Soil suspensions (slurries) are commonly used to estimate the potential of soil microbial communities to mineralize organic contaminants. The preparation of soil slurries disrupts soil structure, however, potentially affecting both the bacterial populations and their protozoan predators. We studied the importance of this “slurry effect” on mineralization of the herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA, ¹⁴C-labelled), focussing on the effects of protozoan predation. Mineralization of MCPA was studied in “intact” soil and soil slurries differing in soil:water ratio, both in the presence and absence of the protozoan activity inhibitor cycloheximide. Protozoan predation inhibited mineralization in dense slurry of subsoil (soil:water ratio 1:3), but only in the most dilute slurry of topsoil (soil:water ratio 1:100). Our results demonstrate that protozoan predation in soil slurries may compromise quantification of contaminant mineralization potential, especially when the initial density of degrader bacteria is low and their growth is controlled by predation during the incubation period.

The Great Eastern Japan Earthquake on March 11, 2011, damaged reactor cooling systems at Fukushima Dai-ichi nuclear power plant. The subsequent venting operation and hydrogen explosion resulted in a large radioactive nuclide emission from reactor containers into the environment. Here, we collected environmental samples such as soil, plant species, and water on April 10, 2011, in front of the power plant main gate as well as 35 km away in Iitate village, and observed gamma-rays with a Ge(Li) semiconductor detector. We observed activation products (²³⁹Np and ⁵⁹Fe) and fission products (¹³¹I, ¹³⁴Cs (¹³³Cs), ¹³⁷Cs, ¹¹⁰ᵐAg (¹⁰⁹Ag), ¹³²Te, ¹³²I, ¹⁴⁰Ba, ¹⁴⁰La, ⁹¹Sr, ⁹¹Y, ⁹⁵Zr, and ⁹⁵Nb). ²³⁹Np is the parent nuclide of ²³⁹Pu; ⁵⁹Fe are presumably activation products of ⁵⁸Fe obtained by corrosion of cooling pipes. The results show that these activation and fission products, diffused within a month of the accident.

Melamine formaldehyde resins have hard and durable properties and are found in many products, including automobile paints. These resins contain high concentrations of nitrogen and, if properly composted, can yield valuable products. We evaluated the effects of starter compost, nutrients, gypsum and microbial inoculation on composting of paint sludge containing melamine resin. A bench-scale composting experiment was conducted at 55 °C for 91 days and then at 30 °C for an additional 56 days. After 91 days, the composts were inoculated with a mixed population of melamine-degrading microorganisms. Melamine resin degradation after the entire 147 days of composting varied between 73 and 95% for the treatments with inoculation of microorganisms compared to 55–74% for the treatments without inoculation. Degradation was also enhanced by nutrients and gypsum additions. Our results infer that large scale composting of melamine resins in paint sludge is possible.

Short-term changes in levels of expression of nine stress response genes and oxidative damage of proteins were examined in Eisenia fetida exposed to polyvinylpyrrolidone (PVP) coated Ag nanoparticles (Ag-NP) and AgNO₃ in natural soils. The responses varied significantly among days with the highest number of significant changes occurring on day three. Similarity in gene expression patterns between Ag-NPs and AgNO₃ and significant relationships of expression of CAT and HSP70 with Ag soil concentration suggest similarity in toxicity mechanisms of Ag ions and NPs. Significant increases in the levels of protein carbonyls on day three of the exposure to both ions and Ag-NPs indicate that both treatments induced oxidative stress. Our results suggest that Ag ions drive short term toxicity of Ag-NPs in E. fetida. However, given that <15% of Ag in the NPs was oxidized in these soils, dissolution of Ag-NPs is likely to occur after or during their uptake.

The PAH contamination level and biochemical composition of sinking particles and surficial sediments (0–0.5 cm layer) were assessed at a rural coastal site in the northwestern Mediterranean Sea. Surficial sediment contamination (≈20 ng g⁻¹) was considerably lower than at other Mediterranean sites, yet particles collected in sediment traps had 6–8 times more PAH. Contaminated particles were mostly marine in origin. Temporal variation of contamination levels correlated with organic content of the particles, but some of the observed variability could be attributed to seasonal changes in pyrolytic PAH production. Sinking organic particles were potentially as readily digestible as surficial sediments for prospective consumers however, transfer of PAHs along the benthic food chain is probably enhanced because of the particles' higher nutritional value.

