CASCADA - Toxin or Treat?

21世纪对气候变暖最敏感的冰川位于热带山区，因此，它们是气候变化的宝贵哨兵。迄今为止，由于对全球海平面和水安全的影响，大多数注意力都集中在这些冰川释放的融水的数量上。同时发生的水质变化受到的限制要少得多，但对饮用水、农业和工业都有影响。秘鲁拥有所有热带冰川的71%，所有这些冰川在过去20年里都经历了高质量的损失和退缩。然而，某些由冰川融水注入的河流正在变酸，其金属浓度往往高于世界卫生组织的标准。这被认为是由于在退缩的冰川前区暴露了富含金属（硫化物）的岩石，这些岩石一旦被氧化就会释放出硫酸和金属——这种酸性不再能被发生在冰川下的强烈化学风化所中和。CASCADA将检验的首要假设是，科迪勒拉布兰卡冰川覆盖的集水区正在沿着一条轨迹进化，从冰川径流是下游生态系统重要的营养来源（“治疗”）的原始条件，到同样的径流对生态系统和人类健康有害（“毒素”）的情况。CASCADA将秘鲁水资源、冰川学和生态学专家与英国地球化学家、冰川学家和技术专家联合起来，调查冰川退缩对科迪勒拉布兰卡河水质的级联影响，并提出解决方案。它采用先进的原位监测技术，首次获取科迪勒拉布兰卡河全年水质数据，并开发和测试一种新的湿地管理模式，以修复高金属毒性河流。在一项公民科学计划下与当地用水者委员会建立强有力的伙伴关系，并与政府机构和当地社区组成一个参与委员会，将确保综合湿地管理和水质报告的能力建设和技术转让。因此，CASCADA提供了所需的变革过程理解，以实现我们预测冰川消退地区水质演变的能力的飞跃，并为有毒集水区制定有效的解决方案。

The most sensitive glaciers to climate warming in the 21st century are situated in tropical mountain regions, and thus, serve as valuable sentinels of climate change. Most attention to date has focused on the quantity of meltwater released from these glaciers, because of the impact on global sea level and water security. The concurrent changes in water quality are much more poorly constrained, but have implications for drinking water, agriculture and industry. Peru holds 71% of all tropical glaciers, all of which have undergone high rates of mass loss and retreat in the last two decades. However, certain rivers fed by glacial meltwater are becoming acidic, with concentrations of metals often above World Health Organisation standards. This is thought due to the exposure of metal-rich (sulphidic) rocks in retreating glacier forefields, which release sulphuric acid and metals once oxidised - this acidity can no longer be neutralized by the intense chemical weathering which takes place beneath glaciers. The overarching hypothesis that CASCADA will test is that glaciated catchments in the Cordillera Blanca are evolving along a trajectory from pristine conditions, where glacial runoff is an important nutrient source for downstream ecosystems ("treat"), to those in which the same runoff is toxic to ecosystems and human health ("toxin"). CASCADA unites Peruvian experts in water resources, glaciology and ecology with UK geochemists, glaciologists and technologists to investigate and generate solutions to the cascading impacts of glacier retreat on water quality in Cordillera Blanca rivers. It employs cutting edge in situ monitoring technologies to capture first time data on the year-round quality of Cordillera Blanca rivers and to develop and test a novel wetland management model to remediate rivers with high metal toxicity. A strong partnership with local water users' committees under a citizen science scheme and the formation of an engagement board with governmental institutions and local communities will ensure capacity building and the transfer of technology for integrated wetland management and water quality reporting. Thus, CASCADA provides the transformative process understanding required to deliver a step jump in our ability to predict water quality evolution in deglaciating terrains and to develop effective solutions to toxic catchments.