Posgrado en Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Cd. Universitaria, México, Distrito Federal, Mexico,
Environ Sci Pollut Res Int. 2015 Mar;22(6):4680-94. doi: 10.1007/s11356-014-3703-0. Epub 2014 Oct 21.
Valle de Bravo (VB) is the main water reservoir of the Cutzamala hydraulic system, which provides 40% of the drinking water consumed in the Mexico City Metropolitan Area and exhibits symptoms of eutrophication. Nutrient (C, N and P) concentrations were determined in two sediment cores to reconstruct the water column trophic evolution of the reservoir and C fluxes since its creation in 1947. Radiometric methods ((210)Pb and (137)Cs) were used to obtain sediment chronologies, using the presence of pre-reservoir soil layers in one of the cores as an independent chronological marker. Mass accumulation rates ranged from 0.12 to 0.56 g cm(-2) year(-1) and total organic carbon (TOC) fluxes from 122 to 380 g m(-2) year(-1). Total N ranged 4.9-48 g m(-2) year(-1), and total P 0.6-4.2 g m(-2) year(-1). The sedimentary record shows that all three (C, N and P) fluxes increased significantly after 1991, in good agreement with the assessed trophic evolution of VB and with historic and recent real-time measurements. In the recent years (1992-2006), the TOC flux to the bottom of VB (average 250 g m(-2) year(-1), peaks 323 g m(-2) year(-1)) is similar to that found in highly eutrophic reservoirs and impoundments. Over 1/3 of the total C burial since dam construction, circa 70,000 t, has occurred in this recent period. These results highlight the usefulness of the reconstruction of carbon and nutrient fluxes from the sedimentary record to assess carbon burial and its temporal evolution in freshwater ecosystems.
瓦莱德布拉沃（VB）是库茨马拉开闸系统的主要水源地，为墨西哥城大都市区 40%的饮用水提供水源，并且已经出现富营养化的症状。本研究在两个沉积岩芯中测定了营养物质（C、N 和 P）的浓度，以重建水库水柱的营养演化过程以及自 1947 年水库建成以来的 C 通量。放射性测年方法（（210）Pb 和（137）Cs）被用来获取沉积岩芯的年代，使用其中一个岩芯中存在的水库前土壤层作为独立的年代标记。质量堆积速率的范围为 0.12-0.56 g cm(-2) year(-1)，总有机碳（TOC）通量的范围为 122-380 g m(-2) year(-1)。总 N 的范围为 4.9-48 g m(-2) year(-1)，总 P 的范围为 0.6-4.2 g m(-2) year(-1)。沉积记录表明，所有三种（C、N 和 P）通量在 1991 年后都显著增加，这与 VB 的评估营养演化以及历史和近期实时测量结果一致。在最近几年（1992-2006 年），VB 底部的 TOC 通量（平均 250 g m(-2) year(-1)，峰值 323 g m(-2) year(-1)）与高度富营养化水库和堤坝的通量相当。自大坝建成以来，约有 70,000 吨 C 被埋藏在最近的时期，占总埋藏量的 1/3 以上。这些结果突出了从沉积记录中重建碳和养分通量以评估淡水生态系统中碳埋藏及其时间演化的有用性。
