Pure Seawater Research Articles

Enhanced underwater optical wireless communication using optical code division multiple access with sigma shift matrix code

A high-speed 40 Gbps Underwater Optical Wireless Communication (UOWC) system exploiting code division multiple access is proposed in this paper. Optical Code Division Multiple Access (OCDMA) systems play a crucial role in enhancing transmission capacity by allowing multiple channels to transmit data simultaneously. In this proposed work, four channels each assigned a distinct Sigma Shift Matrix (SSM) code and modulated with a data at 10 Gbps. Laser Diode (LD) sources operating in the green spectrum are used in UOWC systems due to their low attenuation. To ensure the feasibility of implementing the proposed system in real-world environments, the actual scattering and absorption coefficients from five different types of water are considered: Pure Sea (PS), Clear Ocean (CL), Coastal Sea (CS), Harbor I (HI), and Harbor II (HII). The system's performance is evaluated via the Quality Factor (Q-factor), Bit Error Rate (BER), and eye diagrams opening. The simulation results indicate that in PS water, which exhibits the lowest attenuation, the four channels achieve the longest underwater transmission distance of 48 m, with a Q-factor ≥ 4.1, log(BER) ≤ −4.7, and wide eye openings. Since CL and CS have higher attenuation than PS, they enable shorter transmission distances of 27.5 m and 16 m, respectively, while maintaining nearly the same Q-factor, log(BER), and eye diagrams. Conversely, the highest attenuation observed in HI and HII waterbodies results in the shortest underwater spans of 8.2 m and 5.05 m, respectively.

Performance evaluation of an 80 Gbps dual-polarization orbital-angular-momentum-based underwater optical wireless communication system

In this paper, a new underwater optical wireless communication (UOWC) system is proposed. It integrates dual-polarization (DP) states with orbital angular momentum (OAM) beams. By leveraging the inherent orthogonality of different OAM modes, the system achieves enhanced signal quality and increased transmission capacity. Each polarization state carries data of four OAM beams, with each capable of carrying 10 Gbps of information. Additionally, a single laser diode (LD) source operating at 532 nm is employed. To evaluate the performance of the proposed system, the effects of attenuation across various water types are considered. Propagation range, bit error rate (BER), and eye diagrams are utilized as comprehensive performance metrics. The obtained results indicate that, below the error correction threshold (3.8×10−3), our proposed UOWC system achieves impressive underwater transmission ranges. Specifically, we observe a longer range of 44 m for pure sea (PS) water that exhibits the lower attenuation, which is decreased to 26.5 m for clear ocean (CL) and 15.5 m for coastal ocean (CS). Furthermore, it decreased reaching shorter ranges of 8 m for harbor I (HI) and 4.45 m for harbor II (HII), which have the highest attenuation.

Examination of the antioxidant effects of linalool and Lippia alba essential oil in the Pacific whiteleg shrimp, Litopenaeus vannamei, subjected to eyestalk ablation

Essential oils are considered to have the ability to minimize the effects of stress during handling in aquatic animals. This study evaluated the anesthetic effects of Lippia alba essential oil and its major compound, linalool, on the antioxidant responses of eyestalk-ablated female shrimp Litopenaeus vannamei. Female shrimp were divided into the following treatments: pure seawater (control), ethanol (9000 μL L−1 of ethanol), 750 μL L−1 of Lippia alba essential oil, 1000 μL L−1 of Lippia alba essential oil, 350 μL L−1 of linalool, and 500 μL L−1 of linalool. The shrimp were sedated for 3 min. The eyestalks were then ablated unilaterally by cauterization (cutting the eyestalk with hot scissors). Biochemical variables were analyzed in the gill, muscle, and hepatopancreas. The antioxidant capacity against peroxyl radicals in the group that received 750 μL L−1 of Lippia alba essential oil was significantly higher in the hepatopancreas and muscle than in the control group, whereas the ethanol group had a higher antioxidant capacity in the gills and muscle than the control group. An increase in the total antioxidant capacity in the hepatopancreas and muscle was observed in the 750 μL L−1 Lippia alba essential oil group, but not in the ethanol group, relative to the control group. A significant reduction in lipid peroxidation in the gills was observed in females treated with 500 μL L−1 of linalool compared to the ethanol group. Linalool and Lippia alba essential oil contributed to the improvement in the antioxidant defense systems of shrimp gills. Overall, the obtained results suggest that exposure to Lippia alba essential oil and linalool may activate certain components of the antioxidant system that exist in the gills and scavenge peroxyl radicals; this in turn may help maintain homeostasis and improve the welfare of eyestalk-ablated female shrimp.

