Objectifs et principaux résultats

L’article est centré sur le diagnostic de la contamination des eaux de surface du bassin versant de la rivière Kadicha par les produits pharmaceutiques et l’évaluation du risque environnemental potentiel associé à leur présence. Les arguments qui ont justifié la recherche de ce groupe de contaminants au niveau des eaux de la rivière Kadicha sont :

· L’absence de gestion des médicaments périmés au Liban et leur décharge principalement via les flux de déchets solides domestiques (Massoud et al., 2016),

· La croissance démographique au Nord du Liban suite à l’arrivée des réfugiés syriens (AEMS, 2017) qui peut conduire à une augmentation des usages de médicaments,

· Les décharges des eaux usées municipales (source potentielle de résidus pharmaceutiques) directement dans le cours d’eau de la rivière sans traitement préalable.

Afin d’étudier la présence de résidus de médicaments dans les eaux de la rivière Kadicha, 15 produits pharmaceutiques et 9 de leurs métabolites appartenant aux classes thérapeutiques les plus utilisées dans le monde (antiépileptiques, analgésiques, antibiotiques, benzodiazépines, antidépresseurs, hypolipidémiants, bêta-bloquants et substituts d'opiacés) ont été recherché dans les eaux de surface. Deux campagnes d’échantillonnage ont été effectuées couvrant 12 sites au niveau du bassin versant de la rivière Kadicha, répartis sur des zones impactées par des activités rurales, urbaines et des zones mixtes (résidentielle et agricole).

Six médicaments, un anti-épileptique (carbamazépine), deux analgésiques (acétaminophène et diclofenac), deux antibiotiques (sulfaméthoxazole et ofloxacine) et un bêta-bloquant (atenolol) ont été détectés. La carbamazépine est détectée avec la fréquence la plus élevée. La présence de la carbamazépine, l’ofloxacine et l’atenolol est attribuée aux rejets des eaux usées brutes dans le cours d’eau alors que la présence de la sulfaméthoxazole est associée avec son usage comme médicament vétérinaire au niveau des sites spécifiques. Les niveaux de contamination par les produits pharmaceutiques ont montré une variation spatiale : les concentrations les plus élevées sont observées au niveau de l’aval urbain alors que les niveaux les plus faibles sont mesurées dans l’amont rural. Le risque environnemental potentiel associé à la présence de ces contaminants apparaît plus élevé au

187 niveau de l’aval urbain. Parmi les médicaments quantifiés dans les eaux, un risque potentiel élevé pour les espèces aquatiques a été identifié pour l’ofloxacine.

Les concentrations de résidus pharmaceutiques de la présente étude sont du même ordre de grandeur que celles retrouvées dans d’autres sites dans des systèmes riverains dans le monde. Les niveaux de contamination par la carbamazépine, le diclofenac et l’acétaminophène sont du même ordre que celles retrouvées dans des études sur des rivières recevant directement des eaux usées brutes (Osorio et al., 2012, Nakada et al., 2007, Campanha et al., 2015). Les niveaux de contamination par le sulfamethoxazole, l’ofloxacine et l’atenolol sont comparables à ceux observés dans des rivières recevant des effluents de STEP (Gros et al., 2007, Yoon et al., 2010).

En conclusion, cet article souligne la nécessité de collecter et de traiter les eaux usées de ce bassin versant afin d'améliorer la situation de l’environnement. Les produits pharmaceutiques détectés mériteraient d’être inclus dans de futurs programmes de surveillance au niveau des eaux de rivières au Liban pour mieux comprendre la situation la situation de la pollution et définir les futures politiques publiques sur la qualité de l'eau au Liban.

188 4.2.2. Article

Abstract

Contamination of aquatic systems with pharmaceuticals represents a rising concern. The Kadicha river in Northern Lebanon is an illustrative example of a small mediterranean river affected by rapid urbanization and population growth. This paper reports the first study on occurrence and ecological risk assessments on selected pharmaceuticals and their metabolites within the Kadicha river. For this purpose, surface water samples were collected over two sampling campaigns with twelve sites impacted by urban, rural and mixture land uses (residential and agricultural zones) within the Kadicha river basin. Among the studied pharmaceuticals, six compounds (carbamazepine, diclofenac, acetaminophen, sulfamethoxazole, ofloxacin and atenolol) were detected at detection frequency that varies according to the sampling sites. Carbamazepine was the most frequently detected compound and showed the highest concentrations (not detected to290.70 ng/L). The presence of pharmaceuticals carbamazepine, ofloxacine (not detected to190 ng/L) and atenolol (not detected to93.22 ng/L) was related to raw wastewater inputs in water body while the presence of sulfamethoxazole (not detected to23.03 ng/L) was associated with its usage in specific sites with livestock activity. The highest concentrations were observed in the urbanized downstream area while the lowest concentrations were within the rural upstream area. Thus the urbanized downstream area present the highest potential risks for aquatic species. Moreover, ofloxacine may pose high ecotoxicological risks in this watershed. The levels of contamination with pharmaceuticals was in the same range than those reported in the literature. The levels of carbamazepine, diclofenac and acetaminophen were similar to concentrations found in sites receiving raw wastewaters while the concentrations of sulfamethoxazole, ofloxacine and atenolol were similar to concentrations noticed in sites receiving treated wastewaters. This paper highlights the need to collect and treat wastewater in this watershed in order to improve the situation for health and the environment. Monitoring programs on pharmaceutical compounds in Lebanese river waters are needed to better understand the pollution situation and to make future public policies on water quality in Lebanon.

