Effect of biosolids characteristics on retention and release behavior of azithromycin and ciprofloxacin.

Azithromycin (AZ) and ciprofloxacin (CIP) are commonly prescribed antibiotics frequently detected in municipal biosolids and identified by the USEPA as contaminants of emerging concern. The land application of municipal biosolids is an agronomically beneficial practice but is also a potential pathway of CIP and AZ release into the environment. Understanding retention-release behavior is crucial for assessing the environmental fate of and risks from land-applied biosolids-borne target antibiotics. Here, we used batch equilibrations to assess retention and release of environmentally relevant concentrations of CIP and AZ in ten different biosolids. The biosolids included Class A and Class B materials with a range of physiochemical characteristics (e.g. pH, cation exchange capacity (CEC), organic matter content (OM), and iron (Fe) and aluminum (Al)) expected to influence retention and release of AZ and CIP. Retention was linear (R2 > 0.99 for AZ and >0.96 for CIP) and sorption coefficients (Kd) ranged from 52 to 370 L kg-1 for AZ and 430-2300 L kg-1 for CIP. Desorption also varied but was highly hysteretic, with hysteresis coefficients (H) ranging 0.01 to 0.15 for AZ and ≤0.01 for CIP, suggesting limited bioaccessibility. The penalized and shrinkage method least absolute shrinkage and selection operator (LASSO) was used to produce models describing AZ and CIP sorption behavior based on any given biosolids physiochemical characteristics. Multiple linear regression analysis linked AZ sorption behavior to total Fe content, likely due to a predisposition of AZ to participate in reactions with in situ Fe species. CIP sorption behavior was linked to oxalate extractable Al and total phosphorus (P) content, suggesting CIP bonding with amorphous forms of Al and a potential relationship between CIP sorption to biosolids and biosolids production processes, as manifested by correlation of CIP sorption with total P content.

Incorporating Transgenerational Epigenetic Inheritance into Ecological Risk Assessment Frameworks.

Chronic exposure to environmental contaminants can induce heritable "transgenerational" modifications to organisms, potentially affecting future ecosystem health and functionality. Incorporating transgenerational epigenetic heritability into risk assessment procedures has been previously suggested. However, a critical review of existing literature yielded numerous studies claiming transgenerational impacts, with little compelling evidence. Therefore, contaminant-induced epigenetic inheritance may be less common than is reported in the literature. We identified a need for multigeneration epigenetic studies that extend beyond what could be deemed "direct exposure" to F1 and F2 gametes and also include subsequent multiple nonexposed generations to adequately evaluate transgenerational recovery times. Also, increased experimental replication is required to account for the highly variable nature of epigenetic responses and apparent irreproducibility of current studies. Further, epigenetic end points need to be correlated with observable detrimental organism changes before a need for risk management can be properly determined. We suggest that epigenetic-based contaminant studies include concentrations lower than current "EC10-20" or "Lowest Observable Effect Concentrations" for the organism's most sensitive phenotypic end point, as higher concentrations are likely already regulated. Finally, we propose a regulatory framework and optimal experimental design that enables transgenerational epigenetic effects to be assessed and incorporated into conventional ecotoxicological testing.

Toxicogenomic Responses of the Model Legume Medicago truncatula to Aged Biosolids Containing a Mixture of Nanomaterials (TiO2, Ag, and ZnO) from a Pilot Wastewater Treatment Plant.

Toxicogenomic responses in Medicago truncatula A17 were monitored following exposure to biosolids-amended soils. Treatments included biosolids produced using a pilot wastewater treatment plant with either no metal introduced into the influent (control); bulk/ionic TiO2, ZnO, and AgNO3 added to influent (bulk/dissolved treatment); or Ag, ZnO, and TiO2 engineered nanomaterials added to influent (ENM treatment) and then added to soil, which was aged in the field for 6 months. In our companion study, we found inhibition of nodulation in the ENM but not in the bulk/dissolved treatment. Gene expression profiling revealed highly distinct profiles with more than 10-fold down-regulation in 239 genes in M. truncatula roots from the ENM treatment, while gene expression patterns were similar between bulk/dissolved and control treatments. In response to ENM exposure, many of the identified biological pathways, gene ontologies, and individual genes are associated with nitrogen metabolism, nodulation, metal homeostasis, and stress responses. Expression levels of nine genes were independently confirmed with qRT-PCR. Exposure to ENMs induced unique shifts in expression profiles and biological pathways compared with bulk/dissolved treatment, despite the lack of difference in bioavailable metal fractions, metal oxidation state, and coordination environment between ENM and bulk/dissolved biosolids. As populations of Sinorhizobium meliloti Rm2011 were similar in bulk/dissolved and ENM treatments, our results suggest that inhibition of nodulation in the ENM treatment was primarily due to phytotoxicity, likely caused by enhanced bioavailability of Zn ions.

