First, rain

Rain, snow, and sputum are collectively referred to as precipitation, which is relatively pure, but will absorb and absorb impurities and gases as the region and the atmosphere affect. In the precipitation close to the ocean and inland salt lakes, some sodium chloride salts are dissolved, and the Cl- content in the rainwater near the coast is high. Generally, the total salt content of rainwater does not exceed 50mg/L, and the fouling substances (calcium and magnesium) are more micro. At 250C, 1 atm, the pH of the rainwater can reach 5.6 due to the dissolution of COZ in the air. Naturally, it is not chemical pollution. The temperature and pressure are squeaking but not much. The pH is less than 6.5. It is called acid rain.

Second, the river

The suspended solids and dissolved salts contained in the river water vary with the influence of the climate, geological conditions and recharge water flowing through the area. There will be pollution of water quality when industrial and mining enterprises drain along the way. The salinity of river water in China can vary from 13 to 9185 mg/L, while those above 1000 mg/L are less. The water chemistry of river water is Ca z+ > Na+ > Mg2+; HCO3->SO2-4>Cl- general river water is slightly acidic. During the flood peak, the suspended matter content increased and the salt content decreased; the dry season was reversed. Bacteria, algae and organic matter are also high in river water.

The water chemistry characteristics of rivers in China have obvious zonality: bicarbonate is the most widely distributed, accounting for 25.4% of the 680o I chloride salts in the country, and 6.6% of the sulfates are distributed in the west. Land area. The salt content in the southeast coastal river is at least 36.4 mg/L. The salt content in the Tarim River near Milan is 32 732 mg/L (close to seawater salinity), which is nearly 1000 times different. The distribution of hardness categories in river water in China.

Third, the lake

Lakes are the main source of water for industry and drinking, and have many functions such as improving the regional ecological environment. The chemical composition of the lake water is determined by the composition of the water source and the groundwater flow of the recharge lake, and is related to the biological effects in the lake and the natural geographical conditions of the lake surface. Whether there is water flowing out of the lake has special significance for the formation of chemical components of the lake. The undrained lake water consumes evaporation, so the salt entering the lake continues to accumulate, and its concentration continues to rise, with the result that the lake becomes a saltwater lake.

The salt content of the drainage lake usually does not exceed 200 - 300mg / L, the total number of ions in the lagoon can reach 5. 82g / L. The depth, area and capacity of the lake have a significant impact on water quality. The northeastern part of China (the northeastern part of the Songnen Plain) has arid climate, low topography and dense lakes. The distribution of saline and alkaline soils is mostly soda saline soil. The surface water and groundwater have higher salt content. The main component of the water is sodium bicarbonate. The salt content is about 2700mg/L, which is three types of freshwater lake, saltwater lake and brine salt lake. According to the survey data, about 20% of the lakes have good water quality (11-m class), and more than 80% of the lakes are polluted (N-inferior V), which indicates that the current lake water pollution problem in China is very serious.

Fourth, reservoir water

The dissolved salt in the reservoir water mainly depends on the chemical composition of surface water and groundwater in the recharge reservoir; reservoir regulation; precipitation and evaporation; salt content in the reservoir soil; biological and biochemical effects in the reservoir water; Polluted water sources (industrial wastewater, domestic sewage). When determining the chemistry of the reservoir, it is mainly determined by the number and flow of the reservoir (reservoir regulation). From the aspect of water supply sanitation requirements, attention should be paid to the selection of the site and the sanitation of the reservoir and the construction of sanitary protection belts around the reservoir.

Fifth, groundwater

Groundwater is one of the main sources of water for industrial and mining enterprises and urban water supply. Groundwater is also a mineral resource. For example, when sodium chloride is greater than 50 mg/I. and iodine is greater than 20 mg/L, it has value as a raw material. Groundwater originates from atmospheric precipitation and surface water infiltration; condensation of water vapor in soil layers; primary water and symbiotic water. Some believe that the groundwater in the deep underground is formed by the condensation of gas separated from the magma.

The condensation of water vapor in the soil layer has its practical significance. In the desert plain with very little precipitation, this water can be used as an important source of drinking water. In some areas, the groundwater temperature is higher, and the thermal energy of the baby is “energy.” The percolation through the formation. The groundwater is relatively clear, bacteria and microorganisms are not easy to exist, but the dissolved minerals are more, and its composition is related to the nature of the stratum and the water quality of the recharge water. When the groundwater is recharged by the river and the river is recharged by seawater, the chloride ion content in the groundwater Correspondingly, the quality of groundwater extracted from deposits, coal seams, oil fields and mine pits is poor. Groundwater contains radioactive material atmosphere, which has medical effects within a certain range. Groundwater is divided into four categories according to salinity: 1 fresh water, less mineralization Lg / L; 2 brackish water, salinity of 1 ~ 3g / L; 3 semi-salt water, salinity of 3-5g / L; 4 salt water, salinity greater than 5g / L.

