Retrieval of Chlorophyll a Concentration in Water Considering High-Concentration Samples and Spectral Absorption Characteristics

The envelope removal method has the advantage of suppressing the background spectrum and expanding the weak absorption characteristic information. However, for second-class water bodies with a relatively complex water quality, there are few studies on the inversion of chlorophyll a (<inline-formu...

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Autores principales:	Yun Xue, Yi-Min Wen, Zhong-Man Duan, Wei Zhang, Fen-Liang Liu
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	spectral absorption characteristics chlorophyll-a Dongting Lake Environmental effects of industries and plants TD194-195 Renewable energy sources TJ807-830 Environmental sciences GE1-350
Acceso en línea:	https://doaj.org/article/05317471f35f47c2aab46a9cc1af7f22
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id	oai:doaj.org-article:05317471f35f47c2aab46a9cc1af7f22
record_format	dspace
institution	DOAJ
collection	DOAJ
language	EN
topic	spectral absorption characteristics chlorophyll-a Dongting Lake Environmental effects of industries and plants TD194-195 Renewable energy sources TJ807-830 Environmental sciences GE1-350
spellingShingle	spectral absorption characteristics chlorophyll-a Dongting Lake Environmental effects of industries and plants TD194-195 Renewable energy sources TJ807-830 Environmental sciences GE1-350 Yun Xue Yi-Min Wen Zhong-Man Duan Wei Zhang Fen-Liang Liu Retrieval of Chlorophyll a Concentration in Water Considering High-Concentration Samples and Spectral Absorption Characteristics
description	The envelope removal method has the advantage of suppressing the background spectrum and expanding the weak absorption characteristic information. However, for second-class water bodies with a relatively complex water quality, there are few studies on the inversion of chlorophyll a (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><mi>h</mi><mi>l</mi><mrow><mtext>-</mtext><mi mathvariant="normal">a</mi></mrow></mrow></semantics></math></inline-formula>) concentration in water bodies that consider the spectral absorption characteristics. In addition, the current research on the inversion of the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><mi>h</mi><mi>l</mi><mrow><mtext>-</mtext><mi mathvariant="normal">a</mi></mrow></mrow></semantics></math></inline-formula> concentration was carried out under the condition of sample concentration equilibrium. For areas with a highly variable <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><mi>h</mi><mi>l</mi><mrow><mtext>-</mtext><mi mathvariant="normal">a</mi></mrow></mrow></semantics></math></inline-formula> concentration, it is still challenging to establish a highly applicable and accurate <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><mi>h</mi><mi>l</mi><mrow><mtext>-</mtext><mi mathvariant="normal">a</mi></mrow></mrow></semantics></math></inline-formula> concentration inversion model. Taking Dongting Lake in China as an example, this study used high-concentration samples and spectral absorption characteristics to invert the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><mi>h</mi><mi>l</mi><mrow><mtext>-</mtext><mi mathvariant="normal">a</mi></mrow></mrow></semantics></math></inline-formula> concentration. The decap method was used to preprocess the high-concentration samples with large deviations, and the envelope removal method was used to extract the spectral absorption characteristic parameters of the water body. On the basis of the correlation analysis between the water <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><mi>h</mi><mi>l</mi><mrow><mtext>-</mtext><mi mathvariant="normal">a</mi></mrow></mrow></semantics></math></inline-formula> concentration and the spectral absorption characteristics, the water <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><mi>h</mi><mi>l</mi><mrow><mtext>-</mtext><mi mathvariant="normal">a</mi></mrow></mrow></semantics></math></inline-formula> concentration was inverted. The results showed the following: (1) The bands that were significantly related to the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><mi>h</mi><mi>l</mi><mrow><mtext>-</mtext><mi mathvariant="normal">a</mi></mrow></mrow></semantics></math></inline-formula> concentration and had a large correlation coefficient were mainly