Nanomaterials in Biosolids Inhibit Nodulation, Shift Microbial Community Composition, and Result in Increased Metal Uptake Relative to Bulk/Dissolved Metals.

We examined the effects of amending soil with biosolids produced from a pilot-scale wastewater treatment plant containing a mixture of metal-based engineered nanomaterials (ENMs) on the growth of Medicago truncatula, its symbiosis with Sinorhizobium meliloti, and on soil microbial community structure. Treatments consisted of soils amended with biosolids generated with (1) Ag, ZnO, and TiO2 ENMs introduced into the influent wastewater (ENM biosolids), (2) AgNO3, Zn(SO4)2, and micron-sized TiO2 (dissolved/bulk metal biosolids) introduced into the influent wastewater stream, or (3) no metal added to influent wastewater (control). Soils were amended with biosolids to simulate 20 years of metal loading, which resulted in nominal metal concentrations of 1450, 100, and 2400 mg kg(-1) of Zn, Ag, and Ti, respectively, in the dissolved/bulk and ENM treatments. Tissue Zn concentrations were significantly higher in the plants grown in the ENM treatment (182 mg kg(-1)) compared to those from the bulk treatment (103 mg kg(-1)). Large reductions in nodulation frequency, plant growth, and significant shifts in soil microbial community composition were found for the ENM treatment compared to the bulk/dissolved metal treatment. These results suggest differences in metal bioavailability and toxicity between ENMs and bulk/dissolved metals at concentrations relevant to regulatory limits.

Fate of zinc oxide and silver nanoparticles in a pilot wastewater treatment plant and in processed biosolids.

Chemical transformations of silver nanoparticles (Ag NPs) and zinc oxide nanoparticles (ZnO NPs) during wastewater treatment and sludge treatment must be characterized to accurately assess the risks that these nanomaterials pose from land application of biosolids. Here, X-ray absorption spectroscopy (XAS) and supporting characterization methods are used to determine the chemical speciation of Ag and Zn in sludge from a pilot wastewater treatment plant (WWTP) that had received PVP coated 50 nm Ag NPs and 30 nm ZnO NPs, dissolved metal ions, or no added metal. The effects of composting and lime and heat treatment on metal speciation in the resulting biosolids were also examined. All added Ag was converted to Ag2S, regardless of the form of Ag added (NP vs ionic). Zn was transformed to three Zn-containing species, ZnS, Zn3(PO4)2, and Zn associated Fe oxy/hydroxides, also regardless of the form of Zn added. Zn speciation was the same in the unamended control sludge. Ag2S persisted in all sludge treatments. Zn3(PO4)2 persisted in sludge and biosolids, but the ratio of ZnS and Zn associated with Fe oxy/hydroxide depended on the redox state and water content of the biosolids. Limited differences in Zn and Ag speciation among NP-dosed, ion-dosed, and control biosolids indicate that these nanoparticles are transformed to similar chemical forms as bulk metals already entering the WWTP.

Sorption and degradation processes of imidacloprid in Florida soils.

