Modeling the Impact of Salinity Variations on Aquatic Environments: Including Negative and Positive Effects in Life Cycle Assessment

Salinity is changing in aquatic systems due to anthropogenic activities (like irrigation or dam management) and climate change. Although there are studies on the effects of salinity variations on individual species, little is known about the effects on overall ecosystems, these impacts being more uncertain in transitional waters such as estuaries or fiords. The few works that do address this topic have considered these impacts using ecotoxicity models. However, these models state that an increase in the concentration of a pollutant generates an increase in the impacts, disregarding the effects of water freshening. The present research work introduces a general framework to address the impacts of salinity variations, including emission-related positive effects. We validated this framework by applying it to an estuarine area in Galicia (northwestern Spain), where sharp drops in the salt concentration have caused mass mortalities of shellfish in recent decades. This research work addresses for the first time the potential effects on the environment derived from a decrease in the concentration of essential substances, where the effects of an emission can also generate positive impacts. Moreover, it is expected that the framework can also be applied to model the environmental impacts of other essential substances in life cycle assessment (LCA), such as metals and macronutrients.受人类活动（如灌溉、大坝调度）与气候变化影响，水生生态系统的盐度正发生改变。尽管已有诸多研究探讨了盐度变化对单一物种的影响，但针对其对整体生态系统的影响仍知之甚少；在河口、峡湾等过渡水域中，此类影响的不确定性尤为突出。目前仅有的少量相关研究均采用生态毒性模型开展此类影响评估，但此类模型均假定污染物浓度升高会加剧负面影响，却忽略了水体淡化的相关效应。本研究提出一套通用分析框架，可用于全面评估盐度变化带来的各类影响，其中涵盖与排放相关的正向环境效应。我们通过将该框架应用于西班牙西北部加利西亚地区的一处河口区域完成了有效性验证——近数十年来，该区域盐浓度骤降曾引发大规模贝类死亡事件。本研究首次探讨了必需物质浓度降低对环境的潜在影响，此类场景下排放行为也可能产生正向环境效应。此外，该框架还可推广应用于生命周期评价（Life Cycle Assessment，LCA）中，用于模拟金属、大量营养素等其他必需物质的环境影响。