when comparing studies that determined organic C functional groups in materials using NMR-INTEG versus XANES-DECONV.

Wetlands in the Prairie Pothole Region of North America are integrated with farmland and contain mixtures of herbicide contaminants. Passive nonfacilitated diffusion is how most herbicides can move across plant membranes, making this perhaps an important process by which herbicide contaminants are absorbed by wetland vegetation. Prairie wetlands are dominated by native cattail (Typha latifolia) and hybrid cattail (Typha x glauca). The objective of this batch equilibrium study was to compare glyphosate absorption by the shoots and rhizomes of native versus hybrid cattails. Although it has been previously reported for some pesticides that passive diffusion is greater for rhizome than shoot components, this is the first study to demonstrate that the absorption capacity of rhizomes is species dependent, with the glyphosate absorption being significantly greater for rhizomes than shoots in case of native cattails, but with no significant differences in glyphosate absorption between rhizomes and shoots in case of hybrid cattails. Most importantly, glyphosate absorption by native rhizomes far exceeded that of the absorption occurring for hybrid rhizomes, native shoots and hybrid shoots. Glyphosate has long been used to manage invasive hybrid cattails in wetlands in North America, but hybrid cattail expansions continue to occur. Since our results showed limited glyphosate absorption by hybrid shoots and rhizomes, this lack of sorption may partially explain the poorer ability of glyphosate to control hybrid cattails in wetlands.

Approximately 20% of the 600 First Nations reserves across Canada are under a drinking water advisory, often due to unacceptable levels of bacteria. In this study, we detected fecal bacteria at an alarmingly high frequency in drinking water sources in a fly-in First Nations community, most notably in buckets/drums of homes without running water where Escherichia coli levels ranged from 20 to 62,000CFU/100mL. The water leaving the water treatment plant was free of E. coli and its free residual chlorine concentration (0.67mg/L) was within the range typically observed for treated water in Canada. Water samples from taps in homes served by cisterns, and those sampled from the water truck and community standpipe, always showed unacceptable levels of E. coli (1 to 2100CFU/100mL) and free residual chlorine concentrations below the 0.2mg/L required to prevent bacterial regrowth. Samples from taps in homes served by piped water had lower levels of E. coli (0 to 2CFU/100mL). DNA- and RNA-based 16S rRNA Illumina sequencing demonstrated that piped and cisterns water distribution systems showed an abundance of viable cells of Alphaproteobacteria indicative of biofilm formation in pipes and cisterns. The alpha diversity, based on observed OTUs and three other indices, was lowest in water truck samples that supplied water to the cistern and the low free residual chlorine concentration (0.07mg/L) and predominance of Betaproteobacteria (63% of viable cells) that were immediately detected after the truck had filled up at the water treatment plant was indicative of contamination by particulate matter. Given these findings, First Nation residents living without running water and relying on inadequate water distribution systems are at higher risk of contracting water-born illnesses. We urge all governments in Canada to expand their investments in supporting and sustaining water as a human right in Canada's First Nations communities.

To study the structure and function of soil organic matter, soil scientists have performed alkali extractions for soil humic acid (HA) and fulvic acid (FA) fractions for more than 200 years. Over the last few decades aquatic scientists have used similar fractions of dissolved organic matter, extracted by resin adsorption followed by alkali desorption. Critics have claimed that alkali-extractable fractions are laboratory artifacts, hence unsuitable for studying natural organic matter structure and function in field conditions. In response, this review first addresses specific conceptual concerns about humic fractions. Then we discuss several case studies in which HA and FA were extracted from soils, waters, and organic materials to address meaningful problems across diverse research settings. Specifically, one case study demonstrated the importance of humic substances for understanding transport and bioavailability of persistent organic pollutants. An understanding of metal binding sites in FA and HA proved essential to accurately model metal ion behavior in soil and water. In landscape-based studies, pesticides were preferentially bound to HA, reducing their mobility. Compost maturity and acceptability of other organic waste for land application were well evaluated by properties of HA extracted from these materials. A young humic fraction helped understand N cycling in paddy rice (Oryza sativa L.) soils, leading to improved rice management. The HA and FA fractions accurately represent natural organic matter across multiple environments, source materials, and research objectives. Studying them can help resolve important scientific and practical issues.

