Oxygen Was Almost Named Nitrogen.

In his Tractatus Quinque Medico-Physici of 1674, John Mayow wrote that a fifth of atmospheric air is comprised of nitro-aerial spirit. That so-called spirit participates in both respiration and combustion. The etymology of "nitro-aerial spirit" stems from a mineral long called niter and now specified as potassium nitrate. Niter mixed with sulfur and carbon is gunpowder, developed in the ninth century in China. Mayow appreciated that niter was the oxidant in the energy-yielding reaction of gunpowder. The word "oxygen," eventually prompting the word oxidant, was coined a century later by Antoine Lavoisier.

Possible nitrogen fertilization of the early Earth Ocean by microbial continental ecosystems.

While significant efforts have been invested in reconstructing the early evolution of the Earth's atmosphere-ocean-biosphere biogeochemical nitrogen cycle, the potential role of an early continental contribution by a terrestrial, microbial phototrophic biosphere has been largely overlooked. By transposing to the Archean nitrogen fluxes of modern topsoil communities known as biological soil crusts (terrestrial analogs of microbial mats), whose ancestors might have existed as far back as 3.2 Ga ago, we show that they could have impacted the evolution of the nitrogen cycle early on. We calculate that the net output of inorganic nitrogen reaching the Precambrian hydrogeological system could have been of the same order of magnitude as that of modern continents for a range of inhabited area as small as a few percent of that of present day continents. This contradicts the assumption that before the Great Oxidation Event, marine and continental biogeochemical nitrogen cycles were disconnected.

Long-term variation (1960-2003) and causal factors of non-point-source nitrogen and phosphorus in the upper reach of the Yangtze River.

The knowledge of long-term variation and causal factors of non-point source (NPS) pollution in large-scale watersheds is helpful in the development of water quality control programs. In this study, the Improved Export Coefficient Model and the Revised Universal Soil Loss Equation were combined to estimate the temporal and spatial variations (1960-2003) of NPS pollution in the upper reach of the Yangtze River (URYR). Two change points for NPS pollution were successfully detected. In the URYR, the dissolved nitrogen (DN) and dissolved phosphorus (DP) increased before 2000 and decreased after 2000, whereas the inflection points from increase to decline were around 1980 for the adsorbed N (AN) and adsorbed P (AP). The results also indicated that the dissolved pollutants were mainly contributed by the anthropogenic factors, while the adsorbed pollutants were primarily exported by the natural factors. By comparing the load intensities from each source, it revealed that for the dissolved pollutants, the major source of the high load intensity transferred from urban land to dry land after 1980. Simultaneously, the high load intensity areas of the adsorbed pollutants transferred from forest to orchard around 1980, which was mainly attributed to the increasing fertilizer application. These results may be useful for planning and management of the URYR and other large-scale watersheds.

Living lawns, dying waters: The suburban boom, nitrogenous fertilizers, and the nonpoint source pollution dilemma.

The March 1963 issue of Consumer Bulletin included a four-page article titled "How to grow a better lawn", the lead paragraph of which assured readers that "one does not have to be an expert or spend large sums of money to have a good lawn. It is necessary, however, to follow certain established practices in the construction and maintenance of any lawn." These two assertions may have struck readers, as I suspect they would strike lawngrowers today, as somewhat contradictory. Given the list of established practices that followed--"the construction of the lawn base, with proper grading, drainage, and preparation of the seedbed; selection of the type of grass and spreading of the seed; and maintenance, including fertilizing, mowing, and control of weeds"--it is difficult to imagine how the homeowner could have accomplished all of this without large sums of money or expertise. In fact, building lawns in the manner described by Consumer Bulletin required tremendous amounts of both. Recognizing these established practices in lawn construction and maintenance as a technological system allows us to better understand the persistence of this grassy landscape in America.

Recent sedimentary history of organic matter and nutrient accumulation in the Ohuira Lagoon, northwestern Mexico.