Imidacloprid (IDP) is an active ingredient of the Admire brand pesticide used to control the vector (Asian citrus psyllid) that transmits the causative organism Candidatus Liberibacter asiaticus (CLas) for citrus greening or huanglongbing disease. Imidacloprid products are applied via soil drench where citrus roots are mostly concentrated which is between 0 and 60 cm depth. These soil depths exhibit different characteristics that may affect IDP leaching beyond the rooting zone. Representative soil samples were collected from Entisols and Ultisols, which are the dominant soil orders under citrus production in central Florida, at 15 cm increments up to 60 cm to estimate and understand the batch sorption, kinetics, equilibria, and degradation of IDP. Results showed that the equilibrium time for IDP at 0-15 cm depth (10 hours) was 2 times faster than at 15-60 cm (20 hours) for the Entisol. Nevertheless, all depths reached equilibrium within 24 hours for the Entisol. The 0-30 cm depth adsorbed 2 times more IDP than the 30-60 cm depth for both soils. Nevertheless, the adsorption coefficient was approximately ≤ 1 mL g-1 for both soils. The half-life of IDP in both soils ranged from 10 to 17 days. The Entisol showed higher adsorption than the Ultisol at both depths, probably due to relatively lower organic carbon (OC) content in the Ultisol compared to the Entisol. Thus, the Ultisol showed high IDP leaching vulnerability compared to the Entisol. Movement of IDP is affected by the amount of OC in the citrus critical zone.

Per- and polyfluoroalkyl substances in water treatment residuals: Occurrence and desorption.

Per- and polyfluoroalkyl substances (PFAS) in surface and ground waters supplying municipal drinking water are a growing concern. However, PFAS concentrations in water treatment residuals (WTRs)-a solid by-product of water treatment-have yet to be explored. In a first of its kind assessment, we examine PFAS occurrence in seven calcium (Ca)-, iron-, and aluminum-based drinking water treatment residuals (DWTRs) and one wastewater effluent treatment residual (WWETR) produced using aluminum chlorohydrate (ACH). Only perfluoroalkyl acids (PFAAs) were detected, with total PFAA concentrations in the seven DWTRs produced from naturally recharged water sources ranging from 0 to ∼3.3 µg kg-1 ; no PFAS were detected in either of the Ca-DWTRs. The ACH-WWETR contained the highest number and concentration of PFAAs (34 µg kg-1 ). Desorption of resident PFAAs from the WTRs was negligible for the carboxylates (PFCAs). Some desorption of the sulfonates (PFSAs) was detected, particularly for PFOS which had the highest concentration among all resident PFAAs. The ACH-WWETR was further evaluated for its potential to attenuate additional PFAAs (3500 µg mL-1 total PFAAs) in a biosolid-derived porewater matrix. Sorption was highest for long-chain PFAAs and subsequent desorption of the adsorbed PFAAs ranged from 0% to no more than 26%, with the WWETR mass added strongly affecting both PFSA and PFCA sorption/desorption. These findings suggest that WTRs, if introduced into the environment, are unlikely to be a major source of PFAS. Also, the use of particular WTRs as amendments may provide a beneficial reduction in PFAS mobility.

Effects of drinking water treatment residual amendments to biosolids on plant uptake of per- and polyfluoroalkyl substances.

Drinking water treatment residuals (DWTRs), solid by-products of drinking water treatment, are dominated by calcium (Ca), iron (Fe), or aluminum (Al), depending on the coagulant used. DWTRs are often landfilled, but current research is exploring options for beneficial reuse. Previous studies have shown that Al- and Fe-rich materials have potential to reduce the mobility of per- and polyfluoroalkyl substances (PFAS). Here, we investigated how amending biosolids with 5% wt/wt DWTRs affected plant bioavailable PFAS in two different simulated scenarios: (1) agricultural scenario with Solanum lycopersicum (tomato) grown in soil amended with an agronomically relevant rate of DWTR-amended biosolids (0.9% w/w, resulting in 0.045% w/w DWTR in the biosolids-amended soil) and (2) mine reclamation scenario examining PFAS uptake by Lolium perenne (perennial ryegrass) grown in soil that received DWTR-amended biosolids amendment at a rate consistent with the mine remediation (13% w/w, resulting in 0.65% w/w DWTR in the biosolids-amended soil). Amending biosolids with Ca-DWTR significantly reduced perfluorobutanoic acid (PFBA) uptake in ryegrass and perfluorohexanoic acid uptake in tomatoes, possibly due to DWTR-induced pH elevation, while Fe-DWTR amendment reduced PFBA bioaccumulation in ryegrass. The Al-DWTR did not induce a significant reduction in accumulated PFAS compared to controls. Although the reasons for this finding are unclear, the relatively low PFAS concentrations in the biosolids and relatively high Al content in the biosolids and soil may be partially responsible.

PFAS release from wastewater residuals as a function of composition and production practices.

