The upcoming European Soil Monitoring Law: An effective instrument for the protection of terrestrial ecosystems?

Soils are a precious resource consistently placed under several threats and urgently in need of protection within a regulatory framework at the European level. Soils are central to the provision of environmental services as well as human existence on earth. The need to protect soil has been identified by several recent European strategies and fortunately, a specific European regulation for soil protection is on the way-the European Soil Monitoring Law (formerly: Soil Health Law). However, efforts need to ensure that the upcoming Soil Monitoring Law closes gaps between existing regulations for chemicals and acknowledges current European strategies for environmental protection and sustainability. This brief communication started from a fruitful discussion among SETAC Global Soils Interest Group members on a recent public consultation on the newly proposed Soil Monitoring Law of the European Commission and highlights critical points focusing on the chemical pollution of soils. We emphasize urgent needs such as the essential definition of a "healthy state" of soils; the implementation of a suitable set of indicators and quality standards for the description of physical, chemical, and biological states of soils; the enforcement of the "polluter-pays" principle; and the establishment of a Europe-wide monitoring program. Results from monitoring need to be fed back into regulatory frameworks, including the regulation of chemicals. Guidance documents for the risk assessment of chemicals are outdated and need to be updated. Finally, actions need to be taken to foster healthy soils, stop biodiversity decline, and ensure the functioning of ecosystem services for future generations. Integr Environ Assess Manag 2024;20:316-321. © 2023 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Cerium oxide nanoparticles (nCeO2) exert minimal adverse effects on microbial communities in soils with and without biosolids amendment.

Increased use of nano-cerium oxide (nCeO2) in an array of industrial applications has raised environmental concerns due to potential increased loadings to the soil environment. This research investigated the potential adverse effects of nCeO2 (10-30 nm) on the soil microbial community in two exposure scenarios: direct application to soil, and indirect application to soil through chemical spiking of biosolids, followed by mixing into soil. Total Ce in test soils without, and with biosolids amendment, ranged from 44 to 770, and 73 to 664 mg Ce kg-1 soil, respectively. In order to help distinguish whether observed effects were elicited by the solid-phase colloids or the activity of dissolved Ce, a soluble Ce salt (Ce (NO3)3) treatment was included in select assays. A suite of tests was used to investigate effects on critical processes: microbial growth (heterotrophic plate count), microbial activity (organic matter (OM) decomposition, enzyme activity and, nitrification) and diversity (structural and functional). Although results showed significant inhibition on microbial growth in soil without biosolids amendment at ≥ 156 mg Ce kg-1 soil by week 5, these results were inconsistent and non-significant thereafter. In general, nCeO2 showed no evidence of consistent adverse effects on OM decomposition, nitrification, soil enzyme activities and functional diversity. Leucine aminopeptidase showed significant (p< 0.05) stimulatory effects over time at ≥ 44 mg Ce kg-1 in soils without biosolids, which was not observed in soils with biosolids amendment. The lack of inhibitory effects of nCeO2 may be attributed to its low solubility; Ce in soil extracts (0.01 M CaCl2) were all below detection (< 0.003 mg kg-1) in the nCeO2-spiked soils, but detectable in the Ce (NO3)3 samples. In contrast, soluble Ce at 359 mg Ce kg-1 showed a significant reduction in OM decomposition and effects on microbial genomic diversity based on the 16S rDNA data in soils with and without biosolids amendment (359 and 690 mg Ce kg-1). The nCeO2 behaviour and effects information described herein are expected to help fulfill data gaps for the characterization of this priority nanomaterial.

Fate and removal of silver nanoparticles during sludge conditioning and their impact on soil health after simulated land application.