(210)Pb-derived sediment accumulation rates, as well as a suite of geochemical proxies (Al, Fe, delta(13)C, delta(15)N), were used to assess the time-dependent variations of C, N, and P fluxes recorded in two sediment cores collected at Ohuira Lagoon, in the Gulf of California, Mexico, during the last 100 years. Sedimentary C, N, and P concentrations increased with time and were related to land clearing, water impoundment, and agriculture practices, such as fertilization. C:N:P ratios and delta(13)C suggested an estuarine system that is responsive to increased C loading from a N-limited phytoplankton community, whereas delta(15)N values showed the transition between an estuarine-terrestrial to an estuarine-more marine environment, as a consequence of the declining freshwater supply into the estuary due to the channeling and impoundment of El Fuerte River between 1900 and 1956. The recent increases in nutrient fluxes (2- to 9-fold the pre-anthropogenic fluxes of C and N, and 2 to 13 times for P) taking place in the mainland from the 1940s, were related to the expansion of the intensive agriculture fields and to the more recent development of shrimp farming activities.

Historical eutrophication in a river-estuary complex in mid-coast Maine.

European settlement of New England brought about a novel disturbance regime that impacted rivers and estuaries through overfishing, deforestation, dams, and water pollution. The negative consequences of these activities intensified with industrialization in the 19th and 20th centuries, often resulting in ecosystem degradation. Since environmental legislation was implemented in the 1970s, improvement in water quality has been tangible and widespread; however, ecological recovery can require substantial amounts of time and may never be complete. To document the natural baseline conditions and investigate the recovery of a severely degraded river-estuary complex in mid-coast Maine, we examined diatoms, pollen, total organic carbon, total nitrogen, stable isotopes, total phosphorus, biogenic silica, and trace metals in intertidal sediments and established a chronology with 14C, 210Pb, and indicator pollen horizons. Both climate variability and human effects were evident in the sedimentary record of Merrymeeting Bay, the freshwater tidal portion of the Kennebec estuary. Natural climate variability was apparent in an episode of high sedimentation and altered diatom abundance during the 12th and 13th centuries and in changing pollen abundances between the 16th and 19th centuries, indicative of regional cooling. During the 18th century, colonial land clearance began an era of high sedimentation and eutrophication that strongly intensified with industrialization during the late 19th and 20th centuries. Improvements in water quality over the past 30 years in response to environmental regulation had little effect on ecosystem recovery as represented by the sedimentary record. Diatom composition and productivity and high fluxes of organic C, total P, and biogenic Si in recent sediments indicate that rates of nutrient loading remain high. These environmental proxies imply that aquatic productivity in Merrymeeting Bay was originally nutrient limited and water clarity high, relative to today. Further recovery may require more stringent regulation of nutrient inputs from industrial and municipal point sources. This historical study can contribute to public debate about the environmental management of this unusual river-estuary complex by describing its long-term natural baseline, thereby illustrating the upper limit of its potential for recovery.

Feeding the city: food consumption and flow of nitrogen, Paris, 1801-1914.

The flows of foodstuffs (and the nitrogen they contain) through the city of Paris in the 19th and early 20th century were evaluated. Between 1801 and 1914, the fivefold increase in the population of Paris, as well as the threefold increase in the number of horses used in urban transport, gave rise to increased needs for food and feed. The corresponding inputs of nitrogen increased from 6000 tN/year in 1817 to 25,000 tN/year from the rural hinterland to the city. The corresponding per capita inflows were relatively stable throughout the period and may be divided into four more or less equal parts (flour, meat, other human foodstuffs, forage), each representing about 6 gN per inhabitant per day. In total, the demand for foodstuffs was of the order of 24 gN per inhabitant per day, one quarter of which was for transport. The fate of this dietary nitrogen after consumption changed a lot with the techniques used for exploiting urban excreta of all kinds, particularly of nitrogen, which was in great demand until the development of synthetic fertilizers. Dietary nitrogen flow diagrams are established for the years 1817, 1869 and 1913, and reveal an increasing improvement of the agricultural reuse (from 20 to 40% of the inflowing N).

Reappraisal of the 20th-century version of amino acid metabolism.