This study analyzed the microbiological quality of drinking and source water from three First Nations communities in Manitoba, Canada that vary with respect to the source, storage and distribution of drinking water. Community A relies on an aquifer and Community B on a lake as source water to their water treatment plants. Community C does not have a water treatment plant and uses well water. Quantification of free residual chlorine and fecal bacterial (E. coli and coliforms), as well as detection of antibiotic resistance genes (sul, ampC, tet(A), mecA, vanA, blaSHV, blaTEM, blaCTX-M, blaOXA-1, blaCYM-2, blaKPC, blaOXA-48, blaNDM, blaVIM, blaGES and blaIMP) was carried out. While water treatment plants were found to be working properly, as post-treatment water did not contain E. coli or coliforms, once water entered the distribution system, a decline in the chlorine concentration with a concomitant increase in bacterial counts was observed. In particular, water samples from cisterns not only contained high number of E. coli and coliforms, but were also found to contain antibiotic resistance genes. This work shows that proper maintenance of the distribution and storage systems in First Nations communities is essential in order to provide access to clean and safe drinking water.

Wetlands are abundant throughout the agricultural landscape of central Saskatchewan, Canada, and the biota present in these wetlands may be vulnerable to the toxic effects of pesticides used on nearby crops. We hypothesized that herbicide concentrations would be higher in wetlands on minimum-tillage farms than on organic (no herbicide use) farms, and that the principal transport mechanisms of runoff versus atmospheric deposition could be identified based on the concentrations in these two wetland types. To test these hypotheses, 29 herbicides were monitored for 5 yr in 16 wetlands on minimum-tillage farms and in seven wetlands on organic farms. Twenty herbicides were detected in wetlands on minimum-tillage farms versus 12 in wetlands on organic farms. Clopyralid, MCPA, 2,4-D, bromoxynil, dichlorprop, and dicamba were detected at a >50% frequency in wetlands on both minimum-tillage and organic farms. Concentrations of clopyralid were significantly higher in wetlands on minimum-tillage farms than in those on organic farms, whereas no significant difference was observed for any of the other five herbicides. Glyphosate, including its degradation product AMPA, was detected in >50% frequency only in wetlands on minimum-tillage farms where the mean concentration (1278 ng L) was higher than the concentration of other herbicides. Mass applied, vapor pressure, and water solubility were important determinants of herbicide concentrations and detections in wetlands. Herbicide concentrations in all but two samples were less than their respective Canadian guideline for protection of aquatic life, suggesting that, overall, individual herbicide concentrations in the wetlands were not toxic to biota.

Natural steroidal estrogens, such as 17 β-estradiol (E2), as well as antimicrobials such as doxycycline and norfloxacin, are excreted by humans and hence detected in sewage sludge and biosolid. The disposal of human waste products on agricultural land results in estrogens and antibiotics being detected as mixtures in soils. The objective of this study was to examine microbial respiration and E2 mineralization in sewage sludge, biosolid, and soil in the presence and the absence of doxycycline and norfloxacin. The antimicrobials were applied to the media either alone or in combination at total rates of 4 and 40 mg kg-1, with the 4 mg kg-1 rate being an environmentally relevant concentration. The calculated time that half of the applied E2 was mineralized ranged from 294 to 418 days in sewage sludge, from 721 to 869 days in soil, and from 2,258 to 14,146 days in biosolid. E2 mineralization followed first-order and the presence of antimicrobials had no significant effect on mineralization half-lives, except for some antimicrobial applications to the human waste products. At 189 day, total E2 mineralization was significantly greater in sewage sludge (38 ±0.7%) > soil (23 ±0.7%) > biosolid (3 ±0.7%), while total respiration was significantly greater in biosolid (1,258 mg CO2) > sewage sludge (253 mg CO2) ≥ soil (131 mg CO2). Strong sorption of E2 to the organic fraction in biosolid may have resulted in reduced E2 mineralization despite the high microbial activity in this media. Total E2 mineralization at 189 day was not significantly influenced by the presence of doxycycline and/or norfloxacin in the media. Antimicrobial additions also did not significantly influence total respiration in media, except that total CO2 respiration at 189 day was significantly greater for biosolid with 40 mg kg-1 doxycycline added, relative to biosolid without antimicrobials. We conclude that it is unlikely for doxycycline and norfloxacin, or their mixtures, to have a significant effect on E2 mineralization in human waste products and soil. However, the potential for E2 to be persistent in biosolids, with and without the presence of antimicrobials, is posing a challenge for biosolid disposal to agricultural lands.

