Bioaccumulation of trace metals in aquatic food web. A case study, Liaodong Bay, NE China

The recently developed modelling tool MERLIN-Expo was applied to support the exposure assessment of an aquatic food web to trace metals in a coastal environment. The exposure scenario, built on the data from Daliao River estuary in the Liaodong Bay (Bohai Sea, China), affected by long-term and large-scale industrial activities as well as rapid urbanization in Liao River watershed, represents an interesting case-study for ecological exposure modelling due to the availability of local data on metal concentrations in water and sediment. The bioaccumulation of selected trace metals in aquatic organisms was modelled and compared with field data from local aquatic organisms. Both model results and experimental data demonstrated that As, Cd, Cu, Ni, Pb and Zn, out of examined metals, were accumulated most abundantly by invertebrates and less by higher trophic level species. The body parts of the sampled animals with the highest measured concentration of metals were predominantly muscles, intestine and liver and fish skin in the case of Cr.The Morris and extended Fourier Analysis (EFAST) were used to account for variability in selected parameters of the bioaccumulation model. Food assimilation efficiency and slopes and intercepts of two sub-models for calculating metal specific BCFs (BCFmetarexposure concentration) and fish weight (Weightiuh-Lengthfish) were identified as the most influential parameters on ecological exposure to selected metals

A site-specific indicator of nitrogen loads into surface waters from conventional and conservation agriculture practices: Bayesian network model

Agriculture is one of the main sources of diffuse pollution, such as fertilisers, plant protection products, solid particles or pathogens. The short- and long-term impact of agriculture on surface water quality is often driven by on-farm decisions as to what practices are used to manage weeds. Farming practices can affect numerous processes such as surface runoff and soil erosion which mediate release and transport of potential pollutants to edge-of-field water courses. Excessive nitrogen emissions are an ongoing problem of many farmlands, leading to pollution of surface water bodies and causing adverse outcomes such as eutrophication, resulting in deteriorating water quality. We developed a Bayesian Network (BN) model to predict nitrogen load into surface waters at the farm level using site specific characteristics such as landscape, soil, cropping system and, also, to compare different conventional and conservation agriculture practices. The BN was built from well-established and accepted models i.e., surface runoff by water is based on the Curve Number method (CN), the soil erosion rate is calculated with the Universal Soil Loss Equation (USLE), and nitrogen load is calculated based on a multilevel model, where the CN and the USLE outputs are used as inputs. All three sub-models produced satisfactory spread around 1:1 line. A classification technique was applied to evaluate predicted nitrogen loads against the reference data from the US EPA STEPL model with respect to nitrogen load threshold values. Out of all the data simulated with the BN 83 % agree with the reference model for the 20 kg/(ha × yr) nitrogen load threshold, and 97 % agree when the threshold is set to the middle of the prediction range, 100 kg/(ha × yr). The modelling exercise was performed on two pedo-climatic scenarios differing in their potential to generate surface runoff water and by considering the effect of combining three farming practices and two generic groups of crops on emitted nitrogen loads expressed as the Grey Water Footprint (GWF). Sensitivity analysis shows high importance of weather inputs for surface runoff, and topographic information for soil erosion, whereas agricultural treatments were ranked as less important. Under variable precipitation no-till practice would result in reducing emissions of water, soil and nitrogen compared to conventional farming. The results indicate that no-till practice would reduce nitrogen loads on sites with varying risk of runoff, and that a combination of no-till and small grain crops provides the best benefit in reducing nitrogen emissions. We demonstrate that a Baye’s net is a useful, flexible tool for data and knowledge assimilation and a practical approach to test and compare effects of various agricultural interventions on pollutant emissions from a farming system

Integration of environmental and human PBPK exposure models: application of MERLIN-Expo modelling tool to POPs exposure in Venice lagoon

