Sewage is a type of wastewater, produced by a community of people. It is characterized by volume or rate of flow, physical condition and toxic constituents, its bacteriologic status, it consists of greywater, blackwater. Sewage travels from a building's plumbing either into a sewer, which will carry it elsewhere, or into an onsite sewage facility. Whether it is combined with surface runoff in the sewer depends on the sewer design; the reality is, that most wastewater produced globally remains untreated causing widespread water pollution in low-income countries: A global estimate by UNDP and UN-Habitat is that 90% of all wastewater generated is released into the environment untreated. In many developing countries the bulk of domestic and industrial wastewater is discharged without any treatment or after primary treatment only; the term sewage is nowadays regarded as an older term and is being more and more replaced by "wastewater". In general American English usage, the terms "sewage" and "sewerage" mean the same thing.
In common British usage, in American technical and professional English usage, "sewerage" refers to the infrastructure that conveys sewage. Before the 20th century, sewers discharged into a body of water such as a stream, lake, bay, or ocean. There was no treatment, so the breakdown of the human waste was left to the ecosystem. Today, the goal is that sewers route their contents to a wastewater treatment plant rather than directly to a body of water. In many countries, this is the norm. Current approaches to sewage management may include handling surface runoff separately from sewage, handling greywater separately from blackwater, coping better with abnormal events. Proper collection and safe, nuisance-free disposal of the liquid wastes of a community are recognized as a necessity in an urbanized, industrialized society; the wastewater from residences and institutions, carrying bodily wastes, washing water, food preparation wastes, laundry wastes, other waste products of normal living, are classed as domestic or sanitary sewage.
Liquid-carried wastes from stores and service establishments serving the immediate community, termed commercial wastes, are included in the sanitary or domestic sewage category if their characteristics are similar to household flows. Wastes that result from industrial processes such as the production or manufacture of goods are classed as industrial wastewater, not as sewage. Surface runoff known as storm flow or overland flow, is that portion of precipitation that runs over the ground surface to a defined channel. Precipitation absorbs gases and particulates from the atmosphere and leaches materials from vegetation and soil, suspends matter from the land, washes spills and debris from urban streets and highways, carries all these pollutants as wastes in its flow to a collection point. Sewage is a complex mixture of chemicals, with many distinctive chemical characteristics; these include high concentrations of ammonium, nitrogen, high conductivity, high alkalinity, with pH ranging between 7 and 8.
The organic matter of sewage is measured by determining its biological oxygen demand or the chemical oxygen demand. Sewage contains human feces, therefore contains pathogens of one of the four types: Bacteria, Viruses and Parasites such as helminths and their eggs Sewage can be monitored for both disease-causing and benign organisms with a variety of techniques. Traditional techniques involve filtering and examining samples under a microscope. Much more sensitive and specific testing can be accomplished with DNA sequencing, such as when looking for rare organisms, attempting eradication, testing for drug-resistant strains, or discovering new species. Sequencing DNA from an environmental sample is known as metagenomics. Sewage contains environmental persistent pharmaceutical pollutants. Trihalomethanes can be present as a result of past disinfection. Sewage has been analyzed to determine relative rates of use of prescription and illegal drugs among municipal populations. All categories of sewage are to carry pathogenic organisms that can transmit disease to humans and animals.
Sewage contains organic matter that can cause odor and attract flies. Sewage contains nutrients. A system of sewer pipes takes it for treatment or disposal; the system of sewers is called sewerage or sewerage system in British English and sewage system in American English. Where a main sewerage system has not been provided, sewage may be collected from homes by pipes into septic tanks or cesspits, where it may be treated or collected in vehicles and taken for treatment or disposal. Properly functioning septic tanks require emptying every 2–
Volatile organic compound
Volatile organic compounds are organic chemicals that have a high vapor pressure at ordinary room temperature. Their high vapor pressure results from a low boiling point, which causes large numbers of molecules to evaporate or sublimate from the liquid or solid form of the compound and enter the surrounding air, a trait known as volatility. For example, which evaporates from paint and releases from materials like resin, has a boiling point of only –19 °C. VOCs are numerous and ubiquitous, they include both human-made and occurring chemical compounds. Most scents or odors are of VOCs. VOCs play an important role in communication between plants, messages from plants to animals; some VOCs are dangerous to human cause harm to the environment. Anthropogenic VOCs are regulated by law indoors, where concentrations are the highest. Harmful VOCs are not acutely toxic, but have compounding long-term health effects; because the concentrations are low and the symptoms slow to develop, research into VOCs and their effects is difficult.
