Analysis of the characteristics of phosphine production by anaerobic digestion based on microbial community dynamics, metabolic pathways, and isolation of the phosphate-reducing strain.

Although phosphine is ubiquitously present in anaerobic environments, little is known regarding the microbial community dynamics and metabolic pathways associated with phosphine formation in an anaerobic digestion system. This study investigated the production of phosphine in anaerobic digestion, with results indicating that phosphine production mainly occurred during logarithmic microbial growth. Dehydrogenase and hydrogen promoted the production of phosphine, with a maximum phosphine concentration of 300 mg/m3. The abundance of Ruminococcaceae and Escherichia was observed to promote phosphine generation. The analysis of metabolic pathways based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) and the MetaCyc pathway database revealed the highest relative abundance of replication and repair in genetic information processing; further, the cofactor, prosthetic group, electron carrier, and vitamin biosynthesis were observed to be closely related to phosphine formation. A phylogenetic tree was reconstructed based on the neighbor-joining method. The results indicated the clear evolutionary position of the isolated Pseudescherichia sp. SFM4 strain, adjacent to Escherichia, with a stable phosphate-reducing ability for a maximum phosphine concentration of 26 mg/m3. The response surface experiment indicated that the initial optimal conditions for phosphine production by SFM4 could be achieved with nitrogen, carbon, and phosphorus loads of 6.17, 300, and 10 mg/L, respectively, at pH 7.47. These results provide comprehensive insights into the dynamic changes in the microbial structure, isolated single bacterial strain, and metabolic pathways associated with phosphine formation. They also provide information on the molecular biology associated with phosphorus recycling.

Development and validation of a methodology for quantifying parts-per-billion levels of arsine and phosphine in nitrogen, hydrogen and liquefied petroleum gas using a variable pressure sampler coupled to gas chromatography-mass spectrometry.

The reliable determination of arsine (AsH3) and phosphine (PH3) in hydrogen (H2), nitrogen (N2) and liquefied petroleum gas (LPG) is of great importance because of its drastic effects on the efficiency of catalysts, as well as the strict regulations associated with health, safety and environmental issues. It is challenging for an analyst to determine the parts per billion of AsH3 and PH3 in H2, N2, and LPG at low and high pressures without collection procedures using adsorption, desorption, and dissolution techniques. To overcome this analytical need an analytical methodology was developed, employing a variable pressure sampler (VPS) coupled to a gas chromatograph (GC) with mass spectrometry (MS) for the identification and quantification of traces of AsH3 and PH3. The instrumentation, tubing and accessories of the VPS were made of passivated steel to avoid losses from absorption of AsH3 and PH3 in the steel which would generate significant analytical problems. The VPS had a homogeneous heating block that prevented analyte losses from condensation. With the VPS, 24 AsH3 and PH3 standards were prepared between 0.005 and 0.1 mg kg-1 in balance of H2, N2 and LPG. The separation and quantification of the analytes was achieved with an improved GC with 4 valves and 5 columns in series that guaranteed the elimination of impurities. The proposed method was optimized in VPS and GC-MS and then validated showing highly accaptable linearity (r2 > 0.9999), detection limits (<0.0009 mg kg-1), limits of quantification (<0.003 mg kg-1), intra-day and inter-day precision and accuracy (<1.14% and ≤3.0% respectively), recovery for the standard addition (86-109%), P values> 0.05 for the test Student's t paired who evaluated the effect of the matrix on pressure and concentration. The speed of analysis was high (<5.2 min). The method was applied to real samples, showing values between 0.005 and 0.1 mg kg-1 and an effect on the efficiency of the Ziegler Natta catalyst between 5 and 56%.

Optimization and Validation of HS-SPME-GCMS Method for Determination of Multifumigant Residues in Grain, Oilseeds, Nuts, and Dry Fruit.

