Indicators of Water Quality and its Application in Huangpu River

Water is vital to life: it has diverse usages including but not limited to the human body, industrial production, agricultural irrigation, and cleaning. In the human body, water plays a key role in many of our body's main functions, including bringing nutrients to cells, getting rid of wastes, and protecting joints and organs: e.g. blood is comprised of water, protein, and inorganic salt. Its function includes transportation, homeostasis, defense, regulating the osmotic pressure of the human body, and balancing acid and base. Contamination in water might result in huge health hazards: According to the World Health Organization, “Contaminated water and poor sanitation are linked to transmission of diseases such as cholera, diarrhea, dysentery, hepatitis A, typhoid and polio. Absent, inadequate, or inappropriately managed water and sanitation services expose individuals to preventable health risks.” [1]

China has classified water into ranks according to environmental functions and protection objectives of surface waters:

Note: Water that exceeds all five ranks of water quality has no basic usage [2]

It’s clearly shown in the chart that drinking water should satisfy or at least exceed rank II of water quality standards

In addition to a literal description of water quality in each rank, Water quality, an important aspect of environmental monitoring, is often assessed using various indicators. The common indicators of water include Temperature and dissolved Oxygen (DO), pH, Total Dissolved Solids (TDS), Conductivity, & Suspended Sediment, Nutrients level (especially concentration of phosphorus and nitrogen), Metals (heavy metals), Hydrocarbons, and Industrial Chemicals. Here a specific explanation for DO is addressed for clarification: According to the United States Geological Survey, Dissolved Oxygen (DO) is “a measure of how much oxygen is dissolved in the water - the amount of oxygen available to living aquatic organisms.” [3] The values of these indicators are interconnected, and one value can provide insight into the other indicators, leading to a better understanding of the overall water quality. For instance, if DO in water is low, in some situations, it’s expected to see a high nutrient level, suspended sediment, and total dissolved solids. This may suggest that the water has been contaminated by runoff from nearby agricultural land. Integrating Data from document numbering GB-3838, titled Environmental Quality Standards for Surface Water issued by State Environmental Protection Administration of China, a similar chart with values of some indicators in each rank is provided, a reference for later discussion of water quality:

A specific case study is provided for the next part:

Huangpu River, the jewel of Shanghai, is the most important waterway in Shanghai, separating Pudong and Puxi (east and west). With a length of approximately 114 kilometers and a width ranging from 300 to 700 meters, the river is the last tributary of the Yangtze River before it empties into the sea. The river plays a key role in industrial production, irrigation, and the life of citizens, supplying water for diverse purposes. In recent years, partly due to urbanization and increased industrial development in Shanghai, the water quality of the Huangpu River has significantly decreased. Here, a comparison between the different sources of accessing water quality of Huangpu River is provided by reviewing past papers and investigating data.

The waterbody of Huangpu River is overall yellowish and muddy. I'm personally very concerned about that: since only dirty water will show a color of yellow. This turbidity can be attributed to various factors, including the discharge of industrial and urban wastewater, agricultural surface pollution, and high sand content in the river. Most important of all, Shanghai, being a large industrial city, discharges copious amounts of industrial wastewater into the Huangpu River, which contains a high concentration of organic matter, nitrogen, phosphorus, heavy metals, and other harmful substances. This has a significant impact on the water quality of the river. Also, limited sewage treatment capacity results in a considerable amount of untreated sewage being discharged into the Huangpu River. A significant amount of agriculture discharge containing fertilizer run-off also contributes to the problem.

Overall Condition:

The Huangpu River is located downstream of the basin and is greatly affected by the water coming from the upstream, resulting in poor water quality. According to the monitoring data from Shanghai Municipal Bureau of Ecology and Environment in 2021, Huangpu River has overall evaluation of the water quality of the water sources ranging from Category II to Category IV, and some sections of the river and some indicators are Category 5, or even worse than Category V. Especially the water quality of the water sources of Songpu Bridge has not significantly improved, and the indicators of organic matter such as ammonia nitrogen have a tendency to deteriorate, which is not in full compliance with the national quality standards of the surface water environment.

Source: https://sthj.sh.gov.cn/hbzhywp... [4]

Specific Indicators: Data all comes from source [5]

It will be better to look at a Map to figure out which place is upstream and which area is downstream (the source is at Dianfeng):

The above Figure shows the spatial distribution of testing sites along Huangpu River

Nutrient Level Part:

Nutrient level is accessed. According to the study, "TN, ammonia nitrogen, nitrate nitrogen, and TP are main nutrients enriched in the water body." [5] For TN and TP, the lowest value is observed at the DianFeng site, which can be further demonstrated by only DianFeng site of Huangpu River is classified as rank 2 water quality standard, which should give the lowest nutrient level. Overall, the nutrient level significantly increases from the upstream to the downstream site (the order in the graph from left to right is upstream to downstream). The study also proposes that " There were many densely cultivated farms and oyster beds in the upriver areas near Songpu and Linjiang sites", which serve as a cause for high values of nutrient levels especially phosphorus and nitrogen in March, since it's the season for cultivation. [5]

Suspended solids show a similar trend with nutrient level: SS increases along the river from upstream to downstream. Suspended solids are usually directly related to the level of pollution. The highest value of SS is found in Yangpu site. Also, it is found that the river contains more suspended solids during dry seasons than during rainy seasons.

