Study on Nitrogen Forms in Chaohu Lake and Wabu Lake Sediments

Composition and distribution of nitrogen in Chaohu Lake and Wabu Lake sediments were studied.The results showed that the mean total nitrogen content in Chaohu Lake and Wabu Lake was 0.533 g/kg and 0.265 g/kg respectively,and the primary composition of nitrogen was organic nitrogen(94%).The organic index indicated that the organic pollution degree of Wabu Lake was lower than that of Chaohu Lake.

Nitrogen forms and decomposition of organic carbon in the southern Bohai Sea core sediments

Study on form characteristics of nitrogen in marine sediments is the primary method to research its biogeochemical cycling and nitrogen form characteristics in core sediments can reflect the process and results of early diagenesis in a certain degree. In this paper, Sequential extraction process in natural grain size was used for studying the existent forms of nitrogen in five core sediments of the southern Bohai Sea for the first time. Nitrogen was divided into two parts - transferable and fixed based on whether it could be extracted by the reagent. Distributions and early diagenesis of transferable nitrogen forms in the southern Bohai Sea were researched integratedly. Results indicate that IEF - N and OSF-N are predominant forms in transferable part in the studied core sediments. Contents of different nitrogen forms vary differently with depth, and have different diagenesis process. Decomposition constant of organic nitrogen (ON) and OC are about 15.51 -× 10^(-3)a^(-3)and 4.79× 10^(-3)a^(-1) respectively, and the decomposition content of biogenic elements C, N, P, Si has the sequence N>P>CSi. OC/TN (simplified as C/N in the following) ratio is much lower than OC/ON, which indicates that sediment preserves plenty of inorganic nitrogen (IN) and/or fixed nitrogen, and the decrease of OC/ON ratio with depth is due to ON reservation in sediments. Generally, transferable nitrogen accounts for more proportion of TN in the surface layer than in the deep layer of core sediments, whereas, some stable forms of nitrogen can activate and become transferable under appropriate environment, which induces the proportion of transferable nitrogen in TN in the deep layer to be almost the same as that in the surface layer.

Water,organic matter,nitrogen and phosphorus contents in sediment of a large-scale mariculture area in the Zhelin Bay of eastern Guangdong Province,China

The Zhelin Bay is one of the most important bays for large-scale mariculture in Guangdong Province, China. Owing to the increasing human population and the expanding mariculture in the last two decades, the ecological environment has greatly changed with frequent harmful algal blooms. A monthly survey of water content, organic matter （TOM）, and various forms of nitrogen and phosphorous in sediment from July 2002 to July 2003 in the bay was conducted. The results showed that the water content was correlated significantly with TOM and various forms of nitrogen and phosphorus and can be used as proxy for quick and rough estimate of these factors in the future surveys. TOM was also correlated significantly with various forms of nitrogen and phosphorus, indicating that it was one of the key factors affecting the concentrations and distributions of nitrogen and phosphorus in the investigated waters. Average total Kjeldhal nitrogen （TkN） content was（ 1 113.1 ± 382.5）μg/g and average total phosphorus （TP） content was（567.2± 223.3）μg/g, and both were much higher than those of similar estuaries in China and elsewhere. Average nitrogen and phosphorus tended to be higher inside than outside the bay, higher at aquaculture than non-aquaculture areas, and higher at fish-cage culture than oyster culture areas, suggesting that large-scale mariculture inside the bay played an important role in the eutrophication of the Zhelin Bay. Various forms of nitrogen and phosphorus concentrations were higher during the warm season （July--September）, which was due to the increased decomposition and concentration of organic matter resulted from the fast growth and high mortality of the cultured species. Compared with July 2002, TkN and TP contents were much higher in July 2003, in consonance with the eutrophication of the Zhelin Bay. Because exchangeable phosphorus （Ex-P）, iron-bounded phos- phorus （Fe-P） and organic phosphorus （OP） combined accounted for 34.3% of the TP and authigenic phosphorus （Au-P） accounted for 49.2% of the TP, biological phosphorus （BP） that includes Ex-P, Fe-P, OP, and a portion of Au-P, thus accounted for 34.3% to 83.5% of the TP in the Zhelin Bay, which was within the percentage range, but with a high absolute value among the estuaries. Au-P was the most important species of phosphorus and accounted for 49.2% of the TP during the investigation. Since eutrophication in the water column can lead to reduction of pH in sediment and release of phosphorus in Au-P combined with authigenic spodiosite and calcium carbonate, high content of Au-P in the sediment maybe act as a time bomb that can trigger a vicious cycle of eutrophication and large-scale harmful algal bloom in the Zhelin Bay.