Background: Fumigants are approved in many countries and used to treat food, feed, and seed. The amount of residue that remains in fumigated materials is measured and reported. Objective: The optimization and validation of a high-sensitivity headspace solid-phase microextraction gas chromatograph mass spectrometer (HS-SPME-GCMS) method for determination of eight fumigant residues-phosphine, methyl bromide, cyanogen, sulfuryl fluoride, ethylene oxide, propylene oxide, ethyl bromide and ethyl formate-in a range of food matrices were developed. The food matrices included grain, oilseed, dried fruit, and nut. Methods: The new method was used to determine residue levels from a fumigant complex in food matrices by monitoring the change of the absorption of spiked standards and desorption of fumigant from fumigated samples. Results: Based on the observation, the process of physical sorption and chemisorption was defined. The equilibrium time of the sample analysis was chosen at 5 hours. The LODs of the fumigants were in the range of 0.03 to 1.99 ng/g. Response to a range of diluted authentic standards gave significant linear regressions (r² > 0.9983), and the RSDs were ≤8.7% at the 3 ng/g level of aged spiking standard, except for sulfuryl fluoride, for which the LOD was 1.99 ng/g and the RSD value was 39.7% (6.64 ng/g). Conclusions: The performance of the HS-SPME-GCMS method was more sensitive than the use of a gas syringe, except for sulfuryl fluoride. Highlights: An innovative multifumigant residue detection method based on HS-SPME sampling technology with gas chromatograph-mass selective detection (GC-MSD) analysis was established, including phosphine, methyl bromide, cyanogen, sulfuryl fluoride, ethylene oxide, propylene oxide, ethyl bromide, and ethyl formate; The first report of a sorption study of the process of physical sorption and chemisorption of residual fumigant in fruit and food matrices by an HS-SPME-GCMS method; Consider the effect of time on fumigant behavior in dried fruit, grain, and nut; The LODs of the fumigants were in the range of 0.03 to 1.99 ng/g.

Phosphine production in anaerobic wastewater treatment under tetracycline antibiotic pressure.

The influence of tetracycline (TC) antibiotics on phosphine (PH3) production in the anaerobic wastewater treatment was studied. A lab-scale anaerobic baffled reactor with three compartments was employed to simulate this process. The reactor was operated in a TC-absence wastewater and 250µg/L TC-presence wastewater for three months after a start-up period, respectively. The responses of pH, oxidation-reduction potential (ORP), chemical oxygen demand (COD), total phosphorus (TP), enzymes activity (dehydrogenase and acid phosphatase), and microbial community were investigated to reveal the effect of TC on PH3 production. Results suggested that the dehydrogenase (DH) activity, acid phosphatase (ACP) activity and COD have positive relationship with PH3 production, while pH, ORP level and the TP in liquid phase have negative relationship with PH3 production. With prolonged TC exposure, decrease in pH and increase in DH activity are beneficial to PH3 production, while decrease in COD and ACP activity are not the limiting factors for PH3 production.

Redox chemistry in the phosphorus biogeochemical cycle.

The element phosphorus (P) controls growth in many ecosystems as the limiting nutrient, where it is broadly considered to reside as pentavalent P in phosphate minerals and organic esters. Exceptions to pentavalent P include phosphine--PH3--a trace atmospheric gas, and phosphite and hypophosphite, P anions that have been detected recently in lightning strikes, eutrophic lakes, geothermal springs, and termite hindguts. Reduced oxidation state P compounds include the phosphonates, characterized by C-P bonds, which bear up to 25% of total organic dissolved phosphorus. Reduced P compounds have been considered to be rare; however, the microbial ability to use reduced P compounds as sole P sources is ubiquitous. Here we show that between 10% and 20% of dissolved P bears a redox state of less than +5 in water samples from central Florida, on average, with some samples bearing almost as much reduced P as phosphate. If the quantity of reduced P observed in the water samples from Florida studied here is broadly characteristic of similar environments on the global scale, it accounts well for the concentration of atmospheric phosphine and provides a rationale for the ubiquity of phosphite utilization genes in nature. Phosphine is generated at a quantity consistent with thermodynamic equilibrium established by the disproportionation reaction of reduced P species. Comprising 10-20% of the total dissolved P inventory in Florida environments, reduced P compounds could hence be a critical part of the phosphorus biogeochemical cycle, and in turn may impact global carbon cycling and methanogenesis.

