Particulate Organic Nitrate Research Articles

Influence of net cages on water quality and trophic status of Lake Victoria, Kenya: The case of Kadimu Bay

AbstractWater quality is a critical component regulating ecosystem functioning in aquatic habitats, requiring regular monitoring for sustainable ecosystem services. Cage fish farming has the potential to affect water quality because of its rapid increase in many African waterbodies in response to dwindling wild fish stocks. Thus, there is a need for more studies to guide sustainable cage aquaculture in African lakes and reservoirs. This study evaluated the possible effects of cage farming of Nile tilapia (Oreochromis niloticus) on water quality parameters and the trophic state of Kadimu Bay, Lake Victoria, Kenya. Sampling for physicochemical and biological variables, including nutrient load, was conducted from January to October 2021, at five fish cage sites and a control site within the bay. In situ measurements of physical variables were undertaken in the field, while analysis of water samples for nutrient loads, biological and chemical variables was undertaken in the laboratory, following the methods described in APHA (American public health association standard methods for the examination of water and waste water. APHA‐AWWA‐WEF, 2005). The Carlson's Trophic State Index (CTSI) was used to classify the trophic state of the cage sites, while the total nitrogen:total phosphorus (TN:TP) ratio was used to determine the primary productivity limiting nutrient in the bay. The study results indicated electrical conductivity was significantly lower at the control (97.53 ± 4.17 μS/cm), compared to cage sites (105.42 ± 5.32 μS/cm at the Utonga cage site to 112.84 ± 1.94 μS/cm at the Oele cage site), indicating water of relatively lower quality at the cage sites. Similarly, the nitrite concentrations were higher at cage sites (6.35 ± .96 μg/L at the Uwaria cage site to 3.16 ± 2.25 μg/L at the Utonga cage site), and lower at the control site (2.68 ± 1.39 μg/L). In all, 14 physicochemical variables did not vary significantly between the cage and control sites, with nine variables (temperature, turbidity, electrical conductivity, total suspended solids, particulate organic matter, chlorophyll‐a, TP, nitrate and TN) being within the recommended thresholds for aquatic life processes. The bay was evaluated as being in a light eutrophic state, indicating moderate influence of the fish cages on the trophic state of the sites. There was a moderate relationship between chlorophyll‐a and TP concentration at the sampling sites (R2 = .50), compared to a stronger relationship with (R2 = .78). The TN:TP ratios were <10 at the sampling sites, indicating nitrogen was the limiting factor for primary production in the bay. The calculated CTSI suggests that the bay exhibited a light eutrophic state. Overall, although the results of this study showed cage aquaculture is not a current challenge to the water quality of the bay, regular monitoring is nevertheless recommended to inform sustainable aquaculture development in the bay and lake.

Detecting and Characterizing Particulate Organic Nitrates with an Aerodyne Long-ToF Aerosol Mass Spectrometer.

Particulate organic nitrate (pON) can be a major part of secondary organic aerosol (SOA) and is commonly quantified by indirect means from aerosol mass spectrometer (AMS) data. However, pON quantification remains challenging. Here, we set out to quantify and characterize pON in the boreal forest, through direct field observations at Station for Measuring Ecosystem Atmosphere Relationships (SMEAR) II in Hyytiälä, Finland, and targeted single-precursor laboratory studies. We utilized a long time-of-flight AMS (LToF-AMS) for aerosol chemical characterization, with a particular focus to identify C x H y O z N+ ("CHON+") fragments. We estimate that during springtime at SMEAR II, pON (including both the organic and nitrate part) accounts for ∼10% of the particle mass concentration (calculated by the NO+/NO2 + method) and originates mainly from the NO3 radical oxidation of biogenic volatile organic compounds. The majority of the background nitrate aerosol measured is organic. The CHON+ fragment analysis was largely unsuccessful at SMEAR II, mainly due to low concentrations of the few detected fragments. However, our findings may be useful at other sites as we identified 80 unique CHON+ fragments from the laboratory measurements of SOA formed from NO3 radical oxidation of three pON precursors (β-pinene, limonene, and guaiacol). Finally, we noted a significant effect on ion identification during the LToF-AMS high-resolution data processing, resulting in too many ions being fit, depending on whether tungsten ions (W+) were used in the peak width determination. Although this phenomenon may be instrument-specific, we encourage all (LTOF-) AMS users to investigate this effect on their instrument to reduce the possibility of incorrect identifications.

