## 3 Results and Discussion
### Land Use Influence on EDC Distribution and Bacteria Community Structure  
The number of EDCs differed significantly (Chi squared: 9.761; \(p<0.01\)) between springs and streams, and surface water samples. The wastewater point 2575 showed the largest number of EDCs, with a total of 18 compounds detected 56 times (Table 1). In addition, pesticides or their metabolites were detected up to 98 times in springs and streams surrounding the lake. The largest number (23) was recorded at the spring sample point 2571 (Table 1), close to a major irrigation area  
Figure 2: Relative abundance (%) of major families identified in sediment samples from Pétrola Lake. Only families with a relative abundance >2% of total bacteria population were included. (Figure 1). An important part of the EDC load reaches the lake through the small surrounding streams. These streams drain through surface and groundwater runoff and dry and irrigation agricultural areas. The presence of EDCs in springs and streams reveals that one of the most relevant contamination sources to the saline lake is diffuse. Urban outflows, a point pollution source, constitute another key input of pesticides such as cyprodinil, \(O\)-phenyphenol, boscalid, methomyl and atrazine. Some EDCs are common in both agricultural and urban outflows: cyprodinil, \(O\)-phenylphenol and caffeine. Atmospheric deposition as a source of some EDCs cannot be ruled out. This is the case in some polycyclic aromatic hydrocarbons (PAHs) such as fluorene, fluoranthene or phenantrene, which can be transported long distances and deposited with rainfall [50; 51]. Other pesticides that are not volatilized attach to soil particles and are transported by wind and then deposited [52; 53]. The anthropogenic pressures, agriculture and wastewater outflows, the intensity of EDC use and their persistence in the environment can explain the distribution of most of the EDC. For example, the widespread distribution of cyprodinil and \(O\)-phenylphenol can be explained because they are permitted pesticides in common use; in contrast, the spatial distribution of atrazine is more limited because it was banned 13 years ago, but due to its persistence, it is still detected. Regarding the persistence in the environment of EDC, the physico-chemical properties (solubility, soil adsorption coefficient-K\({}_{\rm{oc}}\), Groundwater Ubiquity Score-GUS, Octanol-water partition coefficient-K\({}_{\rm{ow}}\)) of a pollutant and the environmental redox conditions, which can be governed by the activity of microorganisms, can control their distribution and fate. Note that the number of compounds in the lake is lower than in streams and springs, which points to attenuation processes. It is reasonable to assume that the overall number of EDCs in the aquifer is more important than that in the surface water body, because the volume of groundwater is greater. The absence of some compounds in the lake can be explained by the analytical resolution of the employed GC-MS equipment (they are below the detection limit) or by attenuation processes linked to both physical (i.e., adsorption capacity of sediments, photodegradation) and biogeochemical attenuating processes. From a microbial perspective, members of Alpha-, Gamma- and Deltaproteobacteria, Bacteriadia and Clostridia classes--which use carbon, sulphur and nitrogen compounds for energetic and metabolic purposes--were identified in Petrola Lake sediments. They have also been reported in soda and salt ecosystems in Lonar Lake, Lake Grevelingen or Lake Bosten [44; 54; 55]. The co-existence of nitrogen or sulphur-oxidizing, and nitrate or sulphate-reducing, bacteria in Petrola Lake suggests the presence of functional coupled cycles (i.e., redox processes related to S-N-C cycles) at the sediment-water interface. The microbial activity at the sediment-water interface may control redox conditions by utilizing different electron donors (i.e., organic matter) to sustain metabolic activity.