Soluble Organic Nitrogen Research Articles

Investigation of first flushes in a medium-sized mediterranean catchment

The objective of this study is to investigate the significance and characteristic of first flushes in medium-sized agricultural catchments. Therefore, an analysis of the load distribution in the Vène River on the French mediterranean coast was done for first flood events in September 2003 and 2004. It considered total suspended solids (TSS), volatile suspended solids (VSS), total phosphorus (TP), soluble reactive phosphorus (SRP), total nitrogen (TN), organic nitrogen (org-N), nitrate and nitrite–nitrogen (NOx–N) and ammonium–nitrogen (NH4–N). Nutrient export was evaluated in terms of normalized cumulative loads (NCL) and three rating indices. Most important first flushes could be detected for ammonium (FF25 = 0.79) followed by TSS (FF25 = 0.72) and VSS (FF25 = 0.70). In situations, where first flushes can be important for downstream water bodies, a new concept for nutrient discharges should be considered taking into account the ambient pollution of the whole system.

Effect of different crop rotation systems and continuous fallow on soil microbial biomass carbon and nitrogen under different fertilizer treatments

以黄土高原南部半湿润易旱区已进行17年的田间定位试验为研究对象, 研究了不同培肥措施(不施肥、施用氮磷钾及氮磷钾与有机肥配合施用)下两种种植制度(一年1熟及一年两熟)和撂荒对土壤微生物量碳、氮(SMBC、SMBN)及可溶性有机碳、氮(SOC、SON)等含量的影响。结果表明, 与一年1熟的小麦-休闲种植制度相比, 一年两熟小麦-玉米轮作提高了0~10 cm土层SMBC、SMBN、有机碳(TOC)、全氮(TN)和土壤SOC、SON的含量, 而对10~20 cm土层上述测定指标影响不大。与不施肥(CK)或单施化肥处理(NPK)下小麦-休闲和小麦－玉米轮作方式相比, 撂荒处理显著提高了0~10 cm土层各测定指标的含量。不同培肥措施相比, 氮磷钾配施有机肥显著提高了0~10 cm、10~20 cm土层SMBC、SMBN含量; NPK处理0~10 cm土层SMBN含量显著增加, 10~20 cm土层SMBN和0~10 cm、10~20 cm土层SMBC含量增加但未达显著水平。不同培肥措施和种植制度对SMBC/TOC和SMBN/TN的比例无明显影响。

Contents and distribution characteristics of soluble organic nitrogen in surface sediments of lakes

选择鄱阳湖、洞庭湖等6个湖泊的15个表层沉积物样品,用1mol/LKCl溶液提取沉积物中的可溶性有机氮(SON),并研究了SON的含量、分布状况及特性.结果表明,所研究的沉积物SON含量变异较大,在17.18-292.31mg/kg之间波动,平均为134.45mg/kg,占可溶性总氮(TSN)的51.86%,沉积物总氮的7.14%.污染程度重的沉积物中SON含量均较污染程度轻的高,且SON含量与TN、TSN含量呈正相关,即与沉积物氮污染程度呈正相关.分布状况则与湖泊污染程度、人类活动干扰强度等紧密相关.所研究表层湖泊沉积物中游离氨基酸(FAA)含量处于4.69-42.04mg/kg间,平均为23.27mg/kg,占SON的18.80%,TN的1.24%.FAA与SON含量呈显著正相关,在沉积物中的平均含量及在SON中的比例均较土壤中高,说明湖泊沉积物SON有较大的易分解组分.SON与沉积物可溶性无机氮、有机质、CEC等显著相关.因此,SON是湖泊沉积物氮的重要组成部分,对湖泊富营养化具有重要的影响,特别是对污染严重的沉积物而言,更应重视其SON在湖泊氮循环及富营养化中的作用.;The contents and distribution characteristics of soluble organic nitrogen (SON) extracted with 1mol/L KCl from thesediments of six typical lakes including Lake Poyang, Lake Dongting in Hunan and Jiangxi Provinces were studied. The resultsindicated that the SON contents varied greatly from 17.18mg/kg to 292.31mg/kg (mean content,134.45mg/kg), comprising 51.86% oftotal soluble nitrogen (TSN) and 7.14% of total nitrogen (TN) in six lakes. The SON contents were significantly correlated with theircontents of TN and TSN, and SON were higher in the heavily polluted sediments than the light polluted ones. Their distributions ofSON were closely related to their lake pollution levels. The contents of free amino acid in the sediments were also studied, and theyvaried from 4.69 to 42.04mg/kg, comprising 18.80% of SON, and 1.24% of TN, and were significantly correlated with their SONcontents. The mean content of FAA was 23.27mg/kg, higher than those in soils in the same region. It indicated that there was morebioavailable SON from lake sediment than those from soil. The contents of SON in the sediments were also correlated with inorganicnitrogen, OM and CEC and so on. As one of the most important nitrogen compositions in lake sediments, SON should be paid moreattention to the nitrogen cycling and entrophication control in lakes.