Water Quality Assessment and Monitoring of Closed Rearing System of the Sea Cucumber Holothuria scabra

Sea cucumbers are an essential fishery resource. Therefore, effective aquaculture methods should be developed to achieve their optimal production. Sea cucumbers are susceptible to various environmental factors, one of which is water quality. Monitoring water quality based on physical and chemical parameters should be useful to the rearing system in aquaculture. In practical use, farmers usually monitor only temperature, salinity, and pH, neglecting the essential role of chemical parameters. This review focuses on and urges the monitoring of physical and chemical parameters. We explored the water quality parameters that may be crucial to the sea cucumber rearing system, including temperature, salinity, pH, dissolved oxygen, ammonia, turbidity, particulate organic matter, total nitrogen, nitrate, nitrite, ammonium, silicate, and phosphate. Furthermore, this paper presents a practical way to monitor the aquaculture or rearing system of sea cucumbers. It is suggested that temperature and salinity are the crucial physical parameters, while the essential chemical parameters are phosphate, nitrate, and ammonia.

Quantification of Non-refractory Aerosol Nitrate in Ambient Air by Thermal Dissociation Cavity Ring-Down Spectroscopy.

A thermal dissociation cavity ring-down spectrometer (TD-CRDS) for real-time quantification of non-refractory aerosol nitrate in ambient air is described. The instrument uses four parallel detection channels and heated quartz inlets to convert particulate organic nitrate (pON) (at 350 °C) and ammonium nitrate (NH4NO3) aerosol (at 540 °C) to nitrogen dioxide (NO2), whose mixing ratio is monitored via its absorption at 405 nm. Concentrations of aerosol nitrate are determined by difference relative to a parallel TD-CRDS channel in which aerosol is removed by in-line filtering. The method was validated by sampling gas streams containing laboratory-generated NH4NO3 aerosol in parallel to a scanning mobility particle sizer (SMPS). Scatter plots of TD-CRDS and SMPS data correlated (r2 > 0.9) with slopes near unity, confirming quantitative TD-CRDS response to NH4NO3 aerosol. In contrast, no response was observed when sampling (NH4)2SO4 aerosol. Instrument limits of detection (LOD; 2σ, 10 s) were 120 parts per trillion by volume (10-12, pptv) for NO2 and 148 pptv for ammonium nitrate. Partial and unsustained conversion of refractory sodium nitrate (NaNO3) was observed at the inlet temperature used for complete dissociation of HNO3 and NH4NO3, suggesting that this channel may not constitute a robust measurement of total odd nitrogen (NOy) in environments where NaNO3 particles may be present (e.g., the polluted marine boundary layer). A potential application of the TD-CRDS is the calibration of particle counters, for which convenient methods are not currently available. Sample ambient air measurements of pON and total aerosol nitrate in Calgary are presented.