Matrix-bound phosphine, phosphorus fractions and phosphatase activity through sediment profiles in Lake Chaohu, China.

The distribution patterns of matrix-bound phosphine (MBP), phosphorus (P) fractions and neutral phosphatase activity (NPA) were investigated through five sediment profiles in Lake Chaohu, China. MBP was discovered in all sediment profiles within the concentration range of 1.58-50.34 ng kg(-1). These concentrations exhibited a consistent vertical distribution pattern in all profiles, and higher concentrations generally occurred in surface sediments. MBP concentrations showed a significant positive correlation with P fractions, total nitrogen (TN), Cu and Zn under lower levels of inorganic phosphorus (<0.6 g kg(-1)), organic phosphorus (<0.2 g kg(-1)), TN (<0.13%), Cu (<25 mg kg(-1)) and Zn (<150 mg kg(-1)), but no statistically significant correlations were obtained under higher levels. A multiple stepwise regression model ([MBP]=1.36[NPA]-6.21[pH]-0.06[Zn]+0.75[Cu]+49.86) was obtained between MBP concentrations and environmental variables, and MBP concentrations showed a strong positive correlation with NPA (P<0.0001). This indicates that the production of sediment MBP was controlled by microbially mediated processes in Lake Chaohu. This model could be used to predict MBP levels in the sediments. Our results indicate that MBP levels could not be used as indicators for the degree of lake eutrophication. The study of sediment MBP, P factions and NPA will improve our understanding of P cycling and their environmental significance in the eutrophic Lake Chaohu.

Determination of phosphine in plant materials: method optimization and validation in interlaboratory comparison tests.

The optimization and validation of a method for the determination of phosphine in plant materials are described. The method is based on headspace sampling over the sample heated in 5% sulfuric acid. Critical factors such as sample amount, equilibration conditions, method of quantitation, and matrix effects are discussed, and validation data are presented. Grinding of coarse samples does not lead to lower results and is a prerequisite for standard addition experiments, which present the most reliable approach for quantitation because of notable matrix effects. Two interlaboratory comparisons showed that results varied considerably and that an uncertainty of measurement of about 50% has to be assessed. Flame photometric and mass spectrometric detection gave similar results. The proposed method is well reproducible within one laboratory, and results from the authors' laboratories using different injection and detection techniques are very close to each other. The considerable variation in the interlaboratory comparison shows that this analysis is still challenging in practice and further proficiency testing is needed.

Matrix-bound phosphine and phosphorus fractions in surface sediments of Arctic Kongsfjorden, Svalbard: effects of glacial activity and environmental variables.

The surface sediments were collected from the glacial bay (GLAC), the central basin (CENTR) and their transition area (TRANS) along the fjord Kongsfjorden axis on Svalbard, Arctic, and matrix-bound phosphine (MBP), phosphorus fractions and alkaline phosphatase activity (APA) were analyzed. MBP was found in all the sediments with the concentration range of 8.93-59.45 ng kg(-1) dw. The MBP levels in the CENTR sediments were two times higher than those in the GLAC and TRANS sediments, and the yield of phosphine (PH3) as a fraction of total phosphorus ranged from 1.78×10(-8) to 3.53×10(-8) mg PH3 mg(-1)P. The CENTR and TRANS sediments showed higher concentrations of total phosphorus (TP), organic phosphorus (OP) and APA than the GLAC sediments, indicating that glacial activity had an important effect on the spatial variability in the concentrations of MBP and phosphorus fractions. There existed a significant positive correlation (p<0.01) between MBP and seawater depths, OP, TP, APA, total organic matter, total nitrogen and total sulfur. The multiple stepwise regression model ([MBP]=16.1[OP]+18.6[APA]-26.1pH+221.3) was obtained between MBP concentrations and environmental variables. This model could be used to predict MBP levels in the sediments. Our results indicated that the production of MBP was associated with OP decomposition and microbially mediated factors in the sediments of Kongsfjorden in Arctic.