Analysis and behavior of soluble organic nitrogen in forest soils

A large proportion of soil nitrogen (N; >80%) is present in organic form. Current research on plant N uptake in terrestrial ecosystems has focused mainly on inorganic N such as ammonium (NH4 +) and nitrate (NO3 −), while soluble organic N (SON) has received little attention. In recent years, the increasing evidence showing the direct uptake of various amino acids by plants and the predominance of the organic form in N loss by leaching in many forest ecosystems has drawn attention to critically re-examine the nature and the ecological role of soil SON in terrestrial N cycling. However, little is known about the sources and dynamics, chemical nature, and ecological functions of soil SON in forest ecosystems. This paper reviews recent advances in the areas of research on current techniques for characterizing soil SON and the size, nature, and dynamics of soil SON pools in forest ecosystems. The SON represents a significant pool of available and mobile N in forest soils. The SON can be sampled using a number of physical (e.g., suction cup, microdialysis) and chemical (e.g., extraction) methods and analyzed by the wet chemistry method (e.g., persulfate oxidation) and combustion. Chemical and physical fractionation, pyrolysis–mass spectrometry, 13C and 15N nuclear magnetic resonance spectroscopy, and 15N, 13C, and 14C isotopic techniques have been used for investigating the nature and dynamics of SON in forest ecosystems. The amount of SON in soil may vary with land use type, forest species, management practices, and analytical procedures used. Statistical figures, based on 116 datasets available in the literature, have shown that concentrations of soil SON can range from 1 mg N kg−1 (dry weight basis) to up to 448 mg N kg−1, with an average of 35 mg N kg−1, representing an average of 48% of total soluble N. Soil SON consists of a mixture of structurally diverse N-containing compounds, possibly with the amide N, amino acids, and amino sugars being predominant. The biodegradability of SON largely depends upon its chemical characteristics (e.g., C-to-N ratio). Direct utilization of added amino acids by a large number of forest species may present a potentially important new pathway for plant N uptake. However, the evidence of direct utilization of soil native SON by forest plants is still lacking, and the extent of the contribution of SON to forest plants is far from certain. Transformation of soil organic matter into SON, rather than the conversion of SON to NH4 +/NO3 −, may be the rate-limiting step, which regulates the overall N cycling in N-limited forest ecosystems. Future work may well focus on the chemical and biological nature of SON in forest soils, microbial transformation of SON, the nutritional role of the SON pools in the N-limited forest ecosystems, and the potential role of SON in global climate change (e.g., N2O emission).

Soil nitrogen leaching losses in response to freeze–thaw cycles and pulsed warming in a temperate old field

Climate warming and increased climate variability are both predicted to increase the frequency of soil freeze–thaw cycles in temperate regions. We exposed intact soil-plant mesocosms to freeze–thaw cycles and examined the effects on nitrogen leaching losses. Freezing treatments were performed by incubating the mesocosms in the soil with their tops exposed to air to impose freezing from the top down, such that realistic freezing rates and cycle amplitudes were experienced across the soil profile. Leaching events were then initiated by water addition the following day for both the freezing treatment and control mesocosms. While water addition alone explained the major part of soluble organic nitrogen leaching, nitrate leaching approximately doubled in response to freeze–thaw cycles, and nitrogen leaching remained high after 11 freeze–thaw cycles. In a second experiment, pulses of warming were applied in situ to mesocosms over fall, winter or spring, in order to melt snow, and thereby increase freeze–thaw cycling by exposing soils to diurnal fluctuations in air temperature. Warming pulses had little effect on sub-surface soil temperatures and no effect on soil nitrogen leaching. However, warming pulses over spring severely reduced the abundance of the legume Coronilla varia in the following growing season. Overall, the results of these experiments indicate that while increased soil freeze–thaw cycles combined with leaching events are capable of increasing soil nitrogen losses, warming pulses will only promote increased freeze–thaw cycles if they are followed by cold, snow-free weather. The strong effect of warming on the N-fixer C. varia highlights that changes in plant species composition in response to warming may have stronger implications for soil nitrogen dynamics than the direct effects of freeze–thaw cycles on soil nitrogen leaching losses.

