Prognosis and factors related to severe secondary hyperparathyroidism in long-term peritoneal dialysis patients.

Secondary hyperparathyroidism (SHPT) can progress to severe SHPT (sSHPT), which affects the survival rate and quality of life of patients. This retrospective cohort study investigated risk factors for sSHPT and the association between SHPT and mortality (all-cause and infection-related) among 771 clinically stable patients (421 male patients; mean age, 51.2 years; median dialysis vintage, 28.3 months) who underwent >3 months of regular peritoneal dialysis (PD) between January 2013 and March 2021. The sSHPT and non-sSHPT groups comprised 75 (9.7%) (median progression, 35 months) and 696 patients, respectively. sSHPT was defined as a serum intact parathyroid hormone (PTH) level >800 pg/mL observed three times after active vitamin D pulse therapy. The influence of sSHPT on the prognosis of and risk factors for sSHPT progression were evaluated using logistic and Cox regression analyses. After adjusting for confounding factors, higher (each 100-pg/mL increase) baseline PTH levels (95% confidence interval (CI) 1.206-1.649, p < .001), longer (each 1-year increase) dialysis vintages (95% CI 1.013-1.060, p = .002), higher concomitant diabetes rates (95% CI 1.375-10.374, p = .010), and lower (each 1-absolute unit decrease) Kt/V values (95% CI 0.859-0.984, p = .015) were independent risk factors for progression to sSHPT in patients on PD. During follow-up, 211 deaths occurred (sSHPT group, n = 35; non-sSHPT group, n = 176). The sSHPT group had significantly higher infection-related mortality rates than the non-sSHPT group (12.0% vs. 4.3%; p < .05), and sSHPT was associated with increased infection-related mortality. In conclusion, patients with sSHPT are at higher risk for death and infection-related mortality than patients without sSHPT.

Insights into the weathering behavior of pyrite in alkaline soil through electrochemical characterizations: Actual hazards or potentially benefits?

Pyrite is the most common metal sulfide mineral in the crust and readily weathers under natural circumstances to release H+ to acidify surrounding groundwater and soil, resulting in heavy metal ions in the surrounding environment (e.g., meadow and saline soils). Meadow and saline soils are two common, widely distributed alkaline soils and can affect pyrite weathering. Currently, the weathering behaviors of pyrite in saline and meadow soil solutions have not been systematically studied. Electrochemistry coupled with surface analysis methods were employed to study pyrite weathering behaviors in simulated saline and meadow soil solutions in this work. Experimental results suggest that saline soil and higher temperatures increase pyrite weathering rates due to the lower resistance and greater capacitance. Surface reactions and diffusion control the weathering kinetics, and the activation energies for the simulated meadow and saline soil solutions are 27.1 and 15.8 kJ mol-1, respectively. In-depth investigations reveal that pyrite is initially oxidized to Fe(OH)3 and S0, and Fe(OH)3 further transforms into goethite γ-FeOOH and hematite α-Fe2O3, while S0 ultimately converts into sulfate. When these iron compounds enter alkaline soils, the alkalinity of soil changes, and iron (hydr)oxides effectively reduce the bioavailability of heavy metals and benefit alkaline soils. Meanwhile, weathering of natural pyrite ores containing toxic elements (such as Cr, As, and Cd) makes these elements bioavailable and potentially degrades the surrounding environment.

The Supplement of Magnesium Element to Inhibit Colorectal Tumor Cells.

Magnesium ions are essential elements to the human body, with a daily intake of about 350 mg for an adult. Recently, a meta-analysis reported that magnesium ion intake is related to a reduced risk of colorectal tumors. In addition, implantation of biodegradable magnesium pins after colorectal tumor resection could potentially inhibit the residual tumor cells. These impressive results implied that magnesium ions possess inhibitory properties against colorectal carcinoma. However, this hypothesis has yet to be confirmed by experimental results. In this work, different concentrations of magnesium ions were modulated to investigate their inhibitory effects on cell viability through cell cycle arrest, subsequently inducing apoptosis by activating the caspase-3 pathway. The animal experiments revealed that magnesium injection restricted tumor growth after 3 weeks of treatment compared to the control group. According to the immunohistochemistry and transmission electron microscopy results, the remarkable effect may be attributed to promoting the apoptotic rate of tumor cells. The evidence highlights the potential for the clinical use of magnesium implants to inhibit the growth of residual cells after colorectal tumor surgery.

