Influence of the large grid size used in a multimedia mass balance model (POPsME) on the exposure assessment of polychlorinated dibenzo-p-dioxins and dibenzofurans

Spatially resolved environmental fate models: A review

Spatially resolved environmental models are important tools to introduce and highlight the spatial variability of the real world into modeling. Although various spatial models have been developed so far, yet the development and evaluation of these models remain a challenging task due to several difficulties related to model setup, computational cost, and obtaining high-resolution input data (e.g., monitoring and emission data). For example, atmospheric transport models can be used when high resolution predicted concentrations in atmospheric compartments are required, while spatial multimedia fate models may be preferred for regulatory risk assessment, life cycle impact assessment of chemicals, or when the partitioning of chemical substances in a multimedia environment is considered. The goal of this paper is to review and compare different spatially resolved environmental models, according to their spatial, temporal and chemical domains, with a closer insight into spatial multimedia fate models, to achieve a better understanding of their strengths and limitations. This review also points out several requirements for further improvement of existing models as well as for their integration.

New Data Set of Polychlorinated Dibenzo-p-dioxin and Dibenzofuran Half-Lives: Natural Attenuation and Rhizoremediation Using Several Common Plant Species in a Weathered Contaminated Soil

In this paper, a new data set of polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/Fs) half-lives (HLs) in soil is presented. Data are derived from a greenhouse experiment performed with an aged contaminated soil under semi-field conditions, obtained from a National Relevance Site (SIN) located in Northern Italy (SIN Brescia-Caffaro). Ten different treatments (combination of seven plant species with different soil conditions) were considered together with the respective controls (soil without plants). The ability of the plants to stimulate the biodegradation of these compounds was evaluated by measuring the PCDD/F concentration reduction in soil over a period of 18 months. The formation of new bound residues was excluded by using roots as a passive sampler of bioaccessible concentrations. The best treatment which significantly reduced PCDD/F concentrations in soil was the one with Festuca arundinacea (about 11-24% reduction, depending on the congener). These decreases reflected in HLs ranging from 2.5 to 5.8 years. Simulations performed with a dynamic air-vegetation-soil model (SoilPlusVeg) confirmed that these HLs were substantially due to biodegradation rather than other loss processes. Because no coherent PCDD/F degradation HL data sets are currently available for soil, they could substantially improve the predictions of soil remediation time, long-range transport, and food chain transfer of these chemicals using multimedia fate models.

A review of multimedia transport and fate models for chemicals: Principles, features and applicability

The frequent use of chemicals has caused ecosystems and humans to be threatened due to their discharge into the environment. Multimedia environmental fate models could provide a comprehensive picture of transport behaviour and fate for organic chemicals in multiple environmental media. They have been designed and widely used for chemical risk assessment, chemical ranking and management support, and determination of chemical bioaccumulation. This study reviewed the principles, features and applicability of recent commonly used multimedia fate models from peer-reviewed literature. Fugacity-based and concentration-based models are now widely adopted for use in chemical fate evaluation, while they are more appropriate for volatile and semi-volatile chemicals. Or the fugacity-based models can use aquivalence equilibrium criterion to cations, anions and involatile chemicals. The MAMI and SESAMe models based on activity approach are applicable to neutral and ionizable molecules. However, interactions of ionic species with other water solutes are not taken into account in these models. Additionally, they could not directionally simulate how chemicals transported form one grid to another. Future attention should be focused on the reliability of transfer behaviour and fate of ionizable chemicals, as integrating the advantages of these two kinds of models into a reconstructed one may be a better choice. In a word, environmental multimedia models have been beneficial tools for chemical control and management, risk and effect estimation, and decision supporting.

Multimedia modeling of the PAH concentration and distribution in the Yangtze River Delta and human health risk assessment

Emissions of polycyclic aromatic hydrocarbons (PAHs) in China remain at a high level compared to those in developed countries. The Yangtze River Delta (YRD) is an economic and industrial center in China with an extremely large population. The potentially high emissions and excess cancer risk from human exposure in this region cannot be neglected. This study applied a multimedia model to estimate the concentrations of 16 US EPA priority PAHs in the environment in the YRD with a well-developed PAH-emission inventory for 2014. The model predicted that the average concentrations of ΣPAHs were 274 ng/m³ in the air, 255 ng/g in the soil, 15 ng/g in vegetation, 147 ng/L in freshwater and 144 ng/g in sediment, as well as 99 ng/L and 80 ng/g in seawater and sediment, respectively. Soil is the PAH sink in this region, and the net flux of the total PAHs is always from air to soil for each isomer. A deterministic assessment observed that the ELCR (excess lifetime cancer risk) ranged from 2.5 × 10^-6 to 3.0 × 10^-5 for exposure by air inhalation and from 3.5 × 10^-7 to 7.9 × 10^-6 for exposure by soil ingestion. The probabilistic results did not find any probability of ELCR >10^-4 by exposure via soil ingestion in the YRD. The probabilistic ELCR induced by inhalation exposure varied from 8.1 × 10^-7 to 3.1 × 10^-4 in the YRD. This study provided a comprehensive overview of PAHs occurrence in natural environments and of the relevant human health risks. The information presented in this study could help authorities to enact a strategy regarding emission reduction and pollution control relevant to PAHs.

CAPSULE

Multimedia modeling predicted distributions and compositions of PAHs in different environmental compartments, and deterministic and probabilistic ELCRs induced by air inhalation and soil ingestion were also provided.