•No direct photolysis of phosphite occurred in water under natural sunlight.•Indirect photolysis played an important role in the phototransformation.•Suspended solids in THW played important roles in the phototransformation.•Inorganic or organic substances in water changed the phosphite photoreaction.•The phototransformation product of phosphite is phosphate.The phototransformation of phosphite (HPO32−, H2PO3−, +3) from Lake Taihu water (THW) under natural sunlight was evaluated. No direct phosphite photoreaction was observed under sunlight. Suspended solids were shown to play important roles in the indirect photoreaction of phosphite in lake water. The phototransformation of phosphite followed pseudo-first-order reaction kinetics and the kinetics constants (k, d−1) decreased as: 0.0324 (original THW), 0.0236 (sterilized THW), 0.0109 (filtered THW) and 0.0102 (sterilized filtered THW). Original THW with 1 mmol L−1 NO3− added was used to simulate the phosphite removal in lakes with serious N pollution. The results showed that the phototransformation was accelerated (with k increased to 0.0386–0.0463 d−1), and sterilization or filtration shown little effect to the transformation, as the half-lives of phosphite drew closer. Under simulated irradiation in NO3− system, increasing NO3− concentration or decreasing pH value promoted phototransformation. The addition of Fe3+ or Fe2+ accelerated photooxidation, while the addition of Mn2+ or Cd2+ inhibited phototransformation. Br−, NO2− and HCO3− in environmental concentrations decreased phototransformation, and HCO3− showed the strongest inhibition. Suwannee River humic acid or Suwannee River fulvic acid strongly inhibited the photooxidation process, and the inhibiting effects varied with their structure. Phosphite photooxidation was strongly inhibited by adding isopropanol or sodium azide as reactive oxygen species (ROS) quenchers. Electron spin resonance analysis indicated that OH was a main oxidant produced in this system. The increased amount of phosphate coincided with the decreased amount of phosphite, which indicated that the transformation product of phosphite was phosphate. Phosphite is a considerable component of the P redox cycle in Lake Taihu.Download high-res image (117KB)Download full-size image

Phosphite (HPO32−, +3), a reduced P species in the P biogeochemical cycle, was monitored in a full-scale municipal wastewater treatment plant (MWTP) that uses an anaerobic/anoxic/aerobic-membrane bioreactor (A2/O-MBR) technology for treating mixed wastewater (56% industrial wastewater and 44% domestic wastewater) from June 2013 to May 2014. Wastewater samples were collected from influent after having gone through the fine grille, anaerobic tank, anoxic tank, and aerobics tank, respectively. The final stage yielded effluent. Results confirmed the presence of phosphite in the MWTP ranging from 4.62 ± 1.00 μg P L−1 to 34.30 ± 3.49 μg P L−1 in influent and from 1.15 ± 0.5 μg P L−1 to 4.42 ± 0.9 μg P L−1 in effluent. Phosphite accounted for approximately 0.15% to 2.27% of total soluble phosphorus (TSP). During the A2/O-MBR process, the average removal of phosphite was 82.41 ± 7.45%. The anaerobic biological treatment removed the most phosphite from wastewater in this study. Spatially, phosphite concentrations decreased gradually as the wastewater treatment process progressed. Seasonally, the phosphite concentrations in spring and winter were higher than those in summer and autumn. The phosphite concentration in effluent was of the same order of magnitude as that in nearby natural water, which suggested MWTP effluent may be an important phosphite contributor to the natural water.

To understand the transport and fate of antibiotic resistance genes in wastewater treatment plants, 12 resistance genes (ten tetracycline resistance genes, two sulfonamides genes) and class 1 integron gene (intI1) were studied in five wastewater treatment plants with different treatment processes and different sewage sources. Among these resistance genes, sulfonamides genes (sul1 and sul2) were of the most prevalent genes with detection frequency of 100 %. The effluent water contained fewer types of resistance genes than the influent in most selected plants. The abundance of five quantified resistance genes (tetG, tetW, tetX, sul1, and intI1) decreased in effluent of plants treating domestic or industrial wastewater with anaerobic/aerobic or membrane bioreactor (MBR) technologies, but tetG, tetX, sul1, and intI1 increased along the treatment units of plants treating vitamin C production wastewater by anaerobic/aerobic technology. In plant treating cephalosporins production wastewater by UASB/aerobic process, the quantities of tetG, tetX, and sul1 first decreased in anaerobic effluent water but then increased in aerobic effluent water.