Wood-Based Self-Supporting Nanoporous Three-Dimensional Electrode for High-Efficiency Battery Deionization.

Developing highly efficient advanced battery deionization (BDI) electrode materials at a low cost is vital for seawater desalination. Herein, a high-efficiency wood-based BDI electrode has been fabricated for seawater desalination, benefiting from the self-supporting three-dimensional (3D) nanoporous structure and rich redox-active sites. The finely tuned rich electrochemical redox active C═O groups on the surface of the wood electrode derived from the facile thermochemical conversion of lignin play a crucial role in the Faradaic cation removal dynamics of BDI. Coupling the 3D wood electrode and a polyaniline-modified wood electrode as the cathode and anode, an all-wood-electrode-based deionization battery has been successfully assembled with a state-of-the-art ion removal capacity of up to 164 mg g-1 in seawater. Our work reported an example of utilizing wood as the BDI electrode via fine-tuning the redox-active sites, demonstrating a novel resource utilization pathway of converting cheap biomass into BDI electrodes for highly efficient seawater desalination.

Arsenopyrite weathering in acid rain: Arsenic transfer and environmental implications.

Arsenopyrite is widely distributed and weathers readily in the nature, releases As and pollutes the surrounding environment. Acid rain is acidic in nature as contains sulfur oxides (SOx) and nitrogen oxides (NOx), and is a typical hazardous material to human. When arsenopyrite encounters acid rain, their interaction effect may aggregate environmental degradation. In this work, the weathering behavior of arsenopyrite in simulated acid rain was studied using the electrochemical techniques and surface analysis. Cyclic voltammetry and Raman and XPS confirmed that FeAsS was oxidized to Fe2+, AsO33- and S0 at the initial phase, then, Fe2+ was converted to Fe3+, S0 transformed to SO32- and ultimately to SO42-, and AsO33- to AsO43- with the accumulation of H+. Polarization curve revealed higher temperature or higher acidity of acid rain increased the weathering trend and rate of arsenopyrite, and electrochemical impedance spectroscopic measurements showed the causes behind this to be smaller resistance and greater capacitance at the double layer and passivation film. Arsenopyrite weathering rate and temperature has a relationship: lnk = -3824.8/T + 10.305, via a transition state with activation enthalpy 29.37 kJ mol-1 and activation entropy - 167.40 J mol-1 K-1. This study provides a rapid and quantitative in-situ electrochemical method for arsenopyrite weathering and an improved understanding of arsenopyrite weathering in acid rain condition. The results have powerful implications for the remediation and management of As-bearing sites affected by mining activities in acid rain area.

Arsenopyrite weathering in acidic water: Humic acid affection and arsenic transformation.

Arsenopyrite is a common metal sulfide mineral and weathers readily in the open environment, releases As, and pollutes the surrounding environment. Humic acid (HA) is ubiquitous in soils, sediments and waters, and contains various functional groups and complex with arsenic, iron and other metal ions that affect the weathering behavior of arsenopyrite. Because As, iron, and HA are redox-active compounds, electrochemical techniques, including polarization curves, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV), were used to fundamentally investigate the weathering process and mechanism of arsenopyrite over a wide range of environmental relevant conditions. Polarization curves showed higher HA concentrations (0-1000 mg•L-1), higher temperatures (5-35°C) or acidities (pH 1.0-7.0) promoted arsenopyrite weathering; there was a linear relationship between the corrosion current density (icorr), temperature (T) and acidity (pH): icorr = -3691.2/T + 13.942 and icorr = -0.2445pH + 2.2125, respectively. Arsenopyrite weathering readily occurred in the presence of HA as confirmed by its activation energy of 24.1 kJ•mol-1, and EIS measurements confirmed that the kinetics were controlled by surface reaction as confirmed by decreased double layer resistance. CV and surface characterization (FTIR and XPS) showed that arsenopyrite initially oxidized to S0, As(III) and Fe2+, then S0 and Fe2+ were ultimately converted into SO42- and Fe3+, while As(III) oxidized to As(V). Furthermore, the carboxyl (-COOH) and phenolic (-OH) of HA could bind with As(III)/(V) and Fe3+ via a ligand exchange mechanism forming As(III)/(V)-HA and As(III)/(V)-Fe-HA complexes that hinders the formation of FeAsO4 and decreases the bioavailability of As. Findings gained from this study are valuable for the understanding of the fate and transport of As in acidic conditions, and have powerful implications for the remediation and management of As-bearing sites affected by mining activities.

