Fractions and Bioavailability of Soil Inorganic Phosphorus in the Loess Plateau of China under Different Vegetations

Plants play an important role in soil phosphorus nutrition. However, the effect of plants on phosphorus nutrition in soils of the Loess Plateau of China is not well understood. This study was conducted to reveal the relationships between plants and phosphorus＇ fractions and availability in the Loess Plateau of China. Twenty-two plant communities were surveyed and soil samples under different plant canopies were collected for the determination of soil properties and inorganic phosphorus fractionation. The results showed that Leguminosae and Lilaceae reduced pH and increased organic matter, cation exchange capacity, total and Olsen phosphorus in soils under their canopies, while Labiatae and Rosaceae increased pH and decreased organic matter, cation exchange capacity, total and Olsen phosphorus in soils under their canopies. The contents of Ca2P, CasP, AI-P and Fe-P were highly related with soil Oisen phosphorus. They were all higher in soils under Leguminosae and Lilaceae and lower in softs under Labiatae and Rosaceae. The results of this study indicate that Leguminosae and Lilaceae improved phosphorus nutrition in soils, yet Labiatae and Rosaceae impeded the improvement of phosphorus nutrition in soils under their canopies, which will be of more help to instruct vegetation restoration in the region and provide information for soil development.

Internal Loads and Bioavailability of Phosphorus and Nitrogen in Dianchi Lake,China

Sediments have a significant influence on the cycling of nutrient elements in lake environments. In order to assess the distribution characteristics and estimate the bioavailability of phosphorus and nitrogen in Dianchi Lake, organic and inorganic phosphorus and nitrogen forms were analysed. The 210 Pb radiometric dating method was employed to study temporal changes in the phosphorus and nitrogen pools in Dianchi Lake. The result show that the total phosphorus(TP) and total nitrogen(TN) were both at high concentrations, ranging from 697.5–3210.0 mg/kg and 1263.7–7155.2 mg/kg, respectively. Inorganic phosphorus(IP) and total organic nitrogen(TON) were the main constituents, at percentages of 59%–78% and 74%–95%, respectively, in the sediments. Spatially, there was a decreasing trend in phosphorus and nitrogen contents from the south and north to the lake centre, which is related to the distribution pattern of local economic production. The burial rates of the various phosphorus and nitrogen forms increased in same spatially and over time. Particularly in the past two decades, the burial rates doubled, with that TN reached to 1.287 mg/(cm^2·yr) in 2014. As the most reactive forms, nitrate nitrogen(NO_3-N) and ammonia nitrogen(NH_4-N) were buried more rapidly in the south region, implying that the potential for releasing sedimentary nitrogen increased from north to south. Based on their concentrations and burial rates, the internal loads of phosphorus and nitrogen were analysed for the last century. A TP pool of 71597.6 t and a TN pool of 81191.7 t were estimated for Dianchi Lake. Bioavailable phosphorus and nitrogen pools were also estimated at 44468.0 t and 5429.7 t, respectively, for the last century.

Study of chemical forms of phosphorus and their bioavailability in the sediments

Chemical forms of phosphorus in the sediments of the Daya Bay, the Zhujiang River estuary , and the Xiamen Bay are measured with extraction solutions of MgCl2, NaOH, and HC1. Their availabilities to Chlorella sp. and Isochrysis galbana are estimated by using sediments as the sole source of P in the bioassays. The results show that the contents of total phosphorus (TP) in these sediments are 449.3, 650.1 and 643.9 mg/kg, respectively. The contents of non-apatite inorganic P (NAIP) extracted with MgCl2 and NaOH from 3 sediments are 168.8, 146.6 and 118.1 mg/kg, respectively, and account for 18.3% -32.6% of TP. The phosphorus extracted with HC1 solution is greater than that extracted with NaOH solution and the lowest extracted P is MgCl2-extractable P. The greatest relative growth rates of Chlorella sp. and Isochrysis galbana cultured with sediments are in the range of 4.3% -26.9%. The increasing biomasses of these algae correspond to NAIP and AAPP (the estimated algal-available particulate P). AAPP accounts for 42.4% -78.2% of NAIP, 21.1 % - 27.1% of total inorganic P, and 11.8% - 20.3% of TP, respectively.