Effects of Dissolved Oxygen on Nitrogen Release from Jialu River Sediment

[Objective] The aim was to study the effects of dissolved oxygen(DO) on nitrogen release from Jialu River sediment.[Method] Based on the present pollution of Jialu River(in Zhengzhou),the effects of dissolved oxygen on nitrogen transformation in Jialu River sediment were analyzed through simulation test of original columnar sediment.[Result] DO was the main impact factor of nitrogen transformation in Jialu River sediment,and DO with different concentrations had various effects on the transformation time and transformation efficiency of ammonia nitrogen,nitrite nitrogen and nitrate nitrogen.Under aerobic environment,ammoniation,nitrosification and nitrification conducted completely,and the transformation time of ammonia nitrogen,nitrite nitrogen and nitrate nitrogen was less than that under anaerobic environment,while the transformation efficiency was higher than that under anaerobic environment.[Conclusion] The study could provide scientific references for the water pollution control of Jialu River.

Organic carbon and nitrogen isotopes in surface sediments from the western Arctic Ocean and their implications for sedimentary environments

Surface sediments from the Chukchi Sea and adjacent arctic deep sea were investigated for organic carbon and nitrogen isotopes （in δ13Corg and δ15Norg） as well as biogeni＇c silica （BSiO2）. δ13Corg and δ15Norg values of surface sediments in the study area fall between the end-member values of marine and terrestrial organic matter from the surrounding lands and seas, their variations reflect the changes of marine productivity and terrestrial supply in the study area. BSiO2 shows a similar distribution pattern with δ13Corg and δ15Norg, and can be used as an indicator of marine productivity. In the central-west Chukchi Sea and the Chukchi Rise, sediments have higher δ13Corg, δ15Norg and BSiO2 values, indicating the region has high marine productivity influenced by the nutrient-rich branches of the Pacific waters. In the coastal zone off northwestern Alaska, δ13Corg and δ15Norg values become lighter, indicating a weakening marine productivity and an increasing terrigenous supply due to the effects of the least nutrient-rich branch of the Pacific waters. In the north and the northeast of the study area （including the Chukchi Plateau, the Canada Basin and the Beaufort shelf）, δ13Corg, δ15Norg and BSiO2 have the lowest values, and the terrigenous organic matter becomes dominant in surface sediments because this region has the longest ice-covered duration, the least nutrient-rich seawater and the increasing supply of terrestrial materials from the Mackenzie River and the northern Alaska under the action of the clockwise Beaufort gyre. Because the subarctic Pacific waters are continuously discharged into the central basin of the Arctic Ocean through the study area, the nutrient pool in the Chukchi Sea can be considered as a typical open system, the ratio of δ15Norg to BSiO2 content show some tracers that the level of nutrient utilization is contrary to nutrient supply and marine productivity formed in seawater.

Carbon and nitrogen isotopes analysis and sources of organic matter in surface sediments from the Sanggou Bay and its adjacent areas, China

Naturally existing stable carbon and nitrogen isotopes are important in the study of sedimentary organic matter sources. To identify the sources of sedimentary organic matter in Sanggou Bay and its adjacent areas, which is characterized by high-density shellfish and seaweed aquaculture, the grain size, organic carbon （OC）, total nitrogen （TN）, carbon and nitrogen isotopic composition （δ13C andδ15N） of organic matter in the surface sediment were determined. The results showed that, in August, sedimentary OC and TN ranged from 0.17% to 0.76% and 0.04% to 0.14%, respectively. In November, OC and TN ranged from 0.23% to 0.87% and 0.05% to 0.14%, respectively. There was a significant positive correlation between OC and TN （R=0.98, P＆lt;0.0001）, indicating that OC and TN were homologous. In August, theδ13C andδ15N of organic matter varied from -23.06‰ to -21.59‰ and 5.10‰ to 6.31‰, respectively. In November,δ13C andδ15N ranged from -22.87‰ to -21.34‰ and 5.13‰ to 7.31‰, respectively. This study found that the major sources of sedimentary organic matter were marine shellfish biodeposition, seaweed farming, and soil organic matter. Using a three-end-member mixed model, we estimated that the dominant source of sedimentary organic matter was shellfish biodeposition, with an average contribution rate of 65.53% in August and 43.00% in November. Thus, shellfish farming had a significant influence on the coastal carbon cycle.