Per- and polyfluoroalkyl substances (PFAS) are a class of highly persistent contaminants that have been linked to human health effects at low exposure concentrations. Public concerns exist that land-application of biosolids may result in the release of PFAS into terrestrial and aquatic ecosystems. The relative importance of inorganic constituents such as Fe and Al, which are known to impact PFAS retention/release behavior in soils, on PFAS release from wastewater residuals (WWRs, i.e., biosolids and sewage sludges) is not well understood. Here, we examine native concentrations and WWR-water partition coefficients of a range of PFAS in the context of WWRs characteristics including oxalate-extractable Fe and Al, organic matter (OM), dissolved organic carbon, and total protein content. Total PFAS concentrations, which included perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, fluorotelomer sulfonates and some sulfonamides, ranged from ∼480 to 3500 µg PFAS kg-1 dry weight. PFAS WWR-water partition coefficients ranged from ∼10 to 20,000 L kg-1, consistent with the literature. PFAS partitioning was significantly correlated to oxalate extractable Al and Fe as well as bulk OM and protein content. These results have important implications for wastewater treatment facilities that recycle Al- and Fe-based drinking water treatment residuals in terms of both PFAS retention and loading.

The Importance of Fostering and Funding Scientific Research, and its Relevance to Environmental Toxicology and Chemistry.

What do environmental contaminants and climate change have in common with the virus SARS-CoV-2 and the disease COVID-19? We argue that one common element is the wealth of basic and applied scientific research that provides the knowledge and tools essential in developing effective programs for addressing threats to humans and social-ecological systems. Research on various chemicals, including dichlorodiphenyltrichloroethane and per- and polyfluoroalkyl substances, resulted in regulatory action to protect environmental and human health. Moreover, decades of research on coronaviruses, mRNA, and recently SARS-CoV-2 enabled the rapid development of vaccines to fight the COVID-19 pandemic. In the present study, we explore the common elements of basic and applied scientific research breakthroughs that link chemicals, climate change, and SARS-CoV-2/COVID-19 and describe how scientific information was applied for protecting human health and, more broadly, socio-ecological systems. We also offer a cautionary note on the misuse and mistrust of science that is not new in human history, but unfortunately is surging in modern times. Our goal was to illustrate the critical role of scientific research to society, and we argue that research must be intentionally fostered, better funded, and applied appropriately. To that end, we offer evidence that supports the importance of investing in scientific research and, where needed, ways to counter the spread of misinformation and disinformation that undermines legitimate discourse. Environ Toxicol Chem 2023;42:581-593. © 2022 SETAC.

Bioaccumulation of gold nanomaterials by Manduca sexta through dietary uptake of surface contaminated plant tissue.

We investigated the potential for bioaccumulation of engineered nanomaterials (ENMs) by tobacco hornworm (Manduca sexta) caterpillars resulting from the ingestion of plant tissue surface contaminated with ENMs. Caterpillars were fed tomato leaf tissue that had been surface contaminated with 12 nm tannate coated Au ENMs. After dosing was complete, bulk Au concentrations in individual caterpillars were measured after 0, 1, 4, and 7 days of elimination. Growth, mortality, and ingestion rate were monitored. This experiment revealed (1) no evidence that caterpillars were affected by ingestion of ENM contaminated plant tissue; (2) low bioaccumulation factors (BAF = 0.16) compared to a previous study where hornworm caterpillars were fed plants that had previously bioaccumulated Au ENMs (BAF = 6.2-11.6); (3) inefficient elimination of accumulated Au ENMs not associated with hornworm gut contents; and (4) regional differences in translocation of Au ENMs into tissues surrounding the hornworm gut, possibly the result of the interaction between ENM surface chemistry and regional differences in hornworm gut chemistry. These data, along with previous findings, indicate that although ENMs resuspended from soil onto plant surfaces by wind, water, biota, and/or mechanical disturbances are bioavailable to terrestrial consumers, bioaccumulation efficiency may be much lower via this pathway than through direct trophic exposure.

Bioavailability of gold nanomaterials to plants: importance of particle size and surface coating.