This research examined the impact of field-aged phosphate and cadmium (Cd) concentrations, and fresh phosphate co-applications, on glyphosate sorption by soil. Soil samples were collected in 2013 from research plots that had received, from 2002 to 2009, annual applications of mono ammonium phosphate (MAP) at 20, 40 and 80 kg P ha(-1) and from products containing 0.4, 70 or 210 mg Cd kg(-1) as an impurity. A series of batch equilibrium experiments were carried out to quantify the glyphosate sorption distribution constant, Kd. Extractable Cd concentrations in soil had no significant effect on glyphosate sorption. Glyphosate Kd values significantly decreased with increasing Olsen-P concentrations in soil, regardless of the pH conditions studied. Experiments repeated with a commercially available glyphosate formulation showed statistically similar results as the experiments performed with analytical-grade glyphosate. Co-applications of MAP with glyphosate also reduced the available sorption sites to retain glyphosate, but less so when soils already contain large amounts of phosphate. Glyphosate Kd values in soils ranged from 173 to 939 L kg(-1) under very strong to strongly acidic condition but the Kd was always

Sorption parameters (such as Kd values) are among the most sensitive input parameters in pesticide fate models. This study demonstrates that near-infrared spectroscopy (NIRS), in combination with batch equilibrium techniques, can be used to estimate Kd values, thereby increasing throughput of the many samples required to characterize spatial variability of pesticide sorption within fields. The Pesticide Root Zone Model version 3.12.2 (PRZM-3) was used to compare scenarios that used NIRS spectral data, pedotransfer functions, and batch equilibrium methods as inputs for the calculation of 2,4-dichlorophenoxyacetic acid (2,4-D) and atrazine leaching in 591 soil horizons. Based on the 3564 simulation runs conducted, we concluded that the added benefit of NIRS is most useful when the pesticides under study have small sorption potentials and short half-lives in soil. The 2,4-D and atrazine sorption by soil was highly correlated to soil organic C (SOC) content in the fields under study. The feasibility of using NIRS to predict pesticide Kd values largely relies on the sorption of the pesticide being significantly correlated to SOC. In addition, successful regional approaches to predicting Kd values from NIRS spectral data can also be developed when the calibration model is derived by combining a set of fields where each has a similar statistical population characteristic in Kd values.

To provide sufficient food and fiber to the increasing global population, the technologies associated with crop protection are growing ever more sophisticated but, at the same time, societal expectations for the safe use of crop protection chemistry tools are also increasing. The goal of this perspective is to highlight the key issues that face future leaders in crop protection, based on presentations made during a symposium titled "Developing Global Leaders for Research, Regulation and Stewardship of Crop Protection Chemistry in the 21st Century", held in conjunction with the IUPAC 13th International Congress of Pesticide Chemistry in San Francisco, CA, USA, during August 2014. The presentations highlighted the fact that leaders in crop protection must have a good basic scientific training and understand new and evolving technologies, are aware of the needs of both developed and developing countries, and have good communication skills. Concern is expressed over the apparent lack of resources to meet these needs, and ideas are put forward to remedy these deficiencies.

Phosphate fertilizers and herbicides such as glyphosate and MCPA are commonly applied to agricultural land, and antibiotics such as tetracycline have been detected in soils following the application of livestock manures and biosolids to agricultural land. Utilizing a range of batch equilibrium experiments, this research examined the competitive sorption interactions of these chemicals in soil. Soil samples (0-15 cm) collected from long-term experimental plots contained Olsen P concentrations in the typical (13 to 20 mg kg¡1) and elevated (81 to 99 mg kg¡1) range of build-up phosphate in agricultural soils. The elevated Olsen P concentrations in field soils significantly reduced glyphosate sorption up to 50%, but had no significant impact on MCPA and tetracycline sorption. Fresh phosphate additions in the laboratory, introduced to soil prior to, or at the same time with the other chemical applications, had a greater impact on reducing glyphosate sorption (up to 45%) than on reducing tetracycline (up to 13%) and MCPA (up to 8%) sorption. The impact of fresh phosphate additions on the desorption of these three chemicals was also statistically significant, but numerically very small namely < 1% for glyphosate and tetracycline and 3% for MCPA. The presence of MCPA significantly reduced sorption and increased desorption of glyphosate, but only when MCPA was present at concentrations much greater than environmentally relevant and there was no phosphate added to the MCPA solution. Tetracycline addition had no significant effect on glyphosate sorption and desorption in soil. For the four chemicals studied, we conclude that when mixtures of phosphate, herbicides and antibiotics are present in soil, the greatest influence of their competitive interactions is phosphate decreasing glyphosate sorption and the presence of phosphate in solution lessens the potential impact of MCPA on glyphosate sorption. The presence of chemical mixtures in soil solution has an overall greater impact on the sorption than desorption of individual organic chemicals in soil.

