The Hydrologic Cycle

The water on the Earth ungergoes a continuous process of evaporation and condensation called the hydrologic cycle. Since the oceans cover 71% of the Earth's surface, much of the evaporation comes from the ocean. Franks (the source of most of this data) places the total water content of the atmosphere at 6 x 10¹² m³. With a total annual rainfall of 2.25 x 10¹⁴m³ this implies that the water in the atmosphere is cycled about 37 times per year. The runoff of this water from the surface back to the oceans is a major part of the physical shaping of the continental surfaces in the overall geophysics of the Earth.

地球上的水持续经历蒸发和凝结的过程，称为水循环。由于海洋覆盖了地球表面的71%，大部分的蒸发来自海洋。Frank（数据的主要来源）指出大气中的总水量为6×10¹²立方米。考虑到年总降水量为2.25×10¹⁴立方米，这表明大气中的水每年循环约37次。这些水从地表流回海洋的过程是塑造大陆地貌的重要部分，是地球物理学中整体地球物理现象的重要组成部分。

From Ball, Life's Matrix: A Biography of Water, "Each 3100 years, a volume of water equivalent to all the oceans passes through the atmosphere, carried there by evaporation and moved by precipitation .. the Sun's heat removes from the oceans the equivalent of three feet in depth each year - 875 cubic kilometers in total every day."

The human body is 66% water by weight, according to Hill and Kolb. Water is the universal solvent for life, referred to by Nobel Laureate A. Szent-Gyorgy as "the matrix of life".That water serves as the solvent for sodium chloride (salt) and other substances so that the fluids of our bodies are similar to sea water. This leads Hill and Kolb to refer jokingly to us as "walking bags of sea water". Water serves to suspend the red blood cells to carry oxygen to the cells. It is the solvent for the electrolytes and nutrients needed by the cells, and also the solvent to carry waste material away from the cells.

根据Hill和Kolb的说法，人体的重量百分比中有66%是水。水是生命中的通用溶剂，诺贝尔奖得主A. Szent-Gyorgy称其为“生命的基质”。水作为氯化钠（盐）和其他物质的溶剂，使得人体的液体类似于海水。这使得Hill和Kolb开玩笑地称我们为“行走的海水袋”。水用于悬浮红血细胞以将氧气输送到细胞中。它也是细胞所需电解质和营养物质的溶剂，同时也是将废物从细胞中运走的溶剂。

With water as the solvent, osmotic pressure acts to transport the needed water into cells. With cells bathed in the interstitial fluid, diffusion contributes to carrying needed molecules into the cells. When more complex mechanisms control the transport of molecules across the membranes into and out of cells, the presence of water as the surrounding medium and solvent is essential.

当水作为溶剂时，渗透压会促使所需水分进入细胞。当细胞浸浴在Interstitial fluid中时，扩散有助于将所需分子带入细胞。当更复杂的机制控制分子跨膜运输进入和离开细胞时，水作为周围介质和溶剂的存在是必不可少的。

从Ball的《生命之基：水的传记》中引用：‘每3100年，大气层中通过蒸发和降水运输的水量相当于所有海洋的水量……太阳的热量每年从海洋中去除相当于三英尺深度的水量，即每天总计875立方公里。’

As rain falls on the land masses, the solvent action of water carries minerals with the runoff and provides not only the necessary water for plants downstream, but also the essential minerals for plant growth. This erosion of the highlands is aided during cold weather by the fact that water expands upon freezing. Ice in the multiple cracks and crevices helps to break up the minerals and contributes to the making of soil for the lower altitudes. The soil production process produces a matrix which retains water and its cargo of dissolved mineral nutrients. The components of the soil are generally classified as sands, silts and clays along with organic matter that will be collected along with them. The clays are critical to plant life not only because their small particle size allows them to hold water more effectively, but also because the clays hold mineral ions for exchange with plant roots.

当雨水落在陆地时，水的溶解作用会将矿物随地表径流带离，并不仅为下游植物提供必要的水分，还提供了植物生长所必需的矿物。高地的侵蚀在寒冷天气中得到促进，因为水在冻结时会膨胀。冰在多个裂缝和缝隙中帮助破碎矿物，从而为低海拔地区形成土壤。土壤生成过程产生一种能保留水分及其携带的溶解矿物养分的基质。土壤的成分通常分为砂、粉砂和黏土，以及与之一起收集的有机物质。黏土对植物生命至关重要，不仅因为其细小的颗粒大小使其能更有效地保持水分，还因为黏土能保留矿物离子以供植物根系吸收。