Phosphorus In Surface Sediments Research Articles

Geochemical speciation and spatial distributions of phosphorus in surface sediments from the basin of the Marcus-Wake seamounts in the western Pacific Ocean

Geochemical speciation and spatial distributions of phosphorus in surface sediments from the basin of the Marcus-Wake seamounts in the western Pacific Ocean

Characteristics and distribution of phosphorus in surface sediments of a shallow lake

Phosphorus (P) in sediments plays an important role in shallow lake ecosystems and has a major effect on the lake environment. The mobility and bioavailability of P primarily depend on the contents of different P forms, which in turn depend on the sedimentary environment. Here, sediment samples from Baiyangdian (BYD) lake were collected and measured by the Standards, Measurements, and Testing procedure and Phosphorus-31 nuclear magnetic resonance spectroscopy (31P NMR) to characterize different P forms and their relationships with sediment physicochemical properties. The P content in the sediments varied in different areas and had characteristics indicative of exogenous river input. Inorganic P (334–916 mg/kg) was the dominant form of P. The 31P NMR results demonstrated that orthophosphate monoesters (16–110 mg/kg), which may be a source of P when redox conditions change, was the dominant form of organic P (20–305 mg/kg). The distribution of P forms in each region varied greatly because of the effects of anthropogenic activities, and the regions affected by exogenous river input had a higher content of P and a higher risk of P release. Principal component analysis indicated that P bound to Fe, Al, and Mn oxides and hydroxides (NaOH-P) and organic P were mainly derived from industrial and agricultural pollution, respectively. Redundancy analysis indicated that increases in pH lead to the release of NaOH-P. Organic matter plays an important role in the organic P biogeochemical cycle, as it acts as a sink and source of organic P.

Stoichiometric characteristics of carbon, nitrogen and phosphorus in surface sediments of different plant communities in Lake Baiyangdian wetland

白洋淀是雄安新区的核心生态功能区.为探究白洋淀不同植物群落区表层沉积物碳（C）氮（N）磷（P）化学计量特征，采集了96组表层沉积物样品开展对比分析.研究表明：白洋淀湿地表层沉积物总有机碳（TOC）含量均值为39.64 g/kg，范围为14.4~136.82 g/kg，总氮（TN）和总磷（TP）均值分别为2.62和0.75 g/kg，范围分别为0.72~10.57和0.46~1.38 g/kg；不同植物群落区表层沉积物C、N、P化学计量特征存在显著差异，挺水植物分布区表层沉积物TOC和TN含量高于其他区，水田区沉积物TP含量最高；表层沉积物C：N：P比例平均值为141：8：1，C：N比值相对稳定，C：P和N：P比值空间分异性较大；不同水生植物群落区沉积物C、N、P化学计量特征存在差异，挺水植物区沉积物C：P和N：P比值显著高于其他各分区，沉水植物区表层沉积物C：N最大，挺水植物区和沉水植物区C：N：P比例平均值分别为222：13：1和129：6.5：1；白洋淀表层沉积物C、N、P化学计量特征受植物群落生物量、磷氮磷化学计量特征、枯落物分解速率以及人类活动等多个因素影响；与我国东部主要湖泊相比，白洋淀表层沉积物C、N、P含量均处于较高水平，建议在水生植物生长末期收割打捞运出淀外，减少淀内N、P营养盐累积，减缓白洋淀富营养化和沼泽化进程.;Lake Baiyangdian is the main ecological function area of Xiong'an New Area. To explore the stoichiometric characteristics of carbon, nitrogen and phosphorus in surface sediments of different plant communities in Lake Baiyangdian, 96 samples of surface sediment were collected for comparative analysis. Results showed that the average total organic carbon (TOC) contents of the surface sediments were 39.64 g/kg, ranging from 14.4 to 136.82 g/kg, while the average total nitrogen (TN) and total phosphorus (TP) contents were 2.62 and 0.75 g/kg, ranging from 0.72 to 10.57 and 0.46 to 1.38 g/kg, respectively. There were significant differences in carbon and phosphorus stoichiometric characteristics of surface sediments in different plant community regions. TOC and TN contents in surface sediment of emerged aquatic plant areas were higher than those in other areas, and TP contents in surface sediment of paddy fields were the highest. The mean value of the C:N:P ratio in surface sediments was 141:8:1, the C:N ratio was relatively stable, and the C:P and N:P ratios were highly variable. There were significant differences in carbon, nitrogen and phosphorus stoichiometry in sediments of different aquatic plant communities. The ratios of C:P and N:P in surface sediments of emerged aquatic plant areas were significantly higher than those of other regions. The mean C:N:P ratios of emerged aquatic plant area and submerged plants area were 222:13:1 and 129:6.5:1, respectively. The stoichiometric characteristics of carbon, nitrogen and phosphorus in surface sediments of Lake Baiyangdian were affected by many factors, such as plant community biomass, stoichiometric characteristics, decomposition rate and human activities. Compared with the main lakes in eastern China, the contents of carbon, nitrogen and phosphorus in the surface sediments of Lake Baiyangdian were at a higher level. It is suggested to harvest, salvage and transport the aquatic plants out of the lake at the end of the growth period to reduce the accumulation of nitrogen and phosphorus nutrients in the lake and slow down the process of eutrophication and swamping of Lake Baiyangdian.