The limitation of 16S rRNA gene sequencing (DNA-based) for microbial community analyses in water is the inability to differentiate live (dormant cells as well as growing or non-growing metabolically active cells) and dead cells, which can lead to false positive results in the absence of live microbes. Propidium-monoazide (PMA) has been used to selectively remove DNA from dead cells during downstream sequencing process. In comparison, 16S rRNA sequencing (RNA-based) can target live microbial cells in water as both dormant and metabolically active cells produce rRNA. The objective of this study was to compare the efficiency and sensitivity of DNA-based, PMA-based and RNA-based 16S rRNA Illumina sequencing methodologies for live bacteria detection in water samples experimentally spiked with different combination of bacteria (2 gram-negative and 2 gram-positive/acid fast species either all live, all dead, or combinations of live and dead species) or obtained from different sources (First Nation community drinking water; city of Winnipeg tap water; water from Red River, Manitoba, Canada). The RNA-based method, while was superior for detection of live bacterial cells still identified a number of 16S rRNA targets in samples spiked with dead cells. In environmental water samples, the DNA- and PMA-based approaches perhaps overestimated the richness of microbial community compared to RNA-based method. Our results suggest that the RNA-based sequencing was superior to DNA- and PMA-based methods in detecting live bacterial cells in water.

Mineralization studies of natural steroid hormones (e.g., 17β-estradiol, E2) are performed in environmental incubators, usually under a constant temperature such as 20°C. In this paper, we present a microcosm protocol that quantified the mineralization of E2 in soils under field temperatures. The nine agricultural soils tested had a wide range of soil organic carbon (1.1 to 5.2%) and clay (9 to 57%) contents. The calculated time over which half of the applied E2 was mineralized (E2-½) ranged from 299 to 910 d, and total E2 mineralization at 48 d (E2-TOT48) ranged from 4 to 13%. In subsequent laboratory incubations, the same soils were incubated under a constant temperature of 20°C, as well as under cyclic temperatures of 14.5°C (14 h) and 11.5°C (10h), which was within the temperature extremes observed in the field microcosms. E2-½ ranged from 157 to 686 d at 20°C and from 103 to 608 d at the cyclic temperatures, with the E2-TOT48 ranging from 6 to 21% at 20°C and from 7 to 30% under cyclic temperatures. Despite the overall 6.75 °C lower mean temperatures under the cyclic versus constant temperatures, E2 mineralization was stimulated by the temperature cycles in three soils. Regardless of the incubation, the same loamy sand soil always showed larger E2 mineralization than the other eight soils and this loamy sand soil also had the smallest E2 sorption. Current modeling approaches do not take into consideration the effects of temperature fluctuations in the field because the input parameters used to describe degradation are derived from laboratory incubations at a constant temperature. Across the eight soils, E2-½ was on average 1.7 times larger and E2-TOT48 was on average 0.8 times smaller under field temperatures than under a constant 20°C. Hence, we conclude that incubations at 20°C give a reasonable representation of E2 mineralization occurring under field conditions to be expected in a typical Prairie summer season.

Sensitive input parameters such as herbicide sorption coefficients are seldom quantified in sufficient spatial detail, leading to large uncertainties in pesticide fate model predictions at regional and national scales. This study examined the spatial variability of soil characteristics and herbicide sorption coefficients (K d ) in a total of 609 soil samples obtained from 140 soil profiles in two undulating to hummocky soil-landscapes of western Canada. In all soil horizons, K d values were always the largest for glyphosate followed by atrazine then 2,4-D. In each soil-landscape, SOC, 2,4-D and atrazine K d values (all strongly associated) numerically decreased with A > B > C mineral horizons, regardless of the segment of the slope in which the soil profile was located. SOC, 2,4-D K d and atrazine K d values were typically smaller in the eluvial A-horizons (Ae, Aej) than other A-horizons. In several landform elements, glyphosate K d values were numerically greater in the B rather than the A or C mineral horizons. Glyphosate K d values were particularly large in B-horizons with redoximorphic features such as in illuvial B-horizons enriched with clay (Btg, Btgj). When the soil properties and sorption values of similar horizons were compared across the soil-landscapes, SOC and 2,4-D K d demonstrated greater coefficients of variation than atrazine K d and glyphosate K d . The strength of prediction equations for 2,4-D K d and atrazine K d were strong in each soil-landscape when all samples in the soil profile were included in the model. However, the strength of prediction equations by mineral horizon was generally weaker and in some cases not significant. The in-field variability of glyphosate K d values could not be predicted from the measured soil properties data, or calculated digital terrain attributes. Terrain attributes also showed little to no correlation, or predictive strength for describing the variability of 2,4-D and atrazine sorption in the soil-landscapes.