[Distribution of matrix-bound phosphine in surface sediments of Jinpu Bay].

This work investigated the distribution of matrix-bound phosphine in surface sediments of Jinpu Bay and associated environmental factors in summer, using the gas chromatography combined with a pulsed flame detector (GC-PFPD). It showed that phosphine ubiquitously presented in the sediments of Jinpu Bay. Contents of matrix-bound phosphine varied between 62. 58 and 190. 81 ng.kg-1, with the average value of 114.42 ng.kg-1. In addition, the spatial distribution of matrix-bound phosphine indicated that matrix-bound phosphine in inshore sediments had relatively higher contents than those in offshore sediments. Statistical analysis showed that matrix-bound phosphine significantly related to organic phosphorus and alkaline phosphatase activity ( R = 0. 882, P = 0. 01; R = 0. 819, P =0. 023). However, there were no correlations between matrix-bound phosphine and organic nitrogen, inorganic phosphorus and sediment grain sizes. These results implied that accumulation and distribution of matrix-bound phosphined were mainly affected by the decomposition of organic phosphorus by microorganisms.

Phosphine in paddy fields and the effects of environmental factors.

Ambient levels of phosphine (PH3) in the air, phosphine emission fluxes from paddy fields and rice plants, and the distribution of matrix-bound phosphine (MBP) in paddy soils were investigated throughout the growing stages of rice. The relationships between MBP and environmental factors were analyzed to identify the principal factors determining the distribution of MBP. The phosphine ambient levels ranged from 2.368±0.6060 ng m(-3) to 24.83±6.529 ng m(-3) and averaged 14.25±4.547 ng m(-3). The highest phosphine emission flux was 22.54±3.897 ng (m(2)h)(-1), the lowest flux was 7.64±4.83 ng (m(2)h)(-1), and the average flux was 14.17±4.977 ng (m(2)h)(-1). Rice plants transport a significant portion of the phosphine emitted from the paddy fields. The highest contribution rate of rice plants to the phosphine emission fluxes reached 73.73% and the average contribution was 43.00%. The average MBP content of 111.6 ng kg(-1)fluctuated significantly in different stages of rice growth and initially increased then decreased with increasing depth. The peak MBP content in each growth stage occurred approximately 10 cm under the surface of paddy soils. Pearson correlation analyses and stepwise multiple regression analysis showed that soil temperature (Ts), acid phosphatase (ACP) and total phosphorus (TP) were the principal environmental factors, with correlative rankings of Ts>ACP>TP.

Matrix-bound phosphine and phosphorus fractions in paddy soils.

Phosphine (PH(3)) is a natural gaseous carrier of phosphorus (P) in its geochemical cycles, and it might be important to the P balance of natural ecosystems. Paddy fields are thought to be one of the main sources responsible for the production and emission of PH(3) in to the environment. The relationships between matrix-bound PH(3) (MBP) and different P fractions, as well as selected metals were investigated to explore the possible production of MBP and its link to P cycle in the paddy soils. MBP range from 20.8 (-1) to 502 ng kg(-1) with an average of 145 ng kg(-1). Concentrations at the milk stage are significantly higher than at the jointing stage. The total P range from 333 mg kg(-1) to 592 mg kg(-1). Average P fractions decrease in the order: Ca-P (69.9%) > Organic P (16.5%) > occluded P (6.50%) > Fe-P (5.93%) > dissolved P (0.80%) > exchangeable P (0.32%) > Al-P (0.02%). Different levels of nitrogen fertilizer have little effect on the contents of MBP, P fractions and metals. A significant positive correlation between MBP and Ca-P (p = 0.002), as well as between MBP and Ca (p = 0.008) could be observed, suggesting that Ca-P mainly affects the production of MBP in the paddy soils. It is suggested that soil MBP is strongly linked to Ca-P fertilizer use because soil spiked with P-fertilizer produced an additional 758 ± 142 ng of MBP per kg of soil, compared to only 81.7 ± 12.3 ng of MBP per kg of unspiked soil. No correlations are found between MBP and other P fractions, or between MBP and Al, Fe and Mn.