Toxicity, Growth And Survival Of Clarias Gariepinus Juveniles Exposed To Different Concentrations Of Crude Oil Fractions-Polluted Water

Studies were carried out on the toxicity, growth and survival of Clarias gariepinus juveniles exposed to different concentrations of oil-polluted water. Thirty-nine aerated aquaria (60 × 30 × 30 cm3), arranged in a 4 × 3 Complete Randomized Block Design were used for the study. Three oil types: the Bonny light crude oil (BLCO), the premium motor spirit (PMS) and kerosene (DPK) at oilconcentrations of 1.00, 1.50, 2.00 and2.50 ml L -1 were used in triplicates of 5 ml to contaminate 15L of dechlorinated tap water and 20 fingerlings o Clarias gariepinus (22 ± 0.24 g) exposed to it. A control treatment (0.00 ml L -1 ) of non-oil contamination was aso used in riplicates. A 96-hour toxicity phase in the oil-polluted water preceded a 42 days recovery phase. 38% crude proein dietwas fed to fish during exposure and recovery phases at 3% and 5% body weight per day respectively. Water temperature, pH, fish mortality and normalized biomass index (NBI) of each aquarium were monitored. The total organic nitrogen, soluble organic nitrogen and colloidal organic nitrogen in addition to soluble and adsorbed ammonia in the aquaria water and sediments were analyzed using standard methods. Results showed that the water temperature was 26 ± 2.04° C, pH was 6.50 ± 0.30 and fortnighty eed intake of fish increased between days 14 and 42. This increase, which corresponded wth the increase in the fortnightly weight gain, could be attributed to the reduction of stress caused during the 96-h toxicity phase. The increase in the soluble ammonium and the exchangeable ammonium concentrations o water correlated with the increase inthe concentrations (1.50 – 2.50 ml L -1 ) ofBLCO, PMS and DPK. Percent mortality of fsh reduced between days 14 and 42 irrespective o oil treatment while fish exposed to the control treatment had lower percent mortality than those exposed to the oil treatments. This trend was corroborated by the relatively higher NBI for the control during the exposure (-0.02) and recovery{0.08 (14 days), 0.08 (38 days) and 0.21 (42 days)} periods than those of oi treatments (-49.64 to-0.10). Keywords : Clarias gariepinus, Toxicity, Soluble ammonium, Feed intake, Weight gain Animal Research International Vol. 3 (2) 2006 pp. 466-472

Soluble organic nitrogen in forest soils of northeast China

Soluble organic nitrogen (SON) is recognized as a sensitive indicator of soil nitrogen status. The present work was conducted in the temperate forests of northeast China where soils are typically characterized by high organic matter and high organic nitrogen content, and soil sampling was made in early spring just after the freeze-thaw period. The water extracted SON pools in the organic layer of forest soils were measured within the range from 156.0 mg·kg−1 to 292.6 mg·kg−1, a similar magnitude of salt solution extracted SON pools reported in literatures. However, the water soluble SON pools in 0–15 cm mineral soils in present study were much higher (3–10 times) than any other reports, ranging from 58.6 mg·kg−1 to 125.2 mg·kg−1. Water soluble SON varied markedly among the soils under different forests and at different sites. The SON in water extracts were positively and significantly correlated to soil organic matter and total nitrogen contents, but negatively correlated to microbial biomass nitrogen (MBN). The reasons of the abnormally large SON pools and the negative correlations between SON and MBN in the 0–15cm mineral soils in this study were specially discussed.