Periodic assessments of the risk of water contamination by pesticides help decision makers improve the sustainability of agricultural management practices. In Canada, when evaluating the risk of water contamination by pesticides, 2 main constraints arise. First, because the area of interest is large, a pesticide transport model with low computational running time is mandatory. Second, some relevant input data for simulations are not known, and most are known only at coarse scale. This study aims to develop a robust methodology to estimate the evolution of the risk of water contamination by pesticides across Canada. To circumvent the 2 aforementioned issues, we constructed a stochastic model and coupled it to the 1-dimensional pesticide fate model Pesticide Root Zone Model (PRZM). To account for input data uncertainty, the stochastic model uses a Monte Carlo approach to generate several pesticide application scenarios and to randomly select PRZM parameter values. One hundred different scenarios were simulated for each of over 2000 regions (Soil Landscapes of Canada [SLC] polygons) for the years 1981 and 2006. Overall, the results indicated that in those regions in which the risk increased from 1981 to 2006, the increase in risk was mainly attributable to the increased area treated by pesticides or an increase in the number of days with runoff. More specifically, this work identifies the areas at higher risk, where further analyses with finer-scale input data should be performed. The model is specific for Canadian data, but the framework could be adapted for other large countries. Integr Environ Assess Manag 2014;10:429–436. © 2014 SETAC

Natural steroid estrogens (e.g., 17 β-estradiol) and antibiotics (e.g., penicillin) are chemicals detected in livestock manure storage facilities and in manure-amended agricultural soils. The fate of natural steroid estrogens in these media has been studied for the past two decades but seldom in association with antibiotics. This factorial experiment examined estrone (E1) and 17 β-estradiol (E2) mineralization in liquid swine manure, soil and manure-amended soil containing 0, 40 and 200 mg kg−1 penicillin or tetracycline. Maximum mineralization (MAX) across treatments ranged from 13.5% to 49.9% for E1 and from 15.4% to 51.2% for E2. Estrogen mineralization almost always significantly decreased in the order of: manure > soil amended with a low rate of manure = soil > soil amended with a high rate of manure, suggesting that periodically agitated manure was a more favorable medium for biotic removal of estrogens than soil. Both rates of tetracycline in manure induces a lag phase of 40 to 50 days prior to the...

Access to safe drinking water is now recognized as a human right by the United Nations. In developed countries like Canada, access to clean water is generally not a matter of concern. However, one in every five First Nations reserves is under a drinking water advisory, often due to unacceptable microbiological quality. In this study, we analyzed source and potable water from a First Nations community for the presence of coliform bacteria as well as various antibiotic resistance genes. Samples, including those from drinking water sources, were found to be positive for various antibiotic resistance genes, namely, ampC , tet (A), mecA , β-lactamase genes (SHV-type, TEM-type, CTX-M-type, OXA-1, and CMY-2-type), and carbapenemase genes (KPC, IMP, VIM, NDM, GES, and OXA-48 genes). Not surprisingly, substantial numbers of total coliforms, including Escherichia coli , were recovered from these samples, and this result was also confirmed using Illumina sequencing of the 16S rRNA gene. These findings deserve further attention, as the presence of coliforms and antibiotic resistance genes potentially puts the health of the community members at risk. IMPORTANCE In this study, we highlight the poor microbiological quality of drinking water in a First Nations community in Canada. We examined the coliform load as well as the presence of antibiotic resistance genes in these samples. This study examined the presence of antibiotic-resistant genes in drinking water samples from a First Nations Community in Canada. We believe that our findings are of considerable significance, since the issue of poor water quality in First Nations communities in Canada is often ignored, and our findings will help shed some light on this important issue.

Livestock manure contains natural steroid hormones, with the most potent being 17β-estradiol. The transport of steroid hormones from agricultural fields to adjacent water bodies can result in 17β-estradiol environmental contamination impacting aquatic organisms. Sorption coefficients are useful input into models that estimate risk of water contamination. The feasibility of applying near-infrared spectroscopy (NIRS) for determining sorption coefficients of 17β-estradiol in soil was investigated for two irregular undulating to hummocky terrain landscapes in Manitoba and Saskatchewan, Canada. A total of 609 soil samples in 140 soil profiles were collected from several horizons to a depth of 1 m. Air-dried and sieved (2 mm) soil samples were analyzed for soil organic carbon (SOC), soil pH, and soil texture. Sorption coefficients of 17β-estradiol were determined by a batch equilibrium process. Spectral data were collected from soil samples (25 g) using two instruments, the 45VISNIR Zeiss Corona (wavelength range 700-1690 nm) and the Foss NIRSystems 6500 (wavelength range 1100-2500 nm). Regardless of the site and instrument, the predictive models were excellent for both SOC and 17β-estradiol sorption coefficients. The data thus generated can be used as input parameters in fate models for efficient risk assessments and decision-making programs for environmental safety where soils are at risk of receiving inputs of 17β-estradiol. Calibration results for soil pH were also adequate with Corona outperforming the Foss instrument. Soil texture predictions were relatively unsuccessful regardless of the instrument and site.