Influences of sediment dessication on phosphorus transformations in an intertidal marsh: formation and release of phosphine.

This study investigated the effects of sediment dewatering on the phosphorus transformations concerning about the production and emission of phosphine in the intertidal marsh of the Yangtze Estuary. The concentrations of matrix-bound phosphine ranged from 18.62-72.53 ng kg(-1) and 31.14-61.22 ng kg(-1) within the August and January exposure incubations, respectively. The responses of matrix-bound phosphine concentrations to sediment dessication demonstrate that the production (or accumulation) of matrix-bound phosphine significantly increased with water loss at the start of the emersion incubations. However, further dehydration inhibited the formation of matrix-bound phosphine in sediments. The significant correlations of matrix-bound phosphine with the organic-P bacteria abundance and alkaline phosphatase activities implicate that the production of matrix-bound phosphine within the dessication incubations was linked closely to the microbial decomposition of organic P. The emissions of phosphine generally decreased with sediment dewatering, with the fluxes of 7.51-96.73 ng m(-2)h(-1) and 5.34-77.74 ng m(-2)h(-1) over the exposure incubations of both August and January, respectively. Also, it is observed that the releases of phosphine during the entire exposure periods were affected not only by its production but also by sediment water and redox conditions.

Phosphorus fractions and matrix-bound phosphine in coastal surface sediments of the Southwest Yellow Sea.

This paper characterizes the distribution of phosphorus fractions and matrix-bound phosphine (MBP) in coastal surface sediments of the Southwest Yellow Sea from 2006 to 2007. Total phosphorus (TP), inorganic phosphorus (IP) and organic phosphorus (OP) concentrations (mg kg(-1)) range from 278 +/- 3 to 768 +/- 15, 160 +/- 1 to 653 +/- 27, and 3.42+/- 0.05 to 267 +/- 22, respectively. MBP is a small portion of TP with values of 0.69 +/- 0.06 to 179 +/- 29 ng kg(-1). Phosphorus fractions and MBP are influenced strongly by riverine input and hydrodynamic conditions. High TP and MBP are found in the old Yellow River mouth and the Yangtze River mouth. OP and MBP are strongly negatively correlated to mean particle size. Significant positive correlations are found between MBP and IP and OM, suggesting that MBP production may be the microbially intermediated transformation of IP.

A simple molecule with a complex crystal structure: interplay of 31P solid-state NMR spectroscopy and single-crystal x-ray diffraction in the structure determination of a ruthenium diphosphine diamine complex.

A comprehensive 31P solid-state NMR study of Ru(eta1-Ph2PCH2CH2OCH3)2(eta2-en)Cl2 (en = ethylenediamine) (1), by 1D (contact time variation, inversion-recovery, SPARTAN) and 2D techniques (homonuclear J-resolved, SECSY) indicated that the crystal structure of 1 should be complex. The single-crystal x-ray structure determination confirmed the presence of eight independent molecules in the asymmetric unit, with 31P isotropic chemical shifts in the range 27.3-40.1 ppm, while the spans of the phosphorus chemical shift tensors are of the order of 170 ppm. Based on unique structural features and NMR data, one molecule has been tentatively assigned.

[Determination of phosphine liberated in the storage of amorphous red phosphorus by headspace gas chromatography].

