Marine dissolved organic matter (DOM) is a complex mixture of molecules found throughout the world's oceans. It plays a key role in the export, distribution, and sequestration of carbon in the oceanic water column, posited to be a source of atmospheric climate regulation. Biogeochemistry of Marine Dissolved Organic Matter, Second Edition, focuses on the chemical constituents of DOM and its biogeochemical, biological, and ecological significance in the global ocean, and provides a single, unique source for the references, information, and informed judgments of the community of marine biogeochemists. Presented by some of the world's leading scientists, this revised edition reports on the major advances in this area and includes new chapters covering the role of DOM in ancient ocean carbon cycles, the long term stability of marine DOM, the biophysical dynamics of DOM, fluvial DOM qualities and fate, and the Mediterranean Sea. Biogeochemistry of Marine Dissolved Organic Matter, Second Edition, is an extremely useful resource that helps people interested in the largest pool of active carbon on the planet (DOC) get a firm grounding on the general paradigms and many of the relevant references on this topic. * Features up-to-date knowledge of DOM, including five new chapters* The only published work to synthesize recent research on dissolved organic carbon in the Mediterranean Sea* Includes chapters that address inputs from freshwater terrestrial DOM

Biogeochemistry of marine dissolved organic matter

This analysis is based on published measurements of nitrous oxide (N2O) emission from fertilized and unfertilized fields. Data was selected in order to evaluate the importance of factors that regulate N2O production, including soil conditions, type of crop, nitrogen (N) fertilizer type and soil and crop management. Reported N2O losses from anhydrous ammonia and organic N fertilizers or combinations of organic and synthetic N fertilizers are higher than those for other types of N fertilizer. However, the range of management and environmental conditions represented by the data set is inadequate for use in estimating emission factors for each fertilizer type. The data are appropriate for estimating the order of magnitude of emissions. The longer the period over which measurements are made, the higher the fertilizer-induced emission. Therefore, a simple equation to relate the total annual direct N2O−N emission (E) from fertilized fields to the N fertilizer applied (F), was based on the measurements covering periods of one year: E=1+1.25×F, with E and F in kg N ha-1 yr-1. This relationship is independent of the type of fertilizer. Although the above regression equation includes considerable uncertainty, it may be appropriate for global estimates.

Direct emission of nitrous oxide from agricultural soils

Dissolved organic matter (DOM) can be degraded by sunlight into a variety of photoproducts that stimulate the growth and activity of microorganisms in aquatic environments. All biologically labile photoproducts identified to date fall into one of four categories: (1) low-molecular-weight (MW) organic compounds (carbonyl compounds with MW of 20% of the bacterial carbon demand. Likewise, 30% of the bacterial nitrogen demand can be met by photodegradation of the nitrogen components of DOM, a process likely to be of particular importance in nitrogen-limited systems. When considered on a depth-integrated basis around the globe, at least 1.0 X 10 15 g C and 0.15 X 10 15 g N are estimated to be available annually for utilization by planktonic microorganisms through the conversion of light-absorbing fractions of DOM to more biologically labile compounds. By comparison, direct photochemical mineralization of DOM is estimated to convert 12-16 X 10 15 g C to CO 2 annually.

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1997.42.6.1307

Role of photoreactions in the formation of biologically labile compounds from dissolved organic matter

https://moritz.botany.ut.ee/~olli/eutrsem/Crews03.pdf

Legume versus fertilizer sources of nitrogen: ecological tradeoffs and human needs

Greenhouse gases and aerosols

In 1978–1980, measurements of dissolved carbon monoxide in seawater were carried out during three ship expeditions in the northern and southern Atlantic Ocean, covering an area between 53°N and 35°S. Measurements in surface water were performed by a continuously working equilibration technique that allowed for the determination of small and rapid variations of the dissolved CO. Carbon monoxide concentrations in the water body increased toward the sea surface, there reaching saturation factors of up to 50 with respect to atmospheric CO. The daily average CO saturation increased with average chlorophyll a concentration and light intensity and decreased with wind speed. The dissolved CO showed strong diurnal variations, with maximum values in the afternoon. Diurnal variations were observed within the entire euphotic zone, indicating that CO is both produced and consumed in the seawater. Carbon monoxide production in seawater was mainly due to photooxidation of dissolved organic matter. Photobiological and microbial CO production processes were of minor importance. Carbon monoxide destruction was due to a light-independent microbial metabolism. Based on average CO saturation factors of 30±20 in the surface water of the ocean, the total source strength for atmospheric CO is calculated to 10–180 Tg yr−1.

Carbon monoxide in seawater (Atlantic Ocean)

In 1979–1981, experiments were carried out at four field stations near Mainz, Germany, to determine the loss of fertilizer nitrogen into the atmosphere as N2O. Evolution rates from the soil into the atmosphere were measured by using the closed chamber technique. An automatic sampling and analyzing device was developed which allowed frequent determinations of N2O evolution rates (one every 1.5 hours). The N2O production rates were correlated to the surface soil temperature according to the Arrhenius equation and showed a diurnal rhythm with amplitudes reaching, sometimes, 1 order of magnitude. It seems that most of the N2O emitted into the atmosphere is produced in the uppermost soil layer. N2O evolution was stimulated by rain and increased with increasing soil moisture content. Application of fertilizer caused a dramatic increase of N2O evolution rates with values up to 1000 μg N2O–N m−2 h−1. The magnitude of the fertilizer-induced N2O evolution rates was dependent on the type, the application form, and the amount of fertilizer used. The total loss of fertilizer nitrogen as N2O was in the range of 0.001 to 0.94%.Based on these figures, as well as on data from the literature, the total source strength of mineral fertilizers for atmospheric N2O is calculated to 0.02 to 8 Tg N2O–N yr−1.

Factors influencing the loss of fertilizer nitrogen into the atmosphere as N2O

It is shown by laboratory experiments and extensivein-situ measurements that higher plants (Vicia faba, Platanus acerifolia, Fagus silvatica, andPinus silvestris) produce carbon monoxide. The measurements were carried out under natural conditions with respect to the concentrations of O2 and H2O, and temperature. The CO2- and CO-mixing ratios were varied in the ranges 350 to 530 ppm and 3–270 ppb, respectively. The CO-production rates were found to be light dependent with an average value per cm2 of leaf area of 3×10−13 g/sec for a radiation intensity of 5×104 erg/cm2 sec. The production rates are independent of the CO2- and CO-mixing ratios employed in the test atmosphere. Considering the production rate of 3×10−13 g/cm2 sec to be representative for global conditions the total CO-production by plants is estimated to be 0.5–1.0×1014 g/year. In contrast to carbon monoxide atmospheric dinitrogen oxide is not influenced by plants in the same manner.

The influence of plants on atmospheric carbon monoxide and dinitrogen oxide

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Carbon monoxide in seawater (Atlantic Ocean)

Factors influencing the loss of fertilizer nitrogen into the atmosphere as N2O

The influence of plants on atmospheric carbon monoxide and dinitrogen oxide