MERLIN-Expo is a new tool for integrated exposure assessment recently developed under the FP7 project “4FUN”. MERLIN-Expo is a simulation platform providing a library of multimedia and physiologically-based pharmacokinetic (PBPK) models which can be coupled in order to estimate ecological and human exposures in complex scenarios. Models can be used to simulate fate of organic (PAHs, PCBs) and inorganic contaminants. Software enables end-user to apply set of functionalities such as uncertainty and sensitivity analysis, dynamic deterministic and probabilistic simulations in order to address different exposure and chemical fate problems. MERLIN-Expo was applied to assess the ecological and human exposure to PCBs and PCDDs in the Venice lagoon. The Phytoplankton, Aquatic Invertebrate and Fish models were developed and implemented in MERLIN-Expo library, subsequently integrated to create specific aquatic food web to dynamically simulate bioaccumulation in different aquatic species. Concentrations of PCBs and PCDDs in water were used as time-dependent inputs to run long term simulations. The estimated concentrations in edible aquatic species were then used to estimate daily human intake through the consumption of local seafood. The application of the PBPK model allowed to explore the time dependent accumulation of target chemicals in human tissues for several decades. Modelling results are tested against available monitoring data on chemical concentrations in edible aquatic species and concentrations in serum of adult men in Venice area to assess the reliability and applicability of the proposed tool to real complex scenarios. Full chain exposure assessment is then complemented by uncertainty and sensitivity analysis including local sensitivity methods, screening methods (e.g. Morris method), global regression methods (e.g. Standardised Regression Coefficients), and global variance based methods (e.g. FAST, EFAST, Sobol). These methods allow to follow for instance WHO (2008) recommendations to perform three stage uncertainty/sensitivity analysis, adopting qualitative, semi-qualitative, and quantitative methods. Integration of environmental and human exposure models in MERLIN-Expo allows comprehensive assessment of exposure and thus better characterisation of overall risk to human and environment especially in the case of higher tier assessment. This makes the tool interesting and promising for potential applications in different regulatory domains

Modelling ecological and human exposure to POPs in Venice lagoon - Part II: Quantitative uncertainty and sensitivity analysis in coupled exposure models

The study is focused on applying uncertainty and sensitivity analysis to support the application and evaluation of large exposure models where a significant number of parameters and complex exposure scenarios might be involved. The recently developedMERLIN-Expo exposure modelling tool was applied to probabilistically assess the ecological and human exposure to PCB 126 and 2,3,7,8-TCDD in the Venice lagoon (Italy). The 'Phytoplankton', 'Aquatic Invertebrate', 'Fish', 'Human intake' and PBPK models available in MERLIN-Expo library were integrated to create a specific food web to dynamically simulate bioaccumulation in various aquatic species and in the human body over individual lifetimes from 1932 until 1998. MERLIN-Expo is a high tier exposure modelling tool allowing propagation of uncertainty on the model predictions through Monte Carlo simulation. Uncertainty in model output can be further apportioned between parameters by applying built-in sensitivity analysis tools. In this study, uncertainty has been extensively addressed in the distribution functions to describe the data input and the effect on model results by applying sensitivity analysis techniques (screening Morris method, regression analysis, and variance-based method EFAST). In the exposure scenario developed for the Lagoon of Venice, the concentrations of 2,3,7,8-TCDD and PCB 126 in human blood turned out to be mainly influenced by a combination of parameters (half-lives of the chemicals, body weight variability, lipid fraction, food assimilation efficiency), physiological processes (uptake/elimination rates), environmental exposure concentrations (sediment, water, food) and eating behaviours (amount of food eaten). In conclusion, this case study demonstrated feasibility of MERLIN-Expo to be successfully employed in integrated, high tier exposure assessment. (C) 2016 Elsevier B.V. All rights reserved

Modelling ecological and human exposure to POPs in Venice lagoon. Part I - Application of MERLIN-Expo tool for integrated exposure assessment

Industrial and urban emissions over several decades left a legacy of contamination by persistent organic pollutants in the sediments of Venice lagoon (Italy), which might still represent a hazard for the health of ecosystems and population. A new modelling tool for integrated exposure assessment, MERLIN-Expo, was applied to simulate integrated ecological and human exposure to PCBs and dioxins. MERLIN-Expo library provides a set of environmental fate models that can be easily combined to create several scenarios, and coupled to a human intake and a physiologically-based pharmaco-kinetic (PBPK) model to simulate human internal exposure. The Phytoplankton, Invertebrate and Fish models implemented in MERLIN-Expo library were combined to create an aquatic food web and to dynamically simulate bioaccumulation and biomagnification of dioxins and PCBs. Concentrations of PCB and dioxins in water, reconstructed from concentrations in dated sediment cores, were used as time-series inputs to run long term simulations. Estimated concentrations in edible aquatic species were used to estimate daily human intake through the consumption of local seafood. Finally, the application of the PBPK model allowed to explore the accumulation of 2,3,7,8-TCDD and PCB126 in human tissues for several decades. Simulated chemical concentrations in biota were evaluated against monitoring data for four aquatic species, finding an appreciable agreement, with some differences depending on the species and target chemicals. Estimated chemical concentrations in blood were compared to real human biomonitoring data measured in adult men. Despite several assumptions included in the assessment framework, simulated concentrations resulted close to measured data (the same order of magnitude or one order of difference). The results allowed performing a preliminary ecological and human health risk assessment for the selected chemicals by evaluating the exposure estimates against benchmark values available in literature. The study provided useful insights for supporting the verification of MERLIN-Expo in a real complex exposure scenario. (C) 2016 Elsevier B.V. All rights reserved