Biogenic silica, eutrophication risk and different forms of phosphorus in surface sediments of Anzali wetland, Caspian Sea

This investigation aimed to determine the contents of biogenic SiO2 and different phosphorus forms (P) and to evaluate phosphorus ecological risk in surface sediment of Anzali wetland. According to the results, biogenic SiO2 ranged from 0.29 to 3.04%. Also, the average biogenic SiO2 at all studied stations was 1.36 ± 0.83%. Results indicated that total P (TP) was between 493 and 771 ppm, averaged 637.20 ± 79.41 ppm. Moreover, inorganic P (INTP) ranged from 256.63 to 376.89 ppm and composed 51.46 ± 4.68% of total P. The percentage of P-forms was in descending order: residual-P > Fe-P > Ca-P > Al-P > labile-P. Phosphorus pollution index (PPI) ranged from 0.82 to 1.29, with an average of 1.06 in the sediment of the Anzali wetland. The Sediment P saturation (SPS) values varied considerably from 40.96 to 83.57, with an average SPS value of 49.1. Based on the eutrophication risk index, all stations except one had a low eutrophication risk index.

Trends of Nitrogen and Phosphorus in Surface Sediments of the Lagoons of the Northern Adriatic Sea

The analysis of nutrient concentrations in surface sediments is a reliable tool for assessing the trophic status of a water body. Nitrogen and phosphorus concentrations are strongly related to the sediment characteristics but are mainly driven by anthropogenic impacts. The results of the determination of total nitrogen and total inorganic and organic phosphorus in surface sediments of the lagoons and ponds of the northwestern Adriatic Sea (Marano-Grado, Venice, Po Delta, Comacchio Valleys, Pialassa della Baiona) show the merit of this approach. Indeed, when previous data are available, the ratio between the actual and background values can provide useful information on the trophic changes that have occurred in the most recent times, and the results can also explain the conditions present in less studied environments. In this context, numerous studies performed in the Venice lagoon since the second half of the 20th century during different environmental scenarios provide mean concentration ranges and propose the main causes of changes. The results of single datasets available for the other lagoons fall into scenarios that occurred in the Venice lagoon. At present, the most eutrophic basins are Pialassa della Baiona, the Po Delta lagoons and ponds and the Comacchio valleys due to industrial effluents, fish farming and clam harvesting, respectively, whereas the Venice lagoon is now experiencing environmental recovery.

Spatial Distributions of Nitrogen and Phosphorus in Surface Sediments in Intertidal Flats of the Yellow River Delta, China

The spatial distributions of nitrogen (N) and phosphorus (P) in surface sediments are of great significance in studying the ecological process of nutrient cycling in intertidal flats. However, little is known about N and P’s spatial distribution in intertidal flats of the Yellow River Delta (YRD). We analyzed the N and P contents in surface sediments and Suaeda glauca density at the low-tidal level to identify the spatial distributions of nutrients and their influencing factors in coastal tidal flat sediments. The results showed that the total nitrogen (TN) and total phosphorus (TP) concentrations in this study were both lower than the background values of China’s shallow sea sediments. The spatial distributions of N and P had significantly spatial heterogeneity, while those of the nutrients at different distances from the low-tidal level to the coastline showed no significant distance effects. The spatial distribution of S. glauca in coastal tidal flats had significant location characteristics and was closely related to the distribution of TN and pH. The TN in non-estuarine intertidal flats was less than that in estuaries; in contrast, the TP was higher in non-estuaries. There are some differences of N and P between estuary and non-estuary areas.