We used the model organisms Nicotiana tabacum L. cv Xanthi (tobacco) and Triticum aestivum (wheat) to investigate plant uptake of 10-, 30-, and 50-nm diameter Au manufactured nanomaterials (MNMs) coated with either tannate (T-MNMs) or citrate (C-MNMs). Primary particle size, hydrodynamic size, and zeta potential were characterized using transmission electron microscopy (TEM), dynamic light scattering (DLS), and electrophoretic mobility measurements, respectively. Plants were exposed to NPs hydroponically for 3 or 7 days for wheat and tobacco, respectively. Volume averaged Au concentrations were determined using inductively coupled plasma mass spectrometry (ICP-MS). Spatial distribution of Au in tissue samples was determined using laser ablation ICP-MS (LA-ICP-MS) and scanning X-ray fluorescence microscopy (µXRF). Both C-MNMs and T-MNMs of each size treatment bioaccumulated in tobacco, but no bioaccumulation of MNMs was observed for any treatment in wheat. These results indicate that MNMs of a wide range of size and with different surface chemistries are bioavailable to plants, provide mechanistic information regarding the role of cell wall pores in plant uptake of MNMs, and raise questions about the importance of plant species to MNM bioaccumulation.

Copper stress alleviation in corn (Zea mays L.): Comparative efficiency of carbon nanotubes and carbon nanoparticles.

Copper (Cu) stress is one of the predominant crop yield-reducing factors in agriculture. Application of carbon nanomaterials (CNMs) could have promotive effects on crop growth; however, their effects on alleviation of Cu stress for plants have rarely been documented. In this study, we investigated the comparative role of carbon nanotubes (CNTs) and carbon nanoparticles (CNPs) in corn (Zea mays) seed germination, seedling growth as well as Cu stress alleviation. The results showed that CNTs and CNPs stimulated corn seed germination by significantly increasing germination rate (GR), shortening the mean germination time (MGT), and increasing overall germination index (GI). They also significantly elongated seedling length and increased fresh biomass with optimal application rates ranging from 50 to 100 mg L-1. Principle component analysis (PCA) confirmed that seed germination indexes and seedling growth were positively affected by CNTs or CNPs, but inversely influenced by high levels of Cu stress (> 20 mg L-1). Furthermore, higher Cu accumulation and anti-oxidative enzyme activity (SOD, POD, CAT) were observed in plants co-exposed to Cu2+ and either CNTs or CNPs compared to plants exposed to Cu2+ alone. CNPs had stronger improvement on plant growth and Cu stress alleviation than CNTs, which suggest they may be cost-effective agriculture amendments to improve plant growth under heavy metal stress.

Trophic transfer of PFAS from tomato (Solanum lycopersicum) to tobacco hornworm (Manduca sexta) caterpillars.

PFASs are highly persistent in the environment and the potential exists for terrestrial biota to accumulate PFAS, which may result in exposure of higher trophic level organisms to these compounds through consumption. However, trophic transfer of proteinophilic compounds such as PFAS has not been extensively studied and the degree to which plant-accumulated PFAS will be transferred to herbivorous consumers is unclear. Here, we exposed Solanum lycopersicum (tomato) plants to a suite of 7 different PFAS, including 4 carboxylic acids (PFOA, PFHxA, PFHpA and PFDA) and 3 sulfonates (PFBS, PFHxS and PFOS). Exposed leaf tissues were subsequently fed to Manduca sexta (tobacco hornworm) caterpillars. Biomagnification factors (BMFs) were all below 1 and patterns of uptake and elimination were similar between the different PFAS. However, PFOS bioaccumulated in the hornworms to a much higher concentration, with approximately 5-fold higher BMFs and assimilation efficiencies (AEs) than other PFAS tested. AE and BMF, as well as PFAS uptake by the plants, were positively correlated with PFAS carbon chain length for both sulfonates and carboxylic acids, providing evidence that longer chain PFAS may be more efficiently accumulated (or less efficiently eliminated) than shorter-chain PFAS in some contexts.

Correlating soil nutrient test lead with bioaccessible lead in highly-contaminated soils receiving lead-immobilizing amendments.