Carbono orgânico e Nitrogênio em agregados de um Latossolo Vermelho distrófico sob duas coberturas vegetais

A matéria orgânica do solo apresenta constituição variada, incluindo desde frações ativas a mais estáveis, com diferentes taxas de ciclagem. Práticas de manejo alteram os teores de carbono orgânico e N, a qualidade da matéria orgânica e a agregação dos solos. Este trabalho foi realizado com o objetivo de caracterizar o carbono orgânico e o N em agregados de um Latossolo Vermelho distrófico de Minas Gerais sob vegetação natural de Cerradão e sob cultivo com milho durante 30 anos. Para isso, retiraram-se amostras do solo em quatro pontos diferentes nas profundidades de 5-10 e 15-20 cm, que foram fracionadas, por via seca, nas classes de agregados de: 4,75-2,0; 2,0-1,0; 1,0-0,5; 0,5-0,25; 0,25-0,105; e < 0,105 mm de diâmetro. Nesses materiais, determinaram-se: o carbono orgânico total (COT) e o solúvel em água (COS), o N total (NT) e o mineralizado em condição anaeróbia (NMA). Em média, os agregados do solo sob cultivo convencional apresentaram teores de COT superiores, mas os agregados da camada superficial do solo do Cerradão apresentaram maiores teores de NT. Os teores de COS e de NMA, que caracterizam a fração mais ativa da matéria orgânica, foram significativamente maiores nos agregados do solo do Cerradão. Os agregados de menor tamanho tenderam a apresentar maiores teores de COT, NT e NMA. As relações C/N, COT/COS e NT/NMA nos agregados do solo cultivado com milho foram, em média, maiores. Na profundidade de 15-20 cm, os agregados apresentaram relação NT/NMA consistentemente maior. No entanto, independentemente da camada do solo, a menor relação NT/NMA ocorreu na menor classe de agregados, indicando presença de formas mais lábeis de N. Os resultados mostraram que o tipo de cobertura vegetal e o manejo do solo influenciaram tanto os teores de carbono orgânico e de N como a qualidade da matéria orgânica. Os agregados de menor tamanho, além de serem responsáveis pelo maior estoque de matéria orgânica do solo, representam importantes sítios de N mineralizável. O COS, o NMA e as relações COT/COS e NT/NMA constituem medidas promissoras para detectar mudanças na labilidade da matéria orgânica do solo, em função do manejo

Soluble organic nitrogen pools in adjacent native and plantation forests of subtropical Australia

Soil soluble organic nitrogen (SON) can play an important role in soil nitrogen (N) cycling in forest ecosystems. This study examined the effect of land-use change from a native forest (NF) to a first rotation (1R) and subsequent second rotation (2R) hoop pine ( Araucaria cunninghamii) plantation on soil SON pools. The impact of residue management on SON pools was also investigated in the 2R forest, where SON was measured in tree rows (2R-T) and windrows (2R-W). Various extraction techniques were used to measure SON pool size in the 0–10, 10–20 and 20–30 cm layers of soil. The results showed that land-use change had a significant impact on soil SON pools. In the 0–10 cm layer, 3.2–8.7, 14–23, 20–28, 60–160 and 127–340 mg SON kg −1 were extracted by water, 0.5 M K 2SO 4, 2 M KCl, hot water and hot 2 M KCl, respectively. The size of the SON pools and the potential production of SON (PPSON) were generally highest in the NF soil and lowest in the 2R-T soil, and in all forest types decreased with soil depth. The larger SON pools in the NF soil coincided with lower soil, litter and root C:N ratios, suggesting that the difference in the size of SON pools between the NF and 1R soil may be related to differences in the quality of organic matter input under the different forest ecosystems. Differences in the size of SON pools between the 1R soil and the 2R soils and between the 2R-T soil and the 2R-W soil may be related to the quantity of organic matter input and time since disturbance. Significant relationships were found between the SON extracted by 0.5 M K 2SO 4 (SON ps) and 2 M KCl (SON KCl), and also among the SON extracted by hot 2 M KCl (SON hKCl), hot water (SON hw) and water (SON w), suggesting that the organic N released by these groups of extracts may be at least partly from similar pools.