Apportionment of PM2.5 adjacent to the I-710 Harbor Freeway in Long Beach, CA

ABSTRACTDuring August and September 2012, a study was conducted to determine the sources of PM2.5 adjacent to the I-710 Long Beach Freeway. The site is directly affected by the emissions from heavy diesel traffic flowing from major container ports about 10 km south of the sampling site. Hourly average data were obtained for particulate species including PM2.5, black carbon and UV absorbing carbon, EC, fine particulate nonvolatile and semi-volatile organic material (NVOM and SVOM), sulfate, nitrate, chloride, ammonium ion, and Na ion, and for related factors including O3, CO, NOX, SO2, and total traffic flow on the I-710. A total of 520 hourly averaged data sets with 15 measured variables were analyzed by EPA-PMF v5.0. The data were best described by a 10-factor solution. Based on the composition and diurnal patterns of the factors, they were assigned to three diesel-related factors (two of which appeared to represent traffic from the ports and one general freeway diesel factor), a light-duty, spark-ignition vehicle-related factor, three secondary factors (one of which was associated with O3 formation processes), and three factors dominated by sulfate, SO2, and chloride, respectively. The diurnal patterns for these last three factors are strongly correlated. Meteorological and refinery upset data indicate that they are associated with emissions from a nearby refinery. The results of the PMF analysis were combined with nephelometer light scattering, corrected for coarse particle scattering and estimated aerosol water content in a multilinear regression analysis to identify visibility degradation sources. Major contributors were the aerosol water content, and the secondary PMF factors associated with either Nitrate and NVOM or NVOM and SVOM. The use of hourly average data made possible the identification of factors associated with gasoline vehicle emissions and both port and non-port diesel emissions.Implications: Hourly averaged data were obtained for PM2.5, its components and factors related to primary emissions and the formation of secondary material at a near freeway sampling location adjacent to the I-710 freeway just south of the Long Beach Boulevard entrance and 10 km north of the Ports of Long Beach and Los Angeles. The major objective of the study was to determine the impact of traffic from the ports at the monitoring site. This manuscript reports on the PMF analysis of the data set. Factors related to both diesel traffic originating from the ports and diesel traffic from non-port origins were identified. The diesel traffic originating from the ports was responsible for 9% of the total traffic and 95% of the BC measured at the sampling site. The non-port diesel traffic was responsible for 15% of the total traffic and 5% of the BC. While the Port 1 diesel traffic coming from the ports contributed a large fraction of the BC, this source contributed only 2% of the CO and 5% of the NOX at the sampling site. The impact of these traffic sources on light scattering was also small. Analysis of sources of sulfate and SO2 at the sampling site indicated that these species did not come from port activities of ships at or approaching the port, but rather from upset flare events at a nearby oil refinery.

Small-scale heterogeneity of trace metals including rare earth elements and yttrium in deep-sea sediments and porewaters of the Peru Basin, southeastern equatorial Pacific

Abstract. Due to its remoteness, the deep-sea floor remains an understudied ecosystem of our planet. The patchiness of existing data sets makes it difficult to draw conclusions about processes that apply to a wider area. In our study we show how different settings and processes determine sediment heterogeneity on small spatial scales. We sampled solid phase and porewater from the upper 10 m of an approximately 7.4×13 km2 area in the Peru Basin, in the southeastern equatorial Pacific Ocean, at 4100 m water depth. Samples were analyzed for trace metals, including rare earth elements and yttrium (REY), as well as for particulate organic carbon (POC), CaCO3, and nitrate. The analyses revealed the surprisingly high spatial small-scale heterogeneity of the deep-sea sediment composition. While some cores have the typical green layer from Fe(II) in the clay minerals, this layer is missing in other cores, i.e., showing a tan color associated with more Fe(III) in the clay minerals. This is due to varying organic carbon contents: nitrate is depleted at 2–3 m depth in cores with higher total organic carbon contents but is present throughout cores with lower POC contents, thus inhibiting the Fe(III)-to-Fe(II) reduction pathway in organic matter degradation. REY show shale-normalized (SN) patterns similar to seawater, with a relative enrichment of heavy REY over light REY, positive LaSN anomaly, negative CeSN anomaly, and positive YSN anomaly and correlate with the Fe-rich clay layer and, in some cores, also correlate with P. We therefore propose that Fe-rich clay minerals, such as nontronite, as well as phosphates, are the REY-controlling phases in these sediments. Variability is also seen in dissolved Mn and Co concentrations between sites and within cores, which might be due to dissolving nodules in the suboxic sediment, as well as in concentration peaks of U, Mo, As, V, and Cu in two cores, which might be related to deposition of different material at lower-lying areas or precipitation due to shifting redox boundaries.

