Over 2000 surface, ground and raw drinking water samples have been analyzed in the frame of different monitoring projects in Hungary and watercourses in neighboring countries between 1990 and 2015. Effects of pesticide contamination on ecological farming and drinking water supply have been assessed. Main water pollutant ingredients of agricultural origin in Hungary are herbicides related to maize production. After EU pesticide re-registration, diazinon, atrazine, and trifluralin gradually disappeared as contaminants. High levels of water soluble pollutants (e.g., acetochlor) in surface water result in temporarily enhanced levels in raw drinking water as well. Extreme levels observed for herbicide residues were of agrochemical industrial origin.

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Movement of two neonicotinoid insecticide active ingredients, clothianidin (CLO) and thiamethoxam (TMX), was investigated in different soil types (sand, clay, or loam) and in pumice. Elution profiles were determined to explore differences in binding capacity. Soil characterized by high organic matter content retained the ingredients, whereas high clay content resulted in long release of compounds. Decrease in concentration was strongly influenced by soil types: both CLO and TMX were retained in loam and clay soils and showed ready elution through sandy soil and pumice. Elution capability of the active ingredients in sandy soil correlated with their water solubility, indicating approximately 30% higher rapidity for TMX than for CLO. Soil organic carbon-water partitioning coefficients (Koc) determined were in good agreement with literature values with somewhat lower value for CLO in sandy soil and substantially higher values for TMX in clay soil. High mobility of these neonicotinoid active ingredients in given soil types urges stronger precautionary approach taken during their application.

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Neonicotinoids are highly potent and selective systemic insecticides, but their widespread use also has a growing impact on non-target animals and contaminates the environment, including surface waters. We tested the neonicotinoid insecticides commercially available in Hungary (acetamiprid, Mospilan; imidacloprid, Kohinor; thiamethoxam, Actara; clothianidin, Apacs; thiacloprid, Calypso) on cholinergic synapses that exist between the VD4 and RPeD1 neurons in the central nervous system of the pond snail Lymnaea stagnalis. In the concentration range used (0.01-1 mg/ml), neither chemical acted as an acetylcholine (ACh) agonist; instead, both displayed antagonist activity, inhibiting the cholinergic excitatory components of the VD4-RPeD1 connection. Thiacloprid (0.01 mg/ml) blocked almost 90 % of excitatory postsynaptic potentials (EPSPs), while the less effective thiamethoxam (0.1mg/ml) reduced the synaptic responses by about 15 %. The ACh-evoked membrane responses of the RPeD1 neuron were similarly inhibited by the neonicotinoids, confirming that the same ACh receptor (AChR) target was involved. We conclude that neonicotinoids act on nicotinergic acetylcholine receptors (nAChRs) in the snail CNS. This has been established previously in the insect CNS; however, our data indicate differences in the background mechanism or the nAChR binding site in the snail. Here we provide the first results concerning neonicotinoid-related toxic effects on the neuronal connections in the molluscan nervous system. Aquatic animals, including molluscs, are at direct risk while facing contaminated surface waters, and snails may provide a suitable model for further studies of the behavioural/neuronal consequences of intoxication by neonicotinoids.Tihany, Hungary, July 22, 2015 Dr. Mikko Nikinmaa Editorial Office Aquatic ToxicologyDear Dr Nikinmaa, Thank you very much for your response to our manuscript submission. We gratefully thank you and our reviewers for reading the manuscript, and we appreciate all the helpful comments made.After carefully checking the Reviewers' comments we improved the manuscript on the basis of their suggestions. Please find our detailed answers to the Reviewers below. Reviewer #1:We greatly appreciate the Reviewer's comment "one of the best written manuscripts that I have reviewed" Minor points Materials and Methods How was Lymnaea saline obtained? Is this the modified HiDi saline? If not, what is HiDi?For isolating the monosynaptic components of the synaptic responses between two neurons the perfusion chamber was filled with a modified saline which reduces the polysynaptically evoked postsynaptic responses and enhances the monosynaptic component (Berry and Pentreath, 1976). This modified saline contains higher amount of divalent cations (Ca 2+ and Mg 2+ ), therefore often nicknamed as HiDi saline (Brierly et al., 1997, Sivaramakrishnan et al., 2013. We added details to the text accordingly Electrophysiological recordingThere is a Winlow 1991 anda Syed et al. 1990 (PNEC, EC50, mechanistic...) We...