Chemical speciation of phosphorus in surface sediments from the Jiangsu Coast, East China: Influences, provenances and bioavailabilities

Sixty-one surface sediment samples collected from the Jiangsu Coast (JSC), East China were investigated to explore the influences, provenances and bioavailabilities of P species. Authigenic and detrital P fractions were the dominant species, accounting for 28.53% and 44.04% of the total P content, respectively. Exchangeable, Fe-bound and organic P fractions were biologically available, with an average total of 5.94 μmol/g; this value was governed by grain sizes and the organic matter and carbonate contents. Exchangeable and organic P fractions were transformed between each other, while contributing to the formation of Fe-bound and authigenic P. Phosphorus in the JSC sediments originated mainly from the Yellow River. The unique distribution pattern of P species in the JSC depends on P sources and local environments. These findings improve our understanding of the P cycle and eutrophication in the Jiangsu Coastal Zone.

Chemical speciation of phosphorus in surface sediments from a geological phosphorus-rich watershed, South China

In order to clarify the distribution characteristics and potentially environmental effect of phosphorus (P) chemical speciation in river sediments from a typical geological P-rich (GPR) watershed, South China. Forty-eight sediment samples collected from the Huangbai River watershed, Yichang city, Hubei province. The levels of TP in Huangbai River wathershed were remarkably higher than those in most Chinese lakes, reservoirs, and river. The Ca-P and Res-P were the two dominant species that accounted for 78.7% and 13.3% of TP, respectively. Based on the sediment quality guideline (SQGs) and background values of Chinese soil and sediment, the majority of the mean TP concentrations in surface sediments were higher than their background values. The unique distribution pattern of P species in the Huangbai River watershed depends on local environment conditions and P sources. These findings improve our understanding of the eutrophication and P cycle in the GPR watershed.

Distribution and speciation of phosphorus in surface sediments of the intertidal zone in the Yellow River Delta

For better understanding the phosphorus (P) cycle, it is essential to distinguish the contents of different P speciation in sediments. In the study, the content of total phosphorus (TP) in the sediments ranged from 88.80 to 227.56 μg·g-1, with an average of 138.42 μg·g-1. The content of inorganic phosphorus (IP) ranged from 84.21 to 224.26 μg·g-1, accounting for 88.74%-98.55% of the TP content, which was the main occurrence form in the intertidal sediments of the Yellow River Delta. the contents of phosphorus fractions in surface sediments were 37.06 to 106.35 μg·g-1 for detrital phosphorus (De-P), 2.99 to 34.39 μg·g-1 for exchangeable phosphorus (Ex-P), 5.27-106.06 μg·g-1 for iron bound phosphorus (Fe-P). On the whole, the existing forms of inorganic phosphorus could be ranked as follows: De-P > Fe-P > Ex-P > authigenic phosphorus (Au-P). The regression analysis between TOC content and various forms of phosphorus showed that TOC content was negatively correlated with De-P.

Distribution of Geochemical Fractions of Phosphorus in Surface Sediment in Daya Bay, China.

Surface sediment samples were collected from 19 sites throughout Daya Bay, China, to study the concentrations, and spatial distributions of different fractions of phosphorus through sequential extraction methods. Like many coastal and marine areas, De-P was the dominant form of P, contributing 47.5% of TP, followed by O-P, contributing 25.5% of TP. Ex-P and Fe-P contribute the lowest to TP. The concentration of sedimentary TP ranged from 290.3~525.1 µg/g, with the average of 395.3 µg/g, which was a similar range to other estuaries and coastal areas. Based on the spatial distribution, Pearson correlation and Principal component analysis, different fractions of phosphorus showed different spatial distributions due to different sources. The molar ratio of organic carbon to phosphorus (TOC/O-P) ranged from 199 to 609, with the average of 413, which was much higher than the Redfield ratio, suggesting terrestrial sources of organic matter in Daya Bay surface sediment. The average bioavailable phosphorus was 149.6 µg/g and contributed 37.8% (24.6~56.0%) of TP, indicating that the surface sediments of Day Bay act as an important internal source of P.