Chemical composition and hydrolysis of organic nitrate aerosol formed from hydroxyl and nitrate radical oxidation of <i>α</i>-pinene and <i>β</i>-pinene

Abstract. Atmospheric organic nitrate (ON) is thought to play a crucial role in the formation potential of ozone and aerosol, which are the leading air pollutants of concern across the world. Limited fundamental knowledge and understanding of the life cycles of ON currently hinder the ability to quantitatively assess its impacts on the formation of these pollutants. Although hydrolysis is currently considered an important loss mechanism of ON based on prior field measurement studies, this process for atmospherically relevant ON has not been well constrained by fundamental laboratory studies. In this comprehensive study, we investigated the chemical composition and hydrolysis process of particulate ON (pON) formed from the oxidation of α-pinene and β-pinene by hydroxyl (OH⚫) and nitrate radicals (NO3⚫). For pON that undergoes hydrolysis, the hydrolysis lifetime is determined to be no more than 30 min for all systems explored. This is significantly shorter than those reported in previous chamber studies (i.e., 3–6 h) but is consistent with the reported lifetime from bulk solution measurement studies (i.e., 0.02–8.8 h). The discrepancy appears to stem from the choice of proxy used to estimate the hydrolysis lifetime. The measured hydrolyzable fractions of pON (FH) in the α-pinene + OH⚫, β-pinene + OH⚫, α-pinene + NO3⚫, and β-pinene + NO3⚫ systems are 23 %–32 %, 27 %–34 %, 9 %–17 %, and 9 %–15 %, respectively. While a very low FH for the NO3⚫ oxidation system is expected based on prior studies, FH for the OH⚫ oxidation system is surprisingly lower than predicted in past studies. Overall, the hydrolysis lifetime as well as FH obtained in this study serve as experimentally constrained parameters that are required in regional and global chemical transport models to accurately evaluate the impacts of ON on nitrogen budget and formation of ozone and aerosol.

Characterization of nighttime formation of particulate organic nitrates based on high-resolution aerosol mass spectrometry in an urban atmosphere in China

Abstract. Organic nitrates are important atmospheric species that significantly affect the cycling of NOx and ozone production. However, characterization of particulate organic nitrates and their sources in polluted atmosphere is a big challenge and has not been comprehensively studied in Asia. In this study, an aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) was deployed at an urban site in China from 2015 to 2016 to characterize particulate organic nitrates in total nitrates with a high time resolution. Based on the cross-validation of two different data processing methods, organic nitrates were effectively quantified to contribute a notable fraction of organic aerosol (OA), namely 9 %–21 % in spring, 11 %–25 % in summer, and 9 %–20 % in autumn, while contributing a very small fraction in winter. The good correlation between organic nitrates and fresh secondary organic aerosol (SOA) at night, as well as the diurnal trend of size distribution of organic nitrates, indicated a key role of nighttime local secondary formation of organic nitrates. Furthermore, theoretical calculations of nighttime SOA production of NO3 reactions with volatile organic compounds (VOCs) measured during the spring campaign were performed, resulting in three biogenic VOCs (α-pinene, limonene, and camphene) and one anthropogenic VOC (styrene) identified as the possible key VOC precursors to particulate organic nitrates. The comparison with similar studies in the literature implied that nighttime particulate organic nitrate formation is highly relevant to NOx levels. This study proposes that unlike the documented cases in the United States and Europe, modeling nighttime particulate organic nitrate formation in China should incorporate not only biogenic VOCs but also anthropogenic VOCs for urban air pollution, which needs the support of relevant smog chamber studies in the future.

Modeling Nitrogen Decrease in Water Lettuce Ponds from Waste Stabilization Ponds

This paper presents about the dynamic modeling of the Water Lettuce ponds as a form of improvement from the Water Hyacinth ponds. The purpose of this paper is to predict nitrogen decrease and nitrogen transformation in Water Lettuce ponds integrated with Waste Stabilization Ponds. The model consists of 4 mass balances, namely Dissolved Organic Nitrogen (DON), Particulate Organic Nitrogen (PON), ammonium (NH4+), Nitrate and Nitrite (NOx). The process of nitrogen transformation which considered in a Water Lettuce ponds, namely hydrolysis, mineralization, nitrification, denitrification, plant and bacterial uptake processes. Numerical simulations are performed by giving the values of parameters and the initial values of nitrogen compounds based on a review of previous studies. Numerical results show that the rate of change in the concentration of nitrogen compounds in the integration ponds of waste stabilization and water lettuce decreases and reaches stable at different times.

