Nature Of Particulate Organic Matter Research Articles

Variability of particulate bioavailable phosphorus, particulate organic carbon and nitrogen in agricultural and urban rivers

Suspended sediments (SS) play a key role as carriers of particulate nutrients which support primary productivity in aquatic systems. In this study, we assessed the relationship between particulate bioavailable phosphorus (PBAP), particulate organic carbon (POC) and particulate organic nitrogen (PON) in rivers flowing through contrasting land use at high and low flow. PBAP as a percentage of particulate phosphorus varied from 5 to 54%, and at low flow, there was a significant increase in PBAP fraction in the urban river as compared to the agricultural river. In addition, elevated POC and PON concentrations in both rivers were associated with low flow. POC and PON concentrations in both rivers declined at high flow presumably due to the mixing effects of water from different sources in the watershed which could have altered the particulate organic matter composition. A significant correlation existed between POC and SS in both rivers, and POC to PON ratios of SS from the rivers point to the change in the nature of particulate organic matter at varying flow conditions. PBAP exhibited a positive relationship with POC and PON concentration in both rivers possibly an indication that particulate organic matter contributes to bioavailable phosphorus in the rivers.

Stable carbon and nitrogen isotope ratios as tools to evaluate the nature of particulate organic matter in the Venice lagoon

Complex environments, such as transitional waters, are characterized by several sources of particulate organic matter (POM). The analyses of stable isotopes, δ13C and δ15N, are usually used to discriminate between allochthonous and autochthonous POM. This study aimed to characterize the nature of POM through the stable isotopic analysis for the first time in the Venice lagoon. Water samples were seasonally collected during 2011 and 2012 at 28 stations during the monitoring program for the accomplishment of the objectives of the Water Framework Directive (WFD, Directive, 2000/60/CE). Dissolved nutrient concentrations, chlorophyll a, total suspended solids were determined and POM was characterized through δ13C, δ15N and C/N molar ratio. The results showed mixed sources (autochthonous and allochthonous) of POM in all lagoon stations. Nevertheless, in autumn, the enriched 13C and significantly depleted 15N POM suggested the major influence of terrestrial contribution, probably due to the increase of freshwater inputs and land runoff. Differently, in the summer period sewage discharges and biological processes as well as primary production and microbial degradation prevailed, giving a strong seasonal increase in δ15N values (up to 18.2‰).The results of PCA analysis evidenced a spatial distinction of POM load among polyhaline, euhaline not confined and euhaline confined areas, identified for the WFD accomplishment.Through the application of multiple sources mixing model (IsoSource) by means of two variables and five different POM sources, a prevalence of allochthonous sources (82%) over autochthonous was estimated in the Venice lagoon.

Identification of Fulvic Acids and Sulfated and Nitrated Analogues in Atmospheric Aerosol by Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

The water-soluble organic fractions of aerosol samples collected in Riverside, CA, in summer 2005 were analyzed by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). Elemental compositions of about 1000 molecular species were determined in the range m/z 220-420, and four series of organic compounds were identified, fulvic acids, and S-containing, N-containing, and S- and N-containing molecules. Low-resolution product ion spectra proved the presence of organosulfates, organonitrates, and mixed organosulfates and -nitrates that appear to be structurally closely related to each other and to the fulvic acids. This is the first unambiguous detection of fulvic acid molecules and sulfated components in atmospheric aerosol and the first detection even of nitrated analogues. These species provide new clues to the nature of particulate organic matter in atmospheric aerosol.

Pacific oyster ( Crassostrea gigas) feeding responses to a fish-farm effluent

Bivalves have often been used in integrated fish-farming to enhance the economical value of by-products and/or to improve water quality. However, no physiological studies have dealt with the contribution of the two main sources of organic matter potentially present in a fish-farm effluent: living cells of phytoplankton and detritical matter (fish-faeces and uneaten feed). This study evaluated feeding responses of the Pacific oyster ( Crassostrea gigas) to a land-based fish-farm effluent comprised mainly of fish-faeces ( Dicentrarchus labrax) and compared them with those obtained with a diatom ( Skeletonema costatum). A particular distinction of the main sources of organic matter was made in the experiments, the two diets being evaluated separately and mixed. Feeding responses were evaluated using the biodeposit method with special attention being paid to pre-ingestive processes and absorption efficiency (AE). Experiments were carried out between May and July 1998 in the laboratory at constant water temperature (20°C). Results showed that food quality (nature of particulate organic matter, POM, organic content of the total suspended matter, TSM) had no influence on clearance rates. However, clearance rates were significantly reduced for oysters in advanced stage of gametogenesis. S. costatum was preferentially ingested compared to the fish-faeces when offered in a mixed diet. Absorption efficiency and energy content (56% and 15 J mg −1, respectively) of the fish-faeces were lower than those estimated for S. costatum (66–70%, 20 J mg −1). Nevertheless, these values were high for such a detritic type of food. This study confirms that both concepts of biomechanical filter and economical value improvement of fish-farming waste using oysters are of interest.

