Degradation Of Chloramphenicol Research Articles

Study on degradation of chloramphenicol by H2O2/PMS double-oxidation system catalyzed by pipe deposits from water networks

The overuse of antibiotics leads to the emergence of resistant bacteria and antibiotic resistance genes in drinking water distribution system, which destroys the balance of the ecosystem, affects water quality and poses a threat to human health. In this study, the pipe deposits from water networks can be used as catalysts for the Fenton-like system. In this paper, H2O2/peroxymonosulfate (PMS) double-oxidation system was constructed. With the assistance of hydroxylamine, the deposits of the actual water networks was used as catalysts to degrade chloramphenicol (CAP). By adding different deposits components into the catalytic oxidation system, it was found that the removal effect of CAP was different when adding different components into the system. Furthermore, the best experimental conditions were obtained by analyzing different influencing factors. Finally, we analyzed the kinetics of catalytic degradation of CAP by actual pipe network deposits, constructed the degradation model and explored the reaction mechanism. The purpose of this study is to effectively use the deposits in the pipeline to remove pollutants and realize resource utilization. The results could provide a new idea for dealing with antibiotic pollution in water body and provide a theoretical basis for the safety of water quality in drinking water distribution system.

New insight into degradation of chloramphenicol using a nanoporous Pd/Co3O4 cathode: characterization and pathways analysis

The growing chloramphenicol (CAP) in wastewater brought a serious threat to the activity of activated sludge and the spread of antibiotics resistance bacteria. In this study, a highly ordered nanoporous Co3O4 layer on Co foil through anodization was prepared as cathode for nitro-group reduction and electrodeposited with Pd particles for dechlorination to reduce CAP completely. After 3 h treatment, almost 100% of CAP was reduced. Co2+ ions in Co3O4 served as catalytic sites for electrons transfer to CAP through a redox circle Co2+–Co3+–Co2+, which triggered nitro-group reduction at first. With the presence of Pd particles, more atomic H* were generated for dechlorination, which increased 22% of reduction efficiency after 3 h treatment. Therefore, a better capacity was achieved by Pd/Co3O4 cathode (K = 0.0245 min−1, K is reaction constant) than by other cathodes such as Fe/Co3O4 (K = 0.0182 min−1), Cu/Co3O4 (K = 0.0164 min−1), and pure Co3O4 (K = 0.0106 min−1). From the proposed reaction pathway, the ultimate product was carbonyl-reduced AM (dechlorinated aromatic amine product of CAP) without antibacterial activity, which demonstrated this cathodic technology was a feasible way for wastewater pre-treatment.

Degradation of chloramphenicol by Ti/PbO2–La anodes and alteration in bacterial community and antibiotics resistance genes

Antibiotics accumulation in the environment has given rise to multi-drug resistant 'superbugs' and antibiotics resistence genes (ARGs). Chloramphenicol (CAP), a kind of widely used antibiotics, was chosen as the model compound to investigate its degradation during electrochemical treatment process. The prepared Ti/PbO2–La electrodes had a denser surface and a more complete PbO2 crystal structure than Ti/PbO2 electrode. The doping of La increased the onset potential and the overpotential, increased the current value of the oxidation peak and the reduction peak, reduced the impedance, and increased the lifetime. The reactions CAP degradation and TOC removal on Ti/PbO2–La electrode was both primary kinetic reactions. CAP degradation rate increased with current density, and TOC obtained the highest removal at current density of 25 mA cm−2. The electrolyte concentration had a small effect in the range of 0.050–0.150 mol L−1. The effects under acidic and neutral conditions were better than under alkaline conditions. CAP was mainly directly oxidized at the electrode surface and indirect oxidation also took place via generated ·OH and SO4·-. 15 intermediates and 2 degradation pathways have been postulated. The entry of CAP and CAP intermediates into the environment caused the alteration in bacterial community and ARGs, while complete degradation products had little effect on them. Redundancy analysis showed that intI1 was the dominant factor affecting ARGs, and Actinobacteria and Patescibacteria were the main factors affecting the abundances of ARGs in the microbial community.