Nitrogen removal via ammonia volatilization in maturation ponds

A simple apparatus was designed to collect ammonia gas coming out from waste stabilization ponds (WSP). The apparatus has a capture chamber and an absorption system, which were optimized under laboratory conditions prior to being used to assess ammonia volatilization rates in a pilot-scale maturation pond during summer 2005. Under laboratory conditions (water temperature = 17.1 degrees C and pH = 10.1), the average ammonia volatilization rate was 2,517 g NH3-N/ha d and the apparatus absorbed 79% of volatilized ammonia. On site, the mean ammonia volatilization rate was 15 g N/ha d, which corresponds to 3% of the total nitrogen removed (531 g N/ha d) in the maturation pond studied. A net nitrogen mass balance showed that ammonia volatilization was not the most important mechanism involved in either total nitrogen or ammonia removal. Nitrogen fractions (suspended organic nitrogen, soluble organic nitrogen, ammonia, nitrite and nitrate) from the M1 influent and effluent showed that ammonia is removed by biological (mainly algal) uptake and total nitrogen removal by sedimentation of dead algal biomass.

Model evaluation of temperature dependency for carbon and nitrogen removal in a full-scale activated sludge plant treating leather-tanning wastewater

Organic carbon and nitrogen removal performance of a full-scale activated sludge plant treating pre-settled leather tanning wastewater was evaluated under dynamic process temperatures. Emphasis was placed upon observed nitrogen removal depicting a highly variable magnitude with changing process temperatures. As the plant was not specifically designed for this purpose, observed nitrogen removal could be largely attributed to simultaneous nitrification and denitrification presumably occurring at increased process temperatures (T > 25°C) and resulting low dissolved oxygen levels (DO < 0.5 mgO2/L). Model evaluation using long-term data revealed that the yearly performance of activated sludge reactor could be successfully calibrated by means of temperature dependent parameters associated with nitrification, hydrolysis, ammonification and endogenous decay parameters. In this context, the Arrhenius coefficients of (i) for the maximum autotrophic growth rate, A, (ii) maximum hydrolysis rate, khs and (iii) endogenous heterotrophic decay rate, bH were found to be 1.045, 1.070 and 1.035, respectively. The ammonification rate (ka) defining the degradation of soluble organic nitrogen could not be characterized however via an Arrhenius-type equation.

Mathematical Model for Sizing Combined Nitrification and Pre-denitrification Activated Sludge Systems

Two mathematical steady-state models for sizing single activated sludge systems aimed at nitrogen and organics removal from wastewater are proposed. The attention is focused on the combined nitrification system and the pre-denitrification system, considering three (soluble and particulate biodegradable organic matter and ammonia nitrogen) and four (the above cited and nitrate nitrogen) substrates, respectively. Growth and decay of two groups of bacteria (heterotrophic and autotrophic) are taken into account. If the influent flow composition and the kinetic parameters are known and the effluent nitrogen concentration is fixed, both models give explicit expressions of the volumes of the biological reactors. Moreover, the pre-denitrification model makes it possible to define a priori the applicability of the system for a particular wastewater. Model applications show that the nitrification reactor volume increases in the case of a higher influent organic load or to achieve a higher nitrogen ammonia removal efficiency. A smaller denitrification volume is required to face a higher influent organic load. A sensitivity analysis on the kinetic parameters shows an important influence of the maximum ammonia nitrogen removal rate and the ratio between the decay rates of heterotrophic and autotrophic biomass on the nitrification reactor volume.

Impact of significant floods on the annual load in an agricultural catchment in the mediterranean

Summary The purpose of this study is to investigate the characteristics of the annual distribution of pollutant loadings and flush pulses caused by accumulation downstream of point source inflows in the agricultural catchment of the Vene at the Mediterranean French coast. On the basis of the period from October 2002 to October 2004, flow, rainfall and quality parameters such as total suspended solids (TSS), volatile suspended solids (VSS), total phosphorus (TP), soluble reactive phosphorus (SRP), total nitrogen (TN), organic nitrogen (org-N), nitrate and nitrite–nitrogen (NOX–N) and ammonium–nitrogen (NH4–N) were analyzed. The measurements were compared by means of normalized cumulative loadings against normalized cumulative flow and the calculation of relative mass fluxes as the ratio of cumulative load to cumulative flow for an annual scale. The results show strongly varying transport activity with an increased intensity in the beginning of the flow period especially for particulate materials.