Lanthanum molybdate/magnetite for selective phosphate removal from wastewater: characterization, performance, and sorption mechanisms.

Lanthanum molybdate/magnetite (M-La2(MoO4)3) with various LaCl3/Fe3O4 mass ratios was synthesized and optimized for selective phosphate removal from wastewater. M-La2(MoO4)3 (2:1) was selected on the basis of phosphate sorption capacity for further experiments and characterized by a variety of methods. The phosphate sorption kinetics, isotherms, and matrix effect were studied. The maximum sorption capacity at initial pH 7 indicates the possible applicability M-La2(MoO4)3 (2:1) in removing phosphate from the aquatic environment. Phosphate removal by M-La2(MoO4)3 (2:1) with high selectivity was achieved in the presence of other co-existing anions, while calcium and magnesium ions were found to inhibit the sorption process. The sorption isotherm study showed that Freundlich and Sips models fit better the Langmuir model, indicating that heterogeneous multilayer sorption was dominant during the phosphate sorption process. Sorption kinetic results showed that the pseudo-first-order kinetic model can describe well the phosphate sorption process by M-La2(MoO4)3 (2:1). Consecutive sorption-desorption runs showed that M-La2(MoO4)3 (2:1) could be reused for a few cycles. Simultaneous removal of phosphate and organic matter was achieved in real wastewater by using M-La2(MoO4)3 (2:1). The sorption mechanism was inner-sphere complexation.

Galena weathering in simulated alkaline soil: Lead transformation and environmental implications.

Alkaline soils are widely distributed around the world. During the mining and transportation processes galena may be exposed to the alkaline soils. Weathering of galena may lead to the formation of different lead phases having higher bio-accessibility than galena, and thereby increasing the mobility and toxicity of lead. In this study, electrochemical techniques and Raman spectroscopic measurements were used for the evaluation of the interfacial processes that are involved in the galena weathering under the conditions of simulated saline soil and meadow soil solutions. The results showed that the release of Pb2+ and S0 took place during initial stage of the oxidation. Thereafter, further transformation to anglesite would take place, even leading to the transformation to ß-PbO and α-PbO at higher temperatures. Galena weathering prone to saline soil than that in meadow soil, and has a faster weathering rate in the saline soil at same ambient temperature. Higher temperatures was found to promote the weathering of galena, and the rate constant for the release of Pb (II) was approximate 10-9 to 10-8 mol∙m-2∙s-1, while surface reaction was found to control the weathering kinetics. Based on the surface characterization and evaluation of the thermodynamic and kinetic parameters, the weathering mechanism of galena in the alkaline soil and its environmental implications was suggested.

A novel hydrogel for highly efficient adsorption of Cu(II): synthesis, characterization, and mechanisms.

Among the Cu(II) removal methods, adsorption is a favorable technique and has attracted large attention because of its effectiveness and low cost. In quest of seeking for a favorable adsorbent with a high Cu(II) adsorption capacity and excellent reusability, researchers have paid much attention to hydrogels with three-dimensional networks. In this study, a novel hydrogel (P(AMPS-co-VDT) hydrogel) based on free-radical polymerization was synthesized with ionic monomer sodium 2-acrylamido-2-methylpropane sulfate (AMPS-Na+) and 2-vinyl-4, 6-diamino-1, 3, 5-triazine (VDT) and applied for Cu(II) adsorption in aqueous solutions. The hydrogel was characterized for swelling performance, surface morphology, functional groups, thermal gravimetric behavior, and elements. The maximum Cu(II) adsorption capacity (175.75 mg/g) was relatively high compared with other hydrogels. The P(AMPS-co-VDT) hydrogel also was found to have a relatively good Cu(II) desorption and reuse behavior. The adsorption mechanism could be chelation and ion exchange. This work provides a new hydrogel for effective Cu(II) removal in the future.

Arsenopyrite weathering in sodium chloride solution: Arsenic geochemical evolution and environmental effects.