Concentration, fractionation, and ecological risk assessment of heavy metals and phosphorus in surface sediments from lakes in N. Greece.

The presence of phosphorus (P) and heavy metals (HMs) in surface sediments originating from lakes Volvi, Kerkini, and Doirani (N. Greece), as well as their fractionation patterns, wereinvestigated. No statistically significant differences in total P content were observed among the studied lakes, but notable differences were observed among sampling periods. HM contents in all lakes presented a consistent trend, i.e., Mn > Cr > Zn > Pb > Ni > Cu > Cd, while the highest concentrations were recorded in Lake Kerkini. Most of the HMs exceeded probable effect level value indicating a probable biological effect, while Ni in many cases even exceeded threshold effects level, suggesting severe toxic effects. P was dominantly bound to metal oxides, while a significant shift toward the labile fractions was observed during the spring period. The sum of potentially bioavailable HM fractions followed a downward trend of Mn > Cr > Pb > Zn > Cu > Ni > Cd for most lakes. The geoaccumulation index Igeo values of Cr, Cu, Mn, Ni, and Zn in all lakes characterized the sediments as "unpolluted," while many sediments in lakes Volvi and Kerkini were characterized as "moderately to heavily polluted" with regard to Cd. The descending order of potential ecological risk [Formula: see text] was Cd > Pb > Cu > Ni > Cr > Zn > Mn for all the studied lakes. Ni and Cr presented the highest toxic risk index values in all lake sediments. Finally, the role of mineralogical divergences among lake sediments on the contamination degree was signified.

Occurrence of total phosphorus in surface sediments of Chinese lakes and its driving factors and implications

In contrast to instantaneous concentration of phosphorus in water columns, sediments record valuable information on occurrence and sources of phosphorus for a long period associated with human activities and environmental protection. However, much less attention has been paid to phosphorus in sediments. To date the relative contributions of driving factors for TP concentration in sediments has not been elucidated. We investigated the occurrence and driving factors for TP in 270 surface sediments of 83 lakes in the catchments of two large rivers (Yangtze River and Huaihe River) in China, identified the relative contributions of the driving factors, and discussed the implication. The average TP concentration in the surface sediments of these lakes was 0.82 ± 0.04 mg gdw−1. The average TP concentration in the surface sediments of the urban lakes was larger than that in the rural lakes. Mitigation measures, human activities, and lake characteristics contributed 59.0%, 20.5%, and 20.5% to the variation in sediment TP concentration. The average TP concentration in the surface sediments significantly decreased with the percentage of annual investment in pollution control to GDP of the cities where the lakes are located. For the first time we find mitigation measures have exceeded human activities, and lake characteristics to dominate the variation in TP concentration in surface sediments of Chinese lakes. Given the annual investment in pollution control only accounted for 1.14% ± 0.06% of GDP in China from 1991 to 2018, higher percentage would be beneficial to reduce TP concentration in sediments of Chinese lakes.

Geochemical fractionation, potential bioavailability and ecological risk of phosphorus in surface sediments of the Cross River estuary system and adjacent shelf, South East Nigeria (West Africa)