The seasonal occurrence and distribution of phosphite (HPO32-, P) in sedimentary interstitial water from Lake Taihu was monitored from 2011 to 2012 to better understand its possible link to P cycle in the eutrophic shallow lake. Phosphite concentrations ranged from < MDL to 14.32 ± 0.19 μg P/kg with a mean concentration of 1.58 ± 0.33 μg P/kg, which accounts for 5.51% total soluble P (TSPs) in surficial sediments (0–20 cm). Spatially, the concentrations of sedimentary phosphite in the lake’s northern areas were relatively higher than those in the southern areas. Higher phosphite concentrations were always observed in seriously polluted sites. Generally, phosphite in the deeper layers (20–40 cm and 40–60 cm) showed minor fluctuations compared to that in the surficial sediments, which may be associated with the frequent exchange at the sediment–water interface. Phosphite concentrations in surficial or core sediments decreased as spring > autumn > summer > winter. Higher phosphite levels occurred in the areas with lower redox (Eh), higher P contents, and particularly when metal bonded with P to form Al–Ps and Ca–Ps. Phosphite may be an important media in the P biogeochemical cycle in Lake Taihu and contribute to its internal P transportation.

Phosphite, phosphate, glyphosate and aminomethylphosphonic acid (AMPA) in natural water were determined by two-dimensional ion chromatography system coupled with capillary ion chromatography (2D-CIC). After filtrated by a 0.22-μm filter membrane, 25 μL of samples was injected into the first dimensional analytical column (AS11-HC) for preliminary separation. According to the different retention times in the first dimension, the target ions were divided into two groups (one group was phosphite and phosphate, another group was glyphosate and AMPA), then switched to the second dimensional capillary column (MAX-100) for further separation and detection. The effluent flow rates were 0.38 mL min−1 in the first dimension and 0.01 mL min−1 in the second dimension with KOH gradient elution, respectively. The carbonate removal devices were employed. The external standard method was used in all instances to quantitatively analyze. The results showed that the detection limits (S/N = 3) were 0.18 nM for phosphite, 0.073 nM for phosphate, 0.15 nM for glyphosate and 2.6 nM for AMPA. The relative standard deviations (RSD, n = 6) of peak area ranged from 2.7% to 4.6%. The recoveries ranged from 80.1% to 118.4%. The results demonstrated that coupled capillary system could afford the simple detection of trace materials in natural water with complex matrix.

The establishment of a sensitive and specific method for the detection of reduced phosphorus (P) is crucial for understanding P cycle. This paper presents the quantitative evidence of phosphite (P, +3) from the freshwater matrix correspondent to the typically eutrophic Lake Taihu in China. By ion chromatography coupled with gradient elution procedure, efficient separation of micromolar levels of phosphite is possible in the presence of millimolar levels of interfering ions, such as chloride, sulfate, and hydrogen carbonate in freshwater lakes. Optimal suppressed ion chromatography conditions include the use of 500 μL injection volumes and an AS11 HC analytical column heated to 30 °C. The method detection limit of 0.002 μM for phosphite was successfully applied for phosphite determination in natural water samples with recoveries ranging from 90.7 ± 3.2% to 108 ± 1.5%. Phosphite in the freshwater matrix was also verified using a two-dimensional capillary ion chromatography and ion chromatography coupled with mass spectrometry. Results confirmed the presence of phosphite in Lake Taihu ranging from 0.01 ± 0.01 to 0.17 ± 0.01 μM, which correlated to 1–10% of the phosphate. Phosphite is an important component of P and may influence biogeochemical P cycle in lakes.

Phosphine (PH3) 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 PH3 in to the environment. The relationships between matrix-bound PH3 (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.

Phosphine is a natural gaseous compound in the phosphorus biogeochemical cycle. This paper studies the spatial and temporal distributions of matrix-bound phosphine (MBP) and gaseous phosphine in the offshore area of the Southwest Yellow Sea, East Asia. The results show that MBP concentrations in marine surface sediments range from 0.69 ± 0.06 ng/kg (dry) to 179 ± 29 ng/kg (dry). Higher seasonal MBP concentrations in sediments are found in fall than in spring or winter in most sites. High MBP contents are observed in two fish-breeding areas. MBP concentrations decrease with distance to the coast, except in the southeast of the sampling area. MBP levels in marine sediments are found to be higher than those at several other places: freshwater sediments and soil, except eutrophic lakes. Gaseous phosphine contents in fall range from 0.14 ± 0.00 ng/m3 to 9.83 ± 0.97 ng/m3. No correlation is observed between MBP and gaseous phosphine.

Phosphine (PH3) 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 PH3 in to the environment. The relationships between matrix-bound PH3 (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.