Particulate organic nitrates observed in an oil and natural gas production region during wintertime

Abstract. Organic nitrates in both gas and condensed (aerosol) phases were measured during the Uintah Basin Winter Ozone Study from January to February in 2012. A high degree of correlation between total aerosol volume at diameters less than 500 nm and the particulate organic nitrate concentration indicates that organic nitrates are a consistent, if not dominant, fraction of fine aerosol mass. In contrast, a similar correlation with sub-2.5 μm aerosol volume is weaker. The C : N atomic ratio inferred from field measurements of PM2.5 and particulate organic nitrate is 34 : 1. Calculations constrained by the observations indicate that both condensation of gas-phase nitrates and heterogeneous reactions of NO3 / N2O5 are responsible for introducing organic nitrate functionality into the aerosol and that the source molecules are alkanes. Extrapolating the results to urban aerosol suggests organic nitrate production from alkanes may be a major secondary organic aerosol source.

Atmospheric submicron aerosol composition and particulate organic nitrate formation in a boreal forestland–urban mixed region

Abstract. The Puijo aerosol–cloud observation station is a unique measurement site for its location in the mixed region between the boreal forestland and the municipality of Kuopio, Finland. A measurement campaign was carried out at the station during fall 2010. An Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-Tof-AMS) was deployed to characterize the atmospheric submicron aerosols. Positive matrix factorization (PMF) was applied to the unified high-resolution mass spectra organic species with NO+ and NO2+ ions to discover the intrinsic relationships between the organic and inorganic species and their daily cycles. On average, the submicron aerosols in this study were dominated by organic and sulfate species, composing 48.2 and 28.7% of total observed aerosol mass, respectively, with smaller contributions from ammonium (9.3%), nitrate (4.9%), chloride (0.8%) and BC (8.1%). The sources of these species included the primary emissions originating from the city area, secondary formation from both natural and anthropogenic emissions and regional transport. The PMF analysis succeeded in separating the mixed organic and inorganic spectra into three distinct organic and one inorganic factors. For organic factors, the semi-volatile oxygenated organic aerosol (SVOOA) and low-volatility oxygenated OA (LVOOA) accounted for 54.8 and 36.3% of total organic masses, respectively, while the hydrocarbon-like organic aerosol (HOA) accounted for 8.9% of total organics, with its main source from urban emissions. The inorganic factor is identified as NH4NO3, comprising 6.9% of the fitted aerosol mass by PMF. Based on the PMF results, the nitrate species were separated into organic and inorganic components, with the organic nitrates contributing one-third of the total nitrate mass. The results highlight both anthropogenic and biogenic emissions as important atmospheric aerosol sources in a forest–urban mixed region.

Characterization of the Microcystis Bloom and Its Nitrogen Supply in San Francisco Estuary Using Stable Isotopes

A suite of particulate and dissolved organic and inorganic stable isotopes were needed to determine the source of the nutrients and cells that initiate and sustain the toxic cyanobacteria bloom of Microcystis in San Francisco Estuary. Particulate and dissolved inorganic and organic matter in water and plankton samples were collected biweekly during Microcystis blooms in 2007 and 2008. Stable isotopes for particulate and dissolved organic matter, nitrate, and water (POM-δ 13C, POM-δ 15N, DOC-δ 13C, C/N ratio, NO3-δ 15N, NO3-δ 18O, H2O-δ 18O and H2O-δ 2H) were compared with Microcystis cell abundance, dissolved organic carbon, chlorophyll a, and toxic total microcystins concentration, as well as physical and chemical water quality variables, including streamflow. The isotopic composition of particulate organic matter, nitrate, and water differed for the Sacramento and San Joaquin Rivers and varied along the salinity gradient. The variation of particulate organic matter and water isotopes suggested Microcystis primarily entered the estuary from the San Joaquin and Old Rivers, where it was most abundant. Nitrate isotopes along with streamflow variables indicated that the San Joaquin River was a source of nitrate to the estuary. However, stable isotope comparison of the nitrogen in Microcystis cells with the dissolved inorganic nitrate in the San Joaquin River indicated that nitrate was not the primary source of nitrogen that supported the bloom. Instead, ammonium from the Sacramento River was the likely sole source of the nitrogen for most of the bloom. Selective uptake of ammonium may have further contributed to the magnitude of the Microcystis bloom which increased with the percent of ammonium within the total dissolved inorganic nitrogen pool.

