Wednesday, March 18, 2020

How Ballast Water Systems Work

How Ballast Water Systems Work A ballast water system is essential for the safe operation of a ship, but the operation of these systems causes significant threats to the environment and local economy. What Is a Ballast Water System? A ballast water system allows a ship to pump water in and out of very large tanks to compensate for a change in cargo load, shallow draft conditions, or weather. The capacity of ballast water tanks might be millions of gallons on a large vessel. This allows vessels to carry a light or heavy load while maintaining ideal buoyancy and handling conditions in all situations.A ship might discharge all ballast water tanks to pass a shallow area or forward tanks only to raise the bow in rough open seas.Physical components of the system include; raw water intakes, large and small strainers, pumps, distribution pipes, ballast water tanks, treatment system, discharge system, and all the valves, sensors, and controls to run the equipment. Invasive Species in Ballast Water Invasive species are a significant threat to ecosystems and the economies of the affected areas. Researchers think that about one-third of all documented invasive plants and animals are able to travel in the ballast water tanks of ships. Zebra Mussels were introduced into Lake Saint Clair in 1988 when a ship emptied ballast water into the Great Lakes System. The Great Lakes hold nearly twenty percent of the earth’s fresh surface water in a watershed system. The non-native mussels eliminated native varieties once used by industry and have caused an estimated 7 billion dollars (US) in damage by encrusting or clogging underwater equipment essential to industrial and recreational activities.Sea Lamprey and ​Spiny Water Fleas are organisms which feed off of host fish or compete with young fish for food. Many species of fish impacted by these invasive species have significant commercial or sporting value. These animals and others can live in fresh or salt water and may spread into inland waterways from saline ports and harbors.Plants can also travel long distances in ballast water. Eurasian Milfoil is a surface plant which can clog equipment and deter recreation where it forms thick mats. Eurasian Milfoil was introduced to the United States in the 1940s. Because the plant can produce large colonies from only one small fragment it is likely the plant was introduced in the ballast water of a ship. Resolving Ballast Water Issues For years amateurs and professional researchers have experimented with a huge array of weapons to combat invasive species in a ship’s ballast water. Most of the difficulty is due to the fact that huge volumes of water must be treated in a reasonably short period of time. Many land-based systems for treating public supplies takes many hours or days to pass water through their treatment systems. A ship, on the other hand, must be able to discharge ballast water as quickly as cargo is loaded. In emergency situations, ballast tanks need to empty as quickly as possible. A quick pass through most ballast water treatment systems is not enough to kill all the organisms that may be present. Ballast Water Treatment Solutions and Shortcomings No Discharge or Ballast Exchange Rules: International, National, and Local law govern ballast water discharge. Some areas require ballast tanks to be sealed while others allow ballast to be exchanged. Ballast exchange allows tanks to be filled with local waters. Sealed ballast tanks may need to be emptied in an emergency situation and exchange is hindered by the fact that foreign waters must be discharged in close proximity to ​the sensitive area for vessels to operate safely.Mechanical Filters: Filters which are fine enough to remove the small immature young and eggs of invasive species clog quickly and require constant maintenance.Thermal Treatment: The idea is to heat ballast water to kill any unwanted organisms. Unfortunately heating such a huge volume of water is impractical due to time and energy constraints.Other Energy Treatments: Ultraviolet, sonic, and other radiation have all been tried but have similar problems to a thermal treatment; limits on time and energy.Chem ical Treatments: One of the earliest and most dangerous of all the methods used to control invasive species in ballast water. Chlorine bleach and other toxic chemicals will kill existing organisms but the release of these chemicals on the scale necessary to treat every ship would reach toxic levels for all aquatic life near the discharge points. The Future of Ballast Water Treatment Researchers are pursuing this difficult and financially lucrative goal at institutions around the world. In 2011, a team announced their successful small-scale test of a two-phase ballast treatment system which eliminates unwanted organisms and produces sodium bicarbonate as a byproduct. The system is undergoing full-size tests in the Great Lakes. The test for a scalable system is expected to perform well. It is not clear how regulatory agencies around the world will respond to the potential discharge of industrial amounts of sodium bicarbonate into their waters. Sodium bicarbonate is a common and safe chemical in small amounts, but studies must be conducted to assure this method is safe for long term use.