In situ electrochemical techniques and surface analysis were used to investigate the weathering behavior of arsenopyrite in chlorine-containing brine. Cyclic voltammetry measurements showed that arsenopyrite weathering releases S°, As (III) and Fe (II) during the initial step, even contains different concentrations of H+ and Cl-, and terminal transformation into SO42-, As (V) and Fe (III), respectively. Cl- ions promote the arsenopyrite weathering through diffusion control or adsorption control when Cl- ions are at low or high concentrations. When Ccl- increased from 0.00 to 0.05 mol/L, As (III) release increases from 549.33 to 1135.86 g·m-2·y-1, and the promotion efficiency is 107 %; whereas from 0.20 to 0.40 mol/L, the promotion efficiency is only 15.1 %. H+ ions accelerate arsenopyrite weathering for O2 + 4H+ + 4e- → 2H2O, and the relationship between corrosion current density (icorr) and pH is icorr = -26.54 pH + 199.75. Raman spectra confirm that corrosion produces S° and As (V) and EDX shows the passivation layers are mainly composed of elements Fe, As, S and O, while the adsorption layer are mainly composed of elements Fe, As, S and Cl. The experimental results are of great significance for arsenopyrite geological environment assess and removal of arsenic ions.

Degradation of imipramine by vacuum ultraviolet (VUV) system: Influencing parameters, mechanisms, and variation of acute toxicity.

Degradation of imipramine (IMI) in the VUV system (VUV185 + UV254) was firstly evaluated in this study. Both HO• oxidation and UV254 direct photolysis accounted for IMI degradation. The quantum yields of UV254 direct photolysis of deprotonated and protonated IMI were 1.31×10-2 and 3.31×10-3, respectively, resulting in the higher degradation efficiency of IMI at basic condition. Increasing the initial IMI concentration lowered the degradation efficiency of IMI. While elevating reaction temperature significantly improved IMI degradation efficiency through the promotion of both the quantum yields of HO• and the UV254 direct photolysis rate. The apparent activation energy was calculated to be about 26.6 kJ mol-1. Negative-linear relationships between the kobs of IMI degradation and the concentrations of HCO3-/CO32-, NOM and Cl- were obtained. The degradation pathways were proposed that cleavage of side chain and hydroxylation of iminodibenzyl and methyl groups were considered as the initial steps for IMI degradation in the VUV system. Although some high toxic intermediate products would be produced, they can be further transformed to other lower toxic products. The good degradation efficiency of IMI under realistic water matrices further suggests that the VUV system would be a good method to degrade IMI in aquatic environment.

Comparative adsorption of emerging contaminants in water by functional designed magnetic poly(N-isopropylacrylamide)/chitosan hydrogels.

The magnetic poly(N-isopropylacrylamide)/chitosan hydrogel with interpenetrating network (IPN) structure was designed based on the functional groups of targeted emerging contaminants, represented by hydrophilic sulfamethoxazole (SMZ) and hydrophobic bisphenol A (BPA). The average particle size, specific surface area, and total pore volume of the hydrogel were turned out to be 103.7 µm, 60.70 m2/g and 0.0672 cm3/g, respectively. Adsorption results indicated that the maximum adsorption capacity occurred at the pH where SMZ was anionic and BPA was uncharged. When the adsorption temperature increased from 25 °C to 35 °C, the amount of adsorbed SMZ hardly changed, but that of BPA increased by two times. The adsorption capacity of the binary system (i.e., with both SMZ and BPA) was almost the same as that of the single system, indicating that simultaneous adsorption of SMZ and BPA was achieved. The adsorption equilibrium was reached quickly (within 5 min) for both SMZ and BPA. For adsorption isotherm, the Freundlich model fitted well for SMZ at 25, 35 and 45 °C. However, the adsorption of BPA exhibited the sigmoidally shaped isotherm at 25 °C with the Slips model fitting well, and both the Freundlich isotherm and the Slips isotherm fitted the data well at 35 °C and 45 °C, suggesting that the adsorption force was initially weak but greatly enhanced with an increase in adsorbate concentration or ambient temperature. The main adsorption mechanism was inferred to be electrostatic interactions for SMZ, and hydrophobic interactions as well as hydrogen bonding for BPA. The hydrogel adsorbent maintained favorable adsorption capacity for BPA after five adsorption-desorption cycles. These findings may provide a strategy for designing high performance adsorbents that can remove both hydrophilic and hydrophobic organic contaminants in the aquatic environment.

[Interposed abdominal pulling-pressing cardiopulmonary resuscitation improve the resuscitation effect for patients with cardiac arrest].

