Chlorophyll-a In Seawater Research Articles

Effect of phytoplankton biomass in seawater on chemical properties of sea spray aerosols

This study is to investigate the effect of biological seawater properties on sea spray aerosols (SSA). Concentrations of chlorophyll-a and bacteria were measured at coastal site in Korea in fall and summer seasons. Also, aerosol mass spectrometer (AMS) was used to determine chemical constituents (organics, sulfate, nitrate, ammonium, and chloride) of non-refractory submicrometer aerosols sprayed from seawaters using a bubble bursting system. The average concentration of chlorophyll-a in seawater in fall was 1.75±0.78μg/l, whereas it significantly increased to 5.11±2.16μg/l in summer. It was found that the fraction of organics in the submicrometer SSA was higher in summer (68%) than fall (49%), and that the organic fraction in the SSA increased as the concentration of chlorophyll-a increased in seawater, suggesting that the high phytoplankton biomass in seawater could lead to the enhancement of organic species in the SSA.

The Effects of Nano-SiO<sub>2</sub> and Nano-ZnO on the Concentration of Chlorophyll-a in Seawater

Effects of nano-SiO2 and nano-ZnO on the concentration of chlorophyll-a in seawater were studied. Different particle size of nano-SiO2 and nano-ZnO (10~500nm) were added into seawater with different content ranging between 5~100mg/L, led to the v (growth rate) of chlorophyll-a were -11.4~-44.8% and -39.6~-74.0% respectively, and v decreased with the increasing of the concentration of nanoparticles and raised with the increasing of the nanoparticles size, and nano-ZnO had the stronger inhibitory effect than nano-SiO2. While to nano-ZnO and Zn2+(concentrations of zinc were 0.05~1.00mmol/L), chlorophyll-a growth rate decreased as the concentration of zinc increased and the average growth rates were -60.2～-68.8%, meant that nano-ZnO and Zn2+ have the same toxical mechanism. Concentrations of Zn2+ released from nano-ZnO (30nm and 90nm) with content of 5~100mg/L were 1.56~4.29mg/L, and rose with the increasing of nano-ZnO concentration, and 30nmZnO released more Zn2+ than 90nm. To nano-ZnO, percentage of the concentration of Zn2+ released by it and its v values have linear correlation, indicated that the released Zn2+ is the main reason for toxicity of nano-ZnO.

동해에서 해색센서를 이용한 CDOM추정 알고리즘 검증

동해에서 CDOM의 광학적 특성과 순환을 이해하기 위하여 MODIS의 원격탐사반사도(<TEX>$R_{rs}$</TEX>)를 이용한 기존의 CDOM 흡광계수 추정 알고리즘들(Semi-Algorithms (3개), Empirical-Algorithms (3개))을 현장관측 자료와 비교 평가하였다. 2009년부터 2011년까지 총 7번의 현장 관측 자료는 연안 해역에서부터 외양의 다양한 해양환경을 포함하고 있다. 본 연구 결과, 동해에서 Quasi-Analytical Algorithm (QAA_v5) 이 현장 <TEX>$a_{CDOM}$</TEX>(412) 값을 가장 유사하게 추정하였다. Quasi-Analytical Algorithm (QAA_v5) 알고리즘을 기준으로 Semi-analytical 알고리즘은 과소추정하는 경향을 보였다. 그러나 Empirical 알고리즘은 과대추정하는 경향을 보였다. <TEX>$a_{CDOM}$</TEX>(412)의 값이 높은 곳에서 위성관측 엽록소-a (Chlorophyll-a)의 값도 높았다. 이 결과는 CDOM이 엽록소-a의 함량 추정에 영향을 줄 수 있다는 가능성을 제시한다. 본 연구 결과는 세계최초 정지궤도 해색위성인 GOCI의 CDOM 알고리즘을 개선하는데 기초자료로 활용될 것이다. Colored Dissolved Organic Matter (CDOM) is one of the important components of optical properties of seawater to determine ecosystem dynamics in a given marine area. The optical characteristics of CDOM may depend on the various ecosystem and environmental variables in the sea and those variables may vary region to region. Therefore, the retrieval algorithm for determining light absorption coefficient of CDOM (<TEX>$a_{CDOM}$</TEX>) using satellite remote sensing reflectance (<TEX>$R_{rs}$</TEX>) developed from other region may not be directly applicable to the other region, and it must be validated using an in-situ ground-truth observation. We have tested 6 known CDOM algorithms (three Semi-analytical and three Empirical CDOM algorithms) developed from other regions of the world ocean with laboratory determined in-situ values for the East Sea using field data collected during seven oceanographic cruises in the period of 2009~2011. Our field measurements extended from the coastal waters to the open oceanic type CASE-1 Waters. Our study showed that Quasi-Analytical Algorithm (QAA_v5) derived <TEX>$a_{CDOM}$</TEX>(412) appears to match in-situ <TEX>$a_{CDOM}$</TEX>(412) values statistically. Semi-analytical algorithms appeared to underestimate and empirical ones overestimated <TEX>$a_{CDOM}$</TEX> in the East Sea. <TEX>$a_{CDOM}$</TEX>(412) value was found to be relatively high in the relatively high satellite derived-chlorophyll-a area. <TEX>$a_{CDOM}$</TEX>(412) value appears to be influenced by the amount of chlorophyll-a in seawater. The outcome of this work may be referenced to develop <TEX>$a_{CDOM}$</TEX> algorithm for the new Korean Geostationary Ocean Color Imager (GOCI).