Diverse definitions of the term VOC are in use. The definitions of VOCs used for control of precursors of photochemical smog used by the U. S. Environmental Protection Agency and state agencies in the US with independent outdoor air pollution regulations include exemptions for VOCs that are determined to be non-reactive, or of low-reactivity in the smog formation process. In the US, regulatory requirements for VOCs vary among the states. Most prominent is the VOC regulation issued by the South Coast Air Quality Management District in California and by the California Air Resources Board. However, this specific use of the term VOCs can be misleading when applied to indoor air quality because many chemicals that are not regulated as outdoor air pollution can still be important for indoor air pollution. California's ARB uses the term "reactive organic gases" to measure organic gases after public hearing in September 1995; the ARB revised the definition of "Volatile Organic Compounds" used in the consumer products regulations, based on their committee's findings.
Health Canada classifies VOCs as organic compounds that have boiling points in the range of 50 to 250 °C. The emphasis is placed on encountered VOCs that would have an effect on air quality; the European Union defines a VOC as "any organic compound having an initial boiling point less than or equal to 250 °C measured at a standard atmospheric pressure of 101.3 kPa." The VOC Solvents Emissions Directive is the main policy instrument for the reduction of industrial emissions of volatile organic compounds in the European Union. It covers a wide range of solvent using activities, e.g. printing, surface cleaning, vehicle coating, dry cleaning and manufacture of footwear and pharmaceutical products. The VOC Solvents Emissions Directive requires installations in which such activities are applied to comply either with the emission limit values set out in the Directive or with the requirements of the so-called reduction scheme. Article 13 of The Paints Directive, approved in 2004, amended the original VOC Solvents Emissions Directive and limits the use of organic solvents in decorative paints and varnishes and in vehicle finishing products.
The Paints Directive sets out maximum VOC content limit values for paints and varnishes in certain applications. The People's Republic of China defines a VOC as those compounds that have "originated from automobiles, industrial production and civilian use, burning of all types of fuels and transportation of oils, fitment finish, coating for furniture and machines, cooking oil fume and fine particles," and similar sources; the Three-Year Action Plan for Winning the Blue Sky Defence War released by the State Council in July 2018 creates an action plan to reduce 2015 VOC emissions 10% by 2020. The Central Pollution Control Board of India released the Air Act in 1981, amended in 1987, to address concerns about air pollution in India. While the document does not differentiate between VOCs and other air pollutants, the CPCB monitors "oxides of nitrogen, sulphur dioxide, fine particulate matter and suspended particulate matter." VOCs are defined in the various laws and codes under which they are regulated.
Other definitions may be found from government agencies advising about VOCs. EPA regulates VOCs in the air and land; the federal regulations issued under the Safe Drinking Water Act set maximum contaminant level standards for several organic compounds in public water systems. EPA publishes wastewater testing methods for chemical compounds, including a range of VOCs, pursuant to the Clean Water Act. In addition to drinking water, VOCs are regulated in pollutant discharges to surface waters, as hazardous waste, but not in non-industrial indoor air; the Occupational Safety and Health Administration regulates VOC exposure in the workplace. Volatile organic compounds that are classified as hazardous materials are regulated by the Pipeline and Hazardous Materials Safety Administration while being transported. Not counting methane, biological sources emit an estimated 1150 teragrams of carbon per year in the form of VOCs; the majority of VOCs are produced by the main compound being isoprene. The remainder are produced by microbes.
Microbial volatile organic compounds can be beneficial, when used to control plant pathogens, for instance. The strong odor emitted by many plants consists of a subset of VOCs. Emissions are affected by a variety of factors, such as temperature, whi
Uranium is a chemical element with symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 electrons, of which 6 are valence electrons. Uranium is weakly radioactive because all isotopes of uranium are unstable, with half-lives varying between 159,200 years and 4.5 billion years. The most common isotopes in natural uranium are uranium-238 and uranium-235. Uranium has the highest atomic weight of the primordially occurring elements, its density is about 70% higher than that of lead, lower than that of gold or tungsten. It occurs in low concentrations of a few parts per million in soil and water, is commercially extracted from uranium-bearing minerals such as uraninite. In nature, uranium is found as uranium-238, uranium-235, a small amount of uranium-234. Uranium decays by emitting an alpha particle; the half-life of uranium-238 is about 4.47 billion years and that of uranium-235 is 704 million years, making them useful in dating the age of the Earth.
