The management of the anthropogenic water cycle must ensure the preservation of the quality and quantity of water resources and their careful allocation to the different uses. Protection of water resources requires the control of pollution sources that may deteriorate them. This is a challenging task in multi-stressed catchments. This work presents an approach that combines pesticide occurrence patterns and stable isotope analyses of nitrogen (δ¹⁵N-NO₃⁻, δ¹⁵N-NH₄⁺), oxygen (δ¹⁸O-NO₃⁻), and boron (δ¹¹B) to discriminate the origin of pesticides and nitrogen-pollution to tackle this challenge. The approach has been applied to a Mediterranean sub-catchment subject to a variety of natural and anthropogenic pressures. Combining the results from both analytical approaches in selected locations of the basin, the urban/industrial activity was identified as the main pressure on the quality of the surface water resources, and to a large extent also on the groundwater resources, although agriculture may play also an important role, mainly in terms of nitrate and ammonium pollution. Total pesticide concentrations in surface waters were one order of magnitude higher than in groundwaters and believed to originate mainly from soil and/or sediments desorption processes and urban and industrial use, as they were mainly associated with treated wastewaters. These findings were supported by the stable isotope results that pointed to an organic origin of nitrate in surface waters and most groundwater samples. Ammonium pollution observed in some aquifer locations is probably generated by nitrate reduction. Overall, no significant attenuation processes could be inferred for nitrate pollution. The approach presented here exemplifies the investigative monitoring envisioned in the Water Framework Directive.

人为水循环的管理必须确保水资源的质量和数量的保护，并确保对各种用途的谨慎分配。保护水资源需要控制可能使污染源恶化的污染源。在多应力流域，这是一项艰巨的任务。这项工作提出了一种方法，结合了农药发生模式和稳定同位素氮的分析（δ ¹⁵ N-NO ₃ ^- ，δ ¹⁵ N-NH ₄ ⁺），氧（δ ¹⁸ O型NO ₃ ^- ），和硼（δ ¹¹B）区分农药和氮污染的来源以应对这一挑战。该方法已应用于遭受各种自然和人为压力的地中海次流域。结合流域选定地点的两种分析方法的结果，城市/工业活动被确定为地表水资源质量的主要压力，在很大程度上也对地下水资源产生了压力，尽管农业也可能发挥作用重要作用，主要在硝酸盐和铵盐污染​​方面。地表水中的农药总浓度比地下水中的总浓度高一个数量级，据信主要来自土壤和/或沉积物的解吸过程以及城市和工业用途，因为它们主要与处理后的废水有关。这些发现得到了稳定同位素结果的支持，该结果表明了地表水和大多数地下水样品中硝酸盐的有机来源。在某些含水层位置观察到的铵污染可能是硝酸盐还原引起的。总体而言，无法推断出硝酸盐污染的显着衰减过程。本文介绍的方法是水框架指令中设想的调查性监测的例证。