located in the three absorption valleys (400–580, 580–650, and 650–710 nm) of the envelope removal curve. Moreover, the correlation between the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><mi>h</mi><mi>l</mi><mrow><mtext>-</mtext><mi mathvariant="normal">a</mi></mrow></mrow></semantics></math></inline-formula> concentration and the absorption characteristic parameters at 650–710 nm was better than that at 400–580 nm and 580–650 nm. (2) Compared with the conventional inversion model, the uncapped inversion model had a higher R<sub>P</sub><sup>2</sup> and a lower RMSE<sub>P</sub>, and was closer to the predicted value of the 1:1 line. Moreover, the performance of the uncapped inversion model was better than that of the conventional inversion model, indicating that the uncapped method is an effective preprocessing method for high-concentration samples with large deviations. (3) The predictive capabilities of the ER_New model were significantly better than those of the R_New model. This shows that the envelope removal method can significantly amplify the absorption characteristics of the original spectrum, which can significantly improve the performance of the prediction model. (4) From the inversion models for the absorption characteristic parameters, the prediction models of A<sub>650–710 nm</sub>_New and D<sub>650–710 nm</sub>_New exhibited the best performance. The three combined models (A<sub>650–710 nm</sub>&D<sub>650–710 nm</sub>_New, A<sub>650–710 nm</sub>&NI_New, A<sub>650–710 nm</sub>&DI_New) also demonstrated good predictive capabilities. This demonstrates the feasibility of using the spectral absorption feature to retrieve the chlorophyll concentration.
format	article
author	Yun Xue Yi-Min Wen Zhong-Man Duan Wei Zhang Fen-Liang Liu
author_facet	Yun Xue Yi-Min Wen Zhong-Man Duan Wei Zhang Fen-Liang Liu
author_sort	Yun Xue
title	Retrieval of Chlorophyll a Concentration in Water Considering High-Concentration Samples and Spectral Absorption Characteristics
title_short	Retrieval of Chlorophyll a Concentration in Water Considering High-Concentration Samples and Spectral Absorption Characteristics
title_full	Retrieval of Chlorophyll a Concentration in Water Considering High-Concentration Samples and Spectral Absorption Characteristics
title_fullStr	Retrieval of Chlorophyll a Concentration in Water Considering High-Concentration Samples and Spectral Absorption Characteristics
title_full_unstemmed	Retrieval of Chlorophyll a Concentration in Water Considering High-Concentration Samples and Spectral Absorption Characteristics
title_sort	retrieval of chlorophyll a concentration in water considering high-concentration samples and spectral absorption characteristics
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/05317471f35f47c2aab46a9cc1af7f22
work_keys_str_mv	AT yunxue retrievalofchlorophyllaconcentrationinwaterconsideringhighconcentrationsamplesandspectralabsorptioncharacteristics AT yiminwen retrievalofchlorophyllaconcentrationinwaterconsideringhighconcentrationsamplesandspectralabsorptioncharacteristics AT zhongmanduan retrievalofchlorophyllaconcentrationinwaterconsideringhighconcentrationsamplesandspectralabsorptioncharacteristics AT weizhang retrievalofchlorophyllaconcentrationinwaterconsideringhighconcentrationsamplesandspectralabsorptioncharacteristics AT fenliangliu retrievalofchlorophyllaconcentrationinwaterconsideringhighconcentrationsamplesandspectralabsorptioncharacteristics
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spelling	oai:doaj.org-article:05317471f35f47c2aab46a9cc1af7f222021-11-11T19:45:57ZRetrieval of Chlorophyll a Concentration in Water Considering High-Concentration Samples and Spectral Absorption Characteristics10.3390/su1321121442071-1050https://doaj.org/article/05317471f35f47c2aab46a9cc1af7f222021-11-01T00:00:00Zhttps://www.mdpi.com/2071-1050/13/21/12144https://doaj.org/toc/2071-1050The envelope removal method has the advantage of suppressing the background spectrum and expanding the weak absorption characteristic information. However, for second-class water bodies with a relatively complex water quality, there are few studies on the inversion of chlorophyll a (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><mi>h</mi><mi>l</mi><mrow><mtext>-</mtext><mi mathvariant="normal">a</mi></mrow></mrow></semantics></math></inline-formula>) concentration in water bodies that consider the spectral