Abstract Phosphorus (P) as an essential macronutrient, plays a crucial role in the regulation of biological productivity and biogeochemical cycling of other biogenic elements in aquatic environments. Different geochemical fractions of sedimentary P were separated and quantified using the sequential extraction (SEDEX) method to evaluate the abundance, sources, distribution, bioavailability and ecological risk of P in surface sediments of the Cross River estuary system (CRES) and adjacent shelf. Sediment grain size composition and bulk organic carbon were also determined. Total P (TP) ranged from 9.21–18.2 μmol/g (average, 13.30 ± 2.08 μmol/g), and comprised mostly of inorganic P (IP) (IP/TP = ~87%). Generally, authigenic P (Ca-P) was the dominant IP fraction (Ca-P/IP = ~37 ± 11.1%), representing an important long-term P reservoir. The range of organic carbon (OC) to organic P (OP) ratio (OC/OP) indicated the predominance of terrestrial OC, and that leachable OP (Le-OP) may be the major OP form in surface sediments of the study area. The partitioning and distribution of different sedimentary P fractions were controlled by the biogeo- and physicochemical conditions favorable for P transformation, sediment grain size composition and sources of sedimentary organic matter. The ratio (Fe/P) of the extractable Fe in citrate-dithionite-bicarbonate solution (FeCDB) to ferric oxide-bound P(Fe-P) revealed the presence of reactive Fe- matrices having strong sorption capacity for P. The contents of potential bioavailable P (BAP) (~34–60% of TP) indicated that P amount in the overlying water column may increase substantially if released from surface sediments. The Fe-P was the major component of BAP, and the relationship between BAP and extractable FeCDB highlighted the significant impact of Fe(III) (oxyhdr)oxides on P mobility and bioavailability. The estimated P enrichment index (PEI) indicated that surface sediment is less impacted by anthropogenic P and poses less ecological risk with respect to sedimentary TP load in the study area.

Distribution and Release Characteristics of Phosphorus in a Reservoir in Southwest China

Dam construction changes the nutrient transport of a river system. Phosphorus is an important fundamental material in the global biochemical cycle and is always a limiting factor in the primary productivity of reservoirs. Extending the study of phosphorus in reservoirs is necessary given the dam construction in southwest China. Zipingpu Reservoir was chosen as the research site in this study. The form and distribution of phosphorus in the reservoir’s surface sediments and overlying water were analyzed. The results showed that overall, the total phosphorus (TP) content of surface sediments in the Zipingpu Reservoir decreased from the tail to the front of the dam. The TP content ranged from 682.39 to 1609.06 mg/kg, with an average value of 1121.08 mg/kg. The TP content at some sampling points was affected by exogenous input. Inorganic phosphorus (IP) was the main form of phosphorus in surface sediments and had a proportion of 89.38%. Among the forms of IP, the content of Ca-P was larger than that of O-P; Ex-P, Fe-P, and Al-P had the lowest contents. Particulate phosphorus (PP) was the main form of phosphorus in the overlying water of the Zipingpu Reservoir and was strongly affected by hydrodynamic conditions. The content of total dissolved phosphorus (TDP) in the overlying water was relatively low. To further understand the risk of phosphorus release in the surface sediments in the reservoir, the rate and flux of phosphorus exchange at the sediment-overlying water interface were investigated through laboratory experiments. The results showed that both water temperature and pH significantly affected the sediment release rate, but the influence of water temperature was more significant. Acidic and alkaline conditions were conducive to the release of phosphorus from sediment, while a neutral environment was not. The release rate significantly increased with increasing water temperature, and a positive linear relationship was found between these two parameters. The sediment exhibited absorption characteristics when the water temperature was extremely low and exhibited releasing characteristics at a high temperature. These results could provide a theoretical basis for the management and protection of reservoir water environments.

Distribution of Phosphorus Fractions in Surface Sediments of Minjiang Mainstreams

In recent years, the total phosphorus pollution in Minjiang River was serious, and the surface sediments of the Minjiang River also threatened water quality. To study the spatial distributions of phosphorus in the surface sediments of the Minjiang River, samples of surface sediments were collected upstream (Aba District) and downstream (Yibin District) of the Minjiang River in December, 2016. The sediments were analyzed with the modified sequential extraction method (SEDEX) to obtain six forms of phosphorus, including exchangeable phosphorus (Ex-P), exchangeable organic phosphorus (Org-P), iron-bound phosphorus (Fe-P), authigenic phosphorus (Ca-P), detrital phosphorus (De-P), and refractory phosphorus (Res-P). The results indicated that the contents of total phosphorus (TP) in surface sediments ranged from 522.17 μg ·g-1 to 979.22 μg ·g-1, which were far more than the soil phosphorus background values (700 μg ·g-1). The spatial distribution characteristics of the TP of surface sediments indicated that the TP concentrations in sediments at the Meishan sections (the middle reach of the Minjiang River) were higher than those in the other sections. This was related to the smaller particle size and higher OM contents in sediments in the Meishan sections. The main phosphorus forms in the sediments in the Minjiang River were Ca-P and De-P, with their concentrations accounting for 75% of TP in the sediments. The bio-available phosphorus, which included Ex-P, Org-P, and Fe-P, accounted for 0.31%-29.62% of TP in the sediments of the Minjiang River. The concentrations of bio-available phosphorus in sediments at the Meishan sections and Leshan sections (the middle reach) were highest, indicating that bio-available phosphorus in the surface sediments was high, and its potential environmental impact risks were higher.

