Research on the Correlation Between Chlorophyll-a and Organic Matter BOD, COD, Phosphorus, and Total Nitrogen in Stagnant Lake Basins

Song Toan Pham Phu

Abstract We are frequently required to assess, mitigate, and monitor certain environmental risks involved in our daily activities at both the local and global environment levels. Corporations, in particular, can cause environmental pollution or other risks as a result of either accidents or natural events. In order to limit, and hopefully prevent, these environmental impacts, environmental risk management places a strong emphasis on targeting the problems that could arise, and implements a system of metrics that help with prevention and management. Eutrophication is one example of a widespread environmental pollution phenomenon that is currently worsening in lake basins. Proliferation of phytoplankton is due primarily to high concentrations of nitrogen (N) and phosphorus (P) discharged from industrial and urban waste. However, assessing, managing, and forecasting the pollution of basins requires considerable time and support tools to analyze a range of water quality indicators over time and geographical area. This study investigated the relationship between organic matter (chemical oxygen demand, biochemical oxygen demand, total N, and P) and biomass of phytoplankton (indicated by Chlorophyll-a) in order to shorten the period required for analysis, predict eutrophication of lakes ahead of time, and promptly prevent the spread of contaminants. Based on this relationship, we can use Chlorophyll-a as a biological indicator in monitoring and assessing the levels of organic pollution. In addition, we can identify ways to reduce pollution and transportation of pollutants in stagnant lake basins, and contribute to reducing the damage due to environmental risks.

Keywords Chlorophyll-a • Environmental risk management • Eutrophication • Organic pollutants • Phytoplankton

Introduction

Water pollution is a problem of concern all over the world and it involves difficult issues relating to water management and environmental protection. It not only affects a large water surface and destroys aquatic communities, but also impacts on human health and quality of life. In developing countries nowadays, the consequences of industrial development and urban population growth involve issues of water pollution, leading especially to pollution of foodstuffs. This raises the urgent need for a monitoring program with specific early warning targets to enable measures to be taken to prevent pollution in a timely manner.

Eutrophication is a natural process that has been occurring for thousands of years. Its speed has increased rapidly in recent decades due to human activities. Eutrophication involves an increase in nutrients (especially nitrogen and phosphorus) in water, causing excessive growth of the lower species of plants such as algae. It creates major changes in aquatic ecosystems, causing deterioration of water quality. The biochemical basis of the eutrophication process is photochemical reaction, which increases phytoplankton biomass (Fig. 15.1).

There are many indicators to assess water quality including physical, chemical, and biological indicators. Phytoplankton in particular are considered to be an evaluation parameter for organic pollution. Chlorophyll, meanwhile, has long been known as a major pigment with the role of absorbing solar radiation energy as part of the optical response of plant biomass. Therefore, assessment of phytoplankton biomass through chlorophyll analysis requires a combination of chemical and biological methods. From chlorophyll concentration we can establish the relationship between chlorophyll and other pollution parameters to be able to quickly assess the status of eutrophication and organic pollution in a lake basin. Thus we can evaluate water quality through chlorophyll indicators.

Fig. 15.1 The eutrophication process (Source: renault.com)

Table 15.1 OECD classification of nutrients in lakes

Source: OECD-Organization for Economic Co-operation and Development

The role of phytoplankton in nutrient-rich freshwater is large. They provide oxygen for aerobic organisms, disintegrate organic compounds, and remove minerals and other nutrients from the environment. But when excessive growth of phytoplankton occurs, algal blooms reduce the decomposition of algae in the sediment and lead to the destruction of water ecosystems.

There are many methods of assessing phytoplankton biomass, including:

• Calculating individual density combined with measuring average individual volume of all species;

• Measuring the weight of all individuals in a unit volume;

• Measuring carbon concentration derived from organic matter;

• Measuring the pigment concentration;

• Measuring the rate of exchange of oxygen and carbon dioxide;

• Measuring adenosine triphosphate (ATP).

Of the above, measuring pigment concentration is the most viable method. The photosynthetic reaction of phytoplankton generates biomass, which can therefore be assessed just by determining the pigment concentration. This differs from the other parameters above that are integrated in the metabolism of phytoplankton. Therefore analysis of Chlorophyll-a (Chl-a) is a good means of estimating the nutritional status of a lake. This method is simpler, faster, and more economical than estimating phytoplankton biomass by microscopy. Thus Chl-a concentration can determine the level of lake eutrophication (Table 15.1).

 
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