Many contemporary uses of uranium exploit its unique nuclear properties. Uranium-235 is the only occurring fissile isotope, which makes it used in nuclear power plants and nuclear weapons. However, because of the tiny amounts found in nature, uranium needs to undergo enrichment so that enough uranium-235 is present. Uranium-238 is fissionable by fast neutrons, is fertile, meaning it can be transmuted to fissile plutonium-239 in a nuclear reactor. Another fissile isotope, uranium-233, can be produced from natural thorium and is important in nuclear technology. Uranium-238 has a small probability for spontaneous fission or induced fission with fast neutrons. In sufficient concentration, these isotopes maintain a sustained nuclear chain reaction; this generates the heat in nuclear power reactors, produces the fissile material for nuclear weapons. Depleted uranium is used in kinetic energy penetrators and armor plating. Uranium is used as a colorant in uranium glass. Uranium glass fluoresces green in ultraviolet light.
It was used for tinting and shading in early photography. The 1789 discovery of uranium in the mineral pitchblende is credited to Martin Heinrich Klaproth, who named the new element after the discovered planet Uranus. Eugène-Melchior Péligot was the first person to isolate the metal and its radioactive properties were discovered in 1896 by Henri Becquerel. Research by Otto Hahn, Lise Meitner, Enrico Fermi and others, such as J. Robert Oppenheimer starting in 1934 led to its use as a fuel in the nuclear power industry and in Little Boy, the first nuclear weapon used in war. An ensuing arms race during the Cold War between the United States and the Soviet Union produced tens of thousands of nuclear weapons that used uranium metal and uranium-derived plutonium-239; the security of those weapons and their fissile material following the breakup of the Soviet Union in 1991 is an ongoing concern for public health and safety. See Nuclear proliferation; when refined, uranium is a weakly radioactive metal.
It has a Mohs hardness of 6, sufficient to scratch glass and equal to that of titanium, rhodium and niobium. It is malleable, ductile paramagnetic electropositive and a poor electrical conductor. Uranium metal has a high density of 19.1 g/cm3, denser than lead, but less dense than tungsten and gold. Uranium metal reacts with all non-metal elements and their compounds, with reactivity increasing with temperature. Hydrochloric and nitric acids dissolve uranium, but non-oxidizing acids other than hydrochloric acid attack the element slowly; when finely divided, it can react with cold water. Uranium in ores is extracted chemically and converted into uranium dioxide or other chemical forms usable in industry. Uranium-235 was the first isotope, found to be fissile. Other occurring isotopes are fissionable, but not fissile. On bombardment with slow neutrons, its uranium-235 isotope will most of the time divide into two smaller nuclei, releasing nuclear binding energy and more neutrons. If too many of these neutrons are absorbed by other uranium-235 nuclei, a nuclear chain reaction occurs that results in a burst of heat or an explosion.
In a nuclear reactor, such a chain reaction is slowed and controlled by a neutron poison, absorbing some of the free neutrons. Such neutron absorbent materials are part of reactor control rods; as little as 15 lb of uranium-235 can be used to make an atomic bomb. The first nuclear bomb used in war, Little Boy, relied on uranium fission, but the first nuclear explosive and the bomb that destroyed Nagasaki were both plutonium bombs. Uranium metal has three allotropic forms: α stable up to 668 °C. Orthorhombic, space group No. 63, lattice parameters a = 285.4 pm, b = 587 pm, c = 495.5 pm. Β stable from 668 °C to 775 °C. Tetragonal, space group P42/mnm, P42nm, or P4n2, lattice parameters a = 565.6 pm, b = c = 1075.9 pm. Γ from 775 °C to melting point—this is the most malleable and ductile state. Body-centered cubic, lattice parameter a = 352.4 pm. The major application of uranium in the military sector is
Mexicali Municipality is a municipality in the Mexican state of Baja California. Its municipal seat is located in the city of Mexicali; as of 2010, the municipality had a total population of 936,826, according to the 2000 census, it had 764,602 inhabitants. The municipality has an area of 13,700 km² This includes many smaller outlying communities as well as the city of Mexicali; the islands of Baja California located in the Gulf of California are part of the municipality, among them the mudflat islands at the mouth of the Colorado River, Isla Ángel de la Guarda and the islands of the San Lorenzo Marine Archipelago National Park. Mexicali is the northernmost municipality of Latin America; the city of Mexicali was founded in 1903, its name is a portmanteau of Mexico and California, as is the name of Calexico, California across the border. Mexicali has more than 180 maquiladoras, the rapid growth of the city has outstripped the capacity of its sewage system. Mexico and the United States spent $91 million upgrading Mexicali's sewers in recent decades, but funding has dropped in the 2010s.