Nitrogen Supplying Capacity of Brown Forest Soil under Different Cropping Practices and 0.01 M CaCl2 Soluble Organic Nitrogen

The best known and most remarkable example of continuous production in Hungary is the Westsik’s crop rotation experiment, which was established in 1929, and is still in use to study the effects of organic manure treatment, to develop models, and predict the likely effects of different cropping systems on soil properties and crop yields. In this respect, Westsik’s crop rotation experiment provides data of immediate value to farmers concerning the applications of green, straw and farmyard manure, as well as data sets for scientific research.Although commonly ignored, the release of nitrogen by root and green manure crops has a significant impact on soil organic matter turnover. The design of sustainable nitrogen management strategies requires a better understanding of the processes influencing nitrogen supplying capacity, as the effects of soil organic matter on soil productivity and crop yield are still very uncertain and require further research. In the treatments of Westsik’s crop rotation experiment, nutrients removed from soil through plant growth and harvesting are replaced either by fertilisers and/or organic manure. Data can be used to study the nitrogen supplying capacity of soil under different cropping systems and its effect on the 0.01 M CaCl2 soluble organic nitrogen content of soil.The aim of this paper is to present data on the nitrogen supplying capacity of brown forest soil from Westsik’s crop rotation experiment and to study its correlation with hundredth molar calcium-chloride soluble organic nitrogen. The main objective is to determine the effects of root and green manure crops on the nitrogen supplying capacity of soil under different cropping systems. The nitrogen supplying capacity was calculated as a difference of plant uptake, organic manure and fertiliser supply.The 0.01 M CaCl2 soluble organic nitrogen test has proved reliable for determining the nitrogen supplying capacity of soils. Brown forest soils are low in organic matter and in the F-1 fallow-rye-potato rotation, the nitrogen supplying capacity was 15.6 kg/ha/year. 0.01 M CaCl2 soluble organic nitrogen content was as low as 1.73 mg/kg soil. Roots and green manure increased the nitrogen supplying capacity of soil by more than 100%. This increase is caused by lupine, a legumes crop, which is very well adapted to the acidic soil conditions of the Nyírség region, and cultivated as a green or root manure crop to increase soil fertility.

Determination of forest soil organic nitrogen determination using technique of X-ray absorption near-edge structure

The forest soil organic N was investigated using N K-edge X-ray absorption near-edge structure (XANES) to gain an insight into the relationship between N speciation and its transformation in quantity. Soil samples were collected from spruce, hemlock and pine forests in central Taiwan. Results showed that various organic N types could be revealed by XANES spectra. Amide and pyrrolic N are the major parts of the composition in the humic substance, soluble organic nitrogen and original soils. The relative distribution of N speciation differed in treatments and vegetations samples. The spruce had a significant difference from the hemlock in soluble organic nitrogen (SON) spectra at 402.3 eV energy peak. In the A-horizon soils, the relative amount of pyridinic N was much higher than that in the O-horizon soils, indicating N transformation in quantity in the mineral horizon was different from that in the organic horizon, which might play an important role in N cycling of forest ecosystems.

Contribution of water soluble organic nitrogen to total nitrogen in marine aerosols over the East China Sea and western North Pacific

This paper presents information on concentrations, size distributions, geographical distributions and sources of water soluble organic nitrogen (ON ws) in aerosols over the East China Sea and western North Pacific to understand its impact on the atmospheric processes and the oceanic ecosystems in the autumn and spring in the East Asian region. Results revealed ON ws contributions to the total nitrogen in aerosols to be ∼24% and ∼10% over the East China Sea in the autumn and the spring, respectively. The particulate ON ws mainly existed in fine sized particles. Gas to particle conversion may be the major formation process for ON ws. Occurrence of particulate ON ws in both fine and coarse modes during the Kosa event suggests gaseous ON adsorption and/or adhesion to the coarse mode mineral. This behavior of ON ws is unique whereas NH 4 + occurred dominantly in fine mode and NO 3 - in coarse mode.