The growing use of silver nanoparticles (AgNPs) in personal care products and clothing has increased their concentrations in wastewater and subsequently in sludge raising concerns about their fate and toxicity during wastewater treatment and after land application of sludge. This research investigated the fate and removal of AgNPs during chemical conditioning of anaerobically digested sludge and their impact on soil bacteria and health after land application. Ferric chloride (FeCl3), alum (Al2 (SO4)3 • (14-18) H2O), and synthetic (polyacrylamide) polymer were used for sludge conditioning. All conditioners effectively removed AgNPs from the liquid phase and concentrated them in sludge solids. Concentration analyses showed that out of 53.0 mg/L of silver in the sludge, only 0.1 to 0.003 mg/L of silver remained in the sludge supernatant after conditioning and 12 to 20% of this value were particulates. Morphological analyses also showed that AgNPs went through physical, chemical, and morphological changes in sludge that were not observed in nanopure water and the resulting floc structures and the incorporation of nanoparticles were different for each conditioner. The impact of conditioned AgNPs on the biological activities of soil was evaluated by investigating its impact on the presence of five important phyla (Acidobacteria, Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria). The results showed that AgNPs at a concentration of 20 mg AgNPs/g soil had a minimal impact on the presence and diversity of the assessed phyla. Also, using different chemicals for sludge conditioning resulted in different growth behavior of studied phyla. This study provides new insight into how the presence of AgNPs and different chemicals used for sludge conditioning might impact the soil biological activities and hence plant growth. The study also provides a solid basis for further research in the risk assessment of nanoparticle toxicity in biosolids amended soils.

Transformation of Silver Nanoparticles (AgNPs) during Lime Treatment of Wastewater Sludge and Their Impact on Soil Bacteria.

This study investigated the impact of lime stabilization on the fate and transformation of AgNPs. It also evaluated the changes in the population and diversity of the five most relevant bacterial phyla in soil after applying lime-stabilized sludge containing AgNPs. The study was performed by spiking an environmentally relevant concentration of AgNPs (2 mg AgNPs/g TS) in sludge, applying lime stabilization to increase pH to above 12 for two hours, and applying lime-treated sludge to soil samples. Transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) were used to investigate the morphological and compositional changes of AgNPs during lime stabilization. After the application of lime stabilized sludge to the soil, soil samples were periodically analyzed for total genomic DNA and changes in bacterial phyla diversity using quantitative polymerase chain reaction (qPCR). The results showed that lime treatment effectively removed AgNPs from the aqueous phase, and AgNPs were deposited on the lime molecules. The results revealed that AgNPs did not significantly impact the presence and diversity of the assessed phyla in the soil. However, lime stabilized sludge with AgNPs affected the abundance of each phylum over time. No significant effects on the soil total organic carbon (TOC), heterotrophic plate count (HPC), and percentage of the live cells were observed.

Soil invertebrate toxicity and bioaccumulation of nano copper oxide and copper sulphate in soils, with and without biosolids amendment.

The fate, toxicity and bioaccumulation of copper oxide nanoparticles (nCuO) was investigated in soil, with and without biosolids amendment, through chronic exposures using the earthworm, Eisenia andrei, and the collembolan, Folsomia candida. The effects of copper sulphate (CuSO4) were included so as to compare the behavior of nCuO to a readily soluble counterpart. The fate of nCuO was evaluated through characterization of dissolved and nano-particulate fractions (via single particle ICP-MS) as well as extractable Cu2+ throughout the duration of select tests. Neither Cu form was particularly toxic to F. candida, but effects on E. andrei reproduction were significant in all treatments (IC50 range: 98 - 149 mg Cu kg-1 dry soil). There were no significant differences in toxicity between the Cu forms, nor in extractable Cu2+ activities, indicative that particle dissolution within the soil and, subsequent activity of Cu2+ was likely the primary mode of toxicity in the nCuO exposures. The presence of biosolids did not significantly alter toxicity of nCuO, but did affect Cu2+ activity over time. Bioaccumulation of total Cu in E. andrei when exposed to nCuO (kinetic bioaccumulation factor (BAFk): 0.80 with biosolids and 0.81 without) was lower than exposure to CuSO4 (BAFk: 2.31 with biosolids and 1.12 without). Enhanced dark-field hyperspectral imaging showed accumulation of nCuO along the epidermis and gut of E. andrei, with trace amounts observed in muscle and chloragogenous tissue, providing evidence of nCuO translocation within the organism. The present study demonstrates that the current risk assessment approach for trace metals in the environment, based on substance solubility and bioavailability of the dissolved free ion, are applicable for nCuO exposure to soil invertebrates, but that the rate of particle dissolution in different soil environments is an important factor for consideration.

