Applying process-based models to the Borssele scenario

The objective of this paper is to consider the implications of employing process-based models on predictions for radionuclide activity concentrations in grass and cow milk. The FDMT (Food Chain and Dose Module for Terrestrial Pathways as used in the JRODOS and ARGOS decision support systems) model has been transferred to a modelling platform enabling sub-models to be modified and replaced. Primarily, this has involved invoking process-based models for 137Cs and 90Sr that account for soil chemistry in simulating bioavailability and plant transfer. The implementation of such models can lead to quite dramatic differences in predicted activity concentrations of radionuclides in grass and milk compared to a default FDMT set-up for time periods later than a few weeks post deposition. Considering transfer within a spatial context, by combining information from the outputs of process-based models with illustrative soil maps, leads to the observation that the most elevated 137Cs and 90Sr concentrations in grass and milk might not necessarily occur in areas where deposition is highest. Not accounting for soil type when modelling food chain transfer might lead to the sub-optimal allocation of resources or misidentification of the most vulnerable areas in the long-term after an accidental release.

Nanomaterials in Plants: A Review of Hazard and Applications in the Agri-Food Sector

Agricultural food crop plants interact with engineered nanomaterials (ENMs) from the application of agri-food nanotechnologies and from unintentional emissions originating from other nanotechnologies. Both types of exposure present implications for agricultural yield and quality, food chain transfer, and environmental and human health. In this review, the most recent findings from agricultural plant-ENM studies published in 2017 and 2018 are summarized. The aim of this is to identify the current hazard potential of ENMs for plants grown under typical field conditions that originate from both intentional and unintentional exposures and to contribute to knowledge-based decisions on the application of ENMs in food-agriculture. We also address recent knowledge on ENM adsorption, internalization, translocation, and bioaccumulation by plants, ENM impacts on agricultural crop yield and nutrition, and ENM biotransformation. Using adverse effect level concentrations and data on ENM accumulation in environmental matrices, the literature analyses revealed that C-, Ag-, Ce-, and Ti-based ENMs are unlikely to pose a risk to plants grown under typical field conditions, whereas Cu- and Zn-based ENMs require surveillance. Since multiple factors (e.g., ENM concentration, route of exposure, and plant type) influence the effects of ENMs on plants, biomonitoring is recommended for tracking ENM environmental exposure in the future.

Soil quality and vegetation performance indicators for sustainable rehabilitation of bauxite residue disposal areas: a review

The generation of bauxite residue, the by-product of alumina manufacture from bauxite ore, has increased to a global stockpile of some 3 billion tonnes. In the absence of significant reuse options, the bulk of this residue is contained within bauxite residue disposal areas (BRDAs), which can occupy a significant footprint and pose potential environmental risk. Rehabilitation (amendment and vegetation establishment) is viewed as a significant strategy for eventual closure of the BRDAs. Major limitations to plant growth in residue include high pH, salinity, and sodicity, as well as deficiencies of macro- and micronutrients and potentially elevated levels of trace elements. The physical properties are also problematic as residue mud consolidates to form a solid mass that waterlogs easily or dries to form a massive structure, whereas sand has a very low water- and nutrient-holding capacity. A variety of techniques have been trialled at the pot level and at the field scale to bring about reductions in residue alkalinity and sodicity to promote plant establishment, with gypsum amendment viewed as the most promising. Other amendment strategies include use of organic additions or fertiliser applications, and a combined approach can lead to improved residue properties and successful plant establishment. Few reports have focused on longer term plant growth, self-propagation, and residue interactions under field conditions. There is some evidence that rehabilitated residue can support vegetation growth and soil development in the short to medium term (~15 years), but key issues such as nutrient availability and plant uptake require further study. Although rehabilitated residue can support diverse microbial communities and demonstrate trajectory analogous to soil, the ability of rehabilitated residue to support soil biota and key ecosystem processes warrants further study. The bioavailability of trace elements within rehabilitated sites and potential food chain transfer are relatively unexplored. These areas need careful study before definitive statements can be made regarding the sustainability of residue rehabilitation strategies.

Food chain transfer and exposure effects of selenium in salmonid fish communities in two watersheds in the Canadian Rocky Mountains

Selenium (Se) concentrations and fish biomass were examined in streams in two mined watersheds to determine if juvenile salmonids reflect local Se exposure concentrations downstream of surface coal mines and to investigate the relationship between Se exposure and toxicity effects at the fish community level. Se concentrations were measured in water, biofilm, macroinvertebrates, and muscle tissues from juvenile westslope cutthroat trout (Oncorhynchus clarkii lewisi), bull trout (Salvelinus confluentus), rainbow trout (Oncorhynchus mykiss), and brook trout (Salvelinus fontinalis) in mine-affected and reference streams. Significant positive Se transfer relationships were found at each measured level of the lotic food chain. Se accumulation from macroinvertebrates to juvenile fish muscle tissue was not significantly different among fish species, but indicated a significant positive relationship between juvenile fish muscle tissue and dietary Se at capture sites. Mean muscle Se concentrations in some stream reaches exceeded proposed individual-level toxic effective concentrations (EC10) in rainbow trout (3.14 ± 0.38 to 15.07 ± 2.24 mg·kg–1 dry mass) and westslope cutthroat trout (3.31 ± 0.32 to 13.79 ± 1.27 mg·kg–1 dry mass), but fish biomass at the reach scale was only significantly negatively related to mean fish muscle tissue Se concentrations for rainbow trout.