Salinity
Salinity is the saltiness or amount of salt dissolved in a body of water, called saline water. This is measured in g salt k g sea water. Salinity is an important factor in determining many aspects of the chemistry of natural waters and of biological processes within it, is a thermodynamic state variable that, along with temperature and pressure, governs physical characteristics like the density and heat capacity of the water. A contour line of constant salinity is called an isohaline, or sometimes isohale. Salinity in rivers and the ocean is conceptually simple, but technically challenging to define and measure precisely. Conceptually the salinity is the quantity of dissolved salt content of the water. Salts are compounds like sodium chloride, magnesium sulfate, potassium nitrate, sodium bicarbonate which dissolve into ions; the concentration of dissolved chloride ions is sometimes referred to as chlorinity. Operationally, dissolved matter is defined as that which can pass through a fine filter.
Salinity can be expressed in the form of a mass fraction, i.e. the mass of the dissolved material in a unit mass of solution. Seawater has a mass salinity of around 35 g/kg, although lower values are typical near coasts where rivers enter the ocean. Rivers and lakes can have a wide range of salinities, from less than 0.01 g/kg to a few g/kg, although there are many places where higher salinities are found. The Dead Sea has a salinity of more than 200 g/kg. Rainwater before touching the ground has a TDS of 20 mg/L or less. Whatever pore size is used in the definition, the resulting salinity value of a given sample of natural water will not vary by more than a few percent. Physical oceanographers working in the abyssal ocean, are concerned with precision and intercomparability of measurements by different researchers, at different times, to five significant digits. A bottled seawater product known as IAPSO Standard Seawater is used by oceanographers to standardize their measurements with enough precision to meet this requirement.
Measurement and definition difficulties arise because natural waters contain a complex mixture of many different elements from different sources in different molecular forms. The chemical properties of some of these forms depend on pressure. Many of these forms are difficult to measure with high accuracy, in any case complete chemical analysis is not practical when analyzing multiple samples. Different practical definitions of salinity result from different attempts to account for these problems, to different levels of precision, while still remaining reasonably easy to use. For practical reasons salinity is related to the sum of masses of a subset of these dissolved chemical constituents, rather than to the unknown mass of salts that gave rise to this composition. For many purposes this sum can be limited to a set of eight major ions in natural waters, although for seawater at highest precision an additional seven minor ions are included; the major ions dominate the inorganic composition of most natural waters.
Exceptions include some pit waters from some hydrothermal springs. The concentrations of dissolved gases like oxygen and nitrogen are not included in descriptions of salinity. However, carbon dioxide gas, which when dissolved is converted into carbonates and bicarbonates, is included. Silicon in the form of silicic acid, which appears as a neutral molecule in the pH range of most natural waters, may be included for some purposes; the term'salinity' is, for oceanographers associated with one of a set of specific measurement techniques. As the dominant techniques evolve, so do different descriptions of salinity. Salinities were measured using titration-based techniques before the 1980s. Titration with silver nitrate could be used to determine the concentration of halide ions to give a chlorinity; the chlorinity was multiplied by a factor to account for all other constituents. The resulting'Knudsen salinities' are expressed in units of parts per thousand; the use of electrical conductivity measurements to estimate the ionic content of seawater led to the development of the scale called the practical salinity scale 1978.
Salinities measured using PSS-78 do not have units. The suffix psu or PSU is sometimes added to PSS-78 measurement values. In 2010 a new standard for the properties of seawater called the thermodynamic equation of seawater 2010 was introduced, advocating absolute salinity as a replacement for practical salinity, conservative temperature as a replacement for potential temperature; this standard includes. Absolute salinities on this scale are expressed as a mass fraction, in grams per kilogram of solution. Salinities on this scale are determined by combining electrical conductivity measurements with other information that can account for regional changes in the composition of seawater, they can be determined by making direct density measurements. A sample of seawater from most locations with a chlorinity of 19.37 ppt will have a Knudsen salinity of 35.00 ppt, a PSS-78 practical
Anemopsis
The monotypic genus Anemopsis has only one species, Anemopsis californica, with the common names yerba mansa or lizard tail. It is a perennial herb in the lizard tail family and prefers wet soil or shallow water, it is native to southwestern North America in northwest Mexico and the Southwestern United States from California to Oklahoma and Texas to Kansas to Oregon. As it matures, the visible part of the plant develops red stains turning bright red in the fall. Yerba mansa is showy in spring when in bloom; the iconic white "flowers" are borne in early spring, are surrounded by 4–9 large white bracts. Similar to the sunflower family, what appears to be a single bloom is in reality a dense cluster of individually small flowers borne in an inflorescence. In this species the inflorescence is conical and has five to ten large white bracts beneath it, so that along with the tiny white florets, the whole structure is quite striking when it blooms in spring; the conical structure develops into a single, tough fruit that can be carried downstream to spread the tiny, pepper-like seeds.