Impact of anaerobically digested silver and copper oxide nanoparticles in biosolids on soil characteristics and bacterial community.

This study investigated whether 2 and 30 mg AgNPs or CuONPs/g TS present in treated sludge (biosolids) may impact the soil health by monitoring the soil characteristics and soil bacterial community for 105 days after the application of biosolids. AgNPs or CuONPs/g TS were first anaerobically digested with mixed primary and secondary sludge rather than adding pristine nanoparticles to biosolids directly. Both environmentally relevant (under the USEPA ceiling concentration limits) and high concentrations of AgNPs and CuONPs were tested. Soil tests included TOC, TN, TP, pH, cell viability and heterotrophic plate counts (HPC). Metagenomic data was generated by high-throughput sequencing of the 16S rRNA gene to explore bacterial populations and diversity. AgNPs and CuONPs at 2 and 30 mg NPs/g TS of sludge could impact soil health factors such as bacterial diversity, community structure, and the population of plant growth-promoting rhizobacteria (PGPR). The population of the highly abundant bacteria that have important physiological roles in soil decreased, while the less important bacteria for soil function were able to thrive. CuONPs exhibited a higher level of toxicity than the AgNPs at both phylum and genus taxonomic levels, and the HPC decreased with higher concentrations of AgNPs and CuONPs. Initially, most of the studied phyla abundance was affected, but the control and other reactors approached similar levels by the end of the experiments, which may be explained by the decrease in toxicity due to the transformation of nanoparticles and the defence mechanisms of bacteria, and indicates the need for long-term field studies.

Morphological Transformation of Silver Nanoparticles from Commercial Products: Modeling from Product Incorporation, Weathering through Use Scenarios, and Leaching into Wastewater.

There is increasing interest in the environmental fate and effects of engineered nanomaterials due to their ubiquitous use in consumer products. In particular, given the mounting evidence that dramatic transformations can occur to a nanomaterial throughout its product lifecycle, the appropriateness of using pristine nanomaterials in environmental testing is being questioned. Using a combination of transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma-mass spectrometry (ICP-MS), this work examines the morphological and compositional effects of conditions mimicking a typical lifecycle of a nano-enabled product, from the production of the silver nanoparticle (AgNP)-laden textiles, through its use, laundering, and then finally, its leaching and incubation in the wastewater collection system. These simulated weathering conditions showed evidence for the transformation of AgNPs into AgCl and Ag2S. Incubation in raw wastewater had the most dramatic effect on the AgNPs in terms of transformation, no matter what initial weathering was applied to the NPs prior to incubation. However, despite extensive transformation noted, AgNPs were still present within all the samples after the use scenarios.

Oppia nitens C.L. Koch, 1836 (Acari: Oribatida): Current Status of Its Bionomics and Relevance as a Model Invertebrate in Soil Ecotoxicology.

The oribatid soil mite Oppia nitens C.L. Koch, 1836, is a model microarthropod in soil ecotoxicity testing. This species has a significant role in supporting soil functions and as a suitable indicator of soil contamination. Despite its significance to the environment and to ecotoxicology, however, very little is known of its biology, ecology, and suborganismal responses to contaminants in the soil. In the present review, we present detailed and critical insights into the biology and ecology of O. nitens in relation to traits that are crucial to its adaptive responses to contaminants in soil. We used a species sensitivity distribution model to rank the species sensitivity to heavy metals (cadmium and zinc) and neonicotinoids (imidacloprid and thiacloprid) compared with other standardized soil invertebrates. Although the International Organization for Standardization and Environment and Climate Change Canada are currently standardizing a protocol for the use of O. nitens in soil toxicity testing, we believe that O. nitens is limited as a model soil invertebrate until the molecular pathways associated with its response to contaminants are better understood. These pathways can only be elucidated with information from the mites' genome or transcriptome, which is currently lacking. Despite this limitation, we propose a possible molecular pathway to metal tolerance and a putative adverse outcome pathway to heavy metal toxicity in O. nitens. Environ Toxicol Chem 2019;38:2593-2613. © 2019 SETAC.

