Lakhasly

Since the 21st century, with the continuous improvement in human living standards, the problems of global climate change, rapid population growth, and environmental pollution have become increasingly serious.The main water quality parameters include chemical oxygen demand (COD), heavy metal content, nitrate nitrogen (NO3-N), dissolved organic carbon (DOC), and turbidity.In addition, the research progress on the determination of COD, heavy metal ions, nitrate nitrogen, and DOC by UV-Vis spectroscopy was described in detail.In recent years, due to the advantages of high precision, high detection efficiency, nondestructive sampling, environmental protection, low cost, and portability, ultraviolet-visible (UV-Vis) technology combined with a variety of advanced technologies has developed into an excellent and effective tool for detecting pollutants in aqueous environments [7].In recent years, due to the advantages of high precision, high detection efficiency, nondestructive sampling, environmental protection, low cost, and portability, ultraviolet-visible (UV-Vis) technology combined with a variety of advanced technologies has developed into an excellent and effective tool for detecting pollutants in aqueous environments [7].This paper introduced the theoretical basis of determining various water quality parameters by UV-Vis spectroscopy and expounds the complete spectral data analysis process, including data preprocessing (Section 3.1), extraction of the characteristic wavelength (Section 3.2), establishment of absorbance and relevant water quality parameter model (Section 3.3), as shown in Figure 2.This paper introduced the theoretical basis of determining various water quality parameters by UV-Vis spectroscopy and expounds the complete spectral data analysis process, including data preprocessing (Section 3.1), extraction of the characteristic wavelength (Section 3.2), establishment of absorbance and relevant water quality parameter model (Section 3.3), as shown in Figure 2.UV-Vis spectrum analysis is an important development direction for water quality monitoring, which evaluates the degree of water pollution by establishing a correlation model of absorbance, organic matter, and inorganic matter concentration (Section 3.3) [8].UV-Vis spectrum analysis is an important development direction for water quality monitoring, which evaluates the degree of water pollution by establishing a correlation model of absorbance, organic matter, and inorganic matter concentration (Section 3.3) [8].Spectroscopy is a method to identify substances and conduct quantitative determination through the emission or absorption spectra of substances, which have been frequently used in the field of rapid water quality determination in recent years [6].Spectroscopy is a method to identify substances and conduct quantitative determination through the emission or absorption spectra of substances, which have been frequently used in the field of rapid water quality determination in recent years [6].Although some researchers have tried to summarize the field before [9], with the deepening of UV-Vis spectroscopy in this field of water quality detection, its research objects and research methods have also undergone tremendous changes.Although some researchers have tried to summarize the field before [9], with the deepening of UV-Vis spectroscopy in this field of water quality detection, its research objects and research methods have also undergone tremendous changes.With rapid social development and the increasing use of agricultural fertilizers, an increasing number of industrial pollutants are discharged into rivers and oceans, causing eutrophication.For example, Giudicianni et al. [10] used principal component analysis (PCA) and wavelet transform to calculate water quality index.Sci.Sci.

Since the 21st century, with the continuous improvement in human living standards, the problems
of global climate change, rapid population growth, and environmental pollution have become
increasingly serious. Human activities have exerted great pressure on the environment. Among the
many environmental problems, addressing water pollution is an urgent need [1].
Water is an indispensable element of human production and life, and is also related to food security,
environmental protection, and human health, among other aspects. With rapid social development
and the increasing use of agricultural fertilizers, an increasing number of industrial pollutants are
discharged into rivers and oceans, causing eutrophication. When the original ecosystem is destroyed,
the oxygen content of water is reduced, and many fish and other species are killed, leading to challenges
in terms of water resource conservation [2]. As the living standards of consumers have standardized
upward, demand for higher a quality and quantity of water has emerged relative to the past [3].
Scientifically based water quality index (WQI) models then become important to measure the
degree of contamination and advise whether specific water resources require restoration and to
what extent [4]. The main water quality parameters include chemical oxygen demand (COD), heavy
metal content, nitrate nitrogen (NO3-N), dissolved organic carbon (DOC), and turbidity. At present,
the methods for determining water quality parameters mainly include chemical, biological, and physical
methods [5]. As shown in Figure 1, the main chemical methods are titration analysis and electrochemical
analysis, both of which determine the pollutant content in the laboratory. The instrument used is
bulky and expensive, and a large number of reagents are required, leading to secondary pollution;
Appl. Sci. 2020, 10, 6874; doi:10.3390/app10196874 www.mdpi.com/journal/applsci
Appl. Sci. 2020, 10, 6874 2 of 18
further, the results are not real-time results. Biological methods mainly include enrichment analysis
and biosensor technology; however, the detection accuracy and sensitivity are far lower than in other
methods. Physical methods mainly include hyper spectral remote sensing technology and molecular
spectroscopy technology. Spectroscopy is a method to identify substances and conduct quantitative
determination through the emission or absorption spectra of substances, which have been frequently
used in the field of rapid water quality determination in recent years [6].
