Phosphorus speciation in wetland sediments of Zhujiang (Pearl) River Estuary, China

Abstract

Phosphorus fractions and adsorption-release characteristics of sediments in the Zhujiang (Pearl) River estuary wetland were investigated. Results showed that the total phosphorus (TP) content in surface sediments ranged from 648.9 mg/kg to 1064.0 mg/kg; inorganic phosphorus (IP) was the major fraction of TP and ranged from 422.5 mg/kg to 643.9 mg/kg. Among the inorganic phosphorus, the main fractions were phosphorus bound to Al and Fe (Fe/Al-P), and calcium-bound phosphorus (Ca-P), accounting for 23%-42% and 21%-67% of IP, respectively. The vertical distribution of TP contents were significantly positive correlated with organic phosphorus (Org-P) and Fe/Al-P contents. The bio-available phosphorus contents in vertical sediments varied from 128.6 mg/kg to 442.9 mg/kg, mainly existed in Fe-Al/P fraction, and increased from the bottom to top sediments. The transport of phosphorus in sediment-water interface was controlled by the soil characteristics. The active Fe and Al content was considered as the main factor that determines adsorption capacity in vegetated marsh wetland. The P buffering capacity of the sediments in vegetated marsh wetland was greater than that in mudflat wetland. The potential risk of eutrophication in the study area is high. Reducing terrestrial phosphorus discharge and preventing the sediment Fe/Al-P release to the interstitial water are the possible solutions to reduce the risk of eutrophication in estuary wetlands, and planting vegetation in estuary wetland can also reduce the release of phosphorus in surface sediment.

Reclamation Culture Alters Sediment Phosphorus Speciation and Ecological Risk in Coastal Zone of Southeastern China

“…In this study, sediment S i was generally >1 (TP>600 mg kg −1 ) both in natural wetland and reclamation culture ponds, which indicated that potential eutrophication risk is present in the study area . Furthermore, surface sediment S i in the reclamation culture ponds was higher than that in natural marsh wetland, indicating that sediment of culture ponds suffered from more serious P pollution (Figure ).…”

“…The sediment P single‐factor standard index ( S i ) has been widely used to assess the sediment P pollution in some aquatic ecosystems . The equation is as follows: where S i is the sediment P pollution index, C i is the actual sediment P concentration (mg kg −1 ), C s is the standard index of P (600 mg kg −1 ).…”

“…The PSI and DPS donate P sorption index and P adsorption saturation, respectively. The ERI is divided into four levels: very high risk (ERI > 25), high risk (20 < ERI < 25), moderate risk (10 < ERI < 20), and low risk (ERI < 10) …”

“…In recent years, considerable efforts have been made to measure the sediment P species in coastal and lakes wetlands, and these results have revealed that the aquatic ecosystems have a potential eutrophication risk due to higher sediment P loading . Among the sediment P species, loosely adsorbed P (Lsor‐P) and part of organic P (Org‐P) are easily desorbed and released from sediment to the overlying water, and iron and aluminum‐bound P (Fe/Al‐P) is also released easily in the suboxic environment, while calcium‐bound P (Ca‐P) is relatively stable .…”

“…Besides, the degree of P saturation (DPS) also is a potential risk indicator of P loss from sediment . Furthermore, Huang et al have developed the phosphorus‐induced eutrophication risk index (ERI), as the percentage of DPS divided by PSI, to evaluate the potential ecological risk of sediment P. Up to date, numerous studies have evaluated the sediment P‐induced eutrophication risk of coastal estuaries and lakes, but little was known about the sediment P species and associated ecological risk in reclamation culture ponds of coastal wetland.…”