Dissolved Oxygen shows a seasonal and spatial variation (in different sections of Huangpu River). DO shows a trend of higher in winter and lower in summer. This can be explained by a property of oxygen: the solubility of oxygen decreases as temperature increases. The highest value in DO is observed in the upstream site and the lowest in Yangpu site, consistent with the fact that the entire upstream Huangpu River Water Resource Protection Zone is divided into three different levels of protection zones: primary drinking water source protection zones (ranking I), upstream water source protection zones and potential water source protection zones. In its lowest value, DO in July at Yangpu site is less than 2mg/l, which is classified as rank V if refers back to ranking standards.

DO Data

Conclusion:

Overall, Huangpu River's water quality varies among seasons and locations (decreasing from upstream to downstream). The problem of elevated nutrient levels is remarkable: the majority of sites have values higher than the rank II water quality standard for most of the year, which suggests the future path of water treatment. Excessive phosphorus and nitrogen levels in rivers, likely to cause eutrophication, pose potential risks by threatening biodiversity and also public health. Whether for the sake of aesthetics or for the health of the residents, we should pay attention to the Huangpu River water quality management issues, focusing on the run-off from agricultural lands and sewage treatment. There's not much we can do, but we should know this problem's existence.

Reference:

[1]. “Drinking-Water.” Newsroom/Fact Sheets/Detail/Drinking-Water, World Health Organization, 13 Sept. 2023, www.who.int/news-room/fact-sheets/detail/drinking-water#:~:text=Contamin....

[2]. “Water Quality Classification (Water Quality Standards for Surface Water Ranks I,II,III,IV,V).” 中环网, 18 Feb. 2023, epzhw.com:8080/jishu/jishuzhongxin/820651783440982016.html.

[3]. “Dissolved Oxygen and Water Completed.” Dissolved Oxygen and Water, U.S. Geological Survey, 5 June 2018, www.usgs.gov/special-topics/water-science-school/science/dissolved-oxyge...(DO)%20is%20a,lot%20about%20its%20water%20quality.

[4]. “Water Quality of Shanghai Surface Water in 2021 June.” 2021年6月上海市地表水水质状况-信息公开_水环境质量_, Shanghai Municipal Bureau of Ecology and Environment, 15 July 2021, sthj.sh.gov.cn/hbzhywpt1143/hbzhywpt1149/20210715/ebb7e70036ba43ddbe97adc8b0d09103.html.

[5]. Hong-jun YANG, Zhe-min SHEN, Jin-ping ZHANG, Wen-hua WANG,

Water quality characteristics along the course of the Huangpu River (China), Journal of Environmental Sciences, Volume 19, Issue 10, 2007, Pages 1193-1198, ISSN 1001-0742,

https://doi.org/10.1016/S1001-... (https://www.sciencedirect.com/science/article/pii/S1001074207601958)

Abstract: Abstract

Huangpu River is about 114.5 km from upriver Dianfeng to downriver Wusong, near the estuary of the Yangtze River. It plays a key role in supplying water for production, life, shipment and irrigation. With the industrial development, the pollution of the Huangpu River has become serious recently. The biological oxygen demand (BOD), total nitrogen (TN), total phosphorus (TP), oil, phenol and suspended solids (SS) were lower in the upstream sites than in the downstream sites, indicating pollutants being input along its course. Water quality was the worst in the Yangpu site, near the center of Shanghai City. Dissolved oxygen (DO) content was less than 2 mg/L in the site of Yangpu in July. Among relations between thirteen characteristics, relations between BOD, DO, TN, TP, NH4+-N, NO3−-N and the count of total bacteria or Escherichia coli were significant and interdependent. Inner relationships between these main characteristics in the Huangpu River were studied. High nutrient concentration led to growth of microorganisms, including E. coli. Degradation of organic matters and respiration of bacteria made oxygen concentration decreased in the water body, and DO was a key factor for nitrification-denitrification process of nitrogen. In the Yangpu site, DO was decreased to less than 3.0 mg/L with BOD higher than 7.5 mg/L in May and July. Low DO concentration will decrease nitrification rate. Nitrification need at higher DO value than other organic substrate oxidation. Consequently, river water contains low NO3−-N values with high amounts of TN and NH4+-N there. This will block the self-purification of surface water, by decreasing the rate of nitrification-denitrification transformation process in the water body.

Keywords: water quality; ecological assessment; Huangpu River; nitrification