Juliska Princz

Ecotoxicity of siloxane D5 in soil.

Decamethylcyclopentasiloxane (D5) is a cyclic volatile methyl siloxane (cVMS) commonly found in commercially available products. D5 is expected to enter the terrestrial environment through the deposit of biosolids from sewage treatment plants onto agricultural fields for nutrient enrichment. Little to no information currently exists as to the risks of D5 to the terrestrial environment. In order to evaluate the potential risk to terrestrial organisms, the toxicity of a D5 contaminated biosolid in an agricultural soil was assessed with a battery of standardized soil toxicity tests. D5 was spiked into a surrogate biosolid and then mixed with a sandy loam soil to create test concentrations ranging from 0 to 4074 mg kg(-1). Plant (Hordeum vulgare (barley) and Trifolium pratense (red clover)) and soil invertebrates (Eisenia andrei (earthworm) and Folsomia candida (springtail)) toxicity tests were completed to assess for lethal and sub-lethal effects. Plant testing evaluated the effects on seedling emergence, shoot and root length, and shoot and root dry mass. Invertebrate test endpoints included adult lethality, juvenile production, and individual juvenile dry mass (earthworms only). Soil samples were collected over time to confirm test concentrations and evaluate the loss of chemical over the duration of a test. The toxicity of the D5 was species and endpoint dependent, such that no significant adverse effects were observed for T. pratense or E. andrei test endpoints, however, toxicity was observed for H. vulgare plant growth and F. candida survival and reproduction. Chemical losses of up to 50% were observed throughout the tests, most significantly at high concentrations.

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.

Oribatid mites in soil toxicity testing-the use of Oppia nitens (C.L. Koch) as a new test species.

Few soil invertebrate species are available for the toxic assessment of soils from boreal or other northern ecozones, yet these soils cover the majority of Canadas landmass as well as significant portions of Eurasia. Oppia nitens (C.L. Koch) is an herbivorous and fungivorous oribatid mite found in soil throughout Holarctic regions, including Canada. Soil tests using O. nitens were performed using 15 different forest soil types and horizons to investigate test variability in adult survival and reproduction. Adult survival (86.1 +/- 1.1%) was consistent across soil types, with a coefficient of variation (CV) of 15%. However, reproduction varied significantly, ranging from 2.9 (+/-1.1) to 86.2 (+/-11.7) individuals, with a corresponding CV of 118 and 30%, respectively. Of the soil factors assessed (NH(3), NO(3), pH, phosphorus [P], organic matter content (OM), carbon:nitrogen (C:N), sand, silt, clay, and sodium adsorption ratio), soil organic matter (OM) explained 68% of the variation observed for reproduction. Increasing the OM using Sphagnum sp. peat moss resulted in optimal reproduction at 7% OM (8% peat content) with the lowest variability (CV of 20%). When assessing the toxicity of a reference chemical, boric acid, the effect of peat amendment reduced lethality to adults with no observable difference on reproduction. The use an age-synchronized culture reduced the test variability for reproduction relative to the use of unsynchronized cultures. Oppia nitens is a good candidate species for a standardized test design, with adult survival easily assessed in a relatively simple design. A long-term reproduction test with O. nitens will require the use of a synchronized population and, on occasion, OM amendment when testing soils with low organic matter content.

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

Abstract 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.

Can avoidance behavior of the mite Oppia nitens be used as a rapid toxicity test for soils contaminated with metals or organic chemicals

Survival and reproduction soil toxicity tests for a new mite test species, Oppia nitens, have recently been developed for boreal ecosystems; however, the tests require 28 to 35 d. Avoidance tests have the potential to allow for rapid preliminary screening assessments of soils. The objective of this investigation was to determine the relevance of the avoidance test with the oribatid mite O. nitens as a short screening test in lower-tier environmental risk assessment. We assessed the effects of soil properties and chemicals on O. nitens avoidance behavior as well as the minimum time required to obtain a significant avoidance response from the mite. Specimens of this mite were exposed in Organisation for Economic Co-Operation and Development (OECD) artificial soils that had been adjusted to achieve varying soil properties as well as to a range of concentrations of the following contaminants: Cu, Zn, Cd, Pb, phenanthrene, benzo[a]pyrene, geraniol, and boric acid over 1, 2, or 5 d. The results were then compared with those of parallel life-cycle toxicity studies. The results showed that 24 h was adequate to obtain a significant response of the mites and that the soil properties tested (moisture, pH, organic matter, and clay content) had little influence on mite avoidance. The median effective concentration (EC50) for avoidance response was lower than or in the same range as the reproduction EC50 values for the organic compounds (phenanthrene and geraniol) and metals (Cu and Zn) or the median lethal concentration (LC50) values for Pb. The 24-h mite avoidance test is a suitable screening method across a range of soil properties and chemicals.