Lead (Pb) is one of the most common metals exceeding human health risk guidelines for soil concentrations worldwide. Pb bioaccessibility is known to vary depending on soil physiochemical characteristics and, as a result, in vitro and in vivo tests exist that are used to estimate bioaccessible Pb in contaminated soils. Although in vitro tests such as the relative bioaccessibility leaching procedure (RBALP) present simpler and more cost-effective risk assessments than in vivo methods, soil tests such as Mehlich-3, Modified Morgan, and ammonium bicarbonate-diethylenetriamine pentaacetate (AB-DTPA) extractions are extremely routine and even more cost-effective. Currently, there are few comparisons examining the viability of common soil nutrient tests for assessing Pb bioaccessibility in soils from contaminated sites with extremely high total Pb concentrations or for sites that have received amendments, such as those containing compost, iron, and/or phosphorus, intended to immobilize Pb. Here, we examine the correlation between RBALP Pb and Pb as determined using three commonly utilized soil tests, Mehlich-3, Modified Morgan, and AB-DTPA, in archived samples from one Pb-contaminated site receiving compost amendment (Seattle, WA, USA) and one extremely Pb-contaminated site receiving mixtures of compost, P, and Fe (Joplin, MO, USA). At both the Seattle and Joplin sites separately, RBALP Pb was significantly correlated with all three soil nutrient test values, regardless of soil amendment. However, RBALP was only significantly correlated with Modified Morgan and total Pb when examining the Joplin and Seattle data together, likely resulting from different factors controlling Pb solubility at the two sites. These findings suggest that a diverse suite of relatively inexpensive and accessible soil nutrient test methods correlate with bioaccessible Pb at a specific site, regardless of whether Pb-immobilizing amendments have been used.

Evidence for biomagnification of gold nanoparticles within a terrestrial food chain.

Nanoparticles from the rapidly increasing number of consumer products that contain manufactured nanomaterials are being discharged into waste streams. Increasing evidence suggests that several classes of nanomaterials may accumulate in sludge derived from wastewater treatment and ultimately in soil following land application as biosolids. Little research has been conducted to evaluate the impact of nanoparticles on terrestrial ecosystems, despite the fact that land application of biosolids from wastewater treatment will be a major pathway for the introduction of manufactured nanomaterials to the environment. To begin addressing this knowledge gap, we used the model organisms Nicotiana tabacum L. cv Xanthi and Manduca sexta (tobacco hornworm) to investigate plant uptake and the potential for trophic transfer of 5, 10, and 15 nm diameter gold (Au) nanoparticles (NPs). Samples were analyzed using both bulk analysis by inductively coupled plasma mass spectrometry (ICP-MS) as well as spatially resolved methods such as laser ablation inductively coupled mass spectrometry (LA-ICP-MS) and X-ray fluorescence (µXRF). Our results demonstrate trophic transfer and biomagnification of gold nanoparticles from a primary producer to a primary consumer by mean factors of 6.2, 11.6, and 9.6 for the 5, 10, and 15 nm treatments, respectively. This result has important implications for risks associated with nanotechnology, including the potential for human exposure.

Transport and retention of polymeric and other engineered nanoparticles in porous media.

Increasing applications of nanoparticles (NPs) in agriculture have raised potential risks to soil and aquatic ecosystems. A comparative study examining the transport of commonly used NPs in porous media is of critical significance for their application and regulation in agroecosystems. In this study, laboratory column leaching experiments were conducted to investigate the transport and retention of polysuccinimide NPs (PSI-NPs) in two saturated porous media with different grain sizes, as compared with multi-walled carbon nanotubes (MWCNTs), nano-Ag and nano-TiO2. Zeta potential of the NPs was negative at pH6.3 and decreased in an order of PSI-NPs > nano-TiO2 > MWCNTs > nano-Ag. The coarse and fine sands used in this study had negative charges with similar zeta potentials. The movement of NPs was affected by grain size, with larger sizes facilitating mobility while finer sizes favoring retention of NPs in the porous matrix. The retention profile significantly varied between the two sand columns, with more NPs transported to deeper layers in the coarse sand than the fine sand. The relative percentage of NPs detected in leachate was found to be positively correlated with the zeta potential of NPs (r = 0.931). Among the NPs, nano-Ag had the most negative zeta potential, and therefore was the most mobile, followed by MWCNTs and nano-TiO2. Having the least negative zeta potential, PSI-NPs had the lowest mobility, as compared with other NPs regardless of matrix grain size. This work reveals grain size and zeta potential of NPs are major factors that influence transport of NPs along the vertical porous profile, as well as demonstrating the relative unimportance of NP composition, which could serve as important guideline in nanomaterials application, risk assessment, and waste management in agroecosystems.

