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Emerging organic contaminants (EOCs) undergoing incomplete removal during wastewater treatment may be found in treated wastewater (TWW) used for irrigation of agricultural products. Following uptake into edible plant parts, EOCs may eventually enter in the food chain, with associated human exposure. In the present study, we used a newly developed steady-state plant uptake model with added phloem transport to predict the uptake of four EOCs (carbamazepine, ibuprofen, ketoprofen and naproxen) into three varieties of lettuce. Input data were derived from an experimental study with vegetables grown in greenhouse and irrigated with TWW spiked with CBZ at 0, 30, 60, 120 and 210 µg/L in each variety of lettuce. Predicted carbamazepine concentrations in leaves were on average 82% higher than in roots, with good agreement between measured and calculated data. We subsequently predicted the uptake of anti-inflammatory compounds ibuprofen, ketoprofen and naproxen, for which the chemical analysis could not provide concentrations above detection limit. These three substances are weak acids and predicted concentrations in roots were higher than in the edible leaves, mainly due to phloem transport downwards. The daily dietary intake of all four EOCs was estimated for consumption of leafy vegetables, being far below usual therapeutic doses.

Environmental fate assessment of chemicals involves standardized simulation tests with isotope-labeled molecules to balance transformation, mineralization, and formation of non-extractable residues (NER). Methods to predict microbial turnover and biogenic NER have been developed, having limited use when metabolites accumulate, the chemicals are not the only C source, or provides for other macro-elements. To improve predictive capability, we extended a recently developed method for microbial growth yield estimation for incomplete degradation and multiple-element assimilation and combined it with a dynamic model for fate description in soils and sediments. We evaluated the results against the unique experimental data of 13C3-15N-co-labelled glyphosate turnover with AMPA formation in water-sediment systems (OECD 308). Balancing 13C- and 15N- fluxes to biomass, showed a pronounced shift of glyphosate transformation from full mineralization to AMPA formation. This may be explained by various hypotheses, e.g. the limited substrate turnover inherent to the batch conditions of the test system causing microbial starvation or inhibition by P release. Modeling results indicate initial N overload due to the lower C/N ratio in glyphosate compared to average cell composition leading to subsequent C demand and accumulation of AMPA.

This study focuses on the development of a new value chain in aquaculture, whereby nutrients from fish tank effluents are first encapsulated in algal biomass. Algal biomass will be fed to copepods, which are a good feed for fish larvae. The study offers a cost-effective algal biomass utilization compared to traditional approaches which require resource intensive processes for harvesting.

An integrated model was developed, calibrated and validated to predict the fate of micropollutants (MPs) and the human health risks that these substances pose when wastewater is reused for agricultural purposes. Results showed that pharmaceuticals (e.g., the anti-inflammatory drug paracetamol) can form during in-sewer transit from other metabolites and posing a potential risk (Hazard Quotient for infants = 10-2) if wastewater is not treated before irrigation. The model can represent a relevant decision-support tool to plan barriers for reducing the risk associated to MPs.

Foliar-applied systemic agrochemicals require entrance into the plant vascular system or into specific subcellular compartments to reach their target in planta or to be imbibed by piercing/sucking pests. An inappropriate subcellular localization, like accumulation of aphicides in vacuoles, might lower the compound's efficiency due to reduced exposure to the target. Permeabilities and mass distributions of 16 compounds covering a broad range of properties were measured across a pH gradient in a PAMPA ("parallel artificial membrane permeability assay") system, providing experimental evidence for ion trapping of acids and bases in basic and acidic compartments, respectively. The results validated a predictive model which was then expanded to simulate a standardized plant cell (cytosol and vacuole) with a vascular system (phloem and xylem). This approach underlined that the absolute mass distribution across aqueous phases is defined by membrane retention, whereas the relative mass distribution is determined by the species (neutral, acidic, basic) of compounds. These processes depend largely on pK(a) and log K-ow of the test compounds, which subsequently determine the partitioning of the substances in plant cell compartments. The validated model can be used as a tool in agrochemistry research to tailor the subcellular distribution by chemistry design and to interpret biology results.

Chlorinated phenols have been intensively investigated from an eco-toxicological point of view, however almost nothing is known about toxicity of tetrachlorophenol (TeCP) to higher terrestrial plants. This paper applied the willow tree acute toxicity test to study the toxicity of 2,3,5,6-TeCP to willows Salix viminalis (S. viminalis) at neutral and acidic conditions (roughly pH 7 and 4) with inhibition of transpiration as toxic endpoint. At neutral pH the EC50 was >10 mg L−1 while the EC50 at acidic conditions was 0.32 ± 0.17 mg L−1, clearly indicating that toxicity is exerted by the non-ionic chemical fraction. Standard tests running at neutral pH are therefore not capturing the full toxicity of weak acids and bases.