Lethal and Sublethal Toxicity of Thiamethoxam and Clothianidin Commercial Formulations to Soil Invertebrates in a Natural Soil.

The use of neonicotinoids in agriculture is a critical environmental protection issue. Although there has been considerable research on pollinator exposure and aquatic toxicological effects, few studies have investigated the chronic impacts on soil-dwelling species. Given the application of neonicotinoids into soil systems, there is the potential for risk to soil invertebrates. The toxicity of 2 commercial formulations containing the active ingredients (a.i.) thiamethoxam (Actara® 240SC) or clothianidin (Titan™) was investigated using 3 soil invertebrate species: Oppia nitens, Eisenia andrei, and Folsomia candida. No adverse effects were observed for O. nitens at the highest tested concentrations (≥92 mg a.i./kg dry soil) after a 28-d exposure. Exposure to clothianidin resulted in a 28-d median inhibitory concentration (IC50) of 0.069 (95% confidence limits: 0.039-0.12) mg/kg dry soil for F. candida, and a 56-d IC50 of 0.26 (0.22-3.2) mg a.i./kg dry soil for E. andrei. Exposure to thiamethoxam was less toxic, with IC50s of 0.36 (0.19-0.66) and 3.0 (2.2-4.0) mg a.i./kg dry soil for F. candida and E. andrei reproduction, respectively. The observed toxicity for F. candida adult survival and reproduction and for E. andrei reproduction occurred at environmentally relevant concentrations. However, because clothianidin is a degradation product of thiamethoxam, and detection of clothianidin rose to levels of concern in the thiamethoxam-amended soils over time, the observed toxicity may be partly attributed to the presence of clothianidin. Environ Toxicol Chem 2019;38:2111-2120. © 2019 Crown in the right of Canada. Published by Wiley Periodicals Inc. on behalf of SETAC.

Perfluorooctane sulfonate in surface soils: Effects on reproduction in the collembolan, Folsomia candida, and the oribatid mite, Oppia nitens.

Perfluorooctane sulfonate (PFOS) is a persistent organic pollutant, which has been detected at significant concentrations in soils at sites used for fire-fighting training operations. Recent ecotoxicological research has mainly focused on earthworms to assess the toxicity of PFOS in soil. However, the inclusion of other soil taxonomic groups allow for a more holistic estimate of contaminant risk, including the derivation of more comprehensive soil quality guidelines. The present study assessed the toxicity of PFOS using the collembolan, Folsomia candida, and the oribatid mite, Oppia nitens, in two types of soil: a coarse-textured sandy loam (VSL) and fine-textured clay loam (NRS). As a standard O. nitens reproduction test is being formalized, the results of the study were also used to compare sensitivity across test species. Effects were soil dependent, with test species being 2-4 times more susceptible to PFOS in VSL, relative to NRS, likely due to differences in organic matter and clay content. Oppia nitens was significantly more sensitive to PFOS, regardless of soil type, in comparison to F. candida. The IC50s for reproduction for O. nitens were 23 mg kg-1 (95% confidence interval: 17-32 mg kg-1) in the VSL and 95 mg kg-1 (69-134 mg kg-1) in the NRS, and for F. candida were 94 mg kg-1 (72-122 mg kg-1) in the VSL and 233 mg kg-1 (177-306 mg kg-1) in the NRS. The present study demonstrates the application and inclusion of the oribatid mite, O. nitens, for the risk assessment of contaminants in soil.

The ecotoxicity of zinc and zinc-containing substances in soil with consideration of metal-moiety approaches and organometal complexes.

