Environmental Sciences Program, São Paulo State University - UNESP, Sorocaba campus, Avenida Três de Março 511, Alto da Boa Vista, Sorocaba, SP, 18087-180, Brazil.
Chemistry Department, Institute of Oceanography, University of São Paulo, Praça do Oceanográico, 191, São Paulo, SP, 05508-120, Brazil.
Environ Sci Pollut Res Int. 2018 Nov;25(31):31776-31789. doi: 10.1007/s11356-018-2923-0. Epub 2018 Aug 29.
The impacts of anthropic activities have had profound effects on the nitrogen (N) and phosphorus (P) cycles in many aquatic ecosystems. We investigated the spatial and temporal distributions of carbon (C), N, and P in the sediments of a tropical Paiva Castro Reservoir (São Paulo, Brazil), as well as their release and retention in the system. In 2010, surface sediments were collected at nine sites in the reservoir, and a core was obtained in the limnetic zone, in 2010. The core was dated using the Pb technique. The organic C content was estimated from organic matter concentration, which was measured by the loss-on-ignition method, and the concentrations of P and N were determined by spectrophotometry. Marked spatial heterogeneity in the Paiva Castro sediments associated with both natural variations in the water body and variations induced by human impacts was observed. Heterogeneity was evidenced by a decrease in the allochthonous contribution of organic matter (C/N) in the upstream-downstream direction and increases of N and P, mainly associated with water flows in the different compartments of the reservoir. In the core, C and N concentrations display significant positive correlations with increases in population and agricultural activities in the drainage basin through time. The C/P molar ratios in surface sediments are indicative of human impacts in the region, as C:P ratios in the sediment are low (7.8:1) compared to the Redfield ratio (C:P = 108:1). Predominance of oxic conditions at the sediment surface and particles sizes < 63 μm provided favorable conditions for P retention in the sediments, which helps prevent eutrophication. Approaches used in this research should be extended to other locations, especially in mesotrophic and oligotrophic reservoirs, to provide information on historical impacts in such aquatic ecosystems.
人为活动对许多水生生态系统的氮（N）和磷（P）循环产生了深远的影响。我们研究了巴伊亚·卡斯特罗水库（巴西圣保罗）沉积物中碳（C）、N 和 P 的时空分布及其在系统中的释放和保留。2010 年，在水库的九个地点采集了表层沉积物，并在 2010 年在湖沼区获得了一个岩芯。该岩芯使用 Pb 技术进行了定年。通过燃烧损失法测量有机物浓度来估算有机 C 含量，并用分光光度法测定 P 和 N 的浓度。观察到 Paiva Castro 沉积物存在明显的空间异质性，这与水体的自然变化和人为影响引起的变化有关。这种异质性表现在，从上游到下游，有机物的异源贡献（C/N）减少，N 和 P 增加，这主要与水库不同部分的水流有关。在岩芯中，C 和 N 浓度与流域内人口和农业活动的增加呈显著正相关。表层沉积物中 C/P 摩尔比表明该地区受到了人为影响，因为沉积物中的 C:P 比（7.8:1）低于雷德菲尔德比（C:P = 108:1）。在沉积物表面和粒径小于 63μm 的颗粒中存在好氧条件，为 P 在沉积物中的保留提供了有利条件，这有助于防止富营养化。本研究中使用的方法应扩展到其他地区，特别是在中营养和贫营养水库中，以提供有关这些水生生态系统历史影响的信息。