Las Arenitas wastewater plant opened in 2007 south of Mexicali improving water quality bacteria levels. However the overburdened sewer system began periodically dumping raw sewage into the river, resulting in spikes in bacterial levels. In 2016 the Mexicali Public Service Commission took over regulation of wastewater discharge from the Environmental Protection Department of the state of Baja California, increasing oversight. In 2009 California Governor Arnold Schwarzenegger signed a bill creating the New River Improvement Project. Funding was approved in 2016 for a scaled-down project that would encase the river in a pipe underground and reroute it away from Calexico; the municipality of Mexicali, is divided into 14 administrative boroughs of which the city of Mexicali occupies 3 beside the city proper area. These boroughs offer administrative services such as urban planning, civil registry, verification, public works and community development and are served by a delegado; the boroughs of Mexicali Municipality city are: Los Algodones, located in the Valley Zone.
Batáquez, located in the Valley Zone. Cerro Prieto, located in the Urban Zone, is part of the Mexicali metropolitan area. Venustiano Carranza, located in the Valley Zone. Ciudad Morelos, informally known as Cuervos, located in the Valley Zone. Colonias Nuevas, informally known as Km 57, located in the Valley Zone. Progreso, located in the Urban Zone, is part of the Mexicali metropolitan area. Ejido Hermosillo, located in the Valley Zone. Estación Delta, located in the Valley Zone. Guadalupe Victoria, informally known as Km 43, located in the Valley Zone. González Ortega, informally known as Palaco, located in the Urban Zone, is part of the Mexicali metropolitan area. Hechicera, located in the Valley Zone. San Felipe, located in the Coastal Zone, to the south on the Gulf of California. Benito Juárez, informally known as Tecolotes, located in the Valley Zone; the former borough of Compuertas is located in the eastern part of the city of Mexicali. As of 2010, the city of Mexicali had a population of 936,826.
Other than the city of Mexicali, the municipality had 2,553 localities, the largest of which were: Santa Isabel, Ciudad Guadalupe Victoria, San Felipe, Progreso, Ciudad Morelos, Colonia Venustiano Carranza, Ciudad Coahuila, Vicente Guerrero, Delta, EJido Hermosillo, Benito Juárez, Batáquez, Nuevo León, Poblado Paredones, Michoacán de Ocampo, Ejido Hechicera, Viñas del Sol, Ejido Sinaloa, classified as urban, Ejido Lázaro Cárdenas, Poblado Lázaro Cárdenas, Ejido Quintana Roo, Islas Agrarias Grupo A, Ejido Jiquilpan, Ejido Plan de Ayala, Ejido Yucatán, Ejido Durango, Ejido Saltillo, Ejido Pátzcuaro, Ejido Sonora, Nayarit Llamada, Ejido Vicente Guerrero, Ejido Veracruz Dos, Ejido Colima 1, Colonia José María Rodríguez Mérida, Rincones del Puebla, Ejido Netzahualcóyotl, Ejido Toluca, Islas Agrarias Grupo B, Estación Pescaderos, Ejido Tabasco, Veracruz Uno, Ejido Doctor Alberto Oviedo Mota, classified as rural. San Luis Río Colorado Municipality, Sonora - east Ensenada Municipality - south and southwest Tecate Municipality - west Imperial County, California - north Yuma County, Arizona - northeast Municipalities of Baja California Baja California Calexico, California New River Link to tables of population data from the 2005 Census, INEGI: Instituto Nacional de Estadística, Geografía e Informática.
