Answer: By utilizing the fluorescence excitation properties of phycocyanin in cyanobacteria, a specific wavelength light beam excites the phycocyanin.
The intensity of the emitted fluorescence is then measured to accurately calculate the cyanobacteria concentration.

Yes. Water purifier filter cartridges have a limited lifespan. Failure to replace them over time can lead to reduced filtration effectiveness and even bacterial growth. It is recommended to test the output water quality every 6-12 months to determine if the filter cartridge needs replacement.

Chlorine odor: This is typically residual chlorine from disinfection at the water treatment plant, which is normal. Boiling the water will eliminate the odor, and testing is generally unnecessary.

Fishy or earthy odor: This may indicate aging pipes, contamination in secondary water supply tanks, or the proliferation of algae and microorganisms in the water. Testing for microbial and organic indicators is recommended.

Microbiological indicators: Such as total bacterial count and E. coli. Exceeding standards may cause diseases like diarrhea and gastroenteritis.

Heavy metal indicators: such as lead, mercury, and arsenic. Long-term exposure can damage organs like the liver and kidneys, with greater impacts on children's development.

Physical and chemical indicators: pH (normal range 6.5-8.5), residual chlorine (end-of-tap residual chlorine ≥0.05mg/L to ensure disinfection effectiveness), hardness (excessive levels may cause scale buildup, affecting taste and appliance lifespan).

Sampling containers: Use clean, uncontaminated dedicated containers. Avoid using ordinary plastic or glass bottles (residual substances may affect results).

Sampling timing: For tap water testing, open the faucet and let water run for 5-10 minutes after water supply resumes before sampling to avoid interference from stagnant water in pipes.

Timeliness of submission: Submit samples promptly after collection (generally within 24 hours), especially for microbial testing, to prevent sample degradation.

Simple Tools: Use home water testing kits (to measure basic indicators like pH, residual chlorine, and hardness). These are easy to operate but have limited accuracy.

Professional Testing: Engage a third-party testing agency that provides on-site sampling services.
They can test comprehensive indicators such as heavy metals, microorganisms, and organic compounds, delivering more accurate results.

Domestic Scenarios: Testing tap water and drinking water safety to ensure freedom from harmful microorganisms or heavy metals.

Industrial Scenarios: Testing industrial water (such as cooling water and production water) to prevent equipment corrosion or product quality issues.

Environmental Scenarios: Monitoring water quality in rivers, lakes, seas, and groundwater to assess pollution levels and ecological health.

 

Water quality analysis is the process of using specialized methods to test physical, chemical, and biological indicators in water to assess whether the water meets usage standards (such as for drinking, industrial, agricultural, etc.).

Xiong Yi, Chief Economist for China at Deutsche Bank Group, stated in a research report that the renminbi exchange rate may reach a trend inflection point as trade tensions ease. Deutsche Bank Research forecasts that by the end of 2026, the RMB is expected to appreciate to 6.7 against the US dollar.

The firm believes factors such as seasonal export patterns, low short positions in offshore RMB against the dollar, and improving inflation expectations could drive the RMB back toward its long-term appreciation trend.

National Standard Methods for Determining Total Nitrogen in Water

The primary national standard methods for determining total nitrogen in water are as follows:

 

“Water Quality - Determination of Total Nitrogen - Potassium Persulfate Alkaline Digestion and Ultraviolet Spectrophotometric Method” (HJ 636-2012)

 

Scope of Application: Surface water, groundwater, industrial wastewater, and domestic sewage.

Principle: At 120-124°C, alkaline potassium persulfate solution converts nitrogen in nitrogen-containing compounds to nitrate. Absorbance is measured at wavelengths of 220 nm and 275 nm using ultraviolet spectrophotometry. The relationship between corrected absorbance and total nitrogen content is calculated.

Detection Range: 0.2–7 mg/L, detection limit 0.05 mg/L.

Interferences and Elimination: Iodide ions, bromide ions, hexavalent chromium ions, and trivalent iron ions may cause interference. These can be eliminated by dilution or addition of hydroxylamine hydrochloride solution.

Water Quality - Determination of Total Nitrogen - Gas Phase Molecular Absorption Spectroscopy (HJ 199-2023)

 

Scope of Application: Surface water, groundwater, domestic sewage, industrial wastewater, and seawater.

Principle: Using alkaline potassium persulfate as an oxidant, nitrogen in the sample is oxidized to nitrate nitrogen via high-temperature high-pressure digestion or online UV digestion. It is then reduced to nitric oxide by titanium trichloride and measured using a gas phase molecular absorption spectrometer.

