Laboratory versus field soil aging: Impact on DDE bioavailability and sorption

Bioaccessibility and bioavailability of NPAHs in soils using in vitro-in vivo assays: Comparison of laboratory and outdoor environmental aging effect

Aging process is one of the most important factors that markedly reduces bioaccessibility and bioavailability (bioac-bioav) of organic contaminants. However, only few data on comparison of the effects of laboratory artificial aging (LAA) and outdoor environmental aging (OEA) processes on nitrated polycyclic aromatic hydrocarbons (NPAHs) bioac-bioav are available. In the current study, oral bioac-bioav of NPAHs in LAA and OEA soils (aging time intervals: 0, 45, 90, 120 and 150 d) were measured by in vitro traditional Fed ORganic Estimation human Simulation Test (FOREhST) and Tenax improved FOREhST (TI-FOREhST) methods, and in vivo mouse model. Tenax significantly increased the bioaccessibility of NPAHs in freshly spiked and aging soils from 0.3-40.9 % to 15.6-95.3 %, and 0.3-40.9 % to 1.0-84.5 %, respectively. Aging significantly reduced the NPAHs bioaccessibility (from 36.5 % to 10.7 %, and 12.1 % to 5.1 % as measured by FOREhST and TI-FOREhST, respectively) and bioavailability (from 27.7 % to 9.9 %, as measured by mouse model). The changes in bioac-bioav were mainly observed within the first 120 d of aging. The statistical analyses of NPAHs bioac-bioav showed no significant difference (p > 0.05) among the aging time intervals in LAA and OEA soils, which demonstrated that the LAA can relatively represent the OEA. Determination of TOC content in LAA and OEA soil can intuitively reflect whether the difference of NPAHs bioac-bioav between two aging treatment groups is significant. The mean bioaccessibility of NPAHs in soil measured by TI-FOREhST (mean 20.6 %) is closer to the bioavailability measured by mouse model (mean 19.4 %), indicating that Tenax improved in vitro method is more reliable than traditional methods, to predict the bioavailability of NPAHs.

Effects of soil aging conditions on distributions of cadmium distribution and phosphatase activity in different soil aggregates

Aging behaviors of metals in the field differ from those in a controlled laboratory environment. Whether aging conditions influence the fates of metals in soil remains unclear. In this study, distributions of cadmium (Cd) and phosphatase activity were compared in soil aggregates (i.e., >2, 1-2, 0.25-1, and <0.25 mm) along a profile (0-5, 5-10, and 10-15 cm) at the end of 500-day aging experiments under both controlled laboratory and field conditions. Cd concentration in the 0-5 cm layer was lower and Cd concentration in the 5-10 cm layer was higher in field-aged soil compared to laboratory-aged soil. 25.26-35.62% of soil Cd was loaded in >2 mm aggregates of field-aged soils, and 58.41-66.95% was in laboratory-aged soils. Higher loadings of Cd in 0.25-1 and <0.25 mm aggregates were found in field-aged soil. A higher proportion of exchangeable Cd fraction (20.93% of total soil Cd) was found in the 0-5 cm layer of field-aged soil than in laboratory-aged soil (17.63%), while the opposite tendency was found in deeper soil layers. Soil phosphatase activities in field-aged soils were 1.13-1.26 times higher than in laboratory-aged soils. Phosphatase loadings in the >2 mm aggregates were lower and loadings in both the 1-2 and 0.25-1 mm aggregates were higher in field-aged soils than in laboratory-aged soils. Furthermore, correlation analysis and principal component analysis indicated that available Cd fractions accounted for most of the variations in phosphatase activities. In summary, the fates of the exogenous metal Cd differed between field and controlled laboratory conditions. To better understand the behaviors of heavy metals in soil, especially in a seasonal freeze-thaw area, further field studies are needed.

Desorption Resistance of Polycyclic Aromatic Hydrocarbons in Biochars Incubated in Cow Ruminal Liquid in Vitro and in Vivo

