| 摘要: |
| 沉积物通过对磷的吸附/解吸行为而表现为水体的磷“汇”或“源”，这对海洋初级生产力和水体富营养化具有重要影响。然而，有关亚热带入海河口区沉积物对磷的吸附行为特征尚不明晰。本研究以茅尾海两个主要入海河口区采集的柱状沉积物为基础，通过吸附动力学和等温吸附实验探究粒径大小和盐度变化对磷在沉积物上的吸附行为。采用改进后的连续提取法分析沉积物吸附前后磷形态含量变化以探究沉积物对磷相应的吸附机制。结果显示，茅尾海主要入海河口区沉积物对磷的动力学吸附可用快慢二段一级动力学方程进行描述，等温吸附曲线符合Langmuir交叉型模型。相同站位不同深度沉积物对磷的吸附能力均呈现一定的差异性，2个站点沉积物在磷初始浓度较低时均存在磷的解吸行为。同等质量下粒径越小的沉积物对磷的吸附量越大。盐度增加会降低沉积物对磷的吸附能力，表明低盐度有利于沉积物对磷的吸附。吸附后的沉积物可交换态磷(Ex-P)和铁结合态磷(Fe-P)含量显著增加，吸附过程同时存在物理吸附和化学吸附，其中以物理吸附为主。研究显示，细颗粒物和有机质主要控制着茅尾海入海河口区柱状沉积物磷的吸附，该河口区的盐度能够促进沉积物对磷的吸附，对水体富营养化水平具有一定的调节作用，但物理过程对该河口区沉积物可能存在再次释放磷的风险，应加以防范沉积物内源磷污染问题，这对于入海口的生态环境污染综合治理具有重要意义。 |
| 关键词: 沉积物 磷吸附 粒径 盐度 磷形态 |
| DOI：10.19663/j.issn2095-9869.20240918002 |
| 分类号: |
| 基金项目:国家自然科学基金(42166002)、江苏省自然科学基金(BK20241962)、北部湾大学海洋科学一流学科(TRB002)和连云港市科技计划(JCYJ2313)共同资助 |
|
| Adsorption behaviour characteristics of phosphorus in core sediments from the main estuaries of the Maowei Sea |
|
YANG Bin1,2, FENG Wenhui1, ZHOU Xiaoxuan3, PENG Guangyu4, LI Jiayu2, MO Xiaorong2
|
|
1.Jiangsu Key Laboratory of Marine Biotechnology, Jiangsu Ocean University, Lianyungang 222005, China;2.Guangxi Key Laboratory of Marine Environmental Change and Disaster in Beibu Gulf, Beibu Gulf University, Qinzhou 535011, China;3.Jiangsu Key Laboratory of Marine Biotechnology, Jiangsu Ocean University, Lianyungang 222006, China;4.School of Geography, Geomatics and Planning, Jiangsu Normal University, Xuzhou 221116, China
|
| Abstract: |
| In recent decades, eutrophication, harmful algal blooms, and seasonal hypoxia in the bottom water have been frequently reported in Chinese coastal waters owing to excessive human-induced nutrient input. Phosphorus (P) is an essential biogenic element for marine phytoplankton and is important in eutrophication and harmful algal blooms of the estuarine and marine ecosystems. Sediment has a buffering effect on the P concentration in the overlying water and is an important P source for sustaining pelagic primary production. In addition, the cycling and release of P in sediments play a notable role in maintaining the water trophic status. The biogeochemical cycle of P in sediments is a key topic in marine science worldwide. Understanding the adsorption and desorption behaviors of P in sediments is necessary to comprehend P cycling and assess its potential release risk in estuarine and coastal environments.
Maowei Sea is a typical tropical bay with high density oyster aquaculture where industrialization and urbanization have synchronously altered the natural ecosystem structure and marine ecological environments in northern Beibu Gulf. It is part of the Silk Road Economic Belt and the 21st-Century Maritime Silk Road, which have become an important part of the national developmental strategy of China. Human activities have affected the Maowei Sea’s ecological environment, particularly in the main estuaries of the Maowei Sea. Consequently, the average N/P molar ratios are much higher than the Redfield ratio of 16 : 1. P has become the limiting element for phytoplankton growth in the study area. The adsorption and desorption of P in sediments play an important role in the dynamic cycling of P in aquatic ecosystems. However, compared to other coastal and estuarine regions worldwide, geochemical information about P adsorption behavior characteristics in surface and core sediments in the main estuaries of the Maowei Sea has been largely ignored.
The sediment acts as the “sink” or “source” of P in water through the behaviors of P adsorption/desorption, which has a significant impact on marine primary productivity and water eutrophication. However, the characteristics of the P adsorption behavior of core sediments in the estuaries of the subtropical bay remain unclear. The core sediments of the two main estuarine regions in the Maowei Sea were analyzed to examine the effects of different sediment particle sizes and salinity on sedimentary P adsorption behavior through adsorption kinetics and isothermal adsorption experiments. P speciation in the sediments before and after adsorption experiments was quantified using the improved sequential extraction (SEDEX) method, and the P adsorption mechanisms in sediments were explored. The results showed that the adsorption kinetics of P in sediments could be described by a fast and slow two-stage first-order kinetic equation, and the adsorption isotherms fitted the modified Langmuir-crossover model. The adsorption capacity of P in the sediments at different depths of the same station was relatively different, and the desorption behavior existed on both sites when the initial P concentration was low. Sediments with smaller particle sizes had a high adsorption capacity for P. The increase in salinity reduced the adsorption capacity of P in sediments, indicating that low salinity facilitated P adsorption in sediments. Exchangeable P (Ex-P) and iron-bound P (Fe-P) contents increased significantly in sediments after adsorption. The adsorption processes of P in sediments included physical and chemical adsorptions, with physical adsorption being the main process. The results may provide valuable information for further research on the P biogeochemical cycle and ecological effect, as well as contribute to the development of the beautiful bay construction and sustainable growth of the marine economy. |
| Key words: Sediment Phosphorus adsorption Grain size Salinity Phosphorus speciation |