State Prediction of Algae Reproduction Based on Learning Algorithm of Fuzzy Nearest Neighbor Clustering

In order to forecast the occurrence of red tide in the ocean, it is necessary to observe the state of algae reproduction in seawater. A method was proposed for forecasting the state of algae reproduction indirectly by modeling to predict the concentration of chlorophyll-a. Data-driven learning algorithm of fuzzy nearest neighbor clustering was used for pretreatment of sampling data. State prediction model for concentration of chlorophyll-a in seawater was built based on the optimal fuzzy logic system. Considering the character of sampling data and the demand of decreasing the rank of the model, a kind of improved learning algorithm of fuzzy nearest neighbor clustering was designed, and it was used in the state prediction for concentration of chlorophyll-a. The experiment indicates that the improved method can effectively extract the character of sampling data, reduce the dimension of the data, and improve the convergence speed of algorithm learning. The improved fuzzy nearest neighbor clustering algorithm reduces the complexity of modeling for prediction, and this kind of model has fine performance of generalization. It can effectively predict the state of algae reproduction in seawater.

Soft Sensing for Algae Blooms Based on Physical-Chemical Factors of Marine Environment

Soft sensing can solve the problem of on-line measuring for some variables which are difficult to measure with common instruments commendably. Chlorophyll-a is an important index of water quality for seawater, which can indicate the state of algae reproduction, further more it can predict the disaster of red tide by prediction model. The content of chlorophyll-a of seawater is affected by many physical-chemical factors, this complex relationship among them is difficult to be described by ordinary mechanism expression. In this paper, we use Fuzzy BP model to describe this complex nonlinear system, and detect the content of chlorophyll-a by the method of soft sensing. The PCA(Principal Component Analysis) method had been used to reduce the dimension of the sample data, simplify the complexity of the model system, this method can make the model has a faster convergence rate and a relative low dimension. The experiment illustrates that the result of soft sensing for algae blooms can match the real changes of the content of chlorophyll-a in seawater basically.

Metrological assessment of LIDAR signals in water

Over the years many private companies and governmental institutions have adopted environmental monitoring as an effective practice to minimize harmful impacts on the environment. Remote monitoring is unquestionably a versatile alternative for detecting possible leaking of noxious substances before they become apparent. LIDAR provides a reliable technique for measurements of pigments in seawater. An investigation was carried out to: (i) assess different procedures to improve the signal-to-noise relationship; (ii) preserve the integrity of the wavelength bandwidth of the fluorescence spectrum; (iii) verify the repeatability of wavelength measurements associated with local maximum of the Raman scattering curve of seawater and chlorophyll-a. Two approaches were adopted to calibrate the equipment: in the laboratory, by evaluating fluorescence signal fluctuations of the Raman scattering in seawater for different equipment parameters and on-site, by measuring relative concentrations of chlorophyll-a in seawater for different schemes. An experimental arrangement was eventually set up as calibration standard.

Production of acyclic isoprenoid compounds during the photodegradation of chlorophyll-a in seawater

A suspension of chlorophyll-a in synthetic seawater was irradiated with solar light until bleaching. After irradiation, methyl ethyl maleimide and several isoprenoid photoproducts were identified by gas chromatography and gas chromatography/mass spectrometry analyses. In order to explain the formation of these isoprenoid compounds, various mechanisms involving the initial addition of singlet oxygen on the double bond of the chlorophyll-a phytyl chain were proposed. The photosensitized oxidation of phytyl propionate in the presence of haematoporphyrin confirmed these mechanisms.