Elemental (C, N, H and P) and stable isotope (δ15N and δ13C) signatures in sediments from Zeekoevlei, South Africa: a record of human intervention in the lake
Elemental (C, N, H and P) and stable isotope (δ15N and δ13C) signatures in sediments from Zeekoevlei, South Africa: a record of human intervention in the lake
复制标题
DOI：
10.1007/s10933-007-9110-5
复制
发表时间：
2008-04
影响因子：
2.1
通讯作者：
Supriyo Kumar Das;J. Routh;A. Roychoudhury;J. Klump
中科院分区：
文献类型：
--
作者：
Supriyo Kumar Das;J. Routh;A. Roychoudhury;J. Klump
利用元素碳、氮、磷、氢比值（C/N、N/P和H/C）、总有机碳（TOC）、总磷（TP）和碳、氮稳定同位素（δ 13 C和δ 15 N）研究了南非最大淡水湖Zeekoevlei沉积物中有机质的来源和沉积条件。典型的C/N（10-12）、H/C（≥1.7）和δ 13 C有机值（−22-−19‰）以及TOC浓度的增加表明沉积物柱样中下部（18-22 cm）和顶部（0-8 cm）的初级生产力增加。从附近的废水处理厂渗出的营养物质，快速的城市化和集水区的大量施肥农业是提高生产力的原因。与此相一致的是，测得的δ 15无机值（0.11 ‰）表明，向岩心顶部输入的原污水增加。虽然蓝藻水华在岩芯中段的低δ 15 N值（1.3 ‰）中很明显，但它们的数量并没有超过浮游植物的数量。低N/P比（100- 2，200 mg l−1）和高TP（100- 2，200 mg l−1）支持氮限制条件下蓝藻的生长，而水生植物对有机质库的输入微不足道。1983年的疏浚导致悬浮物和表层沉积物暴露于空气中，并影响了岩芯中上部（12-14 cm）的有机质保存。
We used elemental carbon, nitrogen, phosphorus and hydrogen ratios (C/N, N/P and H/C) with total organic carbon (TOC) and total phosphorus (TP) as well as stable carbon and nitrogen isotopes (δ13C and δ15N) to investigate the source and depositional conditions of organic matter in sediments from Zeekoevlei, the largest freshwater lake in South Africa. Typical C/N (10–12), H/C ratios (≥1.7) and δ13Corganicvalues (−22 to −19‰) together with the increase in TOC concentration indicate elevated primary productivity in lower middle (18–22 cm) and top (0–8 cm) sections of the sediment cores. Seepage of nutrients from a nearby waste water treatment plant, rapid urbanization and heavily fertilized farming in the catchments are responsible for the increased productivity. Consistent with this, measured δ15Norganicvalues (∼11‰) indicate increased raw sewage input towards the top-section of the core. Although cyanobacterial blooms are evident from the low δ15N values (∼3‰) in mid-section of the core, they did not outnumber the phytoplankton population. Low N/P ratio (∼0) and high TP (100–2,200 mg l−1) support cyanobacterial growth under N limited condition, and insignificant input of macrophytes towards the organic matter pool. Dredging in 1983, caused sub-aerial exposure of the suspended and surface sediments, and affected organic matter preservation in the upper mid-section (12–14 cm) of the core.