In her book on herbs of the southwestern USA, Dr. Soule discusses the common name. "Yerba mansa is one of those names. Yerba is Spanish for herb, thus one would think that mansa is from Spanish as well, but all indications point to the fact that it is not. Mansa means tame, calm in Spanish, the plant has no sedative effect, nor did local people use it as a calming agent, its primary use is as an antimicrobial and antifungal. The most explanation is that mansa is a Spanish alteration of the original native word for the plant, now lost in the depths of time." Hartweg, who collected it at León, Guanajuato in 1837, recorded the local name as yerba del manso. It is known as yerba del manso in northern Baja California; the word "manso" could be short for "remanso" which would agree with the areas where the plant thrives. Yerba mansa is used as an antimicrobial, an antibacterial, to treat vaginal candidiasis. Yerba mansa is used to treat inflammation of swollen gums and sore throat. An infusion of roots can be taken as a diuretic to treat rheumatic diseases like gout by ridding the body of excess uric acid, which causes painful inflammation of the joints.
Yerba mansa prevents the buildup of uric acid crystals in the kidneys which could cause kidney stones if left untreated. A powder of dried root can be sprinkled on infected areas to alleviate athlete's foot or diaper rash. Yerba mansa is versatile, it can be taken orally as a tea, infusion or dried in capsule form, it can be used externally for soaking infected areas. It can be ground and used as a dusting powder; some people in Las Cruces, New Mexico use the leaves to make a poultice to relieve muscle swelling and inflammation. Dried floral structures are used in dried arrangements. Dried plant parts are used in potpourri. In the deserts of California, yerba mansa is being used as turf in public parks and ground cover in gardens. Plants For A Future database Medicinal plants Jepson Manual Treatment USDA Plants Profile Medicinal Uses and Harvesting
Tetragonia tetragonoides
Tetragonia tetragonoides called New Zealand spinach and other local names, is a flowering plant in the fig-marigold family. It is cultivated as a leafy vegetable, it is a widespread species, native to eastern Asia and New Zealand. It has been introduced and is an invasive species in many parts of Africa, North America, South America, its natural habitat is sandy shorelines and bluffs in disturbed areas. It grows well in saline ground; the plant has a trailing habit, will form a thick carpet on the ground or climb through other vegetation and hang downwards. It can have erect growth when young; the leaves of the plant are 3–15 cm long, triangular in shape, bright green. The leaves are thick, covered with tiny papillae that look like waterdrops on the top and bottom of the leaves; the flowers of the plant are yellow, the fruit is a small, hard capsule covered with small horns. The species used by indigenous people as a leaf vegetable, was first mentioned by Captain Cook, it was picked and pickled to help fight scurvy, taken with the crew of the Endeavour.
It spread when the explorer and botanist Joseph Banks took seeds back to Kew Gardens during the latter half of the 18th century. For two centuries, T. tetragonioides was the only cultivated vegetable to have originated from Australia and New Zealand. There are some indications that Māori did eat kōkihi more regularly. "To counteract the bitterness of the older leaves of this herb, the Māori boiled it with the roots of the convolvulus". It is grown for the edible leaves, can be used as food or an ornamental plant for ground cover; as some of its names signify, it has similar flavour and texture properties to spinach, is cooked like spinach. Like spinach, it contains oxalates, it thrives in hot weather, is considered an heirloom vegetable. Few insects consume it, slugs and snails do not seem to feed on it; the thick, irregularly-shaped seeds should be planted just after the last spring frost. Before planting, the seeds should be soaked for 3 hours in warm water. Seeds should be planted 5–10 mm deep, spaced 15–30 cm apart.