Optimization of underwater visible light communication transmission using multilevel regression modelling

This paper proposes the 32-Channel Dense wavelength Division Multiplexing (DWDM) system for Underwater Visible Light Communication (UVLC). The proposed DWDM-UVLC system performs the transmission of visible light data under different underwater ocean environmental conditions such as Pure sea, Clear ocean, and Coastal ocean water and ocean pollution such as oil spills, microplastics. The data transmission through visible light in underwater ocean environment is a challenging task due to attenuation in ocean water, which causes variations in water column parameters such as temperature, Ph, salinity, and chemical oil spill contents in water such as water with oil spills, and microplastics. The proposed dense wavelength Division Multiplexing (DWDM) system for Underwater Visible Light Communication (UVLC) is optimized using Bayesian optimized Multiple Regression Learning (BO-MRL) method. The BO-MRL based DWDM for UVLC mitigates the attenuation problems in data transmission, which is in the range of approximately 350m. The proposed DWDM-UVLC system is evaluated through the Performance metrics such as Q-factor, Minimal BER and proper spectral eye characteristics. The proposed BO-MRL based DWDM consists of non-return-to-zero (NRZ) modulation, which performs better in 320 Gbps, transmission in the range of 200m and 350m, and achieves the maximum Q-factor of 19.2364 with a minimal BER of 9.16489 e−083.

In-water lidar simulations: the ALADIN ADM-Aeolus backscattered signal at 355 nm

The Lidar Ocean Color (LiOC) Monte Carlo code has been developed to simulate the in-water propagation of the lidar beam emitted by the ALADIN ADM-Aeolus instrument in the ultraviolet (UV) spectral region (∼ 355 nm). To this end, LiOC accounts for reflection/transmission processes at the sea surface, absorption and multiple scattering in the water volume, and reflection from the sea bottom. The water volume components included in the model are pure seawater, Chlorophyll-a concentration (Chl-a), Colored Dissolved Organic Matter (CDOM), and/or a generic absorbing species. By considering the transmission/reception measurement geometry of ALADIN ADM-Aeolus, the study documents the variability of the normalized backscattered signal in different bio-optical conditions. The potential for data product retrieval based on information at 355 nm is considered by developing a demonstrative lookup table to estimate the absorption budget exceeding that explained by Chl-a. Results acknowledge the interest of space programs in exploiting UV bands for ocean color remote sensing, as, for instance, addressed by the PACE mission of NASA.

Performance analysis of 2D optical code division multiple access through underwater wireless optical medium

The performance of a two-dimensional optical code division multiple access (2D-OCDMA) system using an underwater wireless optical (UWO) medium is assessed in this work. The optical source is an LED with a working wavelength of 532 nm, and the optical detector is a p–i–n photodiode. When calculating the bit error rate (BER), the phase-induced intensity noise (PIIN), thermal noises, and shot sounds are taken into account. The user code address is set using 2D perfect difference (2D-PD) codes. Link distance, inclination angle, beam divergence angle, transmitter power, and the number of concurrent users are all taken into account when determining the BER performance. For various water media, such as pure sea water (PSW), clear ocean water (CLOW), and coastal ocean water (CSOW), the performance of the suggested system is examined.