Effects of particle size on chemical speciation and bioavailability of copper to earthworms (Eisenia fetida) exposed to copper nanoparticles.

To investigate the role of particle size on the oxidation, bioavailability, and adverse effects of manufactured Cu nanoparticles (NPs) in soils, we exposed the earthworm Eisenia ferida to a series of concentrations of commercially produced NPs labeled as 20- to 40-nm or < 100-nm Cu in artificial soil media. Effects on growth, mortality, reproduction, and expression of a variety of genes associated with metal homeostasis, general stress, and oxidative stress were measured. We also used X-ray absorption spectroscopy and scanning X-ray fluorescence microscopy to characterize changes in chemical speciation and spatial distribution of the NPs in soil media and earthworm tissues. Exposure concentrations of Cu NPs up to 65 mg kg(-1) caused no adverse effects on ecologically relevant endpoints. Increases in metallothionein expression occurred at concentrations exceeding 20 mg kg(-1) of Cu NPs and concentrations exceeding 10 mg kg(-1) of CuSO4. Based on the relationship of Cu tissue concentration to metallothionein expression level and the spatial distribution and chemical speciation of Cu in the tissues, we conclude that Cu ions and oxidized Cu NPs were taken up by the earthworms. This study suggests that oxidized Cu NPs may enter food chains from soil but that adverse effects in earthworms are likely to occur only at relatively high concentrations (> 65 mg Cu kg(-1) soil).

Microplastics in municipal mixed-waste organic outputs induce minimal short to long-term toxicity in key terrestrial biota.

Sustainable alternatives to landfill disposal for municipal mixed wastes represents a major challenge to governments and waste management industries. In the state of New South Wales (NSW) Australia, mechanical biological treatment (MBT) is being used to reduce the volume and pathogen content of organic matter isolated from municipal waste. The product of this treatment, a compost-like output (CLO) referred to as mixed waste organic output (MWOO), is being recycled and applied as a soil amendment. However, the presence of contaminants in MWOO including trace organics, trace metals and physical contaminants such as microplastic fragments has raised concerns about potential negative effects on soil health and agriculture following land application. Here, we used multiple lines of evidence to examine the effects of land application of MWOO containing microplastics in three soils to a variety of terrestrial biota. Treatments included unamended soil, MWOO-amended soil and MWOO-amended soil into which additional high-density polyethylene (HDPE), polyethylene terephthalate (PET), or polyvinyl chloride (PVC) microplastics were added. Tests were conducted in soil media that had been incubated for 0, 3 or 9 months. Addition of microplastics had no significant negative effect on wheat seedling emergence, wheat biomass production, earthworm growth, mortality or avoidance behaviour and nematode mortality or reproduction compared to controls. There was also little evidence the microplastics affected microbial community diversity, although measurements of microbial community structure were highly variable with no clear trends.

Colloidal nitrogen is an important and highly-mobile form of nitrogen discharging into the Great Barrier Reef lagoon.

Soil-borne colloids have been linked to long-distance transport of radionuclides, metal(loid)s and nutrients. Colloid-associated nitrogen (N) will have different mechanisms of biogeochemical cycling and potential for water-borne transport over longer distances compared to dissolved N. The role that colloids play in the supply and mobility of N within catchments discharging into the Great Barrier Reef (GBR) lagoon is unexplored. Here, we examine water-dispersible clay (WDC) from soil samples collected from gullies and agricultural drains within three different land uses (sugarcane, non-agricultural land and grazing) within the Townsville area. The proportion of soil N associated with WDC was inversely correlated with total soil N, with up to 45% of the total soil N being colloid-associated in low N gully soils. Within the <0.45 µm fraction of the WDC, only 17-25% of the N was truly dissolved (<3 kDa) at the gully sites compared to 58% in the sugarcane sites. Our results demonstrate the importance of colloidal N and the inaccuracy of assuming N < 0.45 µm is dissolved in the sampled areas, as well as providing an alternate explanation for the large amounts of what has previously been defined as dissolved inorganic N in runoff from non-fertilized grazing land. In particular, they describe why non-fertilized land uses can contribute significant N < 0.45 µm, and why catchment models of nutrient export based on soil N concentrations can over-estimate loads of particulate nitrogen derived from monitoring data (N > 0.45 µm). The findings suggest that managing soil erosion may also contribute to managing N < 0.45 µm.