On the Nature and Ecological Functions of Soil Soluble Organic Nitrogen (SON) in Forest Ecosystems

On the Nature and Ecological Functions of Soil Soluble Organic Nitrogen (SON) in Forest Ecosystems

Possibility of leaching of organic nitrogen in a field under heavy application of organic matter-model experiment using soil columns

pp. 843–848 Leaching of organic nitrogen by heavy application of organic matter was examined using 2 types of columns (same diameter of 5.1, 20 and 60 cm long) which were filled with three different Andosols (A: soil from a tea plantation field of heavy application of organic matter, B: soil from a field receiving organic matter for only two years at 40 Mg ha−1 year−1, C: soil from a field receiving no organic matter before). A mixture of 100 Mg ha−1 of chicken dung and 2.0 Mg ha−1 of rapeseed cake was added to the surface soil layer of each column. These soil columns were watered three times for every 5 days. Our findings were as follows. In the percolating water from the 20 and 60 cm columns filled with soil A, the 20 cm column filled with soil B and 20 cm column filled with soil C, water soluble organic nitrogen was found. This organic nitrogen in the percolated water had the same molecular weight as PEON (Phosphate buffer Extractable Organic Nitrogen), and it was confirmed by HPSEC. These peaks by HPSEC corresponding to PEON were correlated with the protein concentration detected by the protein assay method. This implies that leaching of PEON increased in the field receiving the high amount of organic matter. It was after the 2nd watering processing that the PEON was found in the percolating water of the 20 cm column filled with soil C, and leaching of the PEON was slower than that of the two soil columns filled with soils A and B from fields receiving organic matter. But, in percolated water from 60 cm columns filled with soils B and C from common fields, organic nitrogen was not found. This result suggests that the PEON was increased at the surface soil layer in the case of heavy application of organic matter in a field and some portion of the PEON was leached under rainfall to the deep soil layer. Although PEON exists as fixed forms with iron and/or aluminum in a soil, when a high amount of organic matter was fertilized to a soil, excess free PEONs which are not fixed with iron and/or aluminum in a soil can become water-soluble and leached out.

Soluble Organic Nitrogen Pools in Forest soils of Subtropical Australia

Soil soluble organic N (SON) plays an important role in N biogeochemical cycling. In this study, 22 surface forest soils (0–10 cm) were collected from southeast Queensland, Australia, to investigate the size of SON pools extracted by water and salt solutions. Approximately 5–45 mg SON kg−1, 2–42 mg SON kg−1 and 1–24 SON mg kg−1 were extracted by 2 M KCl, 0.5 M K2SO4 and water, on average, corresponding to about 21.1, 13.5 and 7.0 kg SON ha−1 at the 0–10 cm forest soils, respectively. These SON pools, on average, accounted for 39% (KCl extracts), 42% (K2SO4 extracts) and 43% (water extracts) of total soluble N (TSN), and 2.3% (KCl extracts), 1.3% (K2SO4 extracts) and 0.7% (water extracts) of soil total N, respectively. Large variation in SON pools observed across the sites in the present study may be attributed to a combination of factors including soil types, tree species, management practices and environmental conditions. Significant relationships were observed among the SON pools extracted by water, KCl and K2SO4 and microbial biomass N (MBN). In general, KCl and K2SO4 extracted more SON than water from the forest soils, while KCl extracted more SON than K2SO4. The SON and soluble organic C (SOC) in KCl, K2SO4 and water extracts were all positively related to soil organic C, total N and clay contents. This indicates that clay and soil organic matter play a key role in the retention of SON in soil.

Changes in waste stabilisation pond performance resulting from the retrofit of activated sludge treatment upstream: part I – water quality issues

This paper describes changes in effluent quality occurring before and after an upgrade to the Bolivar Wastewater Treatment Plant in South Australia. Trickling filters (TF) were replaced with an activated sludge (AS) plant, prior to tertiary treatment using waste stabilisation ponds (WSPs). The water quality in the WSPs following the upgrade was significantly improved. Reductions in total and soluble BOD, COD, TKN, suspended solids and organic nitrogen were recorded and the predominant form of inorganic nitrogen changed from NH(4)-N to NO(2)/NO(3)-N. The reduction in ammonium and potentially toxic free ammonia removed a control upon the growth of zooplankton, which may have contributed to decreases in algal biomass in the final ponds and consequently lower dissolved oxygen. Additionally, changes in inorganic nitrogen speciation contributed to a slightly elevated pH which reduced numbers of faecal coliforms in WSPs. The AS pretreated influent recorded significantly lower inorganic molar N:P ratio (10-4:1) compared to those fed with TF effluent (17-13:1). Algae within the WSPs may now be nitrogen limited, a condition which may favour the growth of nitrogen-fixing cyanobacteria. The decrease in algal biomass and in dissolved oxygen levels may enhance sedimentary denitrification, further driving the system towards nitrogen limitation.