Optimized deep learning driven signal detection and adaptive channel estimation in underwater acoustic IoT networks

SummaryNowadays, multiple input multiple outputs with orthogonal frequency division multiplexing (MIMO‐OFDM) provide better communication performance that can be applied to the fast‐growing Internet of Things (IoTs). In underwater IoT, information fades away rapidly due to varying water conditions. Therefore, the MIMO model can be applied to the OFDM acoustic system, enabling high‐speed data transmission without affecting the channel effectively. However, detecting the underwater signal and estimating the channel is highly necessary for enhancing underwater acoustic communication (UWAC). Recently, many techniques have been introduced for effectively performing signal detection and channel estimation. However, those techniques face high time complexity due to increased channel interferences and noises during data transmission. Hence, this article brings a novel technique for SD and CE for the UWAC‐IoT‐enabled MIMO‐OFDM system. An adaptive recursive least square (ARLS) technique is proposed in this study for CE that aids in evaluating the acoustic channel parameters effectively. For performing SD, a bi‐directional deep pelican convolutional neural network (BDPCNN) technique is introduced to ensure the presence and absence of signals at the receiver end. The proposed method is analyzed via the MATLAB platform, and the performances are analyzed under different water types like turbid water, coastal water, clear ocean water, and pure seawater. Different performance metrics like bit error rate (BER), mean square error (MSE), energy efficiency (EE), and time complexity are analyzed with different existing techniques. The experimental section obtains the BER of 0.0086, 0.013, 0.017, and 0.021 for turbid, coastal, clear, and pure seawater, respectively.

Single-Particle ICP-TOFMS with Online Microdroplet Calibration: A Versatile Approach for Accurate Quantification of Nanoparticles, Submicron Particles, and Microplastics in Seawater.

Single particle inductively coupled plasma time-of-flight mass spectrometry (spICP-TOFMS) is a powerful analytical technique for quantifying elements in nanoparticles and microparticles; however, like most ICP-MS-based measurements, matrix effects can be a major challenge for accurate quantification in spICP-MS. Here, we report the use of online microdroplet calibration to overcome extreme matrix effects observed for the analysis of nanoparticles and microparticles in seawater. With online microdroplet calibration, particle-containing samples are introduced into the ICP along with monodisperse microdroplets containing known element mass amounts. The microdroplet standards, which experience the same plasma conditions as the analyte particles, are used to measure matrix-matched absolute element sensitivities. With online microdroplet calibration, one multielemental standard can be used to determine the element mass amounts in diverse types of analyte particles independent of the sample matrix. We evaluate the matrix tolerance of spICP-TOFMS with online microdroplet calibration through the analysis of metal nanoparticles, polystyrene microplastic beads doped with rare-earth elements, and metal-oxide submicrometer particles in artificial seawater. Our results demonstrate mass recoveries of 98-90% for the analysis of individual gold NPs in ultrapure water to 99% seawater. In the analysis of food-grade TiO2 submicron particles, accurate Ti-mass per particle is determined with matrix-caused signal attenuation up to 80% in a pure seawater matrix. We also demonstrate accurate diameter determinations of individual 3.4 μm polystyrene beads at concentrations of up to 80% simulated seawater. Furthermore, simultaneous and accurate quantification of rare-earth elements in the polystyrene beads is achieved.

A synthetic optical database generated by radiative transfer simulations in support of studies in ocean optics and optical remote sensing of the global ocean