189 1. Introduction

Pharmaceutical products constitutes a group of compounds of emerging concern to aquatic systems due to their increasing and continuous use, and to their known and unknown adverse effects for aquatic species exposed to a cocktail of contaminants including pharmaceuticals ((Osorio et al., 2012), (Madureira et al., 2012), (Deblonde and Hartemann, 2013), (Petersen et al., 2014)). The continuous synthesis of new drugs and the growth of elderly population are major reasons for high pharmaceutical consumption (European Community, 2013). The main route of entry of pharmaceutical compounds into the aquatic environment is through wastewater treatment plant effluents due to their incomplete elimination with conventional treatment methods (Conley et al., 2008). Some pharmaceuticals (atenolol, diclofenac, ibuprofen and carbamazepine) are considered by the Global Water Research Coalition of high priority compounds for studies about their occurrence and risk assessment (Global Water Research Coalition, 2008). Hence, the occurrence of pharmaceuticals in surface waters have been widely studied in many countries ((Nakada et al., 2007), (Vieno et al., 2007), (Gros et al., 2007), (Yoon et al., 2010), (Osorio et al., 2012), (Campanha et al., 2015), (Matongo et al., 2015), (Branchet et al., 2019)). However, their occurrence information is very scarce in Lebanon (Mokh et al., 2017). A previous study regarding highly urbanized areas in North Lebanon pointed out that contamination of lebanese river waters with pharmaceutical residues is related to human, agricultural and farm activities (Mokh et al., 2017). The Kadicha river in north Lebanon also known by “Abou Ali” is a small mediterranean river affected by rapid urbanization and population growth. The Kadicha river is characterized by a Mediterranean climate with a moderately warm and dry summer and autumn, and moderately cold, windy, and wet winters with precipitations occurring between November and March (Massoud et al., 2006). The river land use watershed is mixing urban, discontinuous urban and rural areas with agricultural and livestock activities with small industrial facilities. The residential wastewaters are discharged directly to the flood channel without prior treatment (Naja and Volesky, 2013). In addition, the downstream of the watershed have shown a population growth after the arrival of Syrian refugees in recent years (AEMS, 2017) which may lead to an increase of drug consumption. Therefore, this watershed turns into an illustrative example of an anthropogenic mediterranean small river. Furthermore, pharmaceuticals are not part of monitoring programs and are not regulated by environmental laws in Lebanon, thus studies related to their occurrence can be used as an initial tool for

190 future dataset that can help in making future public policies on water quality in Lebanon. In this context, the present study aims i) to investigate the occurrence and spatial distribution of some pharmaceuticals within the Kadicha river and ii) to evaluate their potential toxicological impacts on local environment. For this purpose, fifteen pharmaceuticals (carbamazepine, codeine, ibuprofen, ketoprofen, diclofenac, acetaminophen, ofloxacin, sulfamethoxazole, diazepam, oxazepam, venlaflaxine, pravastatin, atenolol, propranolol, lorazepam and norbuprenorphine) and nine of their metabolites (codeine 6ßD glucuronide, 1-hydroxy-ibuprofen, carboxy-ibuprofen, oxazepam, oxazepam glucuronide, fenobric acid, buprenorphine glucuronide, norbuprenorphine and norbuprenorphine glucuronide) were selected. The selection of the pharmaceuticals was based on their detection in surface waters worldwide ((Hughes et al., 2013), (Campanha et al., 2015)) their representativeness of therapeutic classes (anti-epileptics, analgesics, antibiotics, benzodiazepines, antidepressants, lipid lowering, beta-blockers and opiate substitutes) consumed in large amounts and to identify some metabolites (Branchet et al., 2019). These compounds were analyzed in water samples collected over 2 period sampling surveys (February and November) from 12 sampling sites within Kadicha river basin.

2. Materials and methods