Mexicali, Enciclopedia de los Municipios de México, Instituto Nacional Para el Federalismo y el Desarrollo Municipal, SEGOB. Accessed on line November 15, 2007. Ubicación Geográfica, Mexicali government web site. Describes subdivisions of Mexicali. Ayuntamiento de Mexicali, official government web site. / Mexicali Tourism Guide
In microbiology, a colony-forming unit is a unit used to estimate the number of viable bacteria or fungal cells in a sample. Viable is defined as the ability to multiply via binary fission under the controlled conditions. Counting with colony-forming units requires culturing the microbes and counts only viable cells, in contrast with microscopic examination which counts all cells, living or dead; the visual appearance of a colony in a cell culture requires significant growth, when counting colonies it is uncertain if the colony arose from one cell or a group of cells. Expressing results as colony-forming units reflects this uncertainty; the purpose of plate counting is to estimate the number of cells present based on their ability to give rise to colonies under specific conditions of nutrient medium and time. Theoretically, one viable cell can give rise to a colony through replication. However, solitary cells are the exception in nature, most the progenitor of the colony was a mass of cells deposited together.
In addition, many bacteria grow in clumps. Estimation of microbial numbers by CFU will, in most cases, undercount the number of living cells present in a sample for these reasons; this is because the counting of CFU assumes that every colony is separate and founded by a single viable microbial cell. The plate count is linear for E. coli over the range of 30 - 300 CFU on a standard sized Petri dish. Therefore, to ensure that a sample will yield CFU in this range requires dilution of the sample and plating of several dilutions. Ten-fold dilutions are used, the dilution series is plated in replicates of 2 or 3 over the chosen range of dilutions; the CFU/plate is read from a plate in the linear range, the CFU/g of the original is deduced mathematically, factoring in the amount plated and its dilution factor. An advantage to this method is that different microbial species may give rise to colonies that are different from each other, both microscopically and macroscopically; the colony morphology can be of great use in the identification of the microorganism present.
A prior understanding of the microscopic anatomy of the organism can give a better understanding of how the observed CFU/mL relates to the number of viable cells per milliliter. Alternatively it is possible to decrease the average number of cells per CFU in some cases by vortexing the sample before conducting the dilution; however many microorganisms are delicate and would suffer a decrease in the proportion of cells that are viable when placed in a vortex. Concentrations of colony-forming units can be expressed using logarithmic notation, where the value shown is the base 10 logarithm of the concentration; this allows the log reduction of a decontamination process to be computed as a simple subtraction. Colony-forming units are used to quantify results in many microbiological plating and counting methods, including: The Pour Plate method wherein the sample is suspended in a Petri dish using molten agar cooled to 40-45 °C. After the nutrient agar solidifies the plate is incubated; the Spread Plate method wherein the sample is spread across the surface of a nutrient agar plate and allowed to dry before incubation for counting.
The Membrane Filter method wherein the sample is filtered through a membrane filter the filter placed on the surface of a nutrient agar plate. During incubation nutrients leach up through the filter to support the growing cells; as the surface area of most filters is less than that of a standard Petri dish, the linear range of the plate count will be less. The Miles and Misra Methods or drop-plate method wherein a small aliquot of sample from each dilution in series is dropped onto a Petri dish; the drop dish must be read while the colonies are small to prevent the loss of CFU as they grow together. However, with the techniques that require the use of an agar plate, no fluid solution can be used because the purity of the specimen cannot be unidentified and it is not possible to count the cells one by one in the liquid. Counting colonies is traditionally performed manually using a click-counter; this is a straightforward task, but can become laborious and time-consuming when many plates have to be enumerated.
Alternatively semi-automatic and automatic solutions can be used. Colonies can be enumerated from pictures of plates using software tools; the experimenters would take a picture of each plate they need to count and analyse all the pictures. Since it takes less than 10 seconds to take a single picture, as opposed to several minutes to count CFU manually, this approach saves a lot of time. In addition, it is more objective and allows extraction of other variables such as the size and colour of the colonies. OpenCFU is a free and open-source program designed to optimise user friendliness and robustness, it offers a wide range of filters and control as well as a modern user interface. OpenCFU uses OpenCV for image analysis. NICE is a program written in MATLAB providing an easy way to count colonies from images. ImageJ and CellProfiler: Some ImageJ macros and plugins and some CellProfiler pipelines can be used to count colonies; this requires the user to change the code in order to achieve an efficient work-flow, but can prove useful and flexible.