Abstract. Radiative transfer (RT) simulations have long been used to study the relationships between the inherent optical properties (IOPs) of seawater and light fields within and leaving the ocean, from which ocean apparent optical properties (AOPs) can be calculated. For example, inverse models used to estimate IOPs from ocean color radiometric measurements have been developed and validated using the results of RT simulations. Here we describe the development of a new synthetic optical database based on hyperspectral RT simulations across the spectral range of near-ultraviolet to near-infrared performed with the HydroLight radiative transfer code. The key component of this development is the generation of a synthetic dataset of seawater IOPs that serves as input to RT simulations. Compared to similar developments of optical databases in the past, the present dataset of IOPs is characterized by the probability distributions of IOPs that are consistent with global distributions representative of vast areas of open-ocean pelagic environments and coastal regions, covering a broad range of optical water types. The generation of synthetic data of IOPs associated with particulate and dissolved constituents of seawater was driven largely by an extensive set of field measurements of the phytoplankton absorption coefficient collected in diverse oceanic environments. Overall, the synthetic IOP dataset consists of 3320 combinations of IOPs. Additionally, the pure seawater IOPs were assumed following recent recommendations. The RT simulations were performed using 3320 combinations of input IOPs, assuming vertical homogeneity within an infinitely deep ocean. These input IOPs were used in three simulation scenarios associated with assumptions about inelastic radiative processes in the water column (not considered in previous synthetically generated optical databases) and three simulation scenarios associated with the sun zenith angle. Specifically, the simulations were made assuming no inelastic processes, the presence of Raman scattering by water molecules, and the presence of both Raman scattering and fluorescence of chlorophyll a pigment. Fluorescence of colored dissolved organic matter was omitted from all simulations. For each of these three simulation scenarios, the simulations were made for three sun zenith angles of 0, 30, and 60∘ assuming clear skies, standard atmosphere, and a wind speed of 5 m s−1. Thus, overall 29 880 RT simulations were performed. The output results of these simulations include radiance distributions, plane and scalar irradiances, and a whole set of AOPs, including remote-sensing reflectance, vertical diffuse attenuation coefficients, and mean cosines, where all optical variables are reported in the spectral range of 350 to 750 nm at 5 nm intervals for different depths between the sea surface and 50 m. The consistency of this new synthetic database has been assessed through comparisons with in situ data and previously developed empirical relationships involving IOPs and AOPs. The database is available at the Dryad open-access repository of research data (https://doi.org/10.6076/D1630T, Loisel et al., 2023).

Sensing the profile of particulate beam attenuation coefficient through a single-photon oceanic Raman lidar.

A lidar technique has been proposed and demonstrated for remotely sensing particulate beam attenuation coefficient (cp) profiles using the Raman backscattered signal from water. In Raman lidar, the backscatter coefficient at 180° can be considered constant, allowing for the determination of the lidar attenuation coefficient (Klidar) from the Raman backscattered signal. This scheme has these features. 1) The bandwidth of the filter that used to extract the Raman component from the backscattered signal of the lidar was optimized to ensure sufficient lidar signal strength while minimizing the influence of chlorophyll fluorescence on inversion. 2) A receiving telescope with narrow field of view (FOV) and small aperture was utilized to suppress multi-scattering components in the backscattered signal. 3) A relationship between the beam attenuation coefficient (c) and Klidar was established after simulations via a semi-analytic Monto Carlo. 4) The value of cp was obtained by subtracting the attenuation coefficient of pure seawater (cw) from c. According to the theoretical analysis, the maximum relative error of cp is less than 15% for chlorophyll concentrations up to 10 mg/m3. Due to the water Raman backscattered signal being several orders of magnitude lower than the elastic backscattered signal, a single-photon detector is required to significantly improve the detection sensitivity to the single-photon level. To validate this approach, a field experiment was conducted aboard the R/V Tan Kah Kee in the South China Sea from September 4th to September 5th, 2022, and continuous subsurface profiles of cp were obtained. These measurements confirm the robustness and reliability of the oceanic single-photon Raman lidar system and the inversion method.