Effects of metal‐contaminated forest soils from the Canadian shield to terrestrial organisms

The effects of elevated metal concentrations in forest soils on terrestrial organisms were investigated by determining the toxicity of six site soils from northern Ontario and Quebec, Canada, using a battery of terrestrial toxicity tests. Soils were collected from three sites on each of two transects established downwind of nickel (Sudbury, ON, Canada) and copper (Rouyn-Noranda, PQ, Canada) smelting operations. Site soils were diluted to determine if toxicity estimates for the most-contaminated site soils could be quantified as a percent of site soil. Rouyn-Noranda soils were toxic following acute exposure (14 d) to plants, but not to invertebrates (7 d for collembola and 14 d for earthworms). However, Rouyn-Noranda soils were toxic to all species following chronic exposure (21, 35, and 63 d for plants, collembola, and earthworms, respectively). The toxicity of the Rouyn-Noranda site soils did not correspond to the gradient of metal concentrations in soil. Metal-contaminated Sudbury soils were toxic to plants but not to invertebrates, following acute exposure. Chronic exposure to Sudbury soils caused adverse effects to plant growth and invertebrate survival and reproduction. The toxicity of Sudbury soils corresponded to the metal concentration gradient, with one exception: The reference soil collected in October was toxic to collembola following acute and chronic exposure. This study evaluated the applicability of the new Environment Canada terrestrial toxicity test methods, developed using agricultural soils, to forest soils and also provided useful data to assess the ecological risk associated with mixtures of metals in soil.

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.

Ion exchange technique (IET) to characterise Ag+ exposure in soil extracts contaminated with engineered silver nanoparticles

Environmental context Biosolid-amended soils are likely sinks for manufactured silver nanoparticles, the environmental toxicity of which is believed to be related to the release and accumulation of Ag+ ions. This study demonstrates how an ion exchange technique can be applied to soil extracts to provide Ag+ measurements at low, environmentally relevant levels. The technique is a valuable addition to existing analytical methods for tracking the behaviour of Ag nanoparticles and Ag+ ions in the terrestrial environment. Abstract The lack of silver speciation exposure data in toxicity studies investigating the effects of manufactured silver nanoparticles (AgNPs) in natural soil media limits the ability to discern nano-specific effects from effects of the toxic Ag+ form, which may be released from the manufactured AgNPs contained in wastewater, biosolids or soil environment. Using samples containing Ag+ or mixtures of Ag+ and AgNPs, ranging in total Ag concentrations of 10–5 to 10–9 M, and prepared in de-ionised water and filtered soil extracts, the validity of the ion exchange technique (IET) to quantify Ag+ was investigated by comparing measurements to those of an Ag+ ion selective electrode (ISE) and to the dissolved fraction from single particle inductively coupled plasma–mass spectrometry (SP-ICP-MS) analysis (SP-dissolved). When analysing samples in the filtered soil extract, IET and ISE gave comparable results down to 10–7 M, below which Ag+ activities were below the ISE detection limit. For water samples, SP-dissolved values were generally comparable or slightly greater (on average 65%) compared with IET-Ag+ at all concentrations. The high bias was likely due to inclusion of unresolved particles below the SP-ICP detection limit of 19nm. However, when analysing samples in the soil extract, SP-dissolved values were on average eight-fold greater than IET-Ag+, highlighting the effect that natural colloidal and dissolved soil constituents have on complexing Ag+, as well as the lack of specificity of the SP-dissolved analysis for the Ag+ species. IET is shown here to be a valid procedure to quantify Ag+ activity in soil extracts, and while the study highlights the limitations of using the SP-dissolved fraction to estimate this biologically relevant Ag fraction, it shows that combined, IET and SP-ICP-MS provide a valuable approach for investigating the behaviour of manufactured AgNPs in different matrixes.

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.