Scientific integrity issues in Environmental Toxicology and Chemistry: Improving research reproducibility, credibility, and transparency.

High-profile reports of detrimental scientific practices leading to retractions in the scientific literature contribute to lack of trust in scientific experts. Although the bulk of these have been in the literature of other disciplines, environmental toxicology and chemistry are not free from problems. While we believe that egregious misconduct such as fraud, fabrication of data, or plagiarism is rare, scientific integrity is much broader than the absence of misconduct. We are more concerned with more commonly encountered and nuanced issues such as poor reliability and bias. We review a range of topics including conflicts of interests, competing interests, some particularly challenging situations, reproducibility, bias, and other attributes of ecotoxicological studies that enhance or detract from scientific credibility. Our vision of scientific integrity encourages a self-correcting culture that promotes scientific rigor, relevant reproducible research, transparency in competing interests, methods and results, and education. Integr Environ Assess Manag 2019;00:000-000. © 2019 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.

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.

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 Canada's 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.

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.