Spatial Distribution Characteristics of Nitrogen and Phosphorus in Sediments of Coastal Wetlands

Taking the typical coastal wetlands in the Yellow River Delta as the research object,( i) three parallel strips A1,A2 and A3 were set up along the vertical coastline in the newborn wetland at 60 km south of the Dongwenliu Management Station in the Yellow River Delta Nature Reserve.( ii) Sample plots B( Phragmites communis area),C( Suaeda glauca area),and D( Tamarix chinensis area) were set up near the field ecological station of the coastal wetlands.Through collecting sediment samples and measuring nitrogen and phosphorus contents,the spatial distribution characteristics of nitrogen and phosphorus in sediments of coastal wetlands were studied.Following results were obtained.( i) The concentration of TN in the 0-20 cm surface sediments of the coastal wetlands in the Yellow River Delta was in the range of130-695 mg/kg,the concentration of TP was in the range of 589-778 mg/kg,and the average content of TN and TP was 372.18 and 660.82 mg/kg respectively.( ii) From the remote coastal area of the Yellow River to the near coastal area,the horizontal distribution of TN in the sediments was different at each level,and the TN content in the surface sediments gradually decreased; the content of TP generally increased.( iii) At the profile level,the content of TN and TP generally showed a trend of decreasing gradually from the surface layer and tending to be stable,and the peak appeared at the outermost layer.( iv) In the sediments under different vegetation cover,TN was more evenly distributed on each profile,and the distribution of TP on each profile was different.TN showed the largest distribution in the 0-20 cm surface sediments in the T.chinensis area,while TP had the largest distribution in the 80-100 cm bottom sediments in the T.chinensis area.

Characteristics of nitrogen forms in the southern Huanghai Sea surface sediments

The distributions of different forms of nitrogen in the surface sediments of the southern Huanghai Sea are different and affected by various factors. The contents of IEF-N, SOEF-N and TN gradually decrease eastward, and those of SAEF-N northward, while those of WAEF-N westward. Around the seaport of the old Huanghe (Yellow) River, the contents of both SOEF-N and TN are the highest. Among all the factors, the content of fine sediment is the predominant factor to affect the distributions of different forms of nitrogen. The contents of IEF-N, SOEF-N, and TN have visibly positive correlation with the content of fine sediments, and the correlative coefficient is 0.68, 0.58 and 0.71 respectively, showing that the contents of the three forms of nitrogen increase with those of fine sediments. The content of WAEF-N is related to that of fine sediments to a certain extent, with a correlative coefficient of 0.35; while the content of SAEF-N is not related to that of fine sediments, showing that the content of SAEF-N is not controlled by fine grain-size fractions of sediments. In addition, the distributions of different forms of nitrogen are also interacted one another, and the contents of IEF-N and SOEF-N are obviously affected by TN, while those of inorganic nitrogen (WAEF-N, SAEF-N and IEF-N) are not affected by SOEF-N and TN obviously, although they are interacted each other.

Analyzing biases of nitrogen contents and δ^(15)N values arising from acidified marine sediments with different CaCO_3 concentrations

In some studies, the researchers pretreated and measured organic carbon, nitrogen and their isotopes（δ^（13）C and δ^（15）N） of marine sediment together, to save costs and resources of analysis. However, the procedure of acidification to remove inorganic carbon for analysing δ^（13）C can affect the values of nitrogen and δ^（15）N, and the biases vary a lot depending on the CaCO_3 contents of sediments. In this study, the biases of total nitrogen（TN）and δ^（15）N values arising from acidified sediments were compared between the CaCO_3-poor（1%–16%） and CaCO_3-rich（20%–40%） samples. TN and δ^（15）N values were altered during acid treatment（without centrifugation） that possibly led to N-containing compounds volatilization. For CaCO_3-poor samples, acidification led to a range of 0%–40% TN losses and 0‰–2‰ shift in δ^（15）N values; and 10%–60% TN losses and 1‰–14‰ shift in δ^（15）N values for CaCO_3-rich samples. The biases from most samples exceeded the precision of the instrument（0.002% for TN and 0.08‰ for δ^（15）N）, and high biases could mislead our judgment for the environmental implication of the data. Thus,avoiding co-analysis of organic carbon, nitrogen and their isotopes（δ^（13）C and δ^（15）N） in sediments, even for CaCO_3-poor marine sediments, is necessary.