OBJECTIVE: To study the impact of interposed abdominal pulling-pressing cardiopulmonary resuscitation (IAPP-CPR) for patients with cardiac arrest (CA). METHODS: A prospective study was conducted. A total of 122 CA patients admitted to Department of Emergency of Shandong Provincial Mining Industry Group Company Central Hospital from July 2013 to December 2017 were enrolled. They were divided into standard cardiopulmonary resuscitation (S-CPR) group (n = 62) and IAPP-CPR group (n = 60) according to order of admission. The patients in S-CPR group received external cardiac compression, open airway, endotracheal intubation, mechanical ventilation, routine drug rescue, and defibrillation when ventricular fibrillation was found. And the patients in IAPP-CPR group received the IAPP-CPR on the basis of the routine chest compression. During the relaxation period, the patients were subjected to abdominal lifting and compressing with amplitude of 4-5 cm, frequency of 100 times/min, and the time ratio of lifting to compressing was 1:1. The data of demographics and clinical signs of patients were collected. The markers of respiratory and circulatory performance of all patients after CPR were determined. The rates of restoration of spontaneous circulation (ROSC), successful resuscitation, and the prognosis were recorded. With the success of CRP as the dependent variable, the factors with statistical significance showed by univariate analysis were used as the independent variable to carry out two classification Logistic regression analysis for screening the influence factors of CPR success. Receiver operating characteristic (ROC) curve was plotted to analyze the predictive value of various factors on the success of CPR. RESULTS: 122 patients were enrolled in the analysis. Compared with the S-CPR group, heart rate (HR), mean arterial pressure (MAP), arterial partial pressure of oxygen (PaO2), and end-tidal carbon dioxide partial pressure (PETCO2) were significantly increased at 30 minutes after CPR in IAPP-CPR group [HR (bpm): 66.3±11.5 vs. 53.1±12.6, MAP (mmHg, 1 mmHg = 0.133 kPa): 65.4±6.5 vs. 53.2±5.4, PaO2 (mmHg): 77.7±11.8 vs. 61.8±14.3, PETCO2 (mmHg): 45.5±9.6 vs. 31.8±8.2, all P < 0.05], and arterial partial pressure of carbon dioxide (PaCO2) and lactic acid (Lac) were significantly lowered [PaCO2 (mmHg): 46.7±6.2 vs. 57.9±9.5, Lac (mmol/L): 2.1±1.5 vs. 4.4±2.2, both P < 0.05]. The time of CA to ROSC in IAPP-CPR group was significantly shorter than that in S-CPR group (minutes: 6.3±1.8 vs. 11.2±1.4, P < 0.05), the ROSC rate and CPR success rate were significantly higher than those in S-CPR group [ROSC rate: 61.7% (37/60) vs. 43.5% (27/62), CPR success rate: 40.0% (24/60) vs. 21.0% (13/62), both P < 0.05], and 24-hour survival rate and survival and discharge rate of patients were significantly higher than those in the S-CPR group [24-hour survival rate: 46.7% (28/60) vs. 29.0% (18/62), survival and discharge rate: 20.0% (12/60) vs. 11.3% (7/62), both P < 0.05]. Logistic regression analysis showed that PaO2, PaCO2 and PETCO2 were the factors that affect the success of CPR [PaO2: ß= -3.76, odds ratio (OR) = 0.23, 95% confidence interval (95%CI) = 0.12-0.86, P = 0.031; PaCO2: ß= 1.41, OR = 4.09, 95%CI = 1.70-9.82, P = 0.002, PETCO2: ß= 0.78, OR = 2.18, 95%CI = 1.42-3.35, P = 0.000]. ROC curve analysis showed that the above three factors had good predictive value for the success of CPR. The predictive value of PaCO2 and PETCO2 were better, the area under ROC curve (AUC) was 0.93 and 0.92, respectively, when the cut-off values was 46.7 mmHg and 48.8 mmHg, the sensitivity was 92.0%, 88.0%, respectively, and the specificity was both 94.3%. CONCLUSIONS: PaO2, PaCO2 and PETCO2 are the factors that influence the success of CPR. PaCO2 and PETCO2 have great value in predicting the success of CPR. Compared with the S-CPR group, IAPP-CPR group results in better hemodynamic and pulmonary ventilation effects, and remarkably improve ROSC and successful resuscitation. IAPP-CPR has obvious clinical value for CA patients.

The activated iron system for phosphorus recovery in aqueous environments.

