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Hydrophilic divinylbenzene (DVB) (Bakerbond™) has surfaced as a promising sorbent for active sampling of analytes from aqueous matrices over a very broad polarity range. Given this, hydrophilic DVB may likewise offer potential for passive sampling, if sorbent-water partitioning coefficients (Ksw) were to be available. In this work, static exposure batch experiments were performed to quantitatively study the equilibrium sorption of 131 environmentally relevant organic contaminants (P values ranging from-1.30 to 9.85) on hydrophilic DVB. The superior affinity of hydrophilic DVB, as compared to Oasis HLB, for compounds with a broad polarity range was confirmed by functional FTIR and Raman characterization, demonstrating the presence of carboxyl moieties. Concentration effects were studied by increasing compound concentrations in mixture experiments, and resulted for the steroidal EDCs in higher Ksw, while lower Ksw were obtained for the (alkyl)phenols, personal care products, pesticides, pharmaceuticals and phthalates. Nevertheless, Ksw remained constant in said design for equilibrium water concentrations at environmentally relevant seawater levels. Independent analysis of thermodynamic parameters (change in enthalpy, entropy and Gibbs free energy) revealed the nature of the main partitioning processes. While polar (log P < 4) compounds were mainly served by physisorption, non-polar (log P > 4) compounds also exhibited binding by multiple hydrogen bonding. In conclusion, this research facilitates the future application of hydrophilic DVB for active as well as passive sampling in the analysis of organic contaminants for monitoring purposes but also for toxicity testing.

Neonicotinoid insecticides have become of global concern for the aquatic environment. Harpacticoid copepods are amongst the most sensitive organisms to neonicotinoids. Here, we exposed the brackish copepod Nitocra spinipes to four neonicotinoid insecticides, i.e. clothianidin (CLO), imidacloprid (IMI), thiacloprid (TCP) and thiamethoxam (TMX) to investigate acute toxicity on adults (96-h exposure) and effects on larval development (7-d exposure). We used these results in combination with publicly available ecotoxicity data to derive Environmental Quality Standards (EQS). These EQS were ultimately used in a single-substance and mixture risk assessment for the Belgian part of the North Sea. Acute toxicity testing revealed that immobilization is a more sensitive endpoint than mortality, with 96h-EC 50 values of 6.9, 7.2, 25 and 120 µg L-1 for CLO, TCP, IMI and TMX, respectively. In addition, the larval development tests resulted in 7d-NOECs of 2.5, 2.7, 4.2 and >99 µg L-1 for CLO, TCP, IMI and TMX, This article is protected by copyright. All rights reserved. Accepted Article respectively. The derived saltwater Annual Average (AA-)EQS were 0.05, 0.0048, 0.002 and 0.016 µg L-1 for CLO, TCP, IMI and TMX, respectively. Finally, the risk characterization revealed some exceedances of the AA-EQS in Belgian harbors for IMI (number of exceedances, n = 2/4), TCP (n = 1/4), TMX (n = 1/4) and the mixture of the four neonicotinoids (n = 4/4), but not at the open sea. At the open sea site, the toxic unit sum relative to the AA-EQS was 0.72 and 0.22, suggesting no mixture risk, albeit with a relatively small margin of safety. Including short-term EC 10 (96h) values of N. spinipes for the AA-EQS derivation led to a refinement of the AA-EQS for CLO and TMX, suggesting their use for the AA-EQS derivation since one of the overarching goals of the definition of EQS is to protect species at the population level.