Phosphorus Bioavailability in a Phosphorus-Abundant System under Repeated Sediment Resuspension Conditions

Variation of bioavailable phosphorus(BAP) concentrations,i.e.,the sum of dissolved total phosphorus(DTP) and bioavailable particulate phosphorus(BAPP),was investigated in a phosphorus(P)-abundant system as influenced by repeated sediment resuspension.The overlying water and sediments in the studied system collected from a city canal,with the initial BAP concentration about 0.679 mg·L-1 in the overlying water.The sediments were disturbed with rotating blade once every day for 30 days in the experimental system.Concentrations of dissolved inorganic phosphorus(DIP),DTP,and total phosphorus(TP) in overlying water and algal available phosphorus(AAP),total phosphorus(Tot-P) in suspended particles were determined in diminishing frequency.It was found that the BAP decreased rapidly in the beginning few days in the sediment resuspension system,and then kept decreasing gradually at a low level,compared with the static conditions.This was mainly attributed to the sharp decrease of DIP.It is suggested that repeated sediment resuspension plays a significant role in phosphorus migration and converting it to more stable forms.

Variation of Phosphorus Bioavailability in the Re-suspended Sediments

The variation of phosphorus （P） bioavailability in terms of water soluble P （WSP ）, readily desorbable P （RDP）, algal available P （AAP）, and NaHCo3 extracting P （Olsen-P） in the re-suspended sediments was investigated in laboratory experiments, in which the waters and sediments were taken from campus canal. The results indicate that sediment re-suspension can promote the migration, of soluble reactive P （SRP） from overlying water to sediments. The contents of AAP and Olsen-P in re-suspended sediments reduced obviously, whereas the values of the sediments in the control increased slightly, compared with the initial state, indicating that the P bioavailability in the sediments could be rcduced evidently due to sediment re-suspension. The content and characteristics of iron-bound P （BD-P） significantly affect the formation of AAP. The formation of OlservP has close relationship with the contents of BD-P, almninium-botmd P （AI-P）, and organic P （NaOH-nrP）.

Suitability of Isotope Kinetic Approach to Assess Phosphorus Status and Bioavailability of Major Acidic Soils in Subtropical China

A 32P isotope kinetic approach was used to describe the chemical status and bioavailability of phosphorusin 32 acidic soils from subtropical China. By determining the residual radioactivity rt, in soil solution atdifferent time, t, after introduction of the isotope in an amount of R into the steady soiLwater system, awell-defined isotope kinetic model was established, and upon this model the decrease rate, n, of log(Tt/R)with respect to logt, the mean sojourn time of phosphate ions in solution, the mean exchange rate and themean flux of phosphate ions between soil solid and solution phases were calculated. Other parameters, suchas the exchangeable P within the first minute of isotope exchange (E1), and P in various compartments thatcould be exchanged with solution phosphate ions at different periods of time, were also obtained. For theseacidic soils, the r1/R had a significant correlation with the contents of clay and free Al203 where r1 is theradioactivity in solution 1 minute after introduction of the isotope into the system. Parameter n also hada significant correlation with clay content and a negative correlation with soil pH. E1 values and Cp, theP concentration in soil solution, also significantly correlated with clay and sesquioxide contents of the soils.These indicated that these isotope kinetic parameters were largely infiuenced by P-fixing components of thesoils. For the soils with strong P-fixing ability the E1 values overestimated labile P pools and hence theircorrelations with A values and plant P uptake were not significant. The other isotope kinetic parameters alsohad no significant correlation with plant P uptake. On the other hand, the conventional chemical-extractedP correlated better with plant P uptake. It was concluded that the isotope kinetic method could assess theP chemical status yet it would be inappropriate in predicting plant available P for soils with a high P-fixingability as the problem of an overestimation of soil labile P in these soils was inevitable.

