沈阳市城乡梯度湿地水体碳氮磷含量变化研究

湿地是人类生存和发展的重要环境之一,然而城镇化在带动经济发展的同时也严重影响了湿地生态系统。本文利用城乡梯度研究方法结合湿地分布特征,设置从沈阳城市中心到城市边缘的研究样带,沿着城镇密集区（浑河）—郊区（蒲河）—乡村（卧龙湖,仙子湖）梯度带选取典型湖泊和河流湿地样地为研究对象,系统分析城镇化对湿地水体碳氮磷含量的影响。研究发现湿地水体碳氮磷含量与城乡梯度具有相关性,总碳（TC）和可溶性有机碳（DOC）含量及SUVA₂₈₀值沿城镇密集区—郊区—乡村梯度带逐渐增加,即远离市中心的乡村卧龙湖湿地最高,分别为（120.68±2.34）mg/L,（41.56±6.27）mg/L和（0.35±0.10）L/(mg·m),显著高于位于四环以外乡村仙子湖湿地、流经沈阳市四环蒲河和穿越三环浑河湿地水体。湿地水体氮磷含量总体上沿着城乡梯度带呈降低趋势,但蒲河湿地水体总氮（TN）和总磷（TP）含量最高,分别为（5.35±0.19）mg/L和（1.45±0.07）mg/L,显著高于位于城镇密集区的浑河湿地水体。城镇化作用总体上增加了湿地水体铵态氮（NH₄⁺-N）和硝态氮（NO₃^--N）含量,其中,横穿城镇密集区的浑河湿地水体NH₄⁺-N含量最高,为（1.28±0.14）mg/L;NO₃^--N含量则是位于郊区的蒲河湿地水体最高,为(1.42±0.15) mg/L。研究结果表明城镇化改变了湿地生态系统水体碳氮磷含量,使水体DOC含量降低,小分子化合物增多,不利于DOC在水体中的累积;同时由于人类活动的加剧也使氮磷排放增加,使水体氮磷超标,导致流经城镇密集区部分的浑河和蒲河湿地NH₄⁺-N和NO₃^--N含量高于乡村。未来随着城镇化的不断发展,应严加控制和合理规划,防止城镇化导致的湿地水体污染和生态系统的破坏。

Variations of carbon,nitrogen and phosphorus in wetland water along the urban-rural gradients in Shenyang

Wetland is a major living environment for human being due to its abundant biodiversity landscape and important ecological functions. However, urbanization excessive focuses on economic development, causing wetland ecosystem damage. In this study, using urban-rural gradient method combined with the characteristics of wetland distribution, a research belt from Shenyang urban center to the urban fringe was set up. Along the research belt of town area (Hunhe River), suburb (Puhe River), and rural (Wolong Lake, Xianzi Lake), we systematically studied the impacts of urbanization on water carbon, nitrogen and phosphorus contents in the typical river and lake wetlands. The results showed that carbon, nitrogen, and phosphorus contents of wetland waters were related to the urban-rural gradient. Total carbon (TC), dissolved organic carbon (DOC) and SUVA₂₈₀ values gradually increased along the urban-suburban-rural gradient zone, and the highest values were in the Wolong Lake (away from the city center), being about (120.68±2.34) mg/L, (41.56±6.27) mg/L and (0.35±0.10) L/(mg·m). They were significantly higher than those in the Xianzi Lake (outside of fourth ring area), Puhe River (go through fourth ring area) and Hunhe River (go through third ring area). The wetland water nitrogen and phosphorus contents generally showed decrease trend along the urban-rural gradient, but the highest values were in the Puhe River. The total nitrogen (TN) and total phosphorus (TP) in this River were (5.35±0.19) mg/L and (1.45±0.07) mg/L respectively, which were significantly higher than the Hunhe River. Urbanization generally increased the content of NH₄⁺-N and NO₃^--N contents in wetland water. Among them, the highest value of NH₄⁺-N content was in Hunhe River wetland, being about (1.28±0.14) mg/L, and the highest value of NO₃^--N content was in Puhe River wetland, about (1.42±0.15) mg/L. These results indicated that urbanization changed wetland water carbon, nitrogen and phosphorus contents, lowering DOC concentration, increasing small molecules, and making DOC easy loss. Meanwhile, urbanization with the higher human activities increased nitrogen and phosphorus discharge, making the TP and TN exceeded the standard, and the NH₄⁺-N and NO₃^--N concentrations increase in Hunhe River and Puhe River wetlands. In the future, with the development of urbanization, strict control and rational planning should be considered to prevent wetland water pollution and ecological disturbance.