Formation and liberation of phosphine has been an important factor and concern in the safety of the storage of amorphous red phosphorous. A method was established for the analysis of phosphine, which was determined by gas chromatography with a flame photometric detector and a column of 3 mm i. d. x 2 m glass tube packed with GDX-102 stationary phase. An aliquot of 0.2 mL of the gas was injected by headspace sampler for the determination of the target compound with external standard quantitation. The retention time of phosphine was 1.62 min at 50 degrees C. The minimum detectable amount was 0.001 microg/L, the recovery exceeded 97% and the relative standard deviations were from 2.35% to 6.52%. The accelerated ageing tests at 50 degrees C were used to study phosphine liberation from amorphous red phosphorus in presence of trace water and trace ferric cation. It was found that water was the most important agent in the generation of phosphine as it was the source of hydrogen for the reaction P --> PH3. With the increase of the moisture level in the red phosphorus sample, the reaction speeded up more quickly, and the generation amount of phosphine increased, but the phosphine liberation increased little when the level of moisture reached a certain limit. The reaction was affected by a trace amount of ferric salt. Different acidic ferric salts showed different results. Potassium ferrocyanide was found as an effective inhibitor to slow down phosphine liberation in the presence of trace ferric salt.

Fatal aluminum phosphide poisoning.

A 39-year-old man committed suicide by ingestion of aluminum phosphide, a potent mole pesticide, which was available at the victim's workplace. The judicial authority ordered an autopsy, which ruled out any other cause of death. The victim was discovered 10 days after the ingestion of the pesticide. When aluminum phosphide comes into contact with humidity, it releases large quantities of hydrogen phosphine (PH3), a very toxic gas. Macroscopic examination during the autopsy revealed a very important asphyxia syndrome with major visceral congestion. Blood, urine, liver, kidney, adrenal, and heart samples were analyzed. Phosphine gas was absent in the blood and urine but present in the brain (94 mL/g), the liver (24 mL/g), and the kidneys (41 mL/g). High levels of phosphorus were found in the blood (76.3 mg/L) and liver (8.22 mg/g). Aluminum concentrations were very high in the blood (1.54 mg/L), brain (36 microg/g), and liver (75 microg/g) compared to the usual published values. Microscopic examination revealed congestion of all the organs studied and obvious asphyxia lesions in the pulmonary parenchyma. All these results confirmed a diagnosis of poisoning by aluminum phosphide. This report points out that this type of poisoning is rare and that hydrogen phosphine is very toxic. The phosphorus and aluminum concentrations observed and their distribution in the different viscera are discussed in relation to data in the literature.

Laboratory simulations of PH3 photolysis in the atmospheres of Jupiter and Saturn.

Photolysis of NH3-PH3 mixtures (11 Torr) at 175 degrees K resulted in the same initial rate of P2H4 formation as when the 11 Torr of pure PH3 was photolyzed. A higher yield of P2H4 is obtained at 175 degrees K than at 298 degrees K because some of the P2H4 condenses on the cell wall at 175 degrees K and is not subject to further reaction. Some reaction of P2H4 is taking place as observed by the decrease in its yield and on the formation of red phosphorus on extended photolysis of PH3 at 175 degrees K. No NH2PH2 or (PN)x were detected as photoproducts as indicated by the absence of change in the UV spectral properties of the P2H4 and red phosphorus fraction, respectively, when HN3 is present. Although the pathway for PH3 decomposition is changed, the outcome of the photochemical process is essentially the same in the absence or presence of NH3. The formation of P2H4 and red phosphorus was not inhibited by small amounts of C2H4 and C2H2, so the low levels of hydrocarbons on Jupiter and Saturn will not have a significant effect on the course of PH3 photolysis. The ratio of products of PH3 photolysis are only slightly affected by the wavelength of light used. Use of a xenon lamp, with a continuous emission in the ultraviolet where P2H4 absorbs, results in only a modest decrease in the yield of P2H4 and a modest increase in the rate of formation of red phosphorus as compared to the rates observed with a 206.2-nm light source. The quantum yield for P2H4 formation is pressure independent in the 0.5-11 Torr range. This quantum yield is not affected by lowering the temperature to 157 degrees K or by the addition of 100 Torr of H2. It is concluded that photolysis of PH3 to P2H4 and the subsequent conversion of P2H4 to red phosphorus are likely processes on Jupiter and Saturn and that particles of P2H4 condense in the atmospheres of these planets. The conversion of some of the P2H4 to red phosphorus may take place on Jupiter.