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Behavior and distribution of emerging pollutants in aquatic systems

Periodic Report Summary 2 - BADEPAS (Behavior and distribution of emerging pollutants in aquatic systems)

The main objective of this project is to identify the presence, to characterise the behaviour and distribution and to describe the biogeochemical fate of Alcohol ethoxylates (AEOs), the class of non-ionic surfactants produced in highest volumes in the EU and US, and of a selection of wide used PhACs (Pharmaceutically active compounds) in different aquatic systems from the East Coast of US, and in sewage contaminated aquifers. The results and interpretations from the studies in US environments will be contrasted to findings from new or recent studies conducted in contaminated coastal waters, sediments and groundwaters located in the SW of Spain (Bay of Cadiz). The data obtained during this project will be useful for future risk assessments and provide more confident predictions that can be extrapolated to other coastal systems.

The following specific objectives are proposed for this period:
a) To optimise the extraction and purification techniques for PhACs in both aqueous and solids samples in order to perform a later identification and quantification by Liquid chromatography - mass spectrometry (LC-MS).
b) To characterise the environmental distribution of target compounds in surface waters and in sediment cores in the NY/NJ and Cadiz areas and to detect their presence and tendency to be transported in groundwater where other wastewater contaminants are under present or future study. It is especially interesting to obtain a historical record of PhACs by means of dated cores to evaluate the historical contamination of sampling sites by this kind of chemicals.
c) To study transport, sorption and biodegradation processes for AEOs and some of the most representative PhACs in sediments and aquifer systems acclimated to sewage inputs under controlled conditions by means of laboratory assays.

The outgoing phase of this project took place at Dr Bruce J. Brownawell's group from Stony Brook University (NY). Achievements during that period were mainly related to analysing and studying the distribution and environmental behaviour of the surfactant AEOs and its main degradation metabolites (polyethyleneglycols, PEGs). The study of AEOs has been completed now and the one on PhACs has been carried out at University of Cadiz, the host institution during the returning phase. More specifically, research was conducted at Dr Eduardo González Mazo's group (Faculty of Marine and Environmental Sciences).

The first goal, optimising the extraction and purification techniques for PhACs in both aqueous and solids samples in order to perform a later identification and quantification by LC-MS, has been successfully carried out. The analytical protocol consists in using PLE (Pressurised liquid extraction) for sediment samples followed by Solid phase extraction (SPE) using Oasis HLB cartridges. Recoveries are usually above 70 % for most pharmaceutical compounds, and the protocol was similar to that previously optimised for the analysis of AEOs and other synthetic surfactants, allowing for a comparison between these two different classes of compounds in environmental samples for the first time.

70 PhACs were selected for this study, including analgesics and antiimflammatories (ibuprofen, diclofenac, acetaminophen, ...) antihypertensives (atenolol, enalapril, ...) lipid regulators (clofibric acid, mevastatin, ...) histamine receptor antagonists (loratadine and others), psychiatric drugs (carbamazepine, fluoxetine, ...) and antibiotics (sulfamethazine, trimethoprim, ...). Limits of detection were usually between 10 and 100 ppt for most of them.

Work on the second goal of this project for the returning phase, to characterise the environmental distribution of PhACs in surface waters and in sediment cores in the NY/NJ area is complete. Concentrations of PhACs in water are strongly influenced by tides. They can vary by a factor of three from low tide to high tide. Concentrations rise during the flooding, as sewage contaminated water comes from NY City, whereas they fall during the ebbing, as clean water comes from the ocean. Maximum values are reached during the high tides, whereas lower values are detected during the low tides in spite of the water volume being lower too. The same trend is also found for AEOs and PEGs.

The distribution of PhACs along the water column seems to be uniform, as concentrations are very similar for both surface and bottom (average depth = 13 meters) samples. 31 of the 70 pharmaceuticals analysed were detected in water samples, being analgesics the most prominent group, with some compounds such naproxen and ibuprofen showing average concentrations of 50 and 37.5 ppt, respectively, in seawater.

Most representative compounds from other groups are: metoprolol (antihypertensives), gemfibrozil (lipid regulators), carbamazepine (psychiatric drugs), azithromycin (antibiotics) and hydrochlorothiazide. Their prominence related to other PhACs can be explained as a combination of higher sales and widespread use (e.g. ibuprofen) and/or persistence in the environment (e.g. carbamazepine).

Most PhACs are hardly detected in sediments or suspended solids, mostly due to their low sorption capacity and high solubility. Anyway, some PhACs can be detected at much lower concentrations in sediments (< 20 ppb) compared to other organic contaminants (e.g. AEOs and PEGs), but they seem to be persistent once they reach anoxic depths in the sedimentary column.

The last goal, to study transport, sorption and biodegradation processes for AEOs and PhACs in sediments and aquifers is almost completed. During the last year we have performed anaerobic degradation experiments with AEOs and PEGs. We could observe that degradation of AEOs is relatively fast as more than 95% of the initial amount is removed by the end of the experiment (166 days). There are, however, significant differences between homologues. Those having shorter alkyl chains (C12 and C14 AEO) disappear faster than longer alkyl chain homologues (C16 and C18 AEO), which can be explained due to the higher solubility and, therefore, higher bioavailability of shorter homologues. In the case of PEGs, however, degradation is slower, reaching 85 % after 166 days. This could explain, together with higher sale volumes, why concentrations of PEGs in sediments are generally much higher than those for AEOs. This surfactant was also detected in soils (> 1 ppm), whereas concentrations of PhACs were really low (< 1 ppb).

Percolation experiments using two-dimensional flow cells showed that AEOs are retained in the soil but they migrate slowly to the bottom of the cell. Moreover, although they undergo partial degradation, AEOs and PhACs could be detected in soils deeper than 1.75 meters, reaching the vadose zone, so they can be considered as potential groundwater contaminants.

Results from this project allow for a much better knowledge on the behaviour of AEOs and PhACs, emerging contaminants in aquatic systems. This will be useful not only for developing more effective environmental policies but also for helping the manufacturers to minimise the environmental impact of their products and, ultimately, it will help to increase the life quality of humans and communities living in systems affected by the presence and continuous input of these chemicals.