Bioavailability and geochemical speciation of phosphorus in surface sediments of the Southern Caspian Sea

Spatial and Seasonal Distribution and Transportation of Different Forms of Phosphorus in the Middle Reaches of the Yarlung Zangbo River

“…According to previous research [11,12], by the method used in this research, SP, Al-P, Fe-P, and OP are considered as "external P," which may came from human activities, such as industrial wastewater, domestic sewage, and the abuse of phosphate fertilizer. Ca-P and Oc-P are considered self-generated, which may be derived from rock weathering or the death of organisms, so they are called "internal P." P may enter into overlying water from sediments, but the releasing ability of different forms of P is different, named mobility or bioavailability [13,14]. It is generally considered that SP, Al-P, Fe-P, and OP are mobile or bioavailable to a certain extent, while Ca-P and Oc-P are immobile and biologically unavailable.…”

Comparative Study on the Elucidation of Sedimentary Phosphorus Species Using Two Methods, the SMT and SEDEX Methods

“…Of this, Ex-P was composed of 14.85-43.19% TP, Fe-P was composed of 6.31%-31.50% of TP, and OP was composed of 2.51-12.86% of TP, indicating that these sediments could be released from the Ex-P and OP fractions by the decomposition of organic matter and from the Fe-P during anoxic conditions. In these study areas, the bioavailable P fraction elucidated by both methods was higher than in other locations, such as the East China Sea, which had 6-32% bioavailable P to TP [12,23]; Sishili Bay, China, which had 26.7-35.5% bioavailable P [15]; the eastern coast of Hainan Island, China, which had 20.3-54.2% bioavailable P [17]; the Caspian Sea, which had a mean of 37.2% bioavailable P [18]. us, based on the results of the present study, the Andong salt marsh and the Changjiang Estuary released P during the decomposition of organic matter and under anoxic conditions, which could be utilised by microorganisms.…”

“…In our study areas, the surface sedimentary TP was lower compared to the TP in other locations that were elucidated using the SEDEX method. e results showed the following: TP from 416.5 to 638.5 mg/kg in the East China Sea sediment cores [25]; TP from 465 to 663.4 mg/kg in the Changjiang Estuary and adjacent East China Sea surface sediments [12]; TP from 474 to 1,035 mg/kg in the northern Gulf of Mexico sediment cores [13]; TP from 409.2 to 3,689 mg/kg in the central Pacific Ocean surface sediments [14]; TP of 466.24-669.29 mg/kg in the Sishili Bay, China [15], TP from 246.76 to 692.54 mg/kg at the eastern coast of Hainan Island surface sediment [17]; TP from 369.83 to 739.97 mg/kg in the East China Sea core sediments [26]; TP from 431 to 594 mg/ kg in the Caspian Sea surface sediments [18]. Similarly, in our study areas, the surface sedimentary TPs were lower compared to the sedimentary TPs in other locations elucidated using the SMT method: TP ranging from 520.8 to 1376.4 mg/kg in the Loire Estuary; from 130.2 to 787.4 mg/ kg in the Gironde Estuary; from 189.1 to 576.6 mg/kg in the Bay of Seine [19]; at 412.61 mg/kg in the Gulf of Gdańnsk [20]; from 217.8 to 1,640 mg/kg in the lakes in the mid and lower Changjiang River [27]; from 303.87 to 761.59 mg/kg in the subtropical wetland reserve in southeast China [21]; 87.28-2610.43 mg/kg in the main rivers discharging into the Bohai Sea [22].…”

“…e overall IP and TP ranged from 6.31 to 42.64 mg/kg and from 13.90 to 60.30 mg/kg, respectively. e ranges of sedimentary P species elucidated by the SEDEX method were as follows: authigenic P (37.98-91.54 mg/kg) > Ex-P (20.68-71.43 mg/kg) > Fe-P (9.2-50.6 mg/kg) > OP (3.05- 18.55 mg/kg) > De-P (1.95-3.78 mg/kg). IP and TP ranged from 86.67 to 188.41 mg/kg and from 91.30 to 196.99 mg/ kg, respectively.…”

“…e Ex-P, authigenic P, De-P, IP, and TP in the surface and core sediments of the eastern Hainan Island in the South China Sea were affected by particle size [17]. High OC/OP ratios indicated that the surface sediments in the Caspian Sea were terrestrial in origin [18]. Some studies used the SMT method to elucidate the sedimentary P species in various environments.…”