Incineration of the antibiotic chloramphenicol by electro-peroxone using a smart electrolyzer that produces H2O2 through electrolytic O2

The experimental characterization of the electro-peroxone (E-peroxone) process during the elimination of the antibiotic chloramphenicol (CAP) was carried out in a flow plant using a novel flow-through electrolyzer equipped with two anodes and two cathodes in a cascade configuration, anode-cathode-anode-cathode. The H2O2 is formed at the graphite felt cathodes by reducing O2 provided from the oxygen evolution reaction (OER) performed at the Ti|IrO2-Ta2O5 anodes. This electrolyzer avoids employing an air compressor to supply the O2 for the electrosynthesis of H2O2 during the E-peroxone process. The characterization of E-peroxone was performed by using 2 L of a solution containing 0.05 M Na2SO4 at concentrations of CAP from 20 to 50 mg L−1 TOC (48.9–122.3 mg L−1 CAP), studying the influence of pH (3–9), applied current density (5 ≤ j ≤ 15 mA cm−2), and solution flow rate (0.4 ≤ Q ≤ 1.0 L min−1) on the oxidation of CAP. The best performance reached 100% CAP degradation, 63% TOC removal, at pH 3, j = 10 mA cm−2, Q = 0.4 L min−1 and FO3=17.5 mg min−1. The mineralization current efficiency (MCE) and electrolytic energy consumption (EC) were 19% and 0.202 kWh (g TOC)−1, respectively. The comparison of E-peroxone with anodic oxidation aided by H2O2 (AO-H2O2) and ozonation showed the oxidative power sequence E-peroxone > ozonation > AO-H2O2. The evolution of carboxylic acids and inorganic ions was performed by chromatographic and spectrophotometric techniques. Finally, a route of CAP degradation is proposed.

Фотокаталитическая деградация фармацевтических поллютантов при облучении УФ- и видимым светом с применением железосодержащих металлокерамических композитов

The adsorption and photocatalytic activity of iron-containing metal-ceramic composites produced by the self-propagating combustion of aluminum ferrosilicon in nitrogen with the addition of metallic tantalum (0, 5, 10, 15 wt%) during oxidative degradation of pharmaceutical pollutants (chloramphenicol, metamizole, cinnarizine) under UV and visible light was evaluated. The phase composition of the composite materials was determined by X-ray diffraction and infrared spectroscopy. The morphological features and optical properties of the composites were investigated, and the band gaps of the semiconductors included in the ceramic matrix were determined. The acid properties of the surface of the composites were studied using pH-metry and the Hammett indicator. The correlation of the number of surface-active sites and adsorption of pollutants with the corresponding value of pKa was shown, and the mechanisms of adsorption were proposed. Optimal conditions for the oxidative degradation of chloramphenicol (~100%) under visible light were found: a composite (5% Ta) with the addition of H2O2 to combine heterogeneous catalysis with the homogeneous photo-Fenton system.

Insight into the Mechanisms of Chloramphenicol Degradation by Photocatalysis Coupled Microbial Fuel Cell with Ni/Mxene Photocathode

Insight into the Mechanisms of Chloramphenicol Degradation by Photocatalysis Coupled Microbial Fuel Cell with Ni/Mxene Photocathode

Quorum sensing signals from sludge improving the self-assembly of electrode biofilms in microbial fuel cells for chloramphenicol degradation

AHLs in stratified EPS accelerated self-assembly of CAP-degrading electrode biofilms with superior physicochemical characteristics and mutualistic microbial communities in MFCs.

Synergistic Degradation of Chloramphenicol by an Ultrasound-Enhanced Fenton-like Sponge Iron System

In this study, an ultrasound Fenton-like sponge iron system was used to enhance the degradation efficiency for chloramphenicol (CAP). Three single-factor experiments of reaction pH, hydrogen peroxide (H2O2) concentration, and sponge iron (Fe) concentration were used to explore the impact on CAP degradation efficiency. The response surface method revealed the interactions between various factors. The degradation efficiency for CAP was as high as 99.97% at pH = 3, 3.19 mmol/L H2O2, and a sponge iron concentration of 2.26 g/L. The degradation rate for CAP was significantly reduced upon the addition of some inorganic salts, mainly due to the quenching of OH radicals. Gram-negative (G(−)) Escherichia coli and Gram-positive (G(+)) Staphylococcus aureus were used to evaluate the changes in the antibacterial activity of CAP. Finally, gas chromatography/mass spectrometry (GC-MS) was used to identify the degradation products and the degradation path for the products was proposed based on the detected products.