absorption characteristics. In addition, the current research on the inversion of the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><mi>h</mi><mi>l</mi><mrow><mtext>-</mtext><mi mathvariant="normal">a</mi></mrow></mrow></semantics></math></inline-formula> concentration was carried out under the condition of sample concentration equilibrium. For areas with a highly variable <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><mi>h</mi><mi>l</mi><mrow><mtext>-</mtext><mi mathvariant="normal">a</mi></mrow></mrow></semantics></math></inline-formula> concentration, it is still challenging to establish a highly applicable and accurate <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><mi>h</mi><mi>l</mi><mrow><mtext>-</mtext><mi mathvariant="normal">a</mi></mrow></mrow></semantics></math></inline-formula> concentration inversion model. Taking Dongting Lake in China as an example, this study used high-concentration samples and spectral absorption characteristics to invert the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><mi>h</mi><mi>l</mi><mrow><mtext>-</mtext><mi mathvariant="normal">a</mi></mrow></mrow></semantics></math></inline-formula> concentration. The decap method was used to preprocess the high-concentration samples with large deviations, and the envelope removal method was used to extract the spectral absorption characteristic parameters of the water body. On the basis of the correlation analysis between the water <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><mi>h</mi><mi>l</mi><mrow><mtext>-</mtext><mi mathvariant="normal">a</mi></mrow></mrow></semantics></math></inline-formula> concentration and the spectral absorption characteristics, the water <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><mi>h</mi><mi>l</mi><mrow><mtext>-</mtext><mi mathvariant="normal">a</mi></mrow></mrow></semantics></math></inline-formula> concentration was inverted. The results showed the following: (1) The bands that were significantly related to the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><mi>h</mi><mi>l</mi><mrow><mtext>-</mtext><mi mathvariant="normal">a</mi></mrow></mrow></semantics></math></inline-formula> concentration and had a large correlation coefficient were mainly located in the three absorption valleys (400–580, 580–650, and 650–710 nm) of the envelope removal curve. Moreover, the correlation between the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><mi>h</mi><mi>l</mi><mrow><mtext>-</mtext><mi mathvariant="normal">a</mi></mrow></mrow></semantics></math></inline-formula> concentration and the absorption characteristic parameters at 650–710 nm was better than that at 400–580 nm and 580–650 nm. (2) Compared with the conventional inversion model, the uncapped inversion model had a higher R<sub>P</sub><sup>2</sup> and a lower RMSE<sub>P</sub>, and was closer to the predicted value of the 1:1 line. Moreover, the performance of the uncapped inversion model was better than that of the conventional inversion model, indicating that the uncapped method is an effective preprocessing method for high-concentration samples with large deviations. (3) The predictive capabilities of the ER_New model were significantly better than those of the R_New model. This shows that the envelope removal method can significantly amplify the absorption characteristics of the original spectrum, which can significantly improve the performance of the prediction model. (4) From the inversion models for the absorption characteristic parameters, the prediction models of A<sub>650–710 nm</sub>_New and D<sub>650–710 nm</sub>_New exhibited the best performance. The three combined models (A<sub>650–710 nm</sub>&D<sub>650–710 nm</sub>_New, A<sub>650–710 nm</sub>&NI_New, A<sub>650–710 nm</sub>&DI_New) also demonstrated good predictive capabilities. This demonstrates the feasibility of using the spectral absorption feature to retrieve the chlorophyll concentration.Yun XueYi-Min WenZhong-Man DuanWei ZhangFen-Liang LiuMDPI AGarticlespectral absorption characteristicschlorophyll-aDongting LakeEnvironmental effects of industries and plantsTD194-195Renewable energy sourcesTJ807-830Environmental sciencesGE1-350ENSustainability, Vol 13, Iss 12144, p 12144 (2021)

Retrieval of Chlorophyll a Concentration in Water Considering High-Concentration Samples and Spectral Absorption Characteristics

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