Department of Chemical Oceanography, School of Marine Sciences, Cochin University of Science and Technology, Kochi, 682016, Kerala, India.
Environ Monit Assess. 2013 Mar;185(3):2535-52. doi: 10.1007/s10661-012-2729-3. Epub 2012 Jul 29.
Sequential chemical extraction using chelating agents were used to study the P dynamics and its bioavailability along the surface sediments of the Cochin estuary (southwest coast of India). Sediments were analyzed for major P species (iron bound P, calcium bound P, acid soluble organic P, alkali soluble organic P and residual organic P), Fe, Ca, total carbon, organic carbon, total nitrogen and total sulfur contents. An abrupt increase in the concentration of dissolved inorganic P with increasing salinity was observed in the study region. Iron-bound P exhibited a distinct seasonal pattern with maximum values in the monsoon season when fresh water condition was prevailed in the estuary. As salinity increased, the percentage of iron-bound P decreased, while that of calcium-bound P and total sedimentary sulfur increased. C/P and N/P ratios were low which indicate that large amounts of organic matter enriched with P tend to accumulate in surface sediments. The high organic P contribution in the sedimentary P pool may indicate high organic matter load with incomplete mineralization, as well as comparatively greater percentage of humic substance and resistant organic compounds. Principal component analysis is employed to find the possible processes influencing the speciation of P in the study region and indicate the following processes: (1) the spatial and seasonal variations of calcium bound P and acid soluble organic P was mainly controlled by sediment texture and organic carbon content, (2) sediment redox conditions control the distribution of iron bound P and (3) the terrigenous input of organic P is a significant processes controlling total P content in surface sediments. The bioavailable P was very high in the surface sediments which on an average accounts for 59 % in the pre-monsoon, 65 % in the monsoon and 53 % in the post-monsoon seasons. The surface sediments act as a potential internal source of P in the Cochin estuary.
采用螯合剂连续化学提取法研究了科钦河口（印度西南海岸）表层沉积物中磷的动态及其生物有效性。对沉积物中的主要磷形态（铁结合磷、钙结合磷、酸溶性有机磷、碱溶性有机磷和残留有机磷）、Fe、Ca、总碳、有机碳、总氮和总硫含量进行了分析。研究区域的观测结果表明，随着盐度的增加，溶解无机磷的浓度会急剧增加。铁结合磷表现出明显的季节性模式，在河口处于淡水条件时，其浓度在季风季节达到最高。随着盐度的增加，铁结合磷的比例减少，而钙结合磷和总沉积物硫的比例增加。C/P 和 N/P 比值较低，表明大量富含磷的有机物倾向于在表层沉积物中积累。沉积磷库中高有机磷的贡献可能表明有机负荷高，且矿化不完全，以及腐殖质和抗性有机化合物的比例相对较大。主成分分析用于发现影响研究区域磷形态的可能过程，并指出以下过程：（1）钙结合磷和酸溶性有机磷的空间和季节性变化主要受沉积物质地和有机碳含量控制；（2）沉积氧化还原条件控制铁结合磷的分布；（3）陆源有机磷的输入是控制表层沉积物总磷含量的重要过程。表层沉积物中的可利用磷非常高，在前季风期平均占 59%，在季风期占 65%，在后季风期占 53%。表层沉积物是科钦河口潜在的磷内源。