Organic Phosphorus in Shallow Lake Sediments in Middle and Lower Reaches of the Yangtze River Area in China

Thirteen sediment core samples(0-10 cm) were taken from the seven lakes in the middle and lower reaches of the Yangtze River to determine the contents and distributions of organic phosphorus(P) fractions in the sediments of the shallow lakes in the area.The organic P fractions in the sediments were in the order of moderately labile organic P(MLOP) > moderately resistant organic P(MROP) > highly resistant organic P(HROP) > labile organic P(LOP),with average proportional ratios of 13.2:2.8:1.3:1.0.LOP,MLOP,and MROP were significantly related to the contents of total organic carbon(TOC),water-soluble P(WSP),algal-available P(AAP),NaHCO3-extractable P(Olsen-P),total P(TP),organic P(OP),and inorganic P(IP).However,HROP was significantly related to OP and weakly correlated with TOC,WSP,AAP,Olsen-P,TP or IP.This suggested that organic P,especially LOP and MLOP in sediments,deserved even greater attention than IP in regards to lake eutrophication.In terms of organic P,sediments were more hazardous than soils in lake eutrophication.Although OP concentrations were higher in moderately polluted sediment than those in heavily polluted sediment,LOP and MLOP were higher in the heavily polluted sediment,which indicated that heavily polluted sediment was more hazardous than moderately polluted sediment in lake eutrophication.

Environmental Soil Phosphorus Testing and Phosphorus Release in Taihu Lake,China

A microtiter plate assay (MPA) for soluble reactive phosphorus (SRP) was applied to samples in overlying water and pore water as well as in three forms of environmental soil test phosphorus (P) types: water soluble phosphorus (WSP),diluted calcium chloride extractable phosphorus (PCaCl2), and Olsen-P in the sediments of Taihu Lake, China, where potential P release in response to pH was analyzed. MPA for rapid P analysis was shown to be promising when applied on samples of natural water and sediment extracts. Concentrations of WSP and PCaCl2 in the sediments were much lower than those of Olsen-P. Olsen-P levels in the littoral sediments along the north coast of Meiliang Bay in Taihu Lake (80to 140 mg kg-1) were much higher than those in the mouth of the bay (less than 50 mg kg-1). The risk of P release in the mouth area of Meiliang Bay was lower than that in the north littoral zone with a risk of sediment P release induced by pH increases.

DISTRIBUTION OF BIOAVAILABLE PHOSPHORUS BETWEEN OVERLYING WATER AND SPM UNDER ABRUPT EXPANSION CONDITION

Experiments on Phosphorus （P） fraction characteristics in sediment resuspension were performed under adequate hydrodynamic conditions. It is found that the concentration of Suspended Particulate Matter （SPM） in the eddy current region exhibits the ＂Matthew effect＂. Velocity is an impact factor of the Equilibrium Phosphate Concentration （EPC）, which is related to other hydraulic conditions. Overall bioavailable dissolved P in the SPM causes migration to overlying water and sediment, eventually being converted into a chemical speciation of P. Conditions of resuspension promote A1-P of SPM that migrated to the sediment and water. Concentrations of A1-P in SPM are reduced. P is released from SPM to water bodies, mainly through conversion into particulate P and dissolved total P. Meanwhile, exchange between SPM and sediments occur mainly through Ca-P migration. A1-P and BD-P possess similar geochemical characteristics or source. Ca-P and A1-P exhibit a negative correlation between migration and conversion.