Geochemical characteristics of phosphorus in surface sediments from the continental shelf region of the northern South China Sea

Abstract Forty surface sediment samples were collected from the northern South China Sea (NSCS) during March–April 2014 to study the geochemical forms and characteristics of phosphorus (P), including exchangeable or loosely adsorbed P (Ex-P), Fe-bound P (Fe-P), authigenic P (Ca-P), detrital apatite P (De-P), and organic P (OP), which were separated and quantified through a sequential extraction procedure. Total P (TP) in surface sediments ranged from 5.10 to 18.79 μmol g− 1, and inorganic P (IP) was the dominant form of P. De-P and Ca-P were the main chemical forms of IP in surface sediments. Terrestrial inputs, biological processes, hydrodynamic conditions, Fe oxides, particle size and organic matter degradation were responsible for the geochemical characteristics of different P species in surface sediments of the NSCS. Organic carbon to OP (OC/OP) ratios ranged from 84 to 595 with an average of 151 in surface sediments, which indicates that organic matter deposited on the NSCS shelf can be ascribed to predominantly terrestrial sources. Fe/P ratios indicate that Fe oxides in most surface sediments of the NSCS had elevated capacity for the retention of particulate P. Bioavailable P represented a significant proportion of the sedimentary P pool, and accounted for 17.9–55.7% of TP in surface sediments of the NSCS.

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

The purpose of this study was to quantify phosphorus bioavailability and various forms of this element in surface sediments of the southern Caspian Sea. To do, sediment samples were collected from different depths in autumn 2015 using a Van Veen Grab. Phosphorus forms were recognized by a sequential extraction procedure (SEDEX). Results revealed that the range of total phosphorus (TP) was between 431ppm and 594ppm with a mean value of 535.25±45.05ppm. Organic phosphorus (OP) ranged from 62 to 99ppm and contributed 14.85±2.21% of total phosphorus in average. The contents of loosely phosphorus, iron-bound phosphorus, authigenic phosphorus and detrital phosphorus varied 35–55ppm, 50–94ppm, 125–189ppm and 152–217ppm, respectively. Generally, inorganic phosphorus (IP) was between 365 and 522ppm which comprised 81.9–88.53% of total phosphorus. Findings showed levels of different phosphorus forms in a descending order: detrital P>Authigenic P>Organic P>Fe-P>Loosely P. Bioavailable phosphorus concentration was between 153ppm and 240ppm and consisted 37.21±3% of total phosphorus. Based on molar ratio of TOC/OP, organic matter obtained from the studied stations suggested a terrestrial origin.

Fractions and Release Risk of Phosphorus in Surface Sediments of Three Headwater Streams with Different Styles of Water Supply

From May to September 2015, seasonal sediment samples were collected from three headwater streams and ditches which were discharged from sewage plant tail water, food processing wastewater and agricultural drainage-groundwater seepage, respectively, in Hefei, Chaohu Lake basin. The stream-bed sediments were analyzed for phosphorus fractions. The risk assessment on phosphorus release from sediments was conducted using the phosphorus sorption index (PSI), degree of phosphorus saturation (DPS) and the phosphorus release risk index (ERI). Moreover, nonparametric tests method was used to explore the difference among the three studied streams and ditches. Study results showed that:1 Guanzhenhe Distributary and Taochong Stream were seriously damaged by phosphorus pollution both in waters and stream-bed sediment, and the phosphorus pollution levels could be arranged in the order of Guanzhenhe Distributary >Taochong Stream >Modian Stream. The mean content of total phosphorus (TP) in sediments in Guanzhenhe Distributary was 1376.95 mg·kg-1, which was 2.94 and 1.91 times as high as those of Modian Stream and Taochong Stream, respectively. 2 Significant differences and different sort orders in contents of phosphorus fractions were found for each of the three streams. 3 Obvious seasonal variations existed in PSI for the three streams, and all the sampling points in the same stream had similar changing law, namely, the maximum content emerged in autumn, followed by winter, and the minimum occurred in spring or summer. 4 The same conclusions were drawn in phosphorus release risk according to the PSI, DPS and ERI, and the risk ranked as follows:Guanzhenhe Distributary >Taochong Stream >Modian Stream. 5 According to the difference analysis, significant differences existed in almost all of the indexes among the three streams.