Optical properties and chemical composition of PM2.5 in Shanghai in the spring of 2012

The semi-diurnal mean aerosol mass concentration, chemical composition, and optical properties of PM2.5 were investigated in Shanghai during the spring of 2012. Slight pollution was observed during the study period. The average PM2.5 concentration was 64.11±22.83μg/m3. The mean coefficients of extinction, scattering, and absorption at 532nm were 125.9±78.5, 91.1±56.3, and 34.9±23.6Mm−1, respectively. A relatively low mean single scattering albedo at 532nm (0.73±0.04) and low level of elemental carbon (EC, 2.67±1.96μg/m3) suggested that the light absorption was enhanced due to the internal mixing of the EC. Sulfate contributed the most to aerosol light scattering in Shanghai. The chemical composition of PM2.5 was dominated by particulate organic matter, sulfate, nitrate, ammonium, and EC. Anthropogenic sources made a significant contribution to the emission and loading of the particulate pollutants. A relatively good correlation between the aerosol chemical composition and the cloud condensation nuclei (CCN) activation indicated that aerosol chemistry is an important factor that influences the saturated hygroscopicity and growth of the aerosol.

Controls of plankton production by pelagic fish predation and resource availability in the Alboran and Balearic Seas

A one-dimensional coupled physical and intermediate-complexity biochemical model comprising large and small phytoplankton and zooplankton groups, particulate organic nitrogen, ammonium and nitrate was developed to study the physical–biogeochemical interactions and parameters that control plankton production in the Alboran and Balearic Sea ecosystems. The model findings suggest that pelagic fish predation and resource availability through lateral and vertical nutrient inputs jointly characterize the plankton community structures. In agreement with previous observations, a typical annual plankton structure of the mesotrophic systems involves a vertically homogeneous biomass of large groups of phytoplankton and zooplankton within the upper 50-to-100m layer from mid-November to April and a subsurface biomass accumulation distributed roughly within 25–75m depths in the following months. Their light and temperature limitations constrain the smaller groups into the thermocline zone (25–50m) during late spring and summer. These obtained results were dependent on the zooplankton actively switching between preys (i.e., the food preference coefficients dependent on prey biomass). In the case of no switching, spurious dynamic equilibrium solutions may arise in the case of a constant and weak fish predation rate and using the quadratic predation formulation. The choice of a Holling Type II (i.e., hyperbolic) predation function may, however avoid ambiguous representation of the annual plankton structure in the case of a constant food preference choice under relatively weak predation pressures.

Aerosol scattering coefficients and major chemical compositions of fine particles observed at a rural site in the central Pearl River Delta, South China

Abstract During November-December 2010 aerosol scattering coefficients were monitored using a single-waved (525 nm) Nephelometer at a regional monitoring station in the central Pearl River Delta region and 24-hr fine particle (PM 2.5) samples were also collected during the period using quartz filters for the analysis of major chemical components including organic carbon (OC), elemental carbon (EC), sulfate, nitrate and ammonium. In average, these five components accounted for about 85% of PM 2.5 mass and contributed 42% (OC), 19% (SO 4 2−), 12% (NO 3 −), 8.4% (NH 4 +) and 3.7% (EC), to PM 2.5 mass. A relatively higher mass scattering efficiency of 5.3 m 2/g was obtained for fine particles based on the linear regression between scattering coefficients and PM2.5 mass concentrations. Chemical extinction budget based on IMPROVE approach revealed that ammonium sulfate, particulate organic matter, ammonium nitrate and EC in average contributed about 32%, 28%, 20% and 6% to the light extinction coefficients, respectively.