长江中下游湖泊沉积物生物可利用磷分布特征

利用化学提取方法对太湖6个样点,巢湖4个样点和龙感湖3个样点的表层沉积物和沉积物柱样进行了生物可利用磷(BAP)测定．北太湖表层沉积物的平均含量为259．5mg／kg,而西部湖区平均含量为114 6mg／kg,湖心区平均含量为40．6 mg/kg,而东太湖平均含量为50．7 mg／kg,呈显著北高南低的特点．巢湖西部湖区表层沉积物的BAP平均含量为 254．2 mg／kg,而东部湖区BAP含量降低为101．9mg／kg．龙感湖表层沉积物BAP平均含量为67．8 mg／kg．显著表明污染程度较高的湖区沉积物的BAP相应较高．BAP在沉积物中随深度呈指数降低,显示生物可利用磷在沉积作用下向稳定的非活性磷转化．夏季沉积物中的BAP由于生物活性的增强向溶解态活性磷转化过程增强,显示为较低的BAP含量．BAP 含量与水体溶解态活性磷呈正相关关系,且该相关性在BAP含量较低的样点好于高BAP的样点．

不同方法测定沉积物中生物可利用性磷对铜绿微囊藻生长量的影响

采用梯度扩散薄膜(DGT)技术,以太湖9个采样点所采集的27个沉积物柱样为研究对象,研究沉积物中DGT所测量的磷浓度(DGT-P)与铜绿微囊藻生长量之间的关系,同时与4种常规的生物可利用性磷方法[(水溶性磷(WSP)、易解析磷(RDP)、藻可利用磷(AAP)和NaHCO3提取磷(Olsen-P))]进行比较,评价不同提取方法获得的太湖沉积物生物可利用性磷与铜绿微囊藻生长量的关系.结果表明,DGT-P与藻生长量的相关系数为R2=0.941(P<0.01),高于4种生物可利用性磷提取法的相关系数(WSP,0.780、RDP,0.806、AAP,0.849、Olsen-P,0.910).结果表明DGT技术可以作为预测原位沉积物磷的生物可利用性的工具.

长江输送颗粒态磷的生物可利用性及其环境地球化学意义

模拟不同采样时间长江输送悬浮态颗粒物实验,通过测定藻类增长潜力来讨论颗粒态磷的生物可利用性.结果表明,悬浮物中生物可利用磷(SSBAP)含量在不同采样时间(2001年2月、5月、12月和2002年8月)的平均值分别为(288 3±49 4),(228 2±38 2),(251 6±32 9)和(182 0±8 1)mg·kg-1.不同藻种的SSBAP BAP平均值为:铜绿微囊藻(Microcystisaerugilnosa)54 2%,斜生栅藻(Scendesmusobliquus)60 3%.在4次采样中,通过大通站的BAP浓度均大于水体富营养化的限制值(0 02mg·L-1),说明SSBAP对长江流域、河口及近海区营养盐的贡献是不容忽视的,颗粒态磷是长江河口及近海区富营养化的潜在污染源,它对河口及近海的生态环境造成很大影响.

微生物对巢湖沉积物生物可利用磷的稳定性影响

以巢湖沉积物为研究对象,利用化学提取方法对四个采样点表层沉积物进行生物可利用磷(BAP)的测定。并通过沉积物—湖水体系的好氧厌氧模拟实验,研究添加菌剂对磷的释放或积聚的影响。结果表明:BAP含量与水体中的Chl-a、TP及TDP浓度显著相关,说明表层沉积物的生物可利用磷含量能够反映水体富营养化的强度;好氧环境下,微生物作用有助于磷的积聚;而在厌氧环境下,微生物作用强化了磷的释放;在有菌、无菌厌氧释放实验结束后,BAP含量显著减少。表明微生物在磷的循环中起了重要作用,可以直接或间接影响生物可利用磷中各形态磷的迁移转化。

Effects of field application of phosphate fertilizers on the availability and uptake of lead, zinc and cadmium by cabbage (Brassica chinensis L.) in a mining tailing contaminated soil

A field trial was conducted to evaluate the reduction of bioavailability of heavy metals including lead (Pb), zinc (Zn) and cadmium (Cd) in a soil contaminated by mining tailings in Shaoxing, Zhejiang, China. Three commercial phosphate (P) fertilizers including phosphate rock (PR), calcium magnesium phosphate (CMP), and single superphosphate (SSP) were applied to the plot at three P application rates, 50, 300, and 500 g/m2 with 9 treatments and control (CK). Plants, water soluble and exchangeable (WE) extra...