Applications of Epipelic Diatoms and Probiotics for Pacific White Shrimp Nursery (Litopenaeus vannamei)

Pacific white shrimp (Litopennaeus vannamei) is a type of shrimp that is very easy to cultivate because it has several advantages, it is resistant to disease and has a high survival rate, and productivity can reach 13.6 tons/ha. Very high density because it can use feed and space more efficiently. This is what makes many farmers in Indonesia cultivate it. Despite the many advantages, there are still many obstacles faced by cultivators who experience failure and losses. The failure was caused by poor water quality during cuture and the emergence of disease attacks that caused slow growth decreased production and resulted in huge losses for farmers. To overcome these problems, it is necessary to improve the water quality of the cultivation media used. Water quality improvement was carried out by the application of probiotics for the vannamei nursery. The purpose of this study was to evaluate the optimal dose/cell count on water quality and shrimp growth and evaluate the developmental level of pathogenic bacteria treated with Epipelic Diatoms (DE) and Probiotic. The method used was an experimental method using a completely randomized design (CRD) with 4 treatments and 3 replications. The treatments tested were A (pure seawater), B (100% DE), C (100% PB), D (100% DE+100% PB). The seeds used were PL 6 vannamei shrimp with an average weight of 0.175 g and an average length of 5.5. The results showed that the combination of DE and PB had a significant effect (p<0.05) on water quality and the growth and survival of post-vannamei larvae.

Ice nucleating properties of the sea ice diatom Fragilariopsis cylindrus and its exudates

Abstract. In this study, we investigated the ice nucleation activity of the Antarctic sea ice diatom Fragilariopsis cylindrus. Diatoms are the main primary producers of organic carbon in the Southern Ocean, and the Antarctic sea ice diatom F. cylindrus is one of the predominant species. This psychrophilic diatom is abundant in open waters and within sea ice. It has developed several mechanisms to cope with the extreme conditions of its environment, for example, the production of ice-binding proteins (IBPs) and extracellular polymeric substances known to alter the structure of ice. Here, we investigated the ice nucleation activity of F. cylindrus using a microfluidic device containing individual sub-nanolitre (∼90 µm) droplet samples. The experimental method and a newly implemented Poisson-statistics-based data evaluation procedure applicable to samples with low ice nucleating particle concentrations were validated by comparative ice nucleation experiments with well-investigated bacterial samples from Pseudomonas syringae (Snomax®). The experiments reveal an increase of up to 7.2 ∘C in the ice nucleation temperatures for seawater containing F. cylindrus diatoms when compared to pure seawater. Moreover, F. cylindrus fragments also show ice nucleation activity, while experiments with the F. cylindrus ice-binding protein (fcIBP) show no significant ice nucleation activity. A comparison with experimental results from other diatoms suggests a universal behaviour of polar sea ice diatoms, and we provide a diatom-mass-based parameterization of their ice nucleation activity for use in models.

Relationship of the Quanta-to-Energy Ratio of Photosynthetically Active Radiation with Chlorophyll-a in Case I Seawater

A predetermined quanta-to-energy ratio is often used in many ecosystem models to transform photosynthetically radiant flux density into photosynthetic photon flux density when light penetrates seawater. The calculation formula of the ratio is reduced in this study as the product of a constant and the defined principal wavelength. The principal wavelength is discussed in this paper and may be expressed as an exponential function using theoretical reasoning. The deviation of the principal wavelength is defined as the difference between two natural logarithms of the observed principal wavelength in real seawater and the simulated principal wavelengths of pure seawater under the same surface solar radiation. The deviation has a quasi-linear relationship with the non-water diffuse attenuation coefficient at 490 nm, which is related to the chlorophyll-a concentration. A semi-empirical formula between the deviation and chlorophyll-a concentration is established with a determination coefficient of more than 84%. In pure seawater, an empirical formula for the principal wavelength profile is also constructed. The parameterization formula for the quanta-to-energy ratio is provided as a function of the chlorophyll-a concentration and the surface principal wavelength. When applied to in situ observations, the statistical relative inaccuracy is found to be less than 10%. The parameterization formula can be applied to the ecosystem models to realize the transformation between photos and energy in the PAR waveband.