All chemicals form non-extractable residues (NER) to various extents in environmental media like soil, sediment, plants and animals. NER can be quantified in environmental fate studies using isotope-labeled (such as 14C or 13C) tracer compounds. Previous NER definitions have led to a mismatch of legislation and state of knowledge in research: the residues are assumed to be either irreversibly bound degradation products or at least parts of these residues can be released. In the latter assumption, soils and sediments are a long-term source of slowly released residues. We here present a conceptual experimental and modeling approach to characterize non-extractable residues and provide guidance how they should be considered in the persistence assessment of chemicals and pesticides. Three types of NER can be experimentally discriminated: sequestered and entrapped residues (type I), containing either the parent substance or xenobiotic transformation products or both and having the potential to be released, which has indeed been observed. Type II NER are residues that are covalently bound to organic matter in soils or sediments or to biological tissue in organisms and that are considered being strongly bound with very low remobilization rates like that of humic matter degradation rates. Type III NER comprises biogenic NER (bioNER) after degradation of the xenobiotic chemical and anabolic formation of natural biomolecules like amino acids and phospholipids, and other biomass compounds. We developed the microbial turnover to biomass (MTB) model to predict the formation of bioNER based on the structural properties of chemicals. Further, we proposed an extraction sequence to obtain a matrix containing only NER. Finally, we summarized experimental methods to distinguish the three NER types. Type I NER and type II NER should be considered as potentially remobilizable residues in persistence assessment but the probability of type II release is much lower

Standardized simulation tests using isotope-labelled chemicals are carried out for persistency assessment. In these tests, formation of non-extractable residues (NER) is typically observed. Recent theoretical, experimental and analytical advances have helped deciphering the nature and composition of NER [1]. Among other types, biogenic NER is formed as the microorganisms use the test chemical as a source of carbon and energy, and methods for their prediction based on microbial yield estimations have been accordingly developed [2]. Evaluating and predicting biogenic NER formation still remains a challenge for test chemicals that (i) are utilized as a source of macronutrients (besides carbon); (ii) undergo incomplete degradation via multiple pathways, with formation of dead-end transformation products. In the present study, we addressed this challenge by (i) extending a recently developed microbial yield estimation method (MTB—Microbial Turnover to Biomass) by accounting for macronutrient limitation and incomplete degradation; and (ii) incorporating this method in a dynamic model to describe the fate of glyphosate and its main transformation product (AMPA) in a water-sediment simulation test. Glyphosate is known to be biodegraded via, at least, two pathways, one forming the recalcitrant metabolite AMPA [3]. For the assessment of model simulations, we used published data from turnover experiments using co-labelled 13C315N-glyphosate [4]. Determination of microbial yield for different degradation pathways required consideration of the flow of elements, energy and electrons. By adapting three parameters, namely the number of electrons and the number of C or N atoms that can be acquired in a transformation step, the MTB method could be used to predict the growth yield when either N or C are limiting growth. The results showed that the formation of AMPA reduces the growth yield (taken as g bacteria per mol of glyphosate metabolized) by more than threefold, and that glyphos

Degradation tests with radio or stable isotope labeled compounds enable the detection of the formation of non-extractable residues (NER). In PBT and vPvB assessment, remobilisable NER are considered as a potential risk while biogenic NER from incorporation of labeled carbon into microbial biomass are treated as degradation products. Relationships between yield, released CO2 (as indicator of microbial activity and mineralization) and microbial growth can be used to estimate the formation of biogenic NER. We provide a new approach for calculation of potential substrate transformation to microbial biomass (theoretical yield) based on Gibbs free energy and microbially available electrons. We compare estimated theoretical yields of biotechnological substrates and of chemicals of environmental concern with experimentally determined yields for validation of the presented approach. A five-compartment dynamic model is applied to simulate experiments of 13C-labeled 2,4-D and ibuprofen turnover. The results show that bioNER increase with time, and that most bioNER originate from microbial proteins. Simulations with pre-calculated input data demonstrate that pre-calculation of yields reduces the number of fit parameters considerably, increases confidence in fitted kinetic data and reduces the uncertainty of the simulation results.