Biochar is a new, promising, and sustainable feed additive alternative in agricultural production, which may, however, contain a considerable amount of polycyclic aromatic hydrocarbons (PAHs). As a measure of their bioaccessibility to ruminants, we quantified PAH concentrations in biochars before and after three different incubation experiments. Specifically, the biochars were subjected to (1) an aqueous cyclodextrin suspension with a contaminant trap as (infinite) sink, (2) an in vitro experiment with cow ruminal liquid and a contaminant trap, and (3) an in vivo experiment within cow rumen. Three different biochars were used that contained 13-407 mg/kg_dw of the sum of 16 U.S. EPA PAHs before the exposure. While experiment (1) resulted in no or minimal bioaccessibility (desorption resistance) of the PAHs expressed by their largely unaltered concentrations, experiments (2) and (3) caused concentration reductions on average by 35 and 56%, respectively, presumably mainly due to the presence of the ruminal fluid in (2) and (3), and the extended sorption capacity in (3). Thus, simple and "abiotic" passive sampling methods may not capture all processes contributing to bioaccessibility in complex biological systems. A comparison with average daily PAH intake of ruminants suggests that quality-controlled biochar containing <10 mg/kg_dw PAHs will not pose an increased risk when applied as a feed additive.

Recent Applications and Newly Developed Strategies of Solid-Phase Microextraction in Contaminant Analysis: Through the Environment to Humans

The present review aims to describe the recent and most impactful applications in pollutant analysis using solid-phase microextraction (SPME) technology in environmental, food, and bio-clinical analysis. The covered papers were published in the last 5 years (2014–2019) thus providing the reader with information about the current state-of-the-art and the future potential directions of the research in pollutant monitoring using SPME. To this end, we revised the studies focused on the investigation of persistent organic pollutants (POPs), pesticides, and emerging pollutants (EPs) including personal care products (PPCPs), in different environmental, food, and bio-clinical matrices. We especially emphasized the role that SPME is having in contaminant surveys following the path that goes from the environment to humans passing through the food web. Besides, this review covers the last technological developments encompassing the use of novel extraction coatings (e.g., metal-organic frameworks, covalent organic frameworks, PDMS-overcoated fiber), geometries (e.g., Arrow-SPME, multiple monolithic fiber-SPME), approaches (e.g., vacuum and cold fiber SPME), and on-site devices. The applications of SPME hyphenated with ambient mass spectrometry have also been described.

Influence of soil γ-irradiation and spiking on sorption of p,p'-DDE and soil organic matter chemistry

The fate of organic chemicals and their metabolites in soils is often investigated in model matrices having undergone various pre-treatment steps that may qualitatively or quantitatively interfere with the results. Presently, effects associated with soil sterilization by γ-irradiation and soil spiking using an organic solvent were studied in one freshly spiked soil (sterilization prior to contamination) and its field-contaminated (sterilization after contamination) counterpart for the model organic compound 1,1-Dichloro-2,2-bis(4-chlorophenyl)ethene (p,p'-DDE). Changes in the sorption and potential bioavailability of spiked and native p,p'-DDE were measured by supercritical fluid extraction (SFE), XAD-assisted extraction (XAD), and solid-phase microextraction (SPME) and linked to qualitative changes in soil organic matter (SOM) chemistry measured by diffuse reflectance infrared Fourier-transform (DRIFT) spectroscopy. Reduced sorption of p,p´-DDE detected with XAD and SPME was associated more clearly with spiking than with sterilization, but SFE showed a negligible impact. Spiking resulted in an increase of the DRIFT-derived hydrophobicity index, but irradiation did not. Spectral peak height ratio descriptors indicated increasing hydrophobicity and hydrophilicity in pristine soil following sterilization, and a greater reduction of hydrophobic over hydrophilic groups as a consequence of spiking. In parallel, reduced sorption of p,p´-DDE upon spiking was observed. Based on the present samples, γ-irradiation appears to alter soil sorptive properties to a lesser extent when compared to common laboratory processes such as spiking with organic solvents.

Effect of cetyltrimethyl ammonium bromide on uptake of polycyclic aromatic hydrocarbons by carrots

This is the first study investigating the effect of cationic surfactants on the mobility of polycyclic aromatic hydrocarbons (PAHs) in aged contaminated soils and on PAH bioaccumulation in tuberous vegetables. In an aerobic soil incubation experiment, 150 mg/kg cetyltrimethyl ammonium bromide (CTMAB) decreased the bioavailability of PAHs primarily via immobilization (by 13%). In a carrot pot experiment, the effectiveness of CTMAB to reduce PAH uptake by carrots decreased with time. Accordingly, the bioavailability of PAHs in the soil decreased in the first 90 days and then increased and remained stable until harvest. In the leaching test, the leaching loss of CTMAB (15%) was lower in soils treated with small amounts of CTMAB in several applications than it was in soils (24%) treated once with CTMAB. Therefore, CTMAB, when applied in appropriate doses via addition methods, can effectively reduce the environmental risk of PAH entering humans and livestock through the food chain.