In this article, we advocate the radical revision of the 20th-century version of amino acid metabolism as follows. (1) Classic studies on the incorporation of [15N]ammonia into glutamate, once considered to be an epoch-making event, are not distinctive proof of the ability of animals to utilize ammonia for the synthesis of alpha-amino nitrogen. (2) Mammalian glutamate dehydrogenase has been implicated to function as a glutamate-synthesizing enzyme albeit lack of convincing proof. This enzyme, in combination with aminotransferases, is now known to play an exclusive role in the metabolic removal of amino nitrogen and energy production from excess amino acids. (3) Dr. William C Rose's "nutritionally nonessential amino acids" are, of course, essential in cellular metabolism; the nutritional nonessentiality is related to their carbon skeletons, many of which are intermediates of glycolysis or the TCA cycle. Obviously, the prime importance of amino acid nutrition should be the means of obtaining amino nitrogen. (4) Because there is no evidence of the presence of any glutamate-synthesizing enzymes in mammalian tissues, animals must depend on plants and microorganisms for preformed alpha-amino nitrogen. This is analogous to the case of carbohydrates. (5) In contrast, individual essential amino acids, similar to vitamins and essential fatty acids, should be considered important nutrients that must be included regularly in sufficient amounts in the diet.

Effect of water quality management efforts on wastewater loadings during the past century.

The history of wastewater discharges to the Hudson River watershed from Troy, New York, to the New York City Harbor was traced from 1900 to 2000. The parameters studied include population, flow, type of treatment, biochemical oxygen demand, suspended solids, total nitrogen, and total phosphorus. This paper details a methodology for estimating historic loadings where data are lacking. The data show dramatic changes in wastewater loadings. There has been a continued increase in wastewater flow and population over the past century but a decrease in contaminant loading during the last 25 years. The reduction in effluent loads is directly related to state and federal water quality management programs and the substantial public and private investment made in upgrading point source water pollution control infrastructure. A comparison of point with nonpoint source loads shows that although nonpoint sources are now a significant contributor of contaminants to the river, point sources remain as major sources of total nitrogen and total phosphorus.

Nitrogen use in the United States from 1961-2000 and potential future trends.

Nitrogen inputs to the US from human activity doubled between 1961 and 1997, with most of the increase in the 1960s and 1970s. The largest increase was in use of inorganic N fertilizer, but emissions of NOx from fossil-fuel combustion also increased substantially. In 1961, N fixation in agricultural systems was the largest single source of reactive N in the US. By 1997, even though N fixation had increased, fertilizer use and NOx emissions had increased more rapidly and were both larger inputs. In both 1961 and 1997, two thirds of reactive N inputs were denitrified or stored in soils and biota, while one third was exported. The largest export was in riverine flux to coastal oceans, followed by export in food and feeds, and atmospheric advection to the oceans. The consumption of meat protein is a major driver behind N use in agriculture in the US Without change in diet or agricultural practices, fertilizer use will increase over next 30 years, and fluxes to coastal oceans may increase by another 30%. However, substantial reductions are possible.

The history of cyanobacterial blooms in the Baltic Sea.

Long-term information on possible changes in cyanobacterial blooms in the Baltic Sea, formed mainly by Nodularia spumigena and Aphanizomenon sp., was sought in published records in historical (years 1887-1938) and modern (years 1974-1998) phytoplankton data sets. Old and new sampling methods and fixatives were tested to improve the comparison of data that had been collected and analyzed in different ways. A hundred years ago, plankton was mainly of interest as a source of fish food; eutrophication problems were only locally reported from the coast, mainly in southern haffs and the receiving waters of larger cities. There were few recordings of open-sea blooms before World War II. Abundances of Nodularia spumigena and Aphanizomenon sp. were low in the old material, and 137 summer samples from 1887-1938 showed no peak abundance. High abundances are common in the new material, and the range of the numbers of both taxa has increased markedly relative to the old material. Since the 1960s, cyanobacterial blooms have been common in the open sea in both the Baltic proper and the Gulf of Finland, indicating high availability of nutrients.

Understanding human impact on the Baltic ecosystem: changing views in recent decades.