Effect of Aerosols on Visibility and Radiation in Spring 2009 in Tianjin, China

Meteorological and aerosol data were measured at the atmospheric boundary layer observation station in Tianjin, China, and were analyzed to study the effects of aerosol mass, composition, and size distributions on visibility and short-wave radiation flux. The results show that fine particles played important roles in controlling visibility in Tianjin. The major contributors to light extinction coefficients included sulfate (28.7%), particulate organic matter (27.6%), elemental carbon (19.2%), and nitrate (6.1%). In addition to the measurement of aerosol composition, the size distribution of aerosol number concentrations were also measured and classified between haze days and non-haze days during spring. The extinction characteristics of ambient aerosol in haze days and non-haze days were calculated using Mie theory model. The average extinction coefficient and scattering coefficient of atmospheric aerosols were 0.253 1/km and 0.213 1/km in non-haze days, while 0.767 1/km and 0.665 1/km in haze days. A radiation transmission model LOWTRAN7 is also applied in this study. The model calculated radiant flux densities in haze days and non-haze days, which showed a fairly agreement with the observation results, showing that the heavy aerosol loadings in Tianjin had significantly impact on atmospheric visibility and radiation fluxes.

Effects of Organic Pollution on some Fish and Benthic Macroinvertebrate Groups in Rivers Tigris and Diyala at Baghdad Area.

Various activities taking place within the city of Baghdad have significantly contributed to organic pollution in Rivers Tigris and Diyala. The present study aimed to assess some physical, chemical and biological aspects of six sites on Rivers Tigris and Diyala as they flow through the city of Baghdad. Monthly samples were collected for the period January to December, 2005. Marked differences in the physical and chemical characteristics of water were noted between the two rivers’ sites. Average values during the study period of dissolved oxygen, biochemical oxygen demand, particulate organic matter, nitrate, phosphate and total dissolved solids for Tigris and Diyala were 7.8,4.7; 2.4,10.4; 350.1,921.4;7.8,13.9;1.2,4.8;814,2176 mg / l respectively. The populations of two fish species, known to be present in polluted waters Silurus triostegus and Mystus pelusis, were also investigated. The two species markedly differed in their favored sites, and their numbers were significantly correlated with particulate organic matter. Average length and weight of Silurus triostegus and Mystus pelusius were respectively 40.1mm, 56.8gm and 15.3mm, 68.3gm for River Tigris, and 40.5mm, 67.5gm and 17.9mm, 73gm respectively for River Diyala. Average population densities of the major groups of benthic macro invertebrate fauna [Crustaceans, Annelids, Insects and Mollusks] were 1496, 2640, 2574 and 1744 individual/m2 respectively for River Tigris and 463, 2312, 2287 and 1700 individual/m2 respectively for River Diyala. Most invertebrate groups showed positive correlation with particulate organic matter. Despite the severity of organic enrichment in River Diyala, biotic conditions in its sites were rather similar, unlike sites on River Tigris where they significantly differed in many physical, chemical and biotic respects.

Effects of Organic Pollution on some Fish and Benthic Macroinvertebrate Groups in Rivers Tigris and Diyala at Baghdad Area.

Various activities taking place within the city of Baghdad have significantly contributed to organic pollution in Rivers Tigris and Diyala. The present study aimed to assess some physical, chemical and biological aspects of six sites on Rivers Tigris and Diyala as they flow through the city of Baghdad. Monthly samples were collected for the period January to December, 2005. Marked differences in the physical and chemical characteristics of water were noted between the two rivers’ sites. Average values during the study period of dissolved oxygen, biochemical oxygen demand, particulate organic matter, nitrate, phosphate and total dissolved solids for Tigris and Diyala were 7.8,4.7; 2.4,10.4; 350.1,921.4;7.8,13.9;1.2,4.8;814,2176 mg / l respectively. The populations of two fish species, known to be present in polluted waters Silurus triostegus and Mystus pelusis, were also investigated. The two species markedly differed in their favored sites, and their numbers were significantly correlated with particulate organic matter. Average length and weight of Silurus triostegus and Mystus pelusius were respectively 40.1mm, 56.8gm and 15.3mm, 68.3gm for River Tigris, and 40.5mm, 67.5gm and 17.9mm, 73gm respectively for River Diyala. Average population densities of the major groups of benthic macro invertebrate fauna [Crustaceans, Annelids, Insects and Mollusks] were 1496, 2640, 2574 and 1744 individual/m2 respectively for River Tigris and 463, 2312, 2287 and 1700 individual/m2 respectively for River Diyala. Most invertebrate groups showed positive correlation with particulate organic matter. Despite the severity of organic enrichment in River Diyala, biotic conditions in its sites were rather similar, unlike sites on River Tigris where they significantly differed in many physical, chemical and biotic respects.