Detection Range: Detection limit is 0.05 mg/L for both high-temperature high-pressure digestion and online UV digestion; lower limit of quantification is 0.20 mg/L.

Interferences and Mitigation: Hexavalent chromium, trivalent iron, and high concentrations of organic matter may cause interference. Mitigate by dilution or optimizing digestion conditions.

Water Quality - Determination of Total Nitrogen - Flow Injection-Hydrochloric Acid-Naphthylenediamine Spectrophotometric Method (HJ 668-2013)

 

Scope of Application: Surface water, groundwater, industrial wastewater, and domestic sewage.

Detection Range: 0.12–10 mg/L.

Water Quality—Determination of Total Nitrogen—Continuous Flow-Hydrochloric Acid Naphthylenediamine Spectrophotometric Method (HJ 667-2013)

 

Scope of Application: Surface water, groundwater, industrial wastewater, and domestic sewage.

Detection Range: 0.16–10 mg/L.

Among the above methods, HJ 636-2012 and HJ 199-2023 are currently the most commonly used laboratory determination methods. The specific selection may be determined based on sample type, detection range, and laboratory conditions.

Interrelationships Among Water Testing Parameters in Environmental Monitoring

Relationship Between Hexavalent Chromium and Total Chromium

 

Chromium in water typically exists as trivalent and hexavalent forms, which can convert under certain conditions. Total chromium is the sum of trivalent and hexavalent chromium. Therefore, for the same water sample, the following logical relationship holds:

 

Total Chromium > Hexavalent Chromium

 

Relationship Between Sulfides and Heavy Metals

 

In the same water sample, high sulfide concentrations correlate with lower concentrations of heavy metals (Cu, Pb, Zn, Cd, etc.). However, this relationship may not hold if heavy metals exist in complexed forms.

 

Relationship Between Total Bacteria Count, Coliform Bacteria, and Fecal Coliform Bacteria

 

Coliform bacteria represent only one population among bacterial species and have limited contamination pathways. Long-term testing indicates that samples detecting coliform bacteria also detect total bacteria count. Conversely, samples with high total bacteria counts do not necessarily detect total coliform bacteria. Fecal coliform bacteria belong to the total coliform group and are detected at 44.5°C, which is higher than the 37°C detection temperature for total coliform bacteria. Therefore, fecal coliform values are typically lower than total coliform values, i.e., fecal coliform value < total coliform value.

Interrelationships Among Water Quality Parameters in Environmental Monitoring

Relationship Between Nitrite Nitrogen and Total Nitrogen

 

Nitrogen primarily exists in aquatic environments as nitrate, nitrite, ammonia, and organic nitrogen. Therefore, total nitrogen should equal the sum of nitrite nitrogen and organic nitrogen. For the same water sample, the following logical relationships hold:

 

Total Nitrogen > Ammonia Nitrogen Total Nitrogen > Sum of Ammonia Nitrogen, Nitrate Nitrogen, and Nitrite Nitrogen

 

Interrelationships Among Water Quality Parameters in Environmental Monitoring

Relationship Between Water Temperature and Dissolved Oxygen

 

The distribution and variation of dissolved oxygen in water result from the combined influence of temperature, biological activity, chemical processes, and various physical phenomena. Overall, it is primarily controlled by water temperature, exhibiting pronounced seasonal fluctuations. Dissolved oxygen levels in water show a negative correlation with temperature and generally should not exceed the saturation level corresponding to the prevailing water temperature.

 

Interrelationships Among Water Quality Parameters in Environmental Monitoring

Relationship Between Nitrogen Compounds and Dissolved Oxygen

 

Since the forms of nitrogen present in the environment change with variations in environmental conditions, particularly influenced by the concentration of dissolved oxygen in water bodies, nitrate nitrogen and ammonia nitrogen cannot be high simultaneously. Generally, in water bodies with high dissolved oxygen, the concentration of nitrate nitrogen is higher than that of ammonia nitrogen, and conversely, the concentration of ammonia nitrogen is higher than that of nitrate nitrogen. Nitrite nitrogen concentrations show no significant correlation with these parameters.

Interrelationships Among Water Testing Parameters in Environmental Monitoring

Relationship Between Petroleum Hydrocarbons and CODcr

 

Petroleum hydrocarbons are organic pollutants that can be oxidized by potassium dichromate. Higher concentrations of petroleum hydrocarbons correlate with elevated CODcr values, though no fixed correlation coefficient exists.

