Phosphorus release and sedimentation in three contiguous shallow brackish lakes, as estimated from changes in phosphorus stock and loading from catchment

Abstract

In situ phosphorus release rates in three contiguous shallow brackish lakes were calculated by considering the amount of water inflow, changes in salinity and phosphorus stock, and loading from phosphorus inflow based on monthly data. The annual amount of sedimental phosphorus relative to that of phosphorus inflow was different for each of the three water bodies: 16% for Lake Shinji, 3% for the Honjo area, and -8% for Lake Nakaumi, as estimated in a 10-year period from January 1993 to December 2002. During the warm season, the quantity of phosphorus released surpassed sedimentation in these three water bodies. The low annual sedimentation ratio in Lake Nakaumi is related to a large seawater backflow resulting in phosphorus removal, in addition to a stable stratified structure promoting phosphorus release from sediment due to oxygen depletion in the lower layer. In Lake Nakaumi, field data shows that if dissolved oxygen at the sediment surface falls below 2.54 mg L -1 , phosphorus release from the sediment begins to be accelerated.

Biogenic Phosphorus Compounds in Sediment and Suspended Particles in a Shallow Eutrophic Lake: A 31P-Nuclear Magnetic Resonance (31P NMR) Study

“…For internal P loading, the release of sediment P has commonly been acknowledged as an important source. 45,46 The biogenic P in sediment is derived from that in suspended particles; we herein report a significant difference in the relative abundance of several groups of organic P compounds in suspended particles and sediment. In particular, orthophosphate diesters are responsible for the difference, which was observed consistently in four months both in summer and winter.…”

Water Quality Variation Law and Prediction Method of a Small Reservoir in China

“…It is difficult to establish the relationship between rainfall, water quality and flow if the daily data are used for simulation as there is not rainfall every day. Many studies are based on the monthly average data [22][23][24][25][26][27][28][29][30], which prove that the monthly average data play a representative role in displaying the water quality of reservoirs and lakes. Therefore, this paper adopts the monthly average data.…”

Organic Matter Clogging Results in Undeveloped Hardpan and Soil Mineral Leakage in the Rice Terraces in the Philippine Cordilleras

“…Gas emission or mineral leakage was usually determined by Oxidation-Reduction Potential (ORP). Based on methane gas emission (ORP below −150 mV; [29]), reductive conditions were sufficient for Mn leakage (ORP below the range of +200 to +400 mV; [30]), and P would be released from the soil particles along with Ca [31].…”