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National standard for chlorophyll-a concentration limit in water quality: the cornerstone of safeguarding water ecological health
Date: 2025-11-27Read: 2
Chlorophyll a, as the main pigment for photosynthesis in phytoplankton, is a key indicator of algal biomass in water. Its existence and concentration directly reflect the level of primary productivity in water bodies, thereby revealing the health status of aquatic ecosystems. In short, chlorophyll-a is a barometer of the abundance of algae in water bodies.
In a healthy aquatic ecosystem, an appropriate amount of chlorophyll-a represents the normal growth of aquatic plants and algae, which are the foundation of the aquatic food chain and provide food and oxygen for fish and other aquatic organisms. However, when there is an excess of nutrients (such as nitrogen and phosphorus) in the water, the concentration of chlorophyll-a will sharply increase, leading to overgrowth of algae, commonly known as the "algal bloom" or "red tide" phenomenon. This phenomenon can seriously disrupt the ecological balance of water bodies and affect the survival of aquatic organisms.
It is crucial to pay attention to the concentration of chlorophyll-a in water bodies, as it directly affects the degree of eutrophication of the water. Eutrophication is a major water environmental problem that can lead to reduced water transparency, dissolved oxygen consumption, fish mortality, and even the production of algal toxins, posing a serious threat to human health and the ecological environment. Therefore, by monitoring and controlling the concentration of chlorophyll-a, eutrophication of water bodies can be effectively prevented, ensuring the health of aquatic ecosystems and the sustainable use of water resources.
How does the national standard define the concentration limit of chlorophyll-a?
China has a clear and important basis for the concentration limit of chlorophyll-a in water quality management. One of the most important documents is the "Nutrient Standards for Lakes - Central and Eastern Lake Regions (Total Phosphorus, Total Nitrogen, Chlorophyll a) (2020 Edition)" released by the Ecological Environment of the People's Republic of ChinaThis benchmark is an important nutrient benchmark for lakes in China, providing scientific guidance and legal basis for controlling the concentration of chlorophyll-a in lake water.
According to the "Nutrient Standards for Lakes - Central and Eastern Lake Regions (Total Phosphorus, Total Nitrogen, Chlorophyll a) (2020 Edition)", the national standard for the concentration limit of chlorophyll a (Chl-a) in the nutrient standards for lakes in the central and eastern lake regions is3.4 μg/LThis value has been verified through extensive scientific research and practice, aiming to ensure the healthy and stable ecological functions of lake water bodies and effectively curb the trend of eutrophication.
Although the "Nutrient Standards for Lakes" specify the chlorophyll-a limit for lakes, the evaluation criteria for different types of water bodies such as rivers and reservoirs will be focused on. For example, the Environmental Quality Standards for Surface Water (GB3838-2002)Although there is no direct limit on the concentration of chlorophyll-a, it is considered as one of the five important indicators for evaluating the nutritional status of lakes and reservoirs (the other four being total phosphorus, total nitrogen, transparency, and permanganate index). This means that when evaluating the water quality of rivers and reservoirs, the concentration of chlorophyll-a is also an important parameter for measuring their nutritional status and ecological health, but specific limits may need to be comprehensively evaluated based on factors such as water body function and regional characteristics.
When the concentration of chlorophyll-a in water exceeds the national standard or appropriate range, it can cause a series of serious ecological problems. The direct result is a sharp decrease in water transparency, which affects the photosynthesis of underwater plants and leads to an imbalance in the structure of aquatic ecosystems. Secondly, the decomposition of a large number of algae after death consumes dissolved oxygen in the water, causing hypoxia and even leading to large-scale deaths of fish and other aquatic organisms. More seriously, certain algae (such as blue-green algae) can produce algal toxins, which are not only toxic to aquatic organisms, but also transmitted through the food chain, ultimately threatening human drinking water safety and physical health. For example, when the concentration of chlorophyll-a is too high, the water may appear green or even blue-green, accompanied by an odor, seriously affecting the landscape and functional use of the water.
Monitoring and Application: How to effectively monitor chlorophyll-a and ensure water quality?
At present, the methods for monitoring chlorophyll-a concentration in water mainly include laboratory analysis and on-site rapid determination. The laboratory analysis method usually uses spectrophotometry, which calculates the concentration by filtering the water sample, extracting chlorophyll a, and measuring its absorbance at a specific wavelength. This method has high accuracy, but it takes a long time and is not suitable for real-time monitoring. The on-site rapid measurement method includes fluorescence method, etc., which has the characteristics of fast and convenient, and can meet the needs of real-time monitoring on site.
With the advancement of technology, modern water quality monitoring technology provides a more efficient and convenient solution for precise measurement of chlorophyll-a. ERUN-SP8-ASC-2 developed and produced by Yingrun GroupPortable handheld chlorophyll blue-green algae analyzerERUN-SZ2-B-L3Water quality chlorophyll-a sensor online analyzerFor example, they all use fluorescence sensing technology to achieve rapid and accurate determination of chlorophyll-a concentration in water without the need to add any reagents. Among them, the ERUN-SP8-ASC-2 portable handheld chlorophyll blue-green algae analyzer is suitable for quick on-site measurement, while the ERUN-SZ2-B-L3 water quality chlorophyll a sensor online analyzer can be fixedly installed to achieve continuous real-time monitoring of chlorophyll a concentration in water bodies. These devices have high repeatability and long-term stability, greatly improving the efficiency and accuracy of water quality monitoring, and are widely used in various fields such as rivers, lakes, ponds, marine exploration, aquaculture, and drinking water sources.
Chlorophyll a monitoring data is an important basis for water environment management decisions. Through long-term and continuous monitoring, the trend of changes in chlorophyll-a concentration in water bodies can be grasped, and the risk of eutrophication in water bodies can be detected in a timely manner, providing scientific support for water pollution prevention and ecological restoration. For example, when monitoring data shows that the concentration of chlorophyll-a continues to rise and approaches or exceeds the limit of 3.4 μ g/L, relevant departments can quickly take measures, such as controlling pollution sources entering lakes (reservoirs), carrying out ecological dredging, and releasing biological agents, to avoid the outbreak of algal blooms. In addition, these data also provide quantitative basis for evaluating the effectiveness of water environment governance and formulating more scientific water quality management policies.