Relationship between nutrient pollutants and suspended sediments in upper reaches of Yangtze River

In order to study the relationship between nutrient pollutants and suspended sediments（SS） in the upper reaches of the Yangtze River and two tributaries, water samples were collected from September 1, 2010 to September 30, 2011 at the Zhutuo, Cuntang, Beibei, Wulong, Qingxichang,Wanxian, and Fengjie cross-sections. In the laboratory, the SS concentration and the concentration of SS whose particle size was smaller than0.02 mm were measured. The phosphorus（P）, nitrogen（N）, and permanganate index（CODMn） concentrations in the natural water sample, the settled water sample, and two types of filtered water samples obtained through filter membranes with pore sizes of 0.02 mm and 0.45 mm were monitored synchronously. The results show that there are strong relationships between the P and CODMnconcentrations and the SS concentration. P mainly exists in particulate form, while N mainly exists in dissolved form. SS whose particle size is smaller than 0.02 mm accounts for a high proportion of sediments in the Yangtze River and has a strong effect on water quality. At the seven cross-sections, the amounts of P, N, and CODMnin particulate form in the wet season are higher than in the dry season and the adsorption amounts of P, N, and CODMnper unit mass of sediment are higher in the dry season than in the wet season.

Nitrogen removal for low-carbon wastewater in reversed A^2/O process by regulation technology

Full scale experimental study on nitrogen removal for low-carbon wastewater was conducted in reversed A2/O process in Jiguanshi waste water treatment plant in Chongqing,in order to aid the operation and maintenance of similar WWTP. When the proposed measures,such as using 0.1% (volume fraction of wastewater) landfill leachate,shortening HRT by 2/3 in the primary sedimentation tank and controlling DO at 0.5 mg/L in the 3rd section of aerobic zone,are applied,15% of the carbon source can be complemented,the favorable property of activated sludge is achieved,and the nitrogen removal effect is significantly improved. The effluent NH3-N is 2 mg/L and the removal rate is 90%. The effluent TN is 17 mg/L and the removal rate is 54%. The up-to-standard discharge of the effluent is achieved. And after the optimization,the unit electricity consumption also reaches 0.21 kW/h and saves 20%.

Nutrient exchange and release experiment and its simulation study in lake water-sediment interface

The sediment distributed and insolated under lake was collected for experiments. The nutrient layer distribution conditions of sampled sediment and its physical and chemical characteristics were analyzed to simulate and assess the influence degree to lake water quality. Based on the dynamic water exchanging experiments the nutrient release process in sediment and influence mechanism to substance exchanging on water-sediment interface was studied, and the correlation between the changing content of total phosphors and total nitrogen in sediment and covered water were analyzed for setting up a simulation model. At the same time the influence degree is explained in detail. The experimental results indicated that even if clean water without nutrient contents was used for water exchangement so as to decrease pollution or prevent eutrophication, however owing to the vertical nutrient distribution in lake sediment, it will lead to the increasing release amount greatly especially when the organic nutrient contained in sediment turns into inorganic status because of isolation. Besides the release process of total phosphate （TP） and total nitrogen （TN） were modeled and each nutrient＇s exchanging equation at interface caused by covered water nutrient concentration changing was set up. According to the simulating prediction, TP and TN content of cover water will also sustain a steady higher level in a long period. The nutrient release amount of sediment is not only affected by the covered water concentration but also connects with accumulative time. The experiments provide the fundamental theoretical and practical basis for taking ecological restoration project. And research is helpful to prevent or restore lake eutrophication.

不同配置乡村植被缓冲带阻控径流污染特征研究

植被缓冲带是河湖的重要生态空间屏障,对于减缓人类活动对河湖的直接干扰、阻隔农业面源污染等具有重要意义。为系统研究不同类型缓冲带对农田氮磷等污染物的拦截功效,本研究在定远张山设计8个缓冲带小区,结合自然降雨方式,持续两年观测不同缓冲带对地表径流及其主要污染物(TN、TP、COD)的削减效果。结果表明:林地和3°、8°横垄耕地缓冲带对径流的拦截效率较高,减流率分别达到了62.4%、52.0%和60.6%,径流量随雨强增大先升高后下降。与8°坡耕地缓冲带相比,降坡(3°)处理竖垄、横垄缓冲带泥沙流失量分别降低53.3%、50.9%。降雨产流的养分流失以氮素和有机质为主,林地缓冲带对径流NH4+-N的拦截率平均高达95.2%,此外降坡和横垄耕作措施也能有效减少径流冲刷的氮素流失。不同处理缓冲带对径流TP均有较好的拦蓄效果。3°、8°横垄耕地缓冲带CODMn流失量较低,拦截率达到53.0%、58.6%。林地缓冲带中高覆盖度的植被和发达的根系能够有效减缓降雨对地表的冲刷,减少径流和养分流失。在南方丘陵山地的乡村地区实施横坡垄作是拦蓄径流、降低面源污染风险的有效措施。