A Reinforcement-Learning-Based Beam Adaptation for Underwater Optical Wireless Communications

Underwater optical wireless communications (UOWCs) have recently appeared as an attractive solution for many applications, such as remote controlling and sensing due to its advantages, such as high transmission rate, ultrawide bandwidth, and low latency. However, due to the harsh underwater conditions, UOWC faces challenges, such as water absorption, scattering, and pointing-acquisition-and-tracking (PAT) problems. This is mainly due to the dynamicity existing underwater. Consequently, this leads to packet loss and hence deteriorates the reliability and link quality of such networks. Such a problem can affect the degree of connectivity and end-to-end (E2E) performance of the communication system. The existing solutions in the literature are based on predefined models, assuming full knowledge of the environment. However, such models do not optimally treat the dynamicity existing underwater. This article proposes novel beam adaptation methods based on reinforcement learning (RL) for point-to-point UOWC. The first method aims to optimize the light beamwidth; the second method focuses on adapting the beam orientation, whereas the last one optimizes both the light’s beamwidth and beam orientation. Our proposed RL-based solutions yield optimal positioning and beamwidth of the light source and improve the considered communication link’s success rate. They also guarantee better link quality in terms of signal-to-noise ratio (SNR) compared to the uncertainty disk static method for four different underwater environments, including pure seawater, clean ocean, coastal ocean, and turbid harbor.

Experimental study on underwater continuous-variable quantum key distribution with discrete modulation.

We experimentally demonstrated the feasibility of an underwater continuous-variable quantum key distribution (CV-QKD) system based on four-state protocol, which is promising to guarantee the unconditionally secure underwater wireless optical communication. CV-QKD parameter estimation is performed after transmitting quantum coherent signal from Alice to Bob through a water tank. The secure key rate under collective attack of the demonstrated CV-QKD system is estimated as 22.9 kbits/s at a channel loss of 12.4 dB. In addition, the performance is also investigated with various water types and the maximum underwater transmission distance of the demonstrated CV-QKD system is estimated as 148.7 m in the pure sea water.

Surface conversion derived core-shell nanostructures of Co particles@RuCo alloy for superior hydrogen evolution in alkali and seawater

Hydrogen evolution reaction (HER) in alkali involves higher energy barriers and slow reaction kinetics due to involving water dissociation process. Catalysts with proper surface properties are highly needed to optimize the surface binding energy with reaction intermediates and enhance intrinsic catalytic activity. Herein, we present an effective strategy to construct a self-standing catalyst with core-shell structure, which is composited of metallic Co nanoparticles coated by RuCo alloy layer with optimized surface properties. The Ru attracts electrons from Co and optimizes the surface electronic structure. Theoretical calculations demonstrate that the water dissociation barrier on the Co surface is decreased from 0.65 eV to 0.58 eV after alloying with Ru. Experimental results reveal that the synthesized Co@RuCo-3 features highly efficient catalytic activity together with good stability at large current densities for HER in alkali, as well as in alkaline seawater and pure seawater.

Peningkatan Performa Baterai Air Laut Menggunakan Cu-Zn Berdasarkan Luas Penampang Elektroda

Seawater in Indonesia has considerable potential when used as a source of renewable energy. As it is known that sea water generally contains elements or levels of salt dissolved in it. Due to the presence of these elements or levels of salt, seawater has the potential to produce electrical energy. This is the reason why researchers want to do more in-depth research on this seawater battery. As it is known that several previous studies have conducted experiments using different methods in each research conducted. In this study, we will use several methods that have been there previously aimed at getting an increase in electrical energy that will be generated from marine batteries. This study uses a cross-section of electrodes in the form of copper and zinc by comparing several methods to get a seawater battery design that suits your needs. In this study, the seawater battery used pure seawater and without using an amplifier circuit or voltage booster. With a voltage that can be generated in each 1 cell, which is between 0.78 V and 0.82 V. Overall, this seawater battery has 10 cells arranged in series with each 1 cell consisting of 5 pairs of copper and zinc electrodes arranged in parallel.