Monday, March 2, 2020

Mayan Civilization City of Copan, Honduras

Mayan Civilization City of Copan, Honduras Copn, called Xukpi by its residents, rises out of the mist of western Honduras, in a pocket of alluvial soil amid rugged topography. It is arguably one of the most important royal sites of the Maya civilization. Occupied between AD 400 and 800, Copn covers over 50 acres of temples, altars, stelae, ball courts, several plazas and the magnificent Hieroglyphic Stairway. The culture of Copn was rich in written documentation, today including detailed sculptural inscriptions, which is very rare in precolumbian sites. Sadly, many of the booksand there were books written by the Maya, called codiceswere destroyed by the priests of the Spanish invasion. Explorers of Copn The reason we know so much of the inhabitants of the site of Copn is the result of five hundred years of exploration and study, beginning with Diego Garcà ­a de Palacio who visited the site in 1576. During the late 1830s, John Lloyd Stephens and Frederick Catherwood explored Copn, and their descriptions, and particularly Catherwoods illustrations, are still used today to better study the ruins. Stephens was a 30-year-old attorney and politician when a doctor suggested he take some time off to rest his voice from speech making. He made good use of his vacation, touring around the globe and writing books about his travels. One of his books, Incidents of Travel in Yucatan, was published in 1843 with detailed drawings of the ruins at Copn, made by Catherwood with a camera lucida. These drawings captured the imaginations of scholars the world over; in the 1880s, Alfred Maudslay started the first excavations there, funded by Harvards Peabody Museum. Since that time, many of the best archaeologists of our time have worked at Copn, including Sylvanus Morley, Gordon Willey, William Sanders and David Webster, William and Barbara Fash, and many others. Translating Copan Work by Linda Schele and others has concentrated on translating the written language, which efforts have resulted in the recreation of the dynastic history of the site. Sixteen rulers ran Copn between 426 and 820 AD. Probably the most well-known of the rulers at Copn was 18 Rabbit, the 13th ruler, under whom Copn reached its height. While the level of control held by the rulers of Copn over the surrounding regions is debated among Mayanists, there can be no doubt that the people were aware of the populations at Teotihuacan, over 1,200 kilometers away. Trade items found at the site include jade, marine shell, pottery, sting-ray spines and some small amounts of gold, brought from as far away as Costa Rica or perhaps even Colombia. Obsidian from Ixtepeque quarries in eastern Guatemala is abundant; and some argument has been made for the importance of Copn as a result of its location, on the far eastern frontier of Maya society. Daily Life at Copan Like all of the Maya, the people of Copn were agriculturalists, growing seed crops such as beans and corn, and root crops such as manioc and xanthosoma. Maya villages consisted of multiple buildings around a common plaza, and in the early centuries of the Maya civilizations these villages were self-supporting with a relatively high standard of living. Some researchers argue that the addition of the elite class, as at Copn, resulted in the impoverishment of the commoners. Copn and the Maya Collapse Much has been made of the so-called Maya collapse, which occurred in the 9th century AD and resulted in the abandonment of the big central cities like Copn. But, recent research has shown that as Copn was being depopulated, sites in the Puuc Region such as Uxmal and Labina, as well as Chichen Itza were gaining population. David Webster argues that the collapse was merely a collapse of the ruling elites, probably as a reuslt of internal conflict, and that only the elite residences were abandoned, and not the entire city. Good, intensive archaeological work continues at Copn, and as a result, we have a rich history of the people and their times. Sources This glossary entry is part of the Guide to the Maya Civilization and the Dictionary of Archaeology. A brief bibliography has been assembled and a page detailing the Rulers of Copn is also available. The following is a brief bibliography of the archaeological literature related to the study of Copn. For more information about the site, see the glossary entry for Copn; for more information about the Maya Civilization in general, see the About.com Guide to the Maya Civilization. Bibliography for Copn Andrews, E. Wyllys and William L. Fash (eds.) 2005. Copan: The History of a Maya Kingdom. School of American Research Press, Santa Fe. Bell, Ellen E. 2003. Understanding Early Classic Copan. University Museum Publications, New York. Braswell, Geoffrey E. 1992 Obsidian-hydration dating, the Coner phase, and revisionist chronology at Copan, Honduras. Latin American Antiquity 3:130-147. Chincilla Mazariegos, Oswaldo 1998 Archaeology and nationalism in Guatemala at the time of independence. Antiquity 72:376-386. Clark, Sharri, et al. 1997 Museums and Indigenous Cultures: The power of local knowledge. Cultural Survival Quarterly Spring 36-51. Fash, William L. and Barbara W. Fash. 1993 Scribes, Warriors, and Kings: The City of Copan and the Ancient Maya. Thames and Hudson, London. Manahan, T. K. 2004 The Way Things Fall Apart: Social organization and the Classic Maya collapse of Copan. Ancient Mesoamerica 15:107-126. Morley, Sylvanus. 1999. Inscriptions at Copan. Martino Press. Newsome, Elizabeth A. 2001. Trees of Paradise and Pillars of the World: The Serial Stelae Cycle of 18-Rabbit-God K, King of Copan. University of Texas Press, Austin. Webster, David 1999 The archaeology of Copan, Honduras. Journal of Archaeological Research 7(1):1-53. Webster, David 2001 Copan (Copan, Honduras). Pages 169-176 in Archaeology of Ancient Mexico and Central America. Garland Publishing, New York. Webster, David L. 2000. Copan: The Rise and Fall of a Classic Maya Kingdom. Webster, David, AnnCorinne Freter, and David Rue 1993 The obsidian hydration dating project at Copan: A regional approach and why it works. Latin American Antiquity 4:303-324. This bibliography is part of the Guide to the Maya Civilization.