Interrelationships Among Water Quality Parameters in Environmental Monitoring

Relationship Between TOC, CODCr, and CODMn
 

Total Organic Carbon (TOC) is a comprehensive indicator representing the total organic matter content in water expressed as carbon content. TOC employs combustion methods to fully oxidize organic matter, directly indicating the degree of organic pollution in water bodies. TOC, CODCr, and CODMn are all indicators measuring organic pollution levels in water. Test results from domestic sewage and industrial wastewater across various sectors show significant correlations between TOC and both CODCr and CODMn. Theoretically, CODcr expresses oxygen consumption in terms of oxygen (O₂) consumed, while TOC expresses it in terms of carbon (C). The ratio between them is O₂/C = 32/12 = 2.7. For specific water bodies, this conversion factor is sufficient. However, due to variations in water composition and organic content across different water bodies—and even within the same body of water due to seasonal changes, inflow conditions, production processes, and raw material variations—the conversion relationship between these parameters must be experimentally determined.

Probest with the PUVCOD900-TOC, PCM200-CODCr, PCM200-CODMn, PUVCOD-900-COD water quality monitoring Analysis. 

Interrelationships Among Water Testing Parameters in Environmental Monitoring

Total Dissolved Solids and Total Hardness

 

Since water contains eight primary ions, including Ca²⁺ and Mg²⁺, the total hardness of a water sample is defined as the sum of carbonate hardness and non-carbonate hardness. Non-carbonate hardness must be determined. When total hardness is measured using the CO DMn (acidic method), CO Dcr > BOD₅.

Interrelationships Among Water Testing Parameters in Environmental Monitoring

Total Dissolved Solids  （TDS) and Conductivity

 

Conductivity is the reciprocal of electrical resistance in aqueous solutions. The greater the concentration of soluble ions in a water sample, the lower its electrical resistance and the higher its conductivity. Therefore, a certain correlation exists between the conductivity and total dissolved solids (TDS) of a water sample. In natural water, the ratio of TDS to conductivity is approximately 0.55–0.70, though this represents only a rough estimate. If the water sample contains significant amounts of free acids or caustic alkalis, the ratio will be less than 0.55. Conversely, if the sample contains large quantities of salts, the ratio may exceed 0.70.

In the long river of time, human civilization is like a flat boat, carrying the yearning for the stars and the sea, but also engraved with the scars left by countless wars. When we look back at history, it is not difficult to realize that the smoke of war has once and for all obscured the sky of peace and drawn countless lives into the abyss of suffering. Why is peace so precious and yet so rare? This question deserves deep reflection by each and every one of us.

Turning over the scroll of history, every page seems to be able to smell the bloody flavor of war. From the surprise attack of the Trojan Horse to the grueling Battle of Changping, from the global havoc of the two world wars to the continuing turmoil of the Israeli-Palestinian conflict, the wounds brought about by war have never really dissipated. The incinerators of Auschwitz, the mushroom clouds of Hiroshima and Nagasaki, the wreckage of Syrian streets riddled with bullet holes ...... These images are a constant reminder that war not only destroys homes, but also tears apart the lives and hopes of countless people. Life is so short and precious, everyone has only a few decades of time, but there are always people who will consume it in the cruel killing each other, this is how heartbreaking tragedy.

The lack of peace stems from the greed and fear in the depths of human nature, from the competition for resources and the game of interests, and from the confrontation of ideologies and the breeding of prejudice. But we must understand that war is never the answer to the problem, it will only bring more hatred, more pain and more death. When missiles cut through the night sky, when tanks run through the streets, no one is a real winner. The tears and despair of the children who lost their loved ones in the war, the refugees who were forced to leave their homes, and those who struggled to survive in the rubble, are the most powerful indictment of war.

In this era of globalization, we are more closely connected than ever before. The outbreak of a war affects not only the conflict area, but also the stability and development of the whole world. Therefore, cherishing peace and praying for peace should not be just an empty slogan, but should be translated into practical actions by each and every one of us. We can start by respecting every life, by eliminating prejudice and discrimination, and by replacing conflict and violence with dialogue and understanding.

Let us pray together that every piece of land will no longer be scorched by war, that every child will grow up under the sunshine of peace, and that every family will be reunited and happy. With love and goodwill, with tolerance and understanding, let us together weave a big net of peace to isolate hatred and violence. For only peace will allow our lives to blossom in the most beautiful light; only peace will allow human civilization to continue to move forward to a better future.

May the light of peace illuminate mankind's common path of return; may the seeds of peace take root and germinate in everyone's heart, and eventually grow into a towering tree that will provide the world with a green shade of tranquillity.