Within Canada, screening-level assessments for chemical substances are required to determine whether the substances pose a risk to human health and/or the environment, and as appropriate, risk management strategies. In response to the volume of metal and metal-containing substances, process efficiencies were introduced using a metal-moiety approach, whereby substances that contain a common metal moiety are assessed simultaneously as a group, with the moiety of concern consisting of the metal ion. However, for certain subgroups, such as organometals or organic metal salts, the organic moiety or parent substance may be of concern, rather than simply the metal ion. To further investigate the need for such additional consideration, certain substances were evaluated: zinc (Zn)-containing inorganic (Zn chloride [ZnCl2] and Zn oxide) and organic (organometal: Zn diethyldithiocarbamate [Zn(DDC)2 ] and organic metal salts (Zn stearate [ZnSt] and 4-chloro-2-nitrobenzenediazonium tetrachlorozincate [BCNZ]). The toxicity of the substances were assessed using plant (Trifolium pratense and Elymus lanceolatus) and soil invertebrate (Folsomia candida and Eisenia andrei) tests in a sandy soil. Effect measures were determined based on total metal and total parent analyses (for organic substances). In general, the inorganic Zn substances were less toxic than the organometals and organic metal salts, with 50% effective concentrations ranging from 11 to >5194 mg Zn kg-1 dry soil. The data demonstrate the necessity for alternate approaches in the assessment of organo-metal complexes, with the organic moieties or parent substances warranting consideration rather than the metal ion alone. In this instance, the organometals and organic metal salts were significantly more toxic than other test substances despite their low total Zn content. Environ Toxicol Chem 2017;36:3324-3332. © 2017 Crown in the Right of Canada. Published by Wiley Periodicals Inc. on behalf of SETAC.

The toxicity of silver to soil organisms exposed to silver nanoparticles and silver nitrate in biosolids-amended field soil.

The use of engineered silver nanoparticles (AgNPs) is widespread, with expected release to the terrestrial environment through the application of biosolids onto agricultural lands. The toxicity of AgNPs and silver nitrate (AgNO3 ; as ionic Ag+ ) to plant (Elymus lanceolatus and Trifolium pratense) and soil invertebrate (Eisenia andrei and Folsomia candida) species was assessed using Ag-amended biosolids applied to a natural sandy loam soil. Bioavailable Ag+ in soil samples was estimated using an ion-exchange technique applied to KNO3 soil extracts, whereas exposure to dispersible AgNPs was verified by single-particle inductively coupled plasma-mass spectrometry and transmission electron microscopy-energy dispersive X-ray spectroscopy analysis. Greater toxicity to plant growth and earthworm reproduction was observed in AgNP exposures relative to those of AgNO3 , whereas no difference in toxicity was observed for F. candida reproduction. Transformation products in the AgNP-biosolids exposures resulted in larger pools of extractable Ag+ than those from AgNO3 -biosolids exposures, at similar total Ag soil concentrations. The results of the present study reveal intrinsic differences in the behavior and bioavailability of the 2 different forms of Ag within the biosolids-soils pathway. The present study demonstrates how analytical methods that target biologically relevant fractions can be used to advance the understanding of AgNP behavior and toxicity in terrestrial environments. Environ Toxicol Chem 2017;36:2756-2765. © 2017 Crown in the Right of Canada. Published Wiley Periodicals Inc., on behalf of SETAC.

Ecotoxicity of boric acid in standard laboratory tests with plants and soil organisms.

To verify the continuous sensitivity of ecotoxicological tests (mainly the test organisms), reference substances with known toxicity are regularly tested. Ideally, this substance(s) would lack specificity in its mode action, be bioavailable and readily attainable with cost-effective means of chemical characterization. Boric acid has satisfied these criteria, but has most recently been characterized as a substance of very high concern, due to reproductive effects in humans, thus limiting its recommendation as an ideal reference toxicant. However, there is probably no other chemical for which ecotoxicity in soil has been so intensively studied; an extensive literature review yielded lethal (including avoidance) and sublethal data for 38 taxa. The ecotoxicity data were evaluated using species sensitivity distributions, collectively across all taxa, and separately according to species type, endpoints, soil type and duration. The lack of specificity in the mode of action yielded broad toxicity among soil taxa and soil types, and provided a collective approach to assessing species sensitivity, while taking into consideration differences in test methodologies and exposure durations. Toxicity was species-specific with Folsomia candida and enchytraied species demonstrating the most sensitivity; among plants, the following trend occurred: dicotyledonous (more sensitive) ≫ monocotyledonous ≫ gymnosperm species. Sensitivity was also time and endpoint specific, with endpoints such as lethality and avoidance being less sensitive than reproduction effects. Furthermore, given the breadth of data and toxicity demonstrated by boric acid, lessons learned from its evaluation are discussed to recommend the properties required by an ideal reference substance for the soil compartment.