Reduction of Soil Cadmium Bioavailability by Using Industrial Byproduct Phosphorus Slag

In this study,an alternative and cost-effective industrial byproduct phosphorus slag(PS)was utilized to treat simulated Cd-contaminated soil.The modified European Community Bureau of Reference(BCR)sequential extraction procedure was applied to assess the ability of PS to reduce Cd mobility in contaminated soil by the incubation experiments.The results showed 2%(W/W)PS reduced the exchangeable fraction of Cd by 99.7%,which also increased the pH,electrical conductivity,cation exchange capacity,available phosphorus,and available silicon of the soil.The results suggested that the PS could decrease Cd bioavailability and improve soil nutrition.This was demonstrated by the pot experiments.The Cd accumulation in both pakchoi(Brassica chinensis L.)leaf and root was reduced along with the reduction of the Cd translocation factor(TF)and the bioaccumulation factors(BCF)in pakchoi.In Cd-contaminated soil(3.16 mg·kg^–1),the 2%(W/W)PS reduced the Cd content in the leaf and root of pakchoi by 70.7%and 58.7%,respectively.Meanwhile,the increase of the chlorophyll content in pakchoi and the promotion of pakchoi root system development suggested healthy plant growth in the PS treated soil.

Distribution and origin of biologically available phosphorus in the water of the Meiliang Bay in summer

The investigation and continuous monitoring with an innovative iron oxide embedded cellulose acetate membrane (FeO/CAM) on the concentrations of biologically available phosphorus (BAP) were conducted in the Meiliang Bay of the Taihu Lake during summer in 2004. The results showed that the concentrations of dissolved (FeO-DP), particulate (FeO-PP) and total bioavailable phosphorus (FeO-P) had similar horizontal distribution. The BAP concentrations were the highest in those estuaries in the northern bay. With the decrease of the distance to the estuary or long shore,there was little difference between BAP concentrations in an open lake area. During the observation period, algal blooms occurred in most waters of the northern bay, which was reflected from the high concentrations of chlorophyll a (Chl-a). While they were not highest in the estuarine waters of those major rivers, this is the case for the BAP concentrations. The concentrations of Chl-a had a significantly positive correlation with those of bioavailable phosphorus in the open area of the Meiliang Bay.With the sediment resuspension induced by wind and wave, BAP concentrations increased in a short-term, indicating that the riverine P inputs mainly contribute to the concentrations of BAP in the estuarine water while internal P release was the major source of BAP in the open lake area. In the eutrophic shallow lake, the blooms of alga may cause pH increase and further result in internal P release. The above results showed that the new membrane of FeO/CAM can be used to monitor the concentrations of BAP and provide the scientific justifications for the control strategy of the lake eutrophication.

Phosphorus nutrition of growing pigs

Phosphorus(P)is an essential nutrient for diverse biological processes,which aggregate to the animal's requirement for P,and nutritionists strive to meet this requirement accurately.The P demand for a growing pig comprises requirements for maintenance and tissue deposition.The P in feed ingredients,however,must be digested and absorbed before its ultimate partition between the 2 aforementioned requirement components.Phosphorus from various sources could behave differently during digestion and absorption,which results in their disparate bioavailability for pigs.The system of standardized total tract digestibility reflects true total tract digestibility of P and feed ingredient effects on specific endogenous P loss with relative ease of implementation,and this system guarantees satisfactory additivity in digestible P among the ingredients in a dietdthe foundation for diet formulation.The basal endogenous P loss,which is much easier to measure than the specific endogenous P loss,is considered as part of the pig's maintenance requirement.With this arrangement,a digestibility framework is established both for measuring the P-providing capacity of various feed ingredients and for describing the pig's P requirement.This framework entails basic understanding of the function,digestion,absorption,excretion,and homeostasis of P as support pillars.Understanding the workings of this framework enables potential integration of factors such as environment conditions and disease status in future P requirement models.The current review discusses dietary sources,digestion,absorption,bioavailability and requirement of P for growing pigs to understand the status quo,revealing the points of consensus as well as those of debate,and to encourage further investigation to provide more clarity.