Characteristics and Distribution of Phosphorus in Surface Sediments of Limnetic Ecosystem in Eastern China.

Phosphorus (P) is an essential nutrient for aquatic organisms; however, excessive P inflow to limnetic ecosystems can induce eutrophication. P concentrations in the rivers, wetlands and lakes of Eastern China have been amplified by fertilizer and sewage inputs associated with the development of industry and agriculture. Yet, knowledge of the distribution and speciation of P is lacking at the regional scale. We determined the distribution and speciation of P in limnetic ecosystems in Eastern China using Standards, Measurements and Testing (SMT) and phosphorus nuclear magnetic resonance (31P-NMR). The results indicate that P pollution in surface sediments was serious. Inorganic P (Pi) was the primary drive of variation in total P (TP) among different river systems, and Pi accounted for 71% to 90% of TP in surface sediment in Eastern China. Also, the concentrations of TP and Pi varied among watersheds and Pi primarily drove the variation in TP in different watersheds. Sediments less than 10-cm deep served as the main P reservoir. Environmental factors affect the speciation and origin of P. NaOH-Pi, HCl-Pi and organic P (Po) were related to pH accordingly at the regional scale. The physicochemical properties of sediments from different limnetic ecosystems affect the P speciation. HCl-Pi was higher in wetland sediments than in riverine and lake sediments in Eastern China. Conversely, NaOH-Pi was lowest in wetland sediments. Total Po concentration was lower in riverine sediments than in other sediments, but Mono-P was higher, with an average concentration of 48 mg kg−1. Diesters-P was highest in lake sediments. By revealing the regional distribution of TP, Pi and Po, this study will support eutrophication management in Eastern China.

Geochemical forms and seasonal variations of phosphorus in surface sediments of the East China Sea shelf

Geochemical characteristics of phosphorus (P) in the surface sediments of the East China Sea shelf (ECSS) were studied in spring and autumn, 2014. Distributions, seasonal variations, transformations and their influencing factors were discussed. Besides, burial fluxes of P in different seasons were also calculated. Five operationally defined forms of P, namely exchangeable or loosely sorbed P (Ads-P), iron-bound P (Fe-P), authigenic P (Au-P), detrital apatite plus other inorganic P (De-P) and organic P (OP), were obtained using a sequential extraction procedure. Generally, the concentrations of Ads-P, Fe-P, Au-P and OP decreased seaward and the concentrations of De-P increased seaward in both seasons. In spring, the average concentrations of Ads-P, Fe-P, Au-P, De-P and OP were 13.8±5.0, 21.9±7.6, 148.5±44.5, 153.1±55.8 and 91.7±21.5μgg−1, respectively. The corresponding concentrations in autumn were 11.4±4.3, 20.0±10.9, 170.4±53.6, 225.6±101.7 and 77.1±33.9μgg−1, respectively. The average percentages of P fractions in total P (TP) in spring and autumn were both in the order: De-P>Au-P>OP>Fe-P>Ads-P. The average concentrations of Bio-available P (Bio-P) were 127.4±31.4μgg−1 in spring and 108.5±47.2μgg−1 in autumn, accounting for 29.8%±7.3% and 21.5%±8.2% of corresponding TP, respectively. Seasonal variations of the primary production, hydrodynamic conditions, hypoxia and other environmental conditions were responsible for the seasonal variations of different phosphorus forms. The calculation of burial fluxes reflected that, in most parts of the studied area, TP had relative high burial fluxes in autumn, while Bio-P had relatively high burial fluxes in spring. The burial fluxes of other phosphorus forms also showed different seasonal variations in different parts of the studied area.