Finding a good sorbent for phosphorus (P) recovery from the aquatic environment is critical for preventing eutrophication and providing P resources. The activated iron system (mainly consisted of zero-valent iron (ZVI), Fe3O4 and Fe2+) has been reported to exhibit a favorable performance towards various contaminants in wastewater, but its effect on P recovery has not been studied systematically. In this study, we used Fe2+-nitrate pretreatment reaction to prepare the activated iron system and then applied it to P recovery. Results show that more than 99% P was removed from water in 60 min; co-existing anions (NO3-, Cl- and SO42-) and natural organic matter (NOM) had little effect on P removal. The P removal capacity of activated iron system is very high compared with currently reported sorbents. Externally-supplied Fe2+ plays an important role on P removal in the system. Regeneration study shows that the activated iron system exhibited stable P recovery ability by using 0.1 M NaOH solution. Various methods were applied to characterize the ZVI and iron corrosion, and results conclude that sorption precipitation, and co-precipitation contribute to P removal. This method will be promising and have an application potential in the field for efficient and cost-effective recovery of P with cheap microscale zero valent iron.

Catechin as a new improving agent for a photo-Fenton-like system at near-neutral pH for the removal of inderal.

Photodegradation of inderal in a photo-Fenton like system at near-neutral pH modified with catechin, a natural catecholate siderophore, was investigated under simulated sunlight. The main factors influencing the process, such as Fe(iii)-catechin complexes, pH, and catechin concentration were examined. Photodegradation of inderal was strongly dependent on pH, following the order pH 3.0 < 5.0 < 7.0 < 6.0. Formation of the Fe(iii)-catechin complex resulted in the stabilization of ferric iron and generation of ˙OH under irradiation at near-neutral pH values. The removal of inderal was about 75% under optimal conditions (50 µmol L(-1) Fe(iii) and 200 µmol L(-1) catechin at pH 6.0). The photodegradation products of inderal were identified by LC-ESI-MS and GC-MS, and the photodegradation pathway was proposed. Iron in the Fe(iii)-catechin system was reused by simple addition of catechin to the reaction mixture. Results of this study suggest that the Fe(iii)-catechin complex may be used in the photo-Fenton like process, an advanced approach to the removal of organic pollutants at near-neutral pH.

Photodegradation of hexabromocyclododecane (HBCD) by Fe(III) complexes/H2O 2 under simulated sunlight.

Hexabromocyclododecane (HBCD) is a globally produced brominated flame retardant used primarily as an additive flame retardant in polystyrene and textile products. Photodegradation of HBCD in the presence of Fe(III)-carboxylate complexes/H2O2 was investigated under simulated sunlight. The degradation of HBCD decreased with increasing pH in the Fe(III)-oxalate solutions. In contrast, the optimum pH was 5.0 for the Fe(III)-citrate-catalyzed photodegradation within the range of 3.0 to 7.0. For both Fe(III)-oxalate and Fe(III)-citrate complexes, the increase of carboxylate concentrations facilitated the photodegradation. The photochemical removal of HBCD was related to the photoreactivity and speciation distribution of Fe(III) complexes. The addition of H2O2 markedly accelerated the degradation of HBCD in the presence of Fe(III)-citrate complexes. The quenching experiments showed that ·OH was responsible for the photodegradation of HBCD in the Fe(III)-carboxylate complexes/H2O2 solutions. The results suggest that Fe(III) complexes/H2O2 catalysis is a potential method for the removal of HBCD in the aqueous solutions.

Photodegradation of parabens by Fe(III)-citrate complexes at circumneutral pH: matrix effect and reaction mechanism.

The photodegradation of four parabens including methyl-, ethyl-, propyl-, and butyl-paraben in the presence of Fe(III)-citrate complexes under simulated sunlight was investigated. The degradation of parabens increased with decreasing pH within the range of 5.0-8.0 at the Fe(III)-to-citrate ratio of 10:150 (µM). The addition of low-molecular-weight carboxylic acids showed different effects on the photodegradation of methylparaben. The low-photoreactive carboxylic acids inhibited the photodegradation of methylparaben in the order of formic acid>succinic acid>acetic acid>malonic acid. In contrast, oxalic acid enhanced the photodegradation and exhibited appreciable synergistic effect with Fe(III)-citrate at concentration higher than 500 µM. Up to 99.0% of substrate was degraded after 30 min at pH6.0 in the Fe(III)-citrate-oxalate system. The various fractions of fulvic acid inhibited the photodegradation of methylparaben. The inhibition increased with increasing nominal molecular weight of fractionated fulvic acid. Moreover, the photodegradation of methylparaben was inhibited in natural waters in the order of Liangzi Lake