Performance of nZVC/H2O2 process in degrading chloramphenicol in water

Background: To develop other H2O2-based approaches for the efficient degradation of chloramphenicol, this study elucidates the performance of the nZVC/H2O2 process in the degradation of chloramphenicol in water.Methods: A rotating packed bed (RPB) with blade packings was adopted in the mass-production of nanoscale zero-valent copper (RPB-nZVC). The effects of pH, initial chloramphenicol concentration, nZVC dosage, and H2O2 concentration on the degradation of chloramphenicol using the nZVC/H2O2 process with RPB-nZVC were studied.Significant findings: The results reveal that the optimal nZVC dosage and H2O2 concentration were 250 mg/L and 1.25 mmol/L, respectively. At pH 3 with an initial chloramphenicol concentration of 10 mg/L, an nZVC dosage of 250 mg/L, an H2O2 concentration of 1.25 mmol/L, and a degradation time of 30 min, the nZVC/H2O2 process with the RPB-nZVC degraded 93% of the chloramphenicol. However, at the same operating parameters, the efficiency of degradation of chloramphenicol of 63% was achieved in the nZVC/H2O2 process with commercial nZVC that was obtained from Sigma-Aldrich. Therefore, the nZVC/H2O2 process with RPB-nZVC can be used to degrade strongly chloramphenicol in water.

Biodegradation mechanism of chloramphenicol by Aeromonas media SZW3 and genome analysis

The overuse of chloramphenicol (CAP) due to its low price is detrimental to ecological safety and human health. An earthworm gut content dwelling bacterium, Aeromonas media SZW3, was isolated with capability of CAP biodegradation, and the CAP degradation efficiency reached 55.86% at day 1 and 67.28% at day 6. CAP biodegradation kinetics and characteristic of strain SZW3 determined the factors that affect CAP biodegradation. Thirteen possible biodegradation products were identified, including three novel biodegradation products (CP1, CP2 and CP3), and three potential biodegradation pathway were proposed. Biodegradation reactions include amide bond hydrolysis, nitro group reduction, acetylation, aminoacetylation, dechlorination and oxidation. Genome analysis suggested that the coding gene of RarD (CAP resistance permease), CAP O-acetyltransferase, nitroreductase and haloalkane dehalogenase may be responsible for CAP biodegradation. The proposed complete biodegradation pathway and genome analysis by strain SZW3 provide us new insight of the transformation route and fate of CAP in the environment.

Degradation of Chloramphenicol Using UV-LED Based Advanced Oxidation Processes: Kinetics, Mechanisms, and Enhanced Formation of Disinfection By-Products

As an emerging light source, ultraviolet light emitting diodes (UV-LEDs) are adopted to overcome the shortcomings of the conventional mercury lamp, such as mercury pollution. The degradation of chloramphenicol (CAP) using three UV-LED-based advanced oxidation processes (AOPs)—UV-LED/persulfate (UV-LED/PS), UV-LED/peroxymonosulfate (UV-LED/PMS) and UV-LED/chlorine—was investigated. Results indicate that CAP can be more effectively degraded by the hybrid processes when compared to UV irradiation and oxidants alone. Degradation of CAP using the three UV-LED-based AOPs followed pseudo-first-order kinetics. The degradation rate constants (kobs) for UV-LED/PS, UV-LED/PMS, and UV-LED/chlorine were 0.0522, 0.0437 and 0.0523 min−1, and the CAP removal rates 99%, 98.1% and 96.3%, respectively. The degradation rate constant (kobs) increased with increasing oxidant dosage for UV-LED/chlorine, whereas overdosing reduced CAP degradation using UV-LED/PS and UV-LED/PMS. Ultraviolet wavelength influenced degradation efficiency of the UV-LED based AOPs with maximum CAP degradation observed at a wavelength of 280 nm. The application of UV-LED enhanced the formation DBPs during subsequent chlorination. uUV-LED/PMS produced more disinfection by-products than UV-LED/PS. Compared to UV-LED, UV-LED/PS reduced the formation of dichloroacetonitrile and trichloronitromethane during chlorination owing to its capacity to degrade the nitro group in CAP. The intermediates dichloroacetamide, 4-nitrobenzoic acid, 4-nitrophenol were produced during the degradation of CAP using each of UV-LED, UV-LED/PS and UV-LED/chlorine. The present study provides further evidence supporting the application of UV-LED in AOPs.

