Remediation of nitrate pollution of Earth’s rivers and aquifers is hampered by cumulative biogeochemical processes and nitrogen sources. Isotopes (δ¹⁵N, δ¹⁸O) help unravel spatiotemporal nitrogen(N)-cycling of aquatic nitrate (NO₃⁻). We synthesized nitrate isotope data (n = ~5200) for global rivers and shallow aquifers for common patterns and processes. Rivers had lower median NO₃⁻ (0.3 ± 0.2 mg L⁻¹, n = 2902) compared to aquifers (5.5 ± 5.1 mg L⁻¹, n = 2291) and slightly lower δ¹⁵N values (+7.1 ± 3.8‰, n = 2902 vs +7.7 ± 4.5‰, n = 2291), but were indistinguishable in δ¹⁸O (+2.3 ± 6.2‰, n = 2790 vs +2.3 ± 5.4‰, n = 2235). The isotope composition of NO₃⁻ was correlated with water temperature revealing enhanced N-cascading in warmer climates. Seasonal analyses revealed higher δ¹⁵N and δ¹⁸O values in wintertime, suggesting waste-related N-source signals are better preserved in the cold seasons. Isotopic assays of nitrate biogeochemical transformations are key to understanding nitrate pollution and to inform beneficial agricultural and land management strategies.

Chile contains some of the driest areas in the world, yet human activities in these areas require large volumes of water, the result is regions experiencing high water scarcity leading to environmental degradation, conflicts and reduced industrial productivity. The aim of this paper was to quantify the water scarcity in the central and northern regions by calculating the water scarcity index—the ratio of annual water demand to availability. A focus of the paper was to determine the impact of the main industries in each region and investigate the benefit of implementing water reduction strategies within these industries. The water resources of each investigated region were found to be greatly overexploited and particularly so in the region of Antofagasta. The mining industry was found to be the greatest water consuming sector in this region and further analysis demonstrated that the degree of water scarcity could be greatly reduced by the implementation of water reduction strategies. The agricultural sector dominated water demand in all other regions and it was found that upgrading irrigation efficiency alongside reducing consumption in mining improved the situation in all regions. Nevertheless, given the scale of water scarcity, further investigation is necessary to obtain more recent and accurate data and analyze alternative strategies.