Glyphosate [N-(phosphonomethyl)glycine] is the active ingredient of several herbicide products first registered for use in 1974 under the tradename Roundup. The use of glyphosate-based herbicides has increased dramatically over the last two decades particularly in association with the adoption of glyphosate-tolerant crops. Glyphosate has been detected in a range of surface waters but this is the first study to monitor its fate in prairie wetlands situated in agricultural fields. An ephemeral wetland (E) and a semi-permanent wetland (SP) were each divided into halves using a polyvinyl curtain. One half of each wetland was fortified with glyphosate with the added mass simulating an accidental direct overspray. Glyphosate dissipated rapidly in the water column of the two prairie wetlands studied (DT(50) values of 1.3 and 4.8 d) which may effectively reduce the impact of exposure of aquatic biota to the herbicide. Degradation of glyphosate to its major metabolite aminomethylphosphonic acid (AMPA) and sorption of the herbicide to bottom sediment were more important pathways for the dissipation of glyphosate from the water column than movement of the herbicide with infiltrating water. Presently, we are not aware of any Canadian guidelines for glyphosate residues in sediment of aquatic ecosystems. Since a substantial portion of glyphosate entering prairie wetlands will become associated with bottom sediments, particularly in ephemeral wetlands, guidelines would need to be developed to assess the protection of organisms that spend all or part of their lifecycle in sediment.

Although it has been suggested that atmospheric deposition alone can result in detectable levels of pesticides in wetlands of the Pairie Pothole Region of Canada, this is the first field study to compare the masses of pesticides entering wetlands by atmospheric deposition with those concentrations of pesticides detected in the water-column of prairie wetlands. Weekly air and bulk deposition samples were collected from May 26th to Sept. 15th, 2008 at the Manitoba Zero Tillage Research Association (MZTRA) Farm, Brandon, Manitoba, with four on-site wetlands (approximate sizes 0.15–0.45 ha) monitored every second week. Twelve pesticides were detected in the air, with MCPA (one of the three pesticides applied on the farm in 2008 in addition to clopyralid and glyphosate), triallate, and γ-HCH being detected every week. Calculations were performed to predict wetland pesticide concentrations based on bulk deposits alone for those pesticides that had detectable concentrations in the bulk deposition samples (in order of the highest total seasonal deposition mass to the lowest): MCPA, glyphosate, 2,4-D, clopyralid, bromoxynil, atrazine, dicamba, metolachlor, and mecoprop. The estimated concentrations were closest to actual concentrations for MCPA (Pearson correlation coefficient’s = 0.91 to 0.98; p-values

Recent column studies suggest that pesticide fate models could be used to estimate the fate of estrogens in soil. Estrogens are detected in livestock manure which is used as a nutrient source on agricultural land. This is the first study to examine estrogen mineralization in a wide range of agricultural soils at the regional-scale. Soil samples were collected from upper and lower landscape positions of 18 agricultural fields in an area spanning 49–60 °N longitude and 110–120 °W latitude and these samples were used to determine 17β-estradiol mineralization parameters in microcosm experiments. Maximum 17β-estradiol mineralization (Max) ranged from 5.8% to 19.2% and was, on average, significantly (P

Estrogenic compounds in livestock manure are also present in soils because manure is land applied on account of its value as an important nutrient source in agricultural production. This is the first study to compare the sorption of 17β-estradiol, estrone, estriol and equol in a wide range of soils. Specifically, for each of these four estrogens, the soil sorption coefficient (Kd) and the sorption coefficient per unit organic carbon (Koc) were determined in 121 surface soils (0–15 cm) obtained from upper-slopes, mid-slopes, and lower-slopes in agricultural fields across seven ecoregions in the Province of Alberta, Canada. Soil organic carbon content (SOC), texture, pH, carbonate content, electrical conductivity and cation exchange capacity were also determined on the air-dried and sieved (2 mm) soil. Both Kd and Koc values significantly increased in the order of Kd-estriol (23 L kg− 1 soil and 1059 L kg− 1, respectively) = Kd-17β-estradiol (23 L kg− 1 soil and 1082 L kg− 1, respectively)

The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) is among the most frequently detected pesticides in the water-column of surface waters in Canada. Bottom sediments (0 to 15 cm) were collected in 41 wetlands across the prairie region of Canada and analyzed for organic carbon content (OC), pH, and texture. Using batch equilibrium experiments at 5 and 25°C, the herbicide sorption coefficient, Kd, was determined for 41 sediments, along with more comprehensive herbicide sorption and desorption isotherms for 7 of these 41 sediments. The 2,4-D Kd was positively correlated with OC and negatively correlated with sediment pH. A small (3%) significant increase in the 2,4-D Kd occurred when the temperature was at 25°C rather than 5°C. Desorption rates were faster for sediments with ≤ 2.4% OC and exhibited little or no hysteresis, compared to sediments with ≥ 5.9% OC that consistently exhibited hysteresis. We conclude that bottom sediments could serve as a source of 2,4-D to the water-column regardless of water temperature (5 to 25°C). However, the potential for accumulation of 2,4-D in wetland sediments would be small because between 62 and 100% of the 2,4-D sorbed by sediments was released after 8 hours.