One main issue is the absence of specific GUI which can make the interaction with the processing algorithms tedious. In addition to software based on traditional desktop
An algal bloom or algae bloom is a rapid increase or accumulation in the population of algae in freshwater or marine water systems, is recognized by the discoloration in the water from their pigments. Cyanobacteria were mistaken for algae in the past, so cyanobacterial blooms are sometimes called algal blooms. Blooms which can injure animals or the ecology are called "harmful algal blooms", can lead to fish die-offs, cities cutting off water to residents, or states having to close fisheries. A bloom can block out the sunlight from other organisms, deplete oxygen levels in the water; some algae secrete poisons into the water. Since'algae' is a broad term including organisms of varying sizes, growth rates and nutrient requirements, there is no recognized threshold level as to what is defined as a bloom. For some species, algae can be considered to be blooming at concentrations reaching millions of cells per milliliter, while others form blooms of tens of thousands of cells per liter; the photosynthetic pigments in the algal cells determine the color of the algal bloom, are thus a greenish color, but they can be a wide variety of other colors such as yellow, brown or red, depending on the species of algae and the type of pigments contained therein.
Bright green blooms in freshwater systems are a result of cyanobacteria such as Microcystis. Blooms may consist of macroalgal species; these blooms are recognizable by large blades of algae. Of particular note are the rare harmful algal blooms, which are algal bloom events involving toxic or otherwise harmful phytoplankton such as dinoflagellates of the genus Alexandrium and Karenia, or diatoms of the genus Pseudo-nitzschia; such blooms take on a red or brown hue and are known colloquially as red tides. Freshwater algal blooms are the result of an excess of nutrients some phosphates; the excess of nutrients may originate from fertilizers that are applied to land for agricultural or recreational purposes. They may originate from household cleaning products containing phosphorus; these nutrients can enter watersheds through water runoff. Excess carbon and nitrogen have been suspected as causes. Presence of residual sodium carbonate acts as catalyst for the algae to bloom by providing dissolved carbon dioxide for enhanced photosynthesis in the presence of nutrients.
When phosphates are introduced into water systems, higher concentrations cause increased growth of algae and plants. Algae tend to grow quickly under high nutrient availability, but each alga is short-lived, the result is a high concentration of dead organic matter which starts to decay; the decay process consumes dissolved oxygen in the water. Without sufficient dissolved oxygen in the water and plants may die off in large numbers. Use of an Olszewski tube can help combat these problems with hypolimnetic withdrawal. Blooms may be observed in freshwater aquariums when fish are overfed and excess nutrients are not absorbed by plants; these are harmful for fish, the situation can be corrected by changing the water in the tank and reducing the amount of food given. A harmful algal bloom is an algal bloom that causes negative impacts to other organisms via production of natural toxins, mechanical damage to other organisms, or by other means. HABs are associated with large-scale marine mortality events and have been associated with various types of shellfish poisonings.
In studies at the population level bloom coverage has been related to the risk of non-alcoholic liver disease death. In the marine environment, single-celled, plant-like organisms occur in the well-lit surface layer of any body of water; these organisms, referred to as phytoplankton or microalgae, form the base of the food web upon which nearly all other marine organisms depend. Of the 5000+ species of marine phytoplankton that exist worldwide, about 2% are known to be harmful or toxic. Blooms of harmful algae can have large and varied impacts on marine ecosystems, depending on the species involved, the environment where they are found, the mechanism by which they exert negative effects. Harmful algal blooms have been observed to cause adverse effects to a wide variety of aquatic organisms, most notably marine mammals, sea turtles and finfish; the impacts of HAB toxins on these groups can include harmful changes to their developmental, neurological, or reproductive capacities. The most conspicuous effects of HABs on marine wildlife are large-scale mortality events associated with toxin-producing blooms.
For example, a mass mortality event of 107 bottlenose dolphins occurred along the Florida panhandle in the spring of 2004 due to ingestion of contaminated menhaden with high levels of brevetoxin. Manatee mortalities have been attributed to brevetoxin but unlike dolphins, the main toxin vector was endemic seagrass species in which high concentrations of brevetoxins were detected and subsequently found as a main component of the stomach contents of manatees. Additional marine mammal species, like the endangered North Atlantic Right Whale, have been exposed to neurotoxins by preying on contaminated zooplankton. With the summertime habitat of this species overlapping with seasonal blooms of the toxic dinoflagellate Alexandrium fundyense, subsequent copepod grazing, foraging right whales will ingest large concentrations of these contaminated copepods. Ingestion of such contaminated prey can affect respiratory capabilities, feeding behavior, the reprod
Mexicali is the capital city of the Mexican state of Baja California and seat of the Municipality of Mexicali. The City of Mexicali has a population of 689,775, according to the 2010 census, while the population of the entire metropolitan area reaches 996,826; the city maintains a educated and skilled population, as it has modernized and become an important population center in the desert region. Mexicali's economy has been based on agricultural products, they remain a large sector of the economy. However, its economy has gone from being agricultural to include industry maquiladoras—duty-free factories in which parts from the United States are imported and returned to the United States as finished products. International companies including Honeywell, GKN Aerospace, Kellogg's, Gulfstream, UTC Aerospace Systems, SunPower, Rockwell Collins, LG Electronics, National Oilwell Varco, Autolite, Nestlé, Coca-Cola, Robert Bosch, Goodrich Corporation have built maquiladora plants in the city. Mexicali became the national center for the aerospace industry in Mexico when Rockwell Collins established an operation there in 1966.