Extracting Metallic Nanoparticles from Soils for Quantitative Analysis: Method Development Using Engineered Silver Nanoparticles and SP-ICP-MS.

The lack of an efficient and standardized method to disperse soil particles and quantitatively subsample the nanoparticulate fraction for characterization analyses is hindering progress in assessing the fate and toxicity of metallic engineered nanomaterials in the soil environment. This study investigates various soil extraction and extract preparation techniques for their ability to remove nanoparticulate Ag from a field soil amended with biosolids contaminated with engineered silver nanoparticles (AgNPs), while presenting a suitable suspension for quantitative single-particle inductively coupled plasma mass spectroscopy (SP-ICP-MS) analysis. Extraction parameters investigated included reagent type (water, NaNO3, KNO3, tetrasodium pyrophosphate (TSPP), tetramethylammonium hydroxide (TMAH)), soil-to-reagent ratio, homogenization techniques as well as procedures commonly used to separate nanoparticles from larger colloids prior to analysis (filtration, centrifugation, and sedimentation). We assessed the efficacy of the extraction procedure by testing for the occurrence of potential procedural artifacts (dissolution, agglomeration) using a dissolved/particulate Ag mass ratio and by monitoring the amount of Ag mass in discrete particles. The optimal method employed 2.5 mM TSPP used in a 1:100 (m/v) soil-to-reagent ratio, with ultrasonication to enhance particle dispersion and sedimentation to settle out the micrometer-sized particles. A spiked-sample recovery analysis shows that 96% ± 2% of the total Ag mass added as engineered AgNP is recovered, which includes the recovery of 84.1% of the particles added, while particle recovery in a spiked method blank is ∼100%, indicating that both the extraction and settling procedure have a minimal effect on driving transformation processes. A soil dilution experiment showed that the method extracted a consistent proportion of nanoparticulate Ag (9.2% ± 1.4% of the total Ag) in samples containing 100%, 50%, 25%, and 10% portions of the AgNP-contaminated test soil. The nanoparticulate Ag extracted by this method represents the upper limit of the potentially dispersible nanoparticulate fraction, thus providing a benchmark with which to make quantitative comparisons, while presenting a suspension suitable for a myriad of other characterization analyses.

Single Particle-Inductively Coupled Plasma Mass Spectroscopy Analysis of Metallic Nanoparticles in Environmental Samples with Large Dissolved Analyte Fractions.

There is an increasing interest to use single particle-inductively coupled plasma mass spectroscopy (SP-ICPMS) to help quantify exposure to engineered nanoparticles, and their transformation products, released into the environment. Hindering the use of this analytical technique for environmental samples is the presence of high levels of dissolved analyte which impedes resolution of the particle signal from the dissolved. While sample dilution is often necessary to achieve the low analyte concentrations necessary for SP-ICPMS analysis, and to reduce the occurrence of matrix effects on the analyte signal, it is used here to also reduce the dissolved signal relative to the particulate, while maintaining a matrix chemistry that promotes particle stability. We propose a simple, systematic dilution series approach where by the first dilution is used to quantify the dissolved analyte, the second is used to optimize the particle signal, and the third is used as an analytical quality control. Using simple suspensions of well characterized Au and Ag nanoparticles spiked with the dissolved analyte form, as well as suspensions of complex environmental media (i.e., extracts from soils previously contaminated with engineered silver nanoparticles), we show how this dilution series technique improves resolution of the particle signal which in turn improves the accuracy of particle counts, quantification of particulate mass and determination of particle size. The technique proposed here is meant to offer a systematic and reproducible approach to the SP-ICPMS analysis of environmental samples and improve the quality and consistency of data generated from this relatively new analytical tool.

A comparison of the effects of silver nanoparticles and silver nitrate on a suite of soil dwelling organisms in two field soils.

