Know : Rain Water’s Purity Facts

rain water

The water in a raindrop is one of the cleanest sources of water available. Rainwater can absorb gases such as carbon dioxide, oxygen, nitrogen dioxide, and sulfur dioxide from the atmosphere. It can also capture soot and other microscopic particulates as it falls through the sky. Nevertheless, rainwater is almost 100% pure water before it reaches the ground.

Rainwater is soft water and leaves no limescale; washing clothes and hair in soft water requires less detergent and so reduces water pollution from these compounds. Plants LOVE rainwater. It doesn’t contain chlorine, which is carcinogenic.

Water is made “hard” by dissolving calcium or magnesium ions, neither of which is present in rain water (at least, not until it runs over calcium or magnesium containing compounds on the Earth’s surface). Pure water is considered the universal solvent; it can absorb or dissolve contaminants from almost anything it comes into contact with. That is why it is especially important to design and operate your system so that the rainwater picks up as few contaminants as possible before you consume it.

Although rainwater can be contaminated by absorbing airborne chemicals, most of the chemicals present in harvested rainwater is introduced during collection, treatment, and distribution. By properly designing and operating your rainwater harvesting system, you can minimize your exposure to a variety of chemical contaminants that include organic chemicals, such as volatile and synthetic organics, and inorganic chemicals, such as minerals and metals. 

Chemical composition of rain water :  Rainwater gets its compositions largely by dissolving particulate materials in the atmosphere (upper troposphere) when droplets of water nucleate on atmospheric particulates, and secondarily by dissolving gasses from the atmosphere.

Rainwater compositions vary geographically. In open ocean and coastal areas they have a salt content essentially like that of sea water (same ionic proportions but much more dilute) plus CO2 as bicarbonate anion (acidic pH).

Terrestrial rain compositions vary significantly from place to place because the regional geology can greatly affect the types of particulates that get added to the atmosphere. Likewise, sources of gaseous acids (SO3, NO2) and bases (NH3) vary as a function of biome factors and anthopogenic land use practices. Each of these gasses can be added in varying proportions from natural and non natural input sources (non-natural sources of SO3 and NO2 far outweigh natural ones). Particulate load to the atmosphere can also be greatly affected by human activities.

Finally, local climate (especially the amount of precipitation in one area compared to another) will affect the solute concentrations in terrestrial rainwaters. The result is highly variable compositions, so there isn’t one simple formula. 


Courtesy and Sources : Wholly H2O Ask-An-Earth-Scientist  and Google.

Alert! : World’s Top 10 Cities – Air Pollution

Some of the world’s largest and most densely populated cities have air that’s so polluted that people suffer from lung diseases at rates that are significantly above global averages. Birth defects in these cities are also at extraordinarily high levels, as are heart disease and cancer rates.

Many of these cities are among the fastest-growing in the world. And in some, residents burn wood and coal for warmth, releasing additional deadly pollution into the atmosphere.

But which cities have the world’s worst air? To compile such a list, 24/7 Wall St has reviewed several dozen studies on air quality conducted over the past few years, along with data from government websites and private sources. The review examined data about the following pollutants:

  • Sulfur dioxide: Produced when fossil fuels are burned and is the primary cause of acid rain. Exposure causes eye irritation, coughing, worsening of asthma and respiratory-tract infections.
  • Nitrogen dioxide: Produced by generators, power plants and motor vehicles. It has been shown to cause bronchitis and other pulmonary diseases.
  • Particulates: Refers to a variety of small pollutants, including lead, dust, ammonia, soot and pulverized minerals. They’re a leading cause of lung cancer. According to the World Health Organization (WHO), mortality in cities with high levels of particulates “exceeds that observed in relatively cleaner cities by 15% to 20%.”

With that background, here are 24/7′s 10 cities with the worst air quality:

1) Beijing, China (tie)


Beijing’s air quality has become so bad that the city has recently been engulfed in a hazardous haze. As a result, schools have been forced to cancel outdoor activities, and health experts have asked that children, the elderly and people with respiratory ailments stay indoors. The city recorded the world’s highest level of sulfur dioxide concentrations for 2000 to 2005 and has the third-highest level of nitrogen dioxide behind only Sao Paulo and Mexico City. Pollution improved in 2008 because officials banned roughly half of the city’s cars when it hosted the Olympic Games. Of course, the air got worse again after the games left town.