This study investigates the column leaching of a soil contaminated mainly with Cr and Ni by using two chelants: citric acid (biodegradable) and EDTA (non-biodegradable) followed with water rinse. The chelants lead to Cr and Ni leaching, in addition to major elements (Ca, Fe, Mg, Al, Mn and Zn) showing the dissolution of soil mineral constituents. EDTA leaches more major elements and Ni than citric acid related to the respective stability of metal–chelant complexes; citric acid leaches more Cr than EDTA, certainly because of a substitution reaction with Cr(VI). In the case of alternating chelant/water applications, leaching occurs during the chelant applications, but also during water applications. In the case of chelant/water applications followed by continuous water application, both Cr and Ni leach over time. This increased mobility could be due to the residual chelant present in soil as well as to the dissolution/mobilization of mineral or organic soil fractions.

Next to imposing direct lethal effects, pollutants may also indirectly impose mortality by making prey organisms more vulnerable to predation. We report that four water boatmen species differed strongly in direct endosulfan-imposed mortality, and only the species that suffered highest mortality, Sigara iactans, also showed a reduction in escape swimming speed. While head AChE activity was inhibited in all four species, body ChE was only inhibited in S. iactans where it covaried with escape swimming speed, indicating a mechanistic link between body ChE and swimming speed. Our study underscores the need for risk assessment to consider sublethal pollutant effects, which may considerably affect survival rates under natural conditions, also when testing concentrations of a pesticide that cause direct mortality. Such sublethal effects may generate discrepancies between laboratory and field studies and should be considered when designing safety factors for toxicants where the risk assessment is solely based on LC50 values.

Pre-requisite for reliable O₃ risk assessment for plants is determination of stomatal O₃ uptake. One unaddressed uncertainty in this context relates to transpiration-induced molecular collisions impeding stomatal O₃ influx. This study quantifies, through physical modelling, the error made when estimating stomatal O₃ flux without accounting for molecular collisions arising from transpiratory mass flow of gas out of the leaf. The analysis demonstrates that the error increases with increasing leaf-to-air water vapour mole fraction difference (Δw), being zero in water vapour saturated air and 4.2% overestimation at Δw of 0.05. Overestimation is approximately twice as large in empirical studies quantifying stomatal O₃ flux from measured leaf or canopy water flux, if neglecting both water vapour-dry air collisions (causing overestimation of leaf conductance) and collisions involving O₃. Correction for transpiration-induced molecular collisions is thus relevant for both empirical research and for large-scale modelling of stomatal O₃ flux across strong spatial Δw gradients.

Adsorption of mercury (Hg) on lignin was studied at a range of pH values using a combination of batch adsorption experiments, a surface complexation model (SCM) and synchrotron X-ray absorption spectroscopy (XAS). Surface complexation modeling indicates that three types of acid sites on lignin surfaces, namely aliphatic carboxylic-, aromatic carboxylic- and phenolic-type surface groups, contributed to Hg(II) adsorption. The bond distance and coordination number of Hg(II) adsorption samples at pH 3.0, 4.0 and 5.5 were obtained from extended X-ray absorption fine structure (EXAFS) spectroscopy analysis. The results of SCM and XAS combined reveal that the predominant adsorption species of Hg(II) on lignin changes from HgCl₂ ⁰ to monodentate complex –C–O–HgCl and then bidentate complex –C–O–Hg–O–C– with increasing pH value from 2.0 to 6.0. The good agreement between SCM and XAS results provides new insight into understanding the mechanisms of Hg(II) adsorption on lignin.

Polyethylene passive samplers (PE) were deployed in Narragansett Bay, RI, to examine freely dissolved concentrations of polybrominated diphenyl ethers (PBDEs) in surface, bottom, and sediment porewater. PBDE congeners in the water column and porewater were below 3 pg L⁻¹. In the surface water, only PBDE congeners containing up to 5 bromines were detected, while in the deeper water congeners 153 and 154 (6 bromines) were also detected. Activity ratios of surface-bottom water and porewater-bottom water suggested that lower brominated (di-tetra) congeners reached Narragansett Bay from surface waters and sediments. PBDEs in the surface water probably originated from a combination of air–water exchange, freshwater runoff, rivers, and wastewater treatment plants. It is suggested that deep water was the source of higher brominated PBDEs to the Bay implying that the more hydrophobic PBDEs reached depth on particles and/or that these congeners were degraded in sediments. On-going sources supply PBDEs to Narragansett Bay.