Nanomaterials are increasingly used in a wide range of products, leading to growing concern of their environmental fate. In order to understand the fate and effects of silver nanoparticles in the soil environment, a suite of toxicity tests including: plant growth with Elymus lanceolatus (northern wheatgrass) and Trifolium pratense (red clover); collembolan survival and reproduction (Folsomia candida); and earthworm avoidance, survival and reproduction (Eisenia andrei) was conducted. The effect of silver nanoparticles (AgNP) was compared with the effect of ionic silver (as AgNO3) in two agricultural field soils (a sandy loam and a silt loam). Lethal (LC50) or sub lethal (IC50) effect levels are presented for all endpoints and demonstrate that in most cases AgNO3 (i.e. ionic silver) was found to be more toxic than the AgNP across test species. The difference in effects observed between the two forms of silver varied based on test species, endpoint and soil type. In tests that were conducted across different soil types, organisms in the sandier soil had a greater response to the Ag (ionic and nano) than those in soil with a high silt content. Earthworms (avoidance behavior and reproduction) were the most sensitive to both AgNP and AgNO3, while plant emergence was the least sensitive endpoint to both forms of Ag. The use of a test battery approach using natural field soils demonstrates the need to better quantify the dissolution and transformation products of nanomaterials in order to understand the fate and effects of these materials in the soil environment.

Estimation of the bioaccumulation potential of a nonchlorinated bisphenol and an ionogenic xanthene dye to Eisenia andrei in field-collected soils, in conjunction with predictive in silico profiling.

In silico-based model predictions, originating from structural and mechanistic (e.g., transport, bioavailability, reactivity, and binding potential) profiling, were compared against laboratory-derived data to estimate the bioaccumulation potential in earthworms of 2 organic substances (1 neutral, 1 ionogenic) known to primarily partition to soil. Two compounds representative of specific classes of chemicals were evaluated: a nonchlorinated bisphenol containing an -OH group (4,4'-methylenebis[2,6-di-tert-butylphenol] [Binox]), and an ionogenic xanthene dye (2',4',5',7'-tetrabromo-4,5,6,7-tetrachloro-3',6'-dihydroxy-, disodium salt [Phloxine B]). Soil bioaccumulation studies were conducted using Eisenia andrei and 2 field-collected soils (a clay loam and a sandy soil). In general, the in silico structural and mechanistic profiling was consistent with the observed soil bioaccumulation tests. Binox did not bioaccumulate to a significant extent in E. andrei in either soil type; however, Phloxine B not only accumulated within tissue, but was not depurated from the earthworms during the course of the elimination phase. Structural and mechanistic profiling demonstrated the binding and reactivity potential of Phloxine B; this would not be accounted for using traditional bioaccumulation metrics, which are founded on passive-based diffusion mechanisms. This illustrates the importance of profiling for reactive ionogenic substances; even limited bioavailability combined with reactivity can result in exposures to a hazardous substance not predictable by traditional in silico modeling methods.

Ecotoxicity of xanthene dyes and a non-chlorinated bisphenol in soil.

Soil eco-toxicity testing was conducted in support of Canada's Chemical Management Plan (CMP) to fill data gaps for organic chemicals known to primarily partition to soil, and of which the persistence and inherent toxicity are uncertain. Two compounds representative of specific classes of chemicals: non-chlorinated bisphenols containing an -OH group (4,4'-methylenebis(2,6-di-tert-butylphenol (Binox)) and xanthene dyes (2',4',5',7'-tetrabromo-4,5,6,7-tetrachloro-3',6'-dihydroxy-, disodium salt (Phloxine B), 2',4',5',7'-tetrabromofluorescein (TBF), 4',5'-dibromofluorescein (DBF), and 4,5,6,7-tetrachlorofluorescein (TCF)) were evaluated. The effect of these substances on plant growth (Elymus lanceolatus and Trifolium pratense) and soil invertebrate survival and reproduction (Folsomia candida and Eisenia andrei) were assessed using a field-collected sandy soil. Binox was persistent throughout testing (up to 63 d) with an average recovery of 77±2.9% at test end. Binox was not toxic to plants (IC50s>1076 mg kg(-1)) or E. andrei (IC50s>2651 mg kg(-1)); however, a significant reduction in F. candida adult survival and reproduction (IC50=89 (44-149) mg kg(-1)) was evident. Phloxine B was also persistent throughout testing, with an average recovery of 82±3.0% at test end. Phloxine B was significantly more toxic than Binox, with significant reductions in plant root growth (IC50s ≥ 11 mg kg(-1)) and invertebrate reproduction (IC50s ≥ 22 mg kg(-1)). DBF toxicity was not significantly different from that of Phloxine B for plant root growth (IC50s ≥ 30 mg kg(-1)), but was significantly less toxic for shoot growth (IC50s ≥ 1758 mg kg(-1)), and invertebrate adult survival (IC50s ≥ 2291 mg kg(-1)) and reproduction (IC50s ≥ 451 mg kg(-1)). A comparison between all four xanthene dyes was completed using F. candida, with the degree of toxicity in the order of Phloxine B ≥ TBF∼DBF>TCF. The results from these studies will contribute to data gaps for poorly understood chemicals (and chemical groupings) under review for environmental risk assessments, and will aid in the validation of model predictions used to characterize the fate and effects of these substances in soil environments.