There are few experimental data available on how herbicide sorption coefficients change across small increments within soil profiles. Soil profiles were obtained from three landform elements in a strongly-eroded agricultural field and segmented into 2-cm intervals to 0.6 m depth in the knoll (eroded-upper slope), to 1.0 m depth in the toeslope (deposition zone) and to 1.6 m depth in the trough (eroded water-way). Soil samples were analyzed for soil organic carbon content (SOC) (n = 154), soil pH (n = 155), soil carbonate content (n = 126), CEC (n = 126), soil texture (n = 32), bulk density (n = 160), 2,4-D [2,4-(dichlorophenoxy) acetic acid] or glyphosate [N-phosphonomethylglycine] sorption by soil (Kd) (n = 90), and 2,4-D or glyphosate sorption per unit soil organic carbon (Koc) (n = 90). Considering all soil profiles, 2,4-D Kd values ranged from 0.12 to 2.61 L kg− 1 and were most strongly influenced by variations in SOC. In contrast, glyphosate Kd values ranged from 19 to 547 L kg− 1 and were predominantly controlled by variations in soil pH and clay content. Two hundred and fifty-two PRZM (pesticide root zone model) version 3.12.2 simulations were also performed. PRZM predicted that glyphosate would be immobile in soils even under an extreme rainfall scenario of 384 mm at one day after herbicide application. In contrast, for 2,4-D, PRZM predicted that up to 6% of the applied herbicide would move to a 15 cm depth under an actual rainfall scenario. PRZM output was particularly sensitive to input values of Kd, relative to input values of soil properties. The greatest change to PRZM outputs occurred when Kd values of toeslope profiles, ranging from 0.16 to 1.77 L kg− 1, were replaced by those measured in knoll profiles, ranging from 0.12 to 0.50 L kg− 1, when the amount of 2,4-D leached to a 15 cm depth increased by 29,081% (from 0.09 to 26.17 g ha− 1) under an actual rainfall scenario. We conclude that, when pesticide fate models such as PRZM are being used in policy analyses at larger-scales, data on Kd values in different landform elements and at the soil horizon level could be important for strengthening pesticide leaching predictions.

Sorption and degradation of the herbicide 2,4-D [2,4-dichlorophenoxyacetic acid] were determined for 123 surface soils (0 to 15 cm) collected in 2002 and in 2004 between 49 degrees to 60 degrees north longitude and 110 degrees to 120 degrees west latitude in Alberta, Canada. The soils were characterized by soil organic carbon content (SOC), pH, electrical conductivity, soil texture, cation exchange capacity, carbonate content, and total soil microbial activity. The 2,4-D sorption coefficients, Kd and Koc, were highly variable with coefficients of variation of 89 and 59%, respectively, at the provincial scale. Both Kd and Koc were well described by regression models with SOC and soil pH as variables, regardless of scale. Surprisingly, variations in 2,4-D mineralization were much smaller than variations in sorption. Variability in total 2,4-D mineralization was particularly low, with a coefficient of variation of only 7% at the provincial scale. Average 2,4-D half-lives in ecoregions ranged from 1.7 to 3.5 d, much lower than the field dissipation half-life of 10 d reported for 2,4-D in general pesticide property databases. Regression models describing degradation parameters were generally poor or not significant because 2,4-D mineralization was only weakly associated with measured 2,4-D sorption parameters and soil properties. As such, regional variations in herbicide sorption coefficients should be measured or calculated based on soil properties, to assign distinct pesticide fate model input parameters when estimating 2,4-D off-site transport at the provincial scale. Spatial variations in herbicide degradation appear less important for Alberta as 2,4-D half-lives were similar in soils across the province. The rapid mineralization of 2,4-D is noteworthy because 2,4-D is widely used in Alberta and perhaps adaptation of soil microbial communities allowed for accelerated degradation regardless of soil properties or the extent of 2,4-D sorption by soil.