Isolation, identification and characterization of a chloramphenicol-degrading bacterium

Microorganisms are the dominant players driving the degradation and transformation of chloramphenicol (CAP) in the environment. However, little bacterial strains are able to efficiently degrade and mineralize CAP, and the CAP degrading pathways mediated by oxidative reactions remain unclear. In this study, a highly efficient CAP-degrading microbial consortium, which mainly consists of Rhodococcus (relative abundance >70%), was obtained through an enrichment process using CAP-contaminated activated sludge as the inoculum. A bacterial strain CAP-2 capable of efficiently degrading CAP was isolated from the consortium and identified as Rhodococcus sp. by 16S rRNA gene analysis. Strain CAP-2 can efficiently degrade CAP under different nutrient conditions. Based on the biotransformation characteristics of the detected metabolite p-nitrobenzoic acid and the reported metabolites p-nitrobenzaldehyde and protocatechuate by strain CAP-2, a new oxidative pathway for the degradation of CAP was proposed. The side chain of CAP was oxidized and broken to generate p-nitrobenzaldehyde, which was further oxidized to p-nitrobenzoic acid. Strain CAP-2 can be used to further study the molecular mechanism of CAP catabolism, and has the potential to be used in in situ bioremediation of CAP-contaminated environment.

Removal of chloramphenicol in water by an improved water falling film dielectric barrier discharge reactor: Performance, mechanism, degradation pathway and toxicity evaluation

Chloramphenicol (CAP) is a common antibiotic, which is difficult to be removed in water environment and has caused huge environmental risks. Herein, an improved water falling film dielectric barrier discharge (WFFDBD) reactor was built to treat 20 L of CAP wastewater. The effects of operating parameters of the reactor on CAP degradation were investigated, the main reactive species for CAP degradation were identified, the intermediates and degradation pathway of CAP were analyzed, and the toxicity of degradation products of CAP was evaluated by quantitative structure activity relationship (QSAR) models. The results show that CAP degradation efficiency was significantly increased by covering medical gauze. At 370 W of discharge power, CAP degradation efficiency was 88.7% and 59.9% after 140 min treatment with and without the gauze, and the energy efficiency of WFFDBD reactor with medical gauze was 2.53 times higher than that without medical gauze. The medical gauze significantly increased the yield of the reactive species of WFFDBD. Correlation matrix analysis showed that the contribution of H2O2, O3 and ·OH for CAP removal followed the order of ·OH > H2O2> O3. Moreover, O2⋅− and ·H were also the key species for CAP degradation. A possible degradation pathway was given based on the measured degradation products. The developmental toxicity of CAP and its degradation products were quantified, and the results indicate the toxicity of CAP wastewater was weakened after WFFDBD treatment.

Enhanced degradation of chloramphenicol through peroxymonosulfate and visible light over Z-scheme Photocatalysts: Synergetic performance and mechanism insights

Effective removal of antibiotics in the environment can be a demanding issue concerning the ecosystem and human health. Photocatalysis and peroxymonosulfate (PMS) oxidation have become important methods to effectively remove stubborn pollutants. In this work, by integrating these two technologies, an efficient system for degrading chloramphenicol (CAP) in water was proposed. The system was constructed by coupling strontium-doped lanthanum cobaltate (LSCO5) with chlorine-doped carbon nitride (CGCN). By doping, the increase of oxygen vacancy and the adjustment of bandgap were realized. Photoluminescence and electrochemical impedance experiments showed that the heterojunction can promote electron transfer and photogenerated carrier separation. Under the synergistic effect of PMS oxidation and photocatalysis, the prepared composite with an optimal loading of 40% LSCO5 can degrade 95.6% of CAP within 20 min. Degradation experiments on different pollutants proved the versatility of the catalytic system. The enhanced degradation mechanism of CAP was explored based on the assessment of the degradation efficiency of CAP, electron paramagnetic resonance (EPR), and quenching experiments. Through liquid chromatography-mass spectrometry (LC-MS) analysis, a possible route for CAP degradation was also proposed. This research provides some inspiration for the remediation of polluted water with perovskite-based catalyst under the synergistic effect of PMS and photocatalysis.