Influence of the nature of particulate organic matter on the sorption of cypermethrin: implications on KOC correlations

The sorption of the pyrethroid insecticide, cypermethrin, on clean mineral particles, mineral particles coated with aquatic humic substances, and suspended particles from the Tees Estuary was studied. The sorption process was dominated by the organic carbon or organic matter on the particle surfaces, as shown by the significant increase in the sorptive capacity of montmorillonite after being coated with aquatic humic material. Humic acid, the most aromatic coating, was the strongest sorbent, followed by fulvic acid, hydrophilic macromolecular acid, then natural coatings on estuarine suspended particles. After deduction of the contribution from the clean mineral, K oc values ranged from 160 000 to 810 000; they decreased with increasing mass fraction organic carbon (f oc) and increasing polarity in natural organic matter. A good correlation between K oc and f oc was found for both hydrophilic macromolecular acid coatings and natural coatings on estuarine particles, suggesting that hydrophilic macromolecular acid may be used to model organic coatings on estuarine suspended particles and their sorption behaviour.

Tracers and constituents indicating the nature of organic fluxes, their origin and the effect of environmental conditions

The nature of particulate organic matter was studied in suspended material sampled by bottles, particles collected by sediment traps and deposits from deltaic and open sea ecosystems of the northwestern Mediterranean. Elemental analyses were combined with pyrolysis-gas chromatography-mass spectrometry and with analysis of individual compounds such as phenols separated by high-performance liquid chromatography. In the Rhoˆne delta, a multilayered system was observed. The surficial turbid layer was enriched with fresh material of river origin. Organic matter was more altered and richer in phenols in the bottom nepheloid layer. The river regime determined the nature and quantity of suspended material: when in spate, degraded organic matter previously deposited in the river bed was transported to the sea, thereby inducing an increase of pyrolysis derived aromatic hydrocarbons. On the other hand, phenolic aldehydes increased in the bottom nepheloid layer. When water level was low, organic matter seemed to be of more local origin. The content of phenols and nitrogen-containing compounds increased. The influence of the Rhoˆne River decreased off the mouth, when terrestrial markers were diluted by products deriving from phytoplanktonic activity. Compared with suspended material, trapped organic matter was coarser, more degraded and contained more aromatic hydrocarbons. It was different in nature and size, indicating that it was trapped over a longer period. Deposits contained altered organic matter resulting from degrading processes in the water column. Sediments showed a double trend off the mouth of the river; an increase in nitrogen-containing compounds, indicating a more marine character, and a decrease in phenols and carbohydrates deriving from the terrestrial ligno-cellulosic complex. In the southwestern part of the Gulf of Lions, in the Teˆt prodelta, organic matter from sediment traps was fresher than in the Rhoˆne delta. Phenols and some carbohydrates rapidly decreased from the prodelta due to a lower runoff. During the spate, suspended material was rapidly deposited and sediments were enriched in terrestrial phenols. In the open sea environment, in the Lacaze-Duthiers Canyon at 645 m, in summer, the euphotic zone was rich in amino-sugars and contained a large diversity of phenols deriving from fish fecal pellets. In winter/spring, the development of phytoplanktonic blooms in surficial layers led to high contents of nitrogenous compounds. In deeper layers, the nature of organic matter was different from surficial layers in summer and more homogeneous in winter, although a flux of degraded material rich in pyrolysis-derived aromatic hydrocarbons and poor in nitrogenous compounds progressively sank towards the bottom. The two marine prodeltas were compared: organic matter was more degraded in suspended material and sediments collected in the submarine delta of the Rhoˆne River. Organic material originating from the river was transported further offshore, as indicated by a higher content of aromatic hydrocarbons and phenols. In the southwestern part of the Gulf of Lions, the prodelta reflected the influence of local rivers, with lower discharges.

Nature of particulate organic matter in the River Indus, Pakistan

Suspended sediments from the Indus River collected during 1981 through 1983 were analyzed for POC and its constituent fractions including amino acids, amino sugars and sugars. Percentage of POC decreased with increasing suspended matter concentrations, which suggested dilution of organic matter by mineral matter.The concentrations of amino acids, amino sugars and sugars varied, respectively, between 180 and 2000 μg/l, 5 and 125 μg/l, and 60 and 1100 μg/l. Their contributions to POC varied between 2 and 60% for amino acids and amino sugars, and between 2 and 15% for sugars. They were high during low sediment discharge (February to June), and low during high sediment discharge (August and September). Suspended sediments associated with high sediment discharge periods were characterized by low ratios of: 1.(i) aspartic acid:β-alanine2.(ii) glutamic acid:γ-aminobutyric acid3.(iii) amino acids:amino sugars4.(iv) hexoses:pentoses. These and the relative distribution pattern of the monosaccharides such as galactose, arabinose, mannose and xylose indicated that, not only dilution, but also differences in the sources and processes affect the POC transport in the Indus River. These result in transport of biodegraded organic matter during high sediment discharge periods: this appears to be common to other major rivers of the region, with depositional centers in deep sea areas. These rivers, with their high sediment loads, could contribute up to 8 to 11% of the global annual organic carbon burial in marine sediments.