Rockwell Collins is the oldest company under the maquiladora program nationwide. Founded on March 14, 1903, Mexicali is situated on the Mexico–United States border adjacent to its sister city Calexico, with which it forms a dual-state, international population center, Calexico–Mexicali; the Spaniards arrived in the area after crossing the Sonoran Desert's "Camino del Diablo" or Devil's Road. This led to the evangelization of the area by Catholic missionaries and to the reduction of native populations in the region. Nowadays, indigenous Cocopah people still inhabit a small government-protected corner of the Colorado River delta near the junction of the Hardy and the Colorado; the Cocopah work on agricultural ejidos or fishing. The early European presence in this area was limited to Anza's and subsequent Spanish expeditions across the Colorado Desert and subsequent travelers on the Sonora Road opened by them; the presence of the Jesuits who attempted to establish a mission in what is now Fort Yuma.
They left after a revolt by the Yuma in 1781. After this, the Spanish had little to do with the northeastern corner of the Baja California Peninsula, perceiving it as an untamable, flood-prone desert delta. In the 1820s, the Mexican authorities reopened the Sonoran Road and restored peaceful relations with the Yuma People; the Sonoran Road provided a route for American fur trappers, American troops of Kearny and Cooke passing through the area during the Mexican–American War. The annexation of most of Alta California soon was followed by the California Gold Rush that saw a flood of gold seekers from Mexico on the Sonora Road from Sonora, from the United States via the Southern Emigrant Trail. Herds of cattle and sheep were driven into California across this desert trail also; this route became a U. S. Mail and stagecoach route in 1857 when the San Antonio-San Diego Mail Line and in 1858 Butterfield Overland Mail route passed along the Alamo and New Rivers and established stations there including its New River Station in the vicinity of a Laguna along the New River in what is now Colonia Hidalgo, Mexicali in 1858.
This mail route remained in use until 1877 when the Southern Pacific Railroad came to Yuma making it obsolete. In the mid-19th century, a geologist working for the Southern Pacific Railroad came to the delta area, discovering what the native Yumans had known for centuries: that the thick river sediment deposits made the area prime farming land; these sediments extended far to the west of the river itself, accumulating in a shallow basin below the Sierra de Cucapá. However, from this time period until the 1880s, the area was completely unpopulated due to its harsh climate. In 1888, the federal government granted a large part of northern Baja state, including Mexicali, to Guillermo Andrade, with the purpose of colonizing the area on the created border with the United States. However, around 1900, the only area with any real population, aside from the Cocopah, were concentrated in Los Algodones, to the east of Mexicali. In 1900, the U. S.-based California Development Company received permission from the government of Díaz to cut a canal through the delta's Arroyo Alamo, to link the dry basin with the Colorado River.
To attract farmers to the area, the developers named it the "Imperial Valley". In 1903, the first 500 farmers arrived; the concentration of small housing units that straddled the border was called Calexico on the U. S. side and Mexicali on the Mexican side. Led by Los Angeles Times publisher Harry Chandler, one company controlled 800,000 hectares of land in northern Baja California by 1905, began to build the irrigation system for the Valley. However, instead of using Mexican labor to dig the ditches, Chandler brought in thousands of Chinese laborers. Mexicali became; the Mexican side was named Mexicali by Coronel Agustín Sanguinéz. The area belonged to the municipality of Ensenada; the town of Mexicali was created on 14 March 1903 when Manuel Vizcarra was named as the town's first authority and Assistant Judge. On January 29, 1911, Mexicali was "liberated" by the Liberal Party of Mexico during the Mexican Revolution. Mayor Baltazar Aviléz declared the municipality of Mexicali on November 4, 1914 and called