Removal of chloramphenicol by sulfide-modified nanoscale zero-valent iron activated persulfate: Performance, salt resistance, and reaction mechanisms

Herein, sulfide-modified nanoscale zero-valent iron (S-nZVI) was prepared by a liquid-phase reduction route and then applied to activate persulfate (PS) for the degradation of chloramphenicol (CAP). The effects of Fe/S molar ratio, catalyst dosage, PS concentration, initial pH, and co-existing ions (Cl−, SO42−, CO32−) on the catalytic performance of S-nZVI/PS system were investigated. Simultaneously, the fluctuations of solution pH, oxidation-reduction potential, dissolved oxygen, and Fe2+ concentration were also monitored during the reaction. Results shown that 98.8 % of CAP could be removed under the optimum reaction conditions (S-nZVI dosage = 0.1 g/L, PS concentration = 3 mM, initial pH = 6.86). Compared to the pristine nZVI, the sulfidation behavior could critically improve the removal efficiency of CAP, ascribe to the enhancements of hydrophobicity of nZVI, production of hydroxyl radicals, and salt resistance. Furthermore, possible degradation pathways of CAP in S-nZVI/PS system were inferred based on liquid chromatography-mass spectrometry (LC-MS) and density functional theory (DFT) calculations. This study proves that the S-nZVI is a more promising catalyst for activating PS than nZVI, especially in the field of saline pharmaceutical wastewater treatment.

An enhancement of singlet oxygen generation from dissolved oxygen activated by three-dimensional graphene wrapped nZVI-doped amorphous Al species for chloramphenicol removal in the Fenton-like system

Three-dimensional graphene wrapped nZVI-doped amorphous Al species (3D-GN@Fe/a-Al) was fabricated as a novel Fenton-like catalyst for efficient removal of chloramphenicol (CAP) within a wide pH range. The mechanism of singlet oxygen (1O2) generation from dissolved oxygen (DO) activated by 3D-GN@Fe/a-Al was discovered. 3D-GN@Fe/a-Al was characterized by field emission scanning electron microscopy combined with an energy dispersive spectrometer (SEM-EDS), Brunner–Emmet–Teller (BET) measurement, X-ray diffraction (XRD) pattern and Raman spectroscopy to investigate the morphological and physicochemical properties. The catalytic performance of 3D-GN@Fe/a-Al for DO activation was estimated by the factor experiments of CAP degradation, including CAP concentration, catalyst dose, reaction temperature and pH value. Based on the evolution of the ultraviolet spectrum during the reaction and the results of high performance liquid chromatography-mass spectrometry (HPLC-MS) detection, the degradation pathway of CAP in the 3D-GN@Fe/a-Al–DO system was proposed. More importantly, the generation of singlet oxygen from DO activation mediated by the Al3+-promoted single electron delivery was further explored by the experiments of scavengers, electron spin resonance spectroscopy (ESR), X-ray photoelectron spectroscopy (XPS) analysis and electrochemical tests. The mechanism of 1O2 generation provides a new strategy for improving the degradation of organic pollutants in water by Fenton-like systems.

Graphene oxide mediated Fe(III) reduction for enhancing Fe(III)/H2O2 Fenton and photo-Fenton oxidation toward chloramphenicol degradation

Slow reduction of Fe(III) in iron-mediated Fenton-like systems strongly limits the decomposition of H2O2 to produce hydroxyl radicals (•OH). Here, we report that graphene oxide (GO) possesses excellent reactivity to enhance the Fe(III)/H2O2 Fenton and photo-Fenton oxidation for degrading chloramphenicol (CAP). EPR analysis and quenching tests reveal that •OH is the primary oxidant for CAP degradation. The characterization analysis and iron species transformation experiments demonstrate that Fe(III) can combine with the functional groups on the GO surface to form GO-Fe(III) complexes. The chronopotentiometry and cyclic voltammogram suggest that GO can donate electrons to Fe(III) via intramolecular electron transfer and promote H2O2 induced Fe(III) reduction by increasing the oxidation capability of Fe(III) due to the formation of GO-Fe(III) complexes, resulting in the strong promotion of the Fe(III)/Fe(II) cycle for producing OH. Moreover, the dark- and vis-GO/Fe(III)/H2O2 systems can effectively degrade CAP at initial pH ranging from 2.0 to 4.7. The reusability and stability of GO were evaluated by performing the cyclic degradation experiments of CAP. The OH induced degradation pathway of CAP was proposed involving three stages, based on intermediates analysis of UPLC-QTOF-MS/MS system. Therefore, the GO/Fe(III)/H2O2 system with or without visible light shows high potential for application in environmental remediation.