Spatial and seasonal variability of peatland stream ecosystems

AbstractHeadwater stream ecosystems draining blanket peat‐dominated catchments occur in many high‐latitude river systems. These systems are thought to be very sensitive to threats from climate change, and land‐use modification including artificial drainage, overgrazing, afforestation and vegetation burning. This study examined ten peatland streams in the headwaters of the River Tees to examine spatial and seasonal patterns of instream physicochemical variables and benthic macroinvertebrate communities across the stream network. Principle component analysis revealed significant positive relationships between catchment size and electrical conductivity, sulfate concentration, pH and median bed sediment size, and negative relationships with suspended sediment and aluminium concentrations. Seasonal variability was particularly evident in stream water temperature, benthic particulate organic matter and nitrate and chloride concentrations. Macroinvertebrate community abundance and diversity were typically similar across streams, but redundancy analysis demonstrated turnover of macroinvertebrate assemblages with increases in stream size. In particular, first‐ and second‐order streams hosted small‐sized stoneflies such as Amphinemura standfussi and Nemoura cambrica, while larger streams (third‐ and fourth‐order) supported more mayflies and larger predatory stoneflies (e.g. Dinocras cephalotes and Perla bipunctata). Many environmental drivers of ecological patterns appear to work in synergy in peatland headwater streams, and controlled experiments may be necessary to disentangle some of the variables to guide effective conservation and management strategies in impacted peatland river systems. Copyright © 2010 John Wiley & Sons, Ltd.

Organic nitrate formation in the radical-initiated oxidation of model aerosol particles in the presence of NOx

Using a flow tube reactor coupled to a chemical ionization mass spectrometer, the Cl-initiated oxidation of solid and supercooled liquid brassidic acid (BA, trans-13-docosenoic acid) particles was investigated in the presence of NO and NO2. For the first time, organic nitrate formation from the heterogeneous oxidation of model organic aerosols in the presence of NO was observed, but none was formed by the addition of up to 600 ppb of NO2. Also, no nitrate formation was observed in liquid particles, but the nitrate yields in the solid particles were measured to be as large as 6% with a negative temperature dependence over the range 259-293 K. The corresponding effective activation energy of -7.5 (+/-4.4) kJ mol(-1) suggests that the mechanism of particulate organic nitrate formation is analogous to the termolecular gas-phase reaction of . The yields are smaller than those from analogous gas-phase reactions, but this may result from photodissociation of the nitrate by the UV (355 nm) laser for which there is indirect evidence. Additionally, enhanced rates of the RO2+RO2 reactions in the condensed phase could lead to smaller nitrate yields. The results suggest that slower diffusion of the RO2 radicals in the solid particles compared to the liquid particles makes the RO2+NO reaction competitive with the RO2+RO2 reactions and results in nitrate formation near the surface of the particle. The organic nitrates formed in these experiments are observed intact after the reacted particles have been vaporized at temperatures up to 380 degrees C suggesting that they are thermally stable in the troposphere and may enable long-range transport of NOx if they photodissociate on the timescale of days. The findings from these experiments are not specific to unsaturated carboxylic acids but should apply to nearly all particulate hydrocarbons, and they indicate that the particle phase could be important in determining how organic aerosols evolve chemically through radical-initiated oxidation in polluted atmospheres.