Real-Time Optical-Wireless Video Surveillance System for High Visual-Fidelity Underwater Monitoring

Real-time, dynamic, and visual monitoring of underwater scenes would become an important research topic with the development of underwater wireless optical communication (UWOC), autonomous underwater vehicle, and video fusion technologies. To this end, we developed a UWOC-based 2K real-time digital video surveillance prototype named AquaF-seer. Using a light-emitting diode and an avalanche photodetector based diffused line-of-sight UWOC system, real-time video transmission with a high resolution of 1920 × 1080 pixels is achieved over various channels, i.e., 1.5-m free space channel, pure water channel, pure water channel with 1.53-mL/s bubble-induced turbulence, pure water channel with 42.40-mL/s bubble-induced turbulence, simulated pure sea water channel, and coastal ocean water channel. Moreover, 46-m and 5-m video monitoring are implemented in free space and an outdoor diving pool. It indicates the reliability of the prototype, which is the first step to realize underwater visual monitoring in future human-robot interaction applications.

In-situ synthesis of Bi0 on 3D-3D-shaped (BiO)2CO3 surface for photocatalytic inactivation: Metal self-doping mechanism

Studies have shown that Bi-based semiconductor photocatalysts have been favorably applied in environmental protection. The present study creates Bi-based photocatalysts using the glycol-assisted solvothermal method and examines their efficacy in killing bacteria and purifying ship’s ballast water. This synthesis method encourages the flower-ball-like (BiO)2CO3 packaged within nanosheets to generate Bi nanospherical particles in situ, resulting in the preparation of 3D–3D Bi/(BiO)2CO3 heterojunctions. At the same time, the combined surface plasmon resonance (SPR) effects of semimetallic Bi and (BiO)2CO3 promote the system’s photocatalytic killing of bacteria in ship’s ballast water. The combined characterization shows that the 3BBOC composite sample has the highest photocatalytic sterilization efficiency in pure seawater. The photocatalytic activity is 3 times that of only (BiO)2CO3. The SPR effect of the Bi nanoparticles generated in situ improves the heterojunction’s absorption and utilization of visible light. After periodic stability tests, Bi/(BiO)2CO3 heterojunctions are shown to have excellent environmental adaptability and stability. The experiment of capturing free radicals shows that hydroxyl free radicals are most effective in killing bacteria.

Exploring the influence of concentration fluctuation and matrix effects on a passive sampler of triolein-embedded cellulose acetate membrane measuring polychlorinated biphenyls in water

A membrane of triolein-embedded cellulose acetate membrane (TECAM), as an integrative passive sampler, was applied to adsorb 28 polychlorinated biphenyls (PCBs) from pure water and sea water in order to probe into the influence of concentration fluctuation and water matrix. The results demonstrated the temporal variations of PCBs concentrations in TECAM followed the first-order kinetics model. The periodic refreshment of solution and matrix effects of sea water significantly prolonged the time that PCBs reached equilibrium stage. The refreshment facilitated the uptake mass in TECAM. On the contrary, the matrix effects of sea water and dissolved organic matter (DOM) declined the PCBs absorption to TECAM. The average logKP values of PCBs in pure water were about 1.2 log unit higher than those in sea water in the experiments that the solution was not refreshed, while the difference of average logKP values narrowed to 0.3 log unit if the PCBs solutions were periodically refreshed. The correlation between logKP and logKOW values fitted the quadratic curve well, which was similar to semi-permeable membrane device (SPMD). The appropriate sampling times (t94%) ranged from 98.8 to 819 h (mean 500 h) for pure water with refreshment, much longer than those in sea water with refreshment (80.1~410 h, mean 189 h). The t94% values in the solution with high DOM content increased significantly, up to 409 h. Furthermore, comparing the twoexperiments that the spiked pure water and sea watersolution were refreshedfrequently, the estimated sampling rates (Rs) in pure water (0.154~2.06 L/day with a mean value of 0.605 L/day) were slightlylower than those in sea water (0.292~3.84 L/day with a mean value of 1.69 L/day). However, the Rs values in sea water with DOM declined sharply to 0.042 L/day. Therefore, concentration fluctuation, matrix effect, and DOM contents of sea water evidently posed significant influence on dynamic parameters of TECAM absorption, which would be screened and probed detailed in future.