1) New Delhi, India (tie)


According to WHO’s most recent findings, New Delhi ranks second in concentrations in particulates, at a level more than six times higher than what WHO considers safe. According to the Harvard International Review, two in every five of the city’s 13.8 million residents suffer from respiratory illness. The report says the main cause of New Delhi’s air pollution is car exhaust and dust kicked up from overcrowded roads. As a result, construction workers and taxi drivers are most at risk for debilitating illness or even early death.

3) Santiago, Chile

According to WHO, a city’s airborne particulate matter should not exceed 50 micro-grams per cubic meter. In Santiago, an alert is issued when the level hits 200 micro-grams. In 2008, on some days the city reached 444 micro-grams. Additionally, Santiago has the second-highest level of ground-level ozone, according to WHO.

4) Mexico City, Mexico


According to researchers from the University of Salzburg, Mexico City has high concentrations of nearly every major harmful airborne pollutant, including sulfur dioxide, nitrogen oxides and carbon monoxide. By far the worst problem gripping the city is the massive cloud of smog that hangs over it almost every day. Mexico City has the highest level of ground-level ozone in the world, according to WHO.

5) Ulaanbaatar, Mongolia


In Ulaanbaatar, the annual average particulate matter concentrations are 14 times higher than WHO’s recommended level. The city’s poor air quality has caused high incidences of chronic bronchitis and cardiovascular diseases. A thick smog often blankets the city, and at times daytime visibility is so poor that cars must use their headlights.

6) Cairo, Egypt

Mosques of Sultan Hasan and al-Rifa'i Seen from the Citadel

The most recent WHO data ranked Cairo as having the second-highest levels of particulates in the world after New Delhi. Another WHO report, issued a few years ago, equated living in the city of 17.8 million to smoking a pack of cigarettes a day. Because Egypt doesn’t use unleaded gasoline, citizens are exposed to high levels of lead every day. On occasion, Cairo is also under what’s commonly called “the black cloud”: a dense, poisonous mass of smoke caused by the seasonal burning of rice ashes by local farmers.

7) Chongqing, China


One of the fastest-growing cities in China, Chongqing has extremely high levels of air pollution because of coal-burning by power plants and industry. The poor air quality is sickening the city’s residents. Studies have found that 4.63% of children under 14 suffer from asthma, although prevalence in girls may be under-reported due to cultural bias. Levels of nitrogen oxide are rising because of vehicle emissions.

8) Guangzhou, China


Guangzhou, a provincial capital, has a population of roughly 12 million and one of the worst levels of particulates in China. Total suspended particles, according to a 2007 study, were worse than in Beijing. Sulfur dioxide levels, according to the most recent WHO data, were second only to Beijing. As industrial production and traffic within Guangzhou continue to increase, more people are suffering from shortness of breath, coughing, dizziness, weakness and nausea.

9) Hong Kong


Hong Kong features excessive levels of nitrogen dioxide, ozone, sulfur dioxide and carbon monoxide. The Air Pollution Index, which rates the likelihood of people getting ill from breathing a city’s air, has recently reached 500, the highest possible level, for multiple parts of Hong Kong. This year saw the worst levels of pollution since 1995, prompting the government to warn people against doing outdoor activities. These levels were 12 to 14 times worse than WHO standards. No wonder a recent Gallup poll has shown that 70% of Hong Kong’s population are dissatisfied with their horrible air quality.

10) Kabul, Afghanistan


Because of the war in Afghanistan, the nation’s capital has been flooded by refugees from the surrounding countryside. According to an NPR report, Kabul’s infrastructure is designed for about 500,000 residents, but it now supports more than 5 million. The overcrowded city is full of wood-burning stoves, and gas-powered generators are commonly used to supply electricity that a war-ravaged grid cannot provide. Cars use leaded gasoline, and residents sometimes burn plastic tires to stay warm. As a result of the increasingly high levels of dangerous particulates in the air, President Hamid Karzai has declared a state of emergency in the capital city. According to the director for the Ministry of Public Health, “Air pollution is a huge problem here, it leads to so many diseases — respiratory diseases, allergies, miscarriages and even cancer.”

Courtesy and Source : 24/7 Wall StDaily Finance