Grave environmental problems, including contamination of biota by organochlorines and heavy metals, and increasing deep-water oxygen deficiency, were discovered in the Baltic Sea in the late 1960s. Toxic pollutants, including the newly discovered PCB, were initially seen as the main threat to the Baltic ecosystem, and the impaired reproduction found in Baltic seals and white-tailed eagles implied a threat also to human fish eaters. Countermeasures gradually gave results, and today the struggle to limit toxic pollution of the Baltic is an international environmental success story. Calculations showed that Baltic deep-water oxygen consumption must have increased, and that the Baltic nutrient load had grown about fourfold for nitrogen and 8 times for phosphorus. Evidence of increased organic production at all trophic levels in the ecosystem gradually accumulated. Phosphorus was first thought to limit Baltic primary production, but measurements soon showed that nitrogen is generally limiting in the open Baltic proper, except for nitrogen-fixing cyanobacteria. Today, the debate is concerned with whether phosphorus, by limiting nitrogen-fixers, can control open-sea ecosystem production, even where phytoplankton is clearly nitrogen limited. The Baltic lesson teaches us that our views of newly discovered environmental problems undergo repeated changes, and that it may take decades for scientists to agree on their causes. Once society decides on countermeasures, it may take decades for them to become effective, and for nature to recover. Thus, environmental management decisions can hardly wait for scientific certainty. We should therefore view environmental management decisions as experiments, to be monitored, learned from, and then modified as needed.

The pollution and protection of the inner Oslofjord: redefining the goals of wastewater treatment policy in the 20th century.

The main source of pollution in the inner Oslofjord in the 20th century has been municipal sewage discharges from the city of Oslo. At the beginning of the 20th century, pollution was limited to the coastal waters and the harbor area of Oslo, in the vicinity of sewer outlets. High bacteria content caused a health hazard that city authorities attempted to reduce by constructing a sewerage system, including intercepting sewers and wastewater-treatment plants. Due to population growth, the impact area of increasing wastewater loading expanded. The entire inner Oslofjord was found to be affected in the 1930s. Scientific studies linked municipal sewage discharges to an increase in the algal production. In the 1940s, the bottom layers were found to be anoxic. The Oslo sewerage authorities were aware of the fjord's pollution, but regarded organic matter as the major problem and the activated sludge method as the best solution. The role of nutrients was not commonly acknowledged until in the late 1960s. Phosphorus removal was taken into use in the 1970s, and nitrogen removal was introduced in the late 1990s. Removal of nutrients has resulted in the slow recovery of the fjord.

Use and misuse of nitrogen in agriculture: the German story.

Nitrogen (N) fertilization in agriculture has been discussed controversially in Germany for almost two centuries. The agronomist Carl Sprengel, who published his theory on the mineral nutrition of plants in 1828, advocated the use of mineral N fertilizers. Chemist Justus von Liebig, on the other hand, vehemently denied around 1850 the need for N fertilization. Although it soon became evident that Sprengel was right and Liebig was wrong, not much synthetic N fertilizer was used in German agriculture until around 1915, when the Haber-Bosch technique enabled the commercial production of NH3. The use of N fertilizers since then has grown, especially since 1950. To increase agricultural productivity, German governments have promoted, directly and indirectly, the use of N in crop and in animal production. Unfortunately, it was overlooked that N surpluses in agriculture increased rapidly; around 1980 they amounted yearly to more than 100 kg ha(-1). The extensive use of N in agriculture is causing environmental damage and is contributing substantially to the external costs of present agriculture. The main N compounds that affect the environment are N2O, NH3, and NO3. These compounds are considered to contribute one third to the external costs of agriculture. Additionally, the high rate of human intake of animal proteins and lipids has adversely affected the health of the country's population. Fundamental corrections in German farm policy appear inevitable.

Amino acids, then and now--a reflection on Sir Hans Krebs' contribution to nitrogen metabolism.

H. A. Krebs made an enormous contribution to our knowledge of amino acid metabolism, beginning with his studies on proteolysis in the early 1930s, progressing through his work on urea synthesis to an extensive series of papers on deamination and, then, to work on gluconeogenesis from amino acids. This paper addresses three of Krebs' early contributions-urea synthesis, glutamine metabolism, and D-amino acid oxidase-and relates them to our modern understanding of amino acid metabolism.