Evaluation of a new battery of toxicity tests for boreal forest soils: assessment of the impact of hydrocarbons and salts.

The ability to assess the toxic potential of soil contamination within boreal regions is currently limited to test species representative of arable lands. This study evaluated the use of six boreal plant species (Pinus banksiana, Picea glauca, Picea mariana, Populus tremuloides, Calamagrostis Canadensis, and Solidago canadensis) and four invertebrate species (Dendrodrilus rubidus, Folsomia nivalis, Proisotoma minuta, and Oppia nitens) and compared their performance to a suite of standard agronomic soil test species using site soils impacted by petroleum hydrocarbon (PHC) and salt contamination. To maintain horizon-specific differences, individual soil horizons were collected from impacted sites and relayered within the test vessels. Use of the boreal species was directly applicable to the assessment of the contaminated forest soils and, in the case of the hydrocarbon-impacted soil, demonstrated greater overall sensitivity (25th percentile of estimated species sensitivity distribution [ESSD25] = 5.6% contamination: 10,600 mg/kg fraction 3 [F3; equivalent hydrocarbon range of >C16 to C34] Of/Oh horizon, and 270 mg/kg F3 Ahg horizon) relative to the standard test species (ESSD25 = 23% contamination: 44,000 mg/kg F3 Of/Oh horizon, and 1,100 mg/kg F3 Ahg horizon). For salinity, there was no difference between boreal and standard species with a combined ESSD25 = 2.3%, equating to 0.24 and 0.25 dS/m for the Ah and Ck horizons. The unequal distribution of soil invertebrates within the layered test vessels can confound test results and the interpretation of the toxic potential of a site. The use of test species relevant to boreal eco-zones strengthens the applicability of the data in support of realistic ecological risk assessments applicable to the boreal regions.

Phytotoxkit: a critical look at a rapid assessment tool.

Terrestrial plant toxicity testing contributes critical information to many site risk assessments, but standardized tests can be labor-intensive, use large amounts of soil, and employ long test durations. The Phytotoxkit (MicroBioTests, Environmental Bio-Detection Products) minimizes the time and cost associated with terrestrial plant testing with a unique test setup, a shorter test duration, and less soil. However, the sensitivity of the test remains an open question. In this research, the Phytotoxkit and the standardized Environment Canada terrestrial plant toxicity test (definitive test) are compared using a parallel testing approach. Three different scenarios were examined: a multiconcentration test, in which an inhibiting concentration (ICp) was derived from chemically amended soils; a soil remediation test, in which plant growth in a remediated soil was compared to the original contaminated soil; and a site soil test, in which plant growth in a contaminated soil was compared to a reference soil. The contaminants tested were boric acid, Cr(VI) with cyclodextrin as a remediation agent, and petroleum hydrocarbons. Trifolium pratense (red clover) was used in the first and second scenarios, and six different plant species were used in the third scenario. In the first scenario, the Phytotoxkit results compared well with the definitive test results after 5 and 7 d of exposure. In the second scenario, the Phytotoxkit results agreed with the definitive test when evaluating the effectiveness of remediation. In the third scenario, the Phytotoxkit results were often not in agreement with the results from the definitive test. The reduced sensitivity of the Phytotoxkit in the third scenario may be driven by test unit design, as plant roots are separated from soil by filter paper.