Sedimentary Organic Matter Characterization on a Tropical Continental Shelf in Northeastern Brazil

In continental shelf areas works where the focus is Geochemistry are widely relevant, due to the vast complexity and uses of these relief features (social, environmental and economic). On the Brazilian Northeast tropical shelves, with emphasis on the Pernambuco Continental Shelf (PCS), the published studies are limited and have aimed at portions closer to the coastline. The objective of the present work is the description of the characteristics and origin of sedimentary organic matter (SOM) in the inner and middle Pernambuco shelf, defining and classifying the local geochemical sedimentary facies. The sampling stations (136) were collected in the study area, and the grain-size, contents of total organic matter (TOM), calcium carbonate (CaCO3) were analyzed. The samples were processed in an elemental analyzer coupled with a mass spectrometer after the elimination of calcium carbonate. The obtained data were the grain-size, TOM, CaCO3, elemental (C, N) and the stable isotopic ratios of δ13C e δ15N of SOM. Based on the measured values of carbon and nitrogen, the C/N ratio, associated to δ13C e δ15N, is observed that in the PCS predominates an organic matter of marine origin along its entire length: C < 1%, N < 1%, C/N < 5, δ13C > -21 PDB e δ15N > 8Ar. The PCS presents patches of continental origin SOM, associated to the coastal zones adjacent to estuarine systems mouths and covering the paleochannels, which may indicate that this material was carried from the coastal rivers to the offshore areas, possibly by the paleo-valleys that also act as traps of fine sediments and SOM. The statistical analysis indicates the existence of 6 different sedimentary facies and a prevalence of one of them, characterized by poorly-sorted bioclastic sandy-gravel, with low to medium organic contents of marine origin. This indicates that the coastal sedimentary material contributions are low and the local cover is autochthonous of biogenic origin, and deposited according to the surficial topography, morphosedimentary processes and meteoceanographycal conditionings of the study area, typical of moderate hydrodynamic energy environments.

Impact of Rice-Catfish/Shrimp Co-culture on Nutrients Fluxes Across Sediment-Water Interface in Intensive Aquaculture Ponds

Exchange of nitrogen and phosphorus across sediment-water interface plays an important role in the management of nutrient recycling in the aquaculture pond. In this study, a plot experiment was conducted to study the effect of rice-catfish/shrimp co-culture on the micro-profile of oxygen (O2), pH and nutrient exchange across sediment-water interface in the intensive culture ponds. The results showed that rice-catfish co-culture increased the concentration and penetrating depth of O2, but decreased the pH value across the sediment-water interface, compared with catfish monoculture. Additional rice cultivation significantly reduced the flux rates of ammonium (NH4+) and nitrate (NO3-) across sediment-water interface in the catfish and shrimp ponds. The flux rates of NO2 - and soluble phosphorus (PO43-) showed no significant difference between rice-catfish/shrimp co-culture ponds and catfish/shrimp monoculture ponds. Rice only affected the dissolved inorganic nitrogen and phosphorus fractions in the sediment. The concentrations of NH4 + were significantly lower in the sediment of co-culture ponds than in the monoculture ponds. Additional rice cultivation also significantly reduced the content and percentage of dissolved inorganic phosphorus in the sediment of catfish ponds.

秸秆和生物炭对紫色土坡耕地产流产沙与氮素流失的影响

[目的]探究不同添加量的秸秆和生物炭对紫色土坡耕地的具体改良效果,从而为合理防治三峡库区水土流失提供理论参考。[方法]采用人工模拟降雨的方法,以裸坡为对照,研究了紫色土中添加水稻秸秆(施用量4,7,10 t/hm^(2))和生物炭(含量13,39,65 t/hm^(2))对紫色土坡耕地产流产沙与氮素流失的影响。[结果](1)高强度降雨条件下,紫色土混掺生物炭加快了坡面产流进程,而施加碎混秸秆能延长起始产流时间、削减产流速率;(2)紫色土添加生物炭后累积产沙量较对照增加了0.64%~66.29%,而施加碎混秸秆后减少了42.58%~70.27%,且施加碎混秸秆对坡面产沙的抑制效应远强于对坡面产流的控制作用;(3)地表径流中氮素流失过程以NO-3-N为主,且TN,NO-3-N和NH+4-N的流失量和养分流失模数整体表现为生物炭处理最大,碎混秸秆处理最小。[结论]紫色土坡耕地施加碎混秸秆能促渗阻流、有效控制水土及养分流失,而短期施加生物炭可能会产生负面影响。