Enhanced chloramphenicol-degrading biofilm formation in microbial fuel cells through a novel synchronous acclimation strategy

A novel synchronous acclimation strategy involving the continuous addition of sludge with chloramphenicol (CAP) was established to significantly enhance the formation of a highly efficient CAP-degrading anode biofilm in microbial fuel cells (MFCs). The highest power density of 414.00 mW/m2 and CAP-tolerant concentration of 80 mg/L were obtained from the synchronous MFC, which were 2.05 and 1.67 times higher than those from the control MFC, respectively. The unique loose and porous biofilm with high permeability and cell viability supported by interwoven cobweb-shaped proteins facilitated mass and electron transfer, primarily leading to the improvements. Additionally, more bi-functional bacteria for electricity generation and CAP degradation (e.g., Pseudomonas and Enterococcus) were specifically selected, and more beneficial mutualism occurred among the microbes in the biofilm during the synchronous acclimation process. This study provides a possibility to improve the long-term operation efficiency of antibiotic-degrading electrode biofilms for bioelectrochemical technology through the use of a simple and efficient acclimation strategy.

Co/La modified Ti/PbO2 anodes for chloramphenicol degradation: Catalytic performance and reaction mechanism

Chloramphenicol (CAP) is widely used in daily life, and its abuse hurts human health, so a suitable method is needed to solve the problem. In this study, the Ti/PbO2 electrodes prepared by the electroplating method were characterized. The CAP degradation effect and mechanism were investigated. It was shown that the electrode surface had a dense plating with a characteristic peak of β-PbO2 as the active component. The electrode had an oxygen precipitation potential of 1.695 V and a corrosion potential of 0.553 V, and a long service life (505.4 d). The degradation of CAP at Ti/PbO2 electrode followed a first-order kinetic reaction. The optimal degradation conditions (current density of 12.97 mA cm−2, electrolyte concentration of 50 mM, and solution pH of 6.38) were obtained by the response surface curve method. The degradation rate of CAP was 99.0% at 60 min. The results showed that the reactive groups leading to CAP degradation were mainly ·OH and SO42−, and only a tiny portion of CAP was directly oxidized on the electrode surface. The addition of Cl− favored the degradation of CAP, but reduced the mineralization rate. LC-MS analysis showed that ·OH mainly attacked the asymmetric centers (C1, C2) of weakly bound hydrogen atoms, resulting in underwent addition and substitution reactions. CAP was converted into two substances with m/z = 306 and m/z = 165. Finally, inorganic substances such as CO2 and H2O were generated. This study provided a new idea for preparing Ti/PbO2 electrode with high performance and the safe and efficient degradation of CAP.

Warrior's armor: Study on the aging of sulfidated micro-sized zero valent iron in air and its subsequent reactivity for chloramphenicol degradation in different acid systems

In the practical application process, the reactivity and performance of ZVI-based materials when being placed in the air for a few days, weeks or months was worth studying. Most studies on the aging of ZVI were carried out in solution, only considering the reactivity of ZVI in aqueous solution. In this work, we investigated the degradation of chloramphenicol (CAP) in sulfuric acid (SA) and citric acid (CA) systems by sulfidated micro-sized zero-valent iron (S-mZVI) in air with different aging days. The results showed that with the increase of aging days in the air, the degradation effect of S-mZVI on CAP in different acid systems showed a similar trend (first increasing and then decreasing), the removal effect of S-mZVI on CAP reached the best within the aging time of 5–9 days. The degradation path of CAP could be divided into oxidation path and reduction path. The XPS and XRD characterization results of the materials on different aging days indicated that the characteristic peak of Fe3O4 was detected on the surface of the materials with the increase of aging days, which may be the reason for changing degradation efficiencies of CAP by S-mZVI for different aging days. In addition, in different systems of SA and CA, the degradation curves of CAP differed. This might be caused by two reasons: (1) CA could adsorb on S-mZVI while SA could not; (2) The initial pH of the CA system played a more significant effect on CAP degradation compared to that of the SA system.