The seedlings will emerge in 10–20 days, it will continue to produce greens through the summer. Mature plant will self-seed. Seeds will overwinter up to USDA zone 5; this distributed plant has many common names, depending on its location. In addition to the name New Zealand spinach, it is known as Botany Bay spinach, Cook's cabbage, kōkihi, sea spinach, tetragon, its Australian names of Warrigal Greens and Warrigal Cabbage come from the local use of warrigal to describe plants that are wild. Media related to Tetragonia tetragonioides at Wikimedia Commons
Seawater
Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5%. This means that every kilogram of seawater has 35 grams of dissolved salts. Average density at the surface is 1.025 kg/L. Seawater is denser than both fresh water and pure water because the dissolved salts increase the mass by a larger proportion than the volume; the freezing point of seawater decreases as salt concentration increases. At typical salinity, it freezes at about −2 °C; the coldest seawater recorded was in 2010, in a stream under an Antarctic glacier, measured −2.6 °C. Seawater pH is limited to a range between 7.5 and 8.4. However, there is no universally accepted reference pH-scale for seawater and the difference between measurements based on different reference scales may be up to 0.14 units. Although the vast majority of seawater has a salinity of between 31 g/kg and 38 g/kg, 3.1-3.8%, seawater is not uniformly saline throughout the world. Where mixing occurs with fresh water runoff from river mouths, near melting glaciers or vast amounts of precipitation, seawater can be less saline.
The most saline open sea is the Red Sea, where high rates of evaporation, low precipitation and low river run-off, confined circulation result in unusually salty water. The salinity in isolated bodies of water can be greater still - about ten times higher in the case of the Dead Sea. Several salinity scales were used to approximate the absolute salinity of seawater. A popular scale was the "Practical Salinity Scale" where salinity was measured in "practical salinity units"; the current standard for salinity is the "Reference Salinity" scale with the salinity expressed in units of "g/kg". The density of surface seawater ranges from about 1020 to 1029 kg/m3, depending on the temperature and salinity. At a temperature of 25 °C, salinity of 35 g/kg and 1 atm pressure, the density of seawater is 1023.6 kg/m3. Deep in the ocean, under high pressure, seawater can reach a density of higher; the density of seawater changes with salinity. Brines generated by seawater desalination plants can have salinities up to 120 g/kg.
The density of typical seawater brine of 120 g/kg salinity at 25 °C and atmospheric pressure is 1088 kg/m3. Seawater pH is limited to the range 7.5 to 8.4. The speed of sound in seawater is about 1,500 m/s, varies with water temperature and pressure; the thermal conductivity of seawater is a salinity of 35 g/kg. The thermal conductivity decreases with increasing salinity and increases with increasing temperature. Seawater contains more dissolved ions than all types of freshwater. However, the ratios of solutes differ dramatically. For instance, although seawater contains about 2.8 times more bicarbonate than river water, the percentage of bicarbonate in seawater as a ratio of all dissolved ions is far lower than in river water. Bicarbonate ions constitute 48% of river water solutes but only 0.14% for seawater. Differences like these are due to the varying residence times of seawater solutes; the most abundant dissolved ions in seawater are sodium, magnesium and calcium. Its osmolarity is about 1000 mOsm/l.
Small amounts of other substances are found, including amino acids at concentrations of up to 2 micrograms of nitrogen atoms per liter, which are thought to have played a key role in the origin of life. Research in 1957 by the Scripps Institution of Oceanography sampled water in both pelagic and neritic locations in the Pacific Ocean. Direct microscopic counts and cultures were used, the direct counts in some cases showing up to 10 000 times that obtained from cultures; these differences were attributed to the occurrence of bacteria in aggregates, selective effects of the culture media, the presence of inactive cells. A marked reduction in bacterial culture numbers was noted below the thermocline, but not by direct microscopic observation. Large numbers of spirilli-like forms were seen by microscope but not under cultivation; the disparity in numbers obtained by the two methods is well known in other fields. In the 1990s, improved techniques of detection and identification of microbes by probing just small snippets of DNA, enabled researchers taking part in the Census of Marine Life to identify thousands of unknown microbes present only in small numbers.
This revealed a far greater diversity than suspected, so that a litre of seawater may hold more than 20,000 species. Mitchell Sogin from the Marine Biological Laboratory feels that "the number of different kinds of bacteria in the oceans could eclipse five to 10 million."Bacteria are found at all depths in the water column, as well as in the sediments, some being aerobic, others anaerobic. Most are free-swimming, but some exist as symbionts within other organisms – examples of these being bioluminescent bacteria. Cyanobacteria played an important role in the evolution of ocean processes, enabling the development of stromatolites and oxygen in the atmosphere; some bacteria interact with diatoms, form a critical link in the cycling of silicon in the ocean. One anaerobic species, Thiomargarita namibiensis, plays an important part in the breakdown of hydrogen sulfide eruptions from diatomaceous sediments off the Namibian coast, generated by high rates of phytoplankton