Appl. Sci. 2020, 10, x FOR PEER REVIEW 2 of 18
electrochemical analysis, both of which determine the pollutant content in the laboratory. The
instrument used is bulky and expensive, and a large number of reagents are required, leading to
secondary pollution; further, the results are not real-time results. Biological methods mainly include
enrichment analysis and biosensor technology; however, the detection accuracy and sensitivity are
far lower than in other methods. Physical methods mainly include hyper spectral remote sensing
technology and molecular spectroscopy technology. Spectroscopy is a method to identify
substances and conduct quantitative determination through the emission or absorption spectra of
substances, which have been frequently used in the field of rapid water quality determination in
recent years [6].
Figure 1. Methods for determining water quality.
In recent years, due to the advantages of high precision, high detection efficiency,
nondestructive sampling, environmental protection, low cost, and portability, ultraviolet-visible
(UV-Vis) technology combined with a variety of advanced technologies has developed into an
excellent and effective tool for detecting pollutants in aqueous environments [7]. UV-Vis spectrum
analysis is an important development direction for water quality monitoring, which evaluates the
degree of water pollution by establishing a correlation model of absorbance, organic matter, and
inorganic matter concentration (Section 3.3) [8].
Although some researchers have tried to summarize the field before [9], with the deepening of
UV-Vis spectroscopy in this field of water quality detection, its research objects and research
methods have also undergone tremendous changes. Many researchers have proposed many novel
research methods for different water quality parameters. For example, Giudicianni et al. [10] used
principal component analysis (PCA) and wavelet transform to calculate water quality index. Its
applicability was discussed. Ma et al. [11] used the modified water quality index (WQI) to evaluate
the water quality of the aquaculture area. The main factors affecting water quality were determined
by using PCA. Therefore, a review is very necessary to sort out the research process and methods in
this field, especially in the latest application progress of ultraviolet spectroscopy technology.
This paper introduced the theoretical basis of determining various water quality parameters by
UV-Vis spectroscopy and expounds the complete spectral data analysis process, including data
preprocessing (Section 3.1), extraction of the characteristic wavelength (Section 3.2), establishment
of absorbance and relevant water quality parameter model (Section 3.3), as shown in Figure 2. In
addition, the research progress on the determination of COD, heavy metal ions, nitrate nitrogen,
and DOC by UV-Vis spectroscopy was described in detail.
Figure 1. Methods for determining water quality.
In recent years, due to the advantages of high precision, high detection efficiency, nondestructive
sampling, environmental protection, low cost, and portability, ultraviolet-visible (UV-Vis) technology
combined with a variety of advanced technologies has developed into an excellent and effective tool
for detecting pollutants in aqueous environments [7]. UV-Vis spectrum analysis is an important
development direction for water quality monitoring, which evaluates the degree of water pollution by
establishing a correlation model of absorbance, organic matter, and inorganic matter concentration
(Section 3.3) [8].
Although some researchers have tried to summarize the field before [9], with the deepening of
UV-Vis spectroscopy in this field of water quality detection, its research objects and research methods
have also undergone tremendous changes. Many researchers have proposed many novel research
methods for different water quality parameters. For example, Giudicianni et al. [10] used principal
component analysis (PCA) and wavelet transform to calculate water quality index. Its applicability
was discussed. Ma et al. [11] used the modified water quality index (WQI) to evaluate the water
quality of the aquaculture area. The main factors affecting water quality were determined by using
PCA. Therefore, a review is very necessary to sort out the research process and methods in this field,
especially in the latest application progress of ultraviolet spectroscopy technology.
This paper introduced the theoretical basis of determining various water quality parameters
by UV-Vis spectroscopy and expounds the complete spectral data analysis process, including data
preprocessing (Section 3.1), extraction of the characteristic wavelength (Section 3.2), establishment of
absorbance and relevant water quality parameter model (Section 3.3), as shown in Figure 2. In addition,
the research progress on the determination of COD, hea