The area of ​​the underground freshwater distribution area is about 8,016,500 km', accounting for 85-39% of the total area of ​​the country. The brackish water distribution area is mainly distributed in Hebei, Shandong, Jiangsu, Ningxia Hui Autonomous Region, Xinjiang Uygur Autonomous Region, Inner Mongolia Autonomous Region, Gansu, Shanxi, Shaanxi and Jilin. The area of ​​underground brackish water distribution is about 539,200. Km', accounting for 5.68% of the total area of ​​the country.

The brackish water and salt water distribution areas are mainly distributed in many areas of Xinjiang Uygur Autonomous Region, Ningxia Hui Autonomous Region, Inner Mongolia Autonomous Region, Qinghai, Gansu, and some coastal areas of Tianjin, Hebei, Shandong, Liaoning, Shanghai, Jiangsu, and Guangdong. The area of ​​underground brackish water and salt water distribution area is about 847,300 km', accounting for 8.93% of the total area of ​​the country.

Sixth, sea water

The salt of seawater is collected by rivers and carried together. The average salt content of seawater is 35g/kg (35.7g/L), and the average density of seawater is 1.03g/cm3. The salt concentration of seawater is affected by evaporation and precipitation, and the salt content of seawater in river population is reduced. The freezing point of seawater also varies with salt. When the salt content of seawater is 24.7%, the point is 1.13020C, and the total organic matter content in seawater is about 2mg/L. Due to the balance of dissolution and sedimentation in the ocean, the ocean The various ion proportion components are relatively constant, so the pH value is between 8-8.3. The seawater is generally alkaline. There are about 70 kinds of elements in seawater, but the main ones are more than 10 kinds, see Table 1-23.

Due to the absorption of organisms, calcium may be relatively reduced on the surface. Silica is also removed from the surface seawater in this way, so the content of SiO2 in seawater increases regularly with the probe. COZ is an important factor in controlling the solubility of CaCO3 in the ocean. It also depends on the nature and quantity of biological activity.

The chemical characteristics of seawater are Na>Mg>Ca, Cl>S04>CO3.

The chlorine content of seawater refers to the total mass of chloride ions contained in lkg seawater.

The salinity of seawater refers to the total amount of solid matter dissolved in lkg seawater, and the common unit of both is g/kg%.

Salinity is 35%. It means that the solid matter dissolved in 1 kg of seawater is 35 g and contains % salinity. = 1.806 6% chlorine content.

Seawater with a salt content of 35000mg/L is called standard seawater. This is because most of the world's seawater has the above-mentioned salt content, and the ion composition ratio is very similar all over the world, but the actual total TDS varies widely. The salt water content of the Baltic Sea is 7000mg/L, and the salt content of the sea in the Red Sea and the Persian Gulf is 45000mg/L. Due to soil effects and infiltration of inland water, the salt content and composition of coastal waters vary greatly. The standard seawater composition is shown in Table 1-24.

The scope of seawater utilization mainly includes the following aspects.

(1) Seawater replaces fresh water directly as industrial water. Industrial cooling water accounts for about 80% of industrial water consumption. The use of seawater is mainly to replace fresh water as industrial cooling water. The use of seawater has the following advantages.

1) The water source is stable. The seawater has a strong self-cleaning ability, the water quality is relatively stable, and the amount of use is not limited.

2) The water temperature is suitable. Industrial production uses seawater cooling to remove excess heat from the production process. The temperature of seawater, especially deep seawater, is relatively low, and the water temperature is relatively stable, such as the annual seawater temperature in Dalian sea area. Between 0-25 ° C.

3) Low power consumption. Generally, offshore water intake is adopted, and long-distance transportation is not required.

4) The equipment investment is small and the floor space is small. Compared with fresh water circulation cooling, equipment such as return water equipment and cold water tower can be omitted.

(2) Using seawater as a resin to regenerate a reducing agent and a solvent. In the sodium ion exchange process, when the hardness of the soft water exceeds the specified standard, it indicates that the exchange resin has lost the exchange capacity, and the exchange resin is required to be regenerated and reduced by the salt solution to restore the exchange capacity. In the low-pressure boiler soft water treatment process of industrial enterprises, the traditional method is to prepare a 5%-g% salt solution using tap water to regenerate the resin. In order to save water, coastal cities have gained mature experience using seawater as a reducing agent.

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