This study compared the degradation of [carboxyl- 14 C] 2,4-dichlorophenoxyacetic acid (2,4-D) (C2,4-D) and [ring-U- 14 C] 2,4-D (R2,4-D) in 114 agricultural soils (0–15 cm) as affected by 2,4-D sorption and soil properties (organic carbon content, pH, clay content, carbonate content, cation exchange capacity, total microbial activity). The sample area was confined to Alberta, Canada, located 49–60° north longitude and 110–120° west latitude and soils were grouped by soil organic carbon content (SOC) (0–0.99%, 1–1.99%, 2–2.99%, 3–3.99% and >4% SOC). Degradation rates of C2,4-D and R2,4-D followed first-order kinetics in all soils. Although total microbial activity increased with increasing SOC, degradation rates and total degradation of C2,4-D and R2,4-D decreased with increasing SOC because of increased sorption of 2,4-D by soil and reduced bioavailability of 2,4-D and its metabolites. Rates of R2,4-D degradation were more limited by sorption than rates of C2,4-D degradation, possibly because of greater sorption and formation of bound residues of 2,4-D metabolites relative to the 2,4-D parent molecule. Based on the sorption and degradation parameters quantified, there were two distinct groups of soils, those with less than 1% SOC and those with greater than 1% SOC. Specifically, soils with less than 1% SOC had, on average, 2.4 times smaller soil organic carbon sorption coefficients and 1.4 times smaller 2,4-D half-lives than soils with more than 1% SOC. In regional scale model simulations of pesticide leaching to groundwater, covering many soils, input parameters for each pesticide include a single soil organic carbon sorption coefficient and single half-life value. Our results imply, however, that the approach to these regional scale assessments could be improved by adjusting the values of these two input parameters according to SOC. Specifically, this study indicates that for 2,4-D and Alberta soils containing less than 1% SOC, the 2,4-D pesticide parameters obtained from generic databases should be divided by 2.5 (soil organic carbon sorption coefficient) and 1.5 (half-life value).

Tillage is a driving force of soil movement in cultivated fields. Soil constituents, together with the mass of soil, are redistributed across landscapes by tillage. The pattern of tillage-induced soil constituent redistribution is determined by the pattern of tillage erosion (tillage-induced soil mass loss or gain) and the dispersivity of translocation. In this study, we used a convoluting procedure and developed a Tillage Translocation Model (TillTM) to simulate the tillage translocation process and to demonstrate tillage-induced soil mass and soil organic carbon (OC) (as an example of soil constituents) redistributions across four hypothetical landscapes subjected to different tillage patterns (directions) and over different lengths of tillage period. We determined that the local tillage-erosion rate is mainly dependent on topography and that the effects of tillage pattern and the length of tillage period are relatively minor. The redistribution of OC content in the till layer is mainly determined by the number, location, and size of soil loss positions in the landscape, as well as the soil loss rates at these positions. Net loss of OC content occurs in the till layer and this loss increases with time. In contrast, an increase of OC content in the sublayer occurs at soil accumulation positions. The model was validated against field data collected at a site near Cyrus, MN. The patterns of OC and inorganic C redistribution can be adequately estimated by TillTM. There are discrepancies, however, between the model-estimated values and the field measurements due to the limitations and uncertainties associated with the model. The results clearly showed that tillage translocation causes the vertical redistribution of soil constituents across the landscape, which implies that tillage translocation is one of the driving forces behind the spatial variability of soil properties and properties that impact biophysical processes.

The herbicide 2,4-D [2,4-(dichlorophenoxy) acetic acid] is one of the most widely used pesticides in the Canadian prairies and is frequently detected as a ground and surface water contaminant. The objective of this paper was to determine the magnitude and extent of variation of 2,4-D mineralization in a cultivated undulating prairie landscape. Microcosm incubation experiments, using a 4 x 3 x 2 factorial experimental design (soil moisture, 4 levels: 60, 85, 110, 135% of field capacity; slope position, 3 levels: upper-, mid- and lower-slopes; soil depth, 2 levels: 0-5 and 5-15 cm), were used to assess 2,4-D mineralization. The first-order mineralization rate constant (k(1)) varied from 0.03 to 0.22 day(- 1), while total 2,4-D mineralization varied from 31 to 52%. At near-saturated conditions (110 and 135% of field capacity), the onset of 2,4-D degradation was delayed in soil obtained from the upper- and mid-slopes but not in soils obtained from the lower-slope position. The k(1) and total 2,4-D mineralization was significantly influenced by all three factors and their interactions. The Freundlich sorption coefficient of 2,4-D ranged from 0.83 to 2.46 microg (1-1/n)g(- 1) mL(1/n) and was significantly influenced by variations in soil organic carbon content across slope positions. The infield variability of 2,4-D sorption and mineralization observed across slope positions in this undulating field was comparable in magnitude and extent to the regional variability of 2,4-D sorption and mineralization observed in surface soils across Manitoba. The large variability of 2,4-D mineralization and sorption at different slope positions in this cultivated undulating field suggests that landform segmentation models, which are used to delineate slope positions, are important considerations in pesticide fate studies.