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.

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 continuous nitrogen addition on microbial properties and soil organic matter in a Larix gmelinii plantation in China

Continuous increases in anthropogenic nitrogen（N） deposition are likely to change soil microbial properties, and ultimately to affect soil carbon（C） storage.Temperate plantation forests play key roles in C sequestration, yet mechanisms underlying the influences of N deposition on soil organic matter accumulation are poorly understood. This study assessed the effect of N addition on soil microbial properties and soil organic matter distribution in a larch（Larix gmelinii） plantation. In a 9-year experiment in the plantation, N was applied at100 kg N ha-1 a-1 to study the effects on soil C and N mineralization, microbial biomass, enzyme activity, and C and N in soil organic matter density fractions, and organic matter chemistry. The results showed that N addition had no influence on C and N contents in whole soil. However,soil C in different fractions responded to N addition differently. Soil C in light fractions did not change with N addition, while soil C in heavy fractions increased significantly. These results suggested that more soil C in heavy fractions was stabilized in the N-treated soils. However,microbial biomass C and N and phenol oxidase activity decreased in the N-treated soils and thus soil C increased in heavy fractions. Although N addition reduced microbial biomass and phenol oxidase activity, it had little effect on soil C mineralization, hydrolytic enzyme activities, d13 C value in soil and C–H stretch, carboxylates and amides, and C–O stretch in soil organic matter chemistry measured by Fourier transform infrared spectra. We conclude that N addition（1） altered microbial biomass and activity without affecting soil C in light fractions and（2） resulted in an increase in soil C in heavy fractions and that this increase was controlled by phenol oxidase activity and soil N availability.

Removal of Organic Matter and Ammonia Nitrogen in Azodicarbonamide Wastewater by a Combination of Power Ultrasound Radiation and Hydrogen Peroxide

A simple and efficient sonochemical method was developed for the degradation of organic matter and ammonia nitrogen in azodicarbonamide wastewater.The effects of initial pH,ultrasound format and peripheral water level on the sonolysis of hydrazine,urea,COD and ammonia nitrogen were investigated.It is found that the initial pH has a significant influence on the degradation of hydrazine and ammonia nitrogen,whereas this impact to urea is relatively small.It also shows that a noticeable enhancement of ammonia nitrogen removal could be achieved in a proper intermittent ultrasound operation mode,i.e.,1/1 min on/off mode.The height difference between the periph-eral water level and the inner water level of the flask affects the efficiency of ultrasonic treatment as well.

Measurement and analysis of soil nitrogen and organic matter content using near-infrared spectroscopy techniques

Near infrared reflectance （N1R） spectroscopy is as a rapid, convenient and simple nondestructive technique useful for quantifying several soil properties. This method was used to estimate nitrogen （N） and organic matter （OM） content in a soil of Zhejiang Province, Hangzhou County. A total of 125 soil samples were taken from the field. Ninety-five samples spectra were used during the calibration and cross validation stage. Thirty samples spectra were used to predict N and OM concentration. NIR spectra of these samples were correlated using partial least square regression. The regression coefficients between measured and predicted values of N and OM was 0.92 and 0.93, and SEP （standard error of prediction） were 3.28 and 0.06, respectively, which showed that NIR method had potential to accurately predict these constituents in this soil. The results showed that NIR spectroscopy could be a good tool for precision farming application.

Distribution Characteristics of Soil Organic Matter and Total Nitrogen on the Yajiageng Vertical Belt,Gongga Mountain around the Dadu River Banks

Distribution characteristics of soil organic matter（SOM） and total nitrogen（TN） were studied in different plant communities of the Yajiageng vertical belt in Gongga Mountain around the Dadu River banks. The results show： （1） the contents of SOM and TN of the plant communities gradually decreased with the following order： subalpine coniferous forest （3 027 m）, subalpine meadow （3 873 m）, coniferous broadleaved mixed forest（2 737 m）, subalpine shrub（3 565 m） and treeline（3 564 m）. （2） With soil profile depth increasing, the contents of SOM and TN gradually decreased. For different vegetation types, the contents of SOM and TN in sub-alpine coniferous forest were higher than that of other vegetational types. （3）The ratio of the content of carbon to the content of total nitrogen （Cc/CTN）WaS 13.5-27.6, which was relatively lower than the appropriate Cc/CTN of 25-30, and indicated that the soil in favor of the organic matter decomposed and nutrients released. Cc/CTN in the soil had no correlation with sea level altitude. However, its distribution in the soil x, aried with different vegetation types. （4） Nitrogen in SOM existed mainly in the form of organic nitrogen, and Cc/CTN in the soil was not obvious correlated with SOM and TN.

Sources of particulate organic matter in the Chukchi and Siberian shelves: clues from carbon and nitrogen isotopes

The stable isotopic composition(δ13C andδ15N)and carbon/nitrogen ratio(C/N)of particulate organic matter(POM)in the Chukchi and East Siberian shelves from July to September,2016 were measured to evaluate the spatial variability and origin of POM.Theδ13CPOC values were in the range of−29.5‰to−17.5‰with an average of−25.9‰±2.0‰,and theδ15NPN values ranged from 3.9‰to 13.1‰with an average of 8.0‰±1.6‰.The C/N ratios in the East Siberian shelf were generally higher than those in the Chukchi shelf,while theδ13C andδ15N values were just the opposite.Abnormally low C/N ratios(<4),lowδ13CPOC(almost−28‰)and highδ15NPN(>10‰)values were observed in the Wrangel Island polynya,which was attributed to the early bloom of small phytoplankton.The contributions of terrestrial POM,bloom-produced POM and non-bloom marine POM were estimated using a three end-member mixing model.The spatial distribution of terrestrial POM showed a high fraction in the East Siberian shelf and decreased eastward,indicating the influence of Russian rivers.The distribution of non-bloom marine POM showed a high fraction in the Chukchi shelf with the highest fraction occurring in the Bering Strait and decreased westward,suggesting the stimulation of biological production by the Pacific inflow in the Chukchi shelf.The fractions of bloom-produced POM were highest in the winter polynya and gradually decreased toward the periphery.A negative relationship between the bloom-produced POM and the sea ice meltwater inventory was observed,indicating that the net sea ice loss promotes early bloom in the polynya.Given the high fraction of bloom-produced POM,the early bloom of phytoplankton in the polynyas may play an important role on marine production and POM export in the Arctic shelves.

Effects of Long-Term Fertilization on Distribution of Organic Matters and Nitrogen in Cinnamon Soil Macro-Aggregates

Soil samples collected from a 25-year long-term fertilizer experiment carried out on the Earth-cumulic-Orthic Anthrosols in semi-humid farmland ecological system, were used to study the distribution of soil organic matters, total nitrogen, nitrate nitrogen, and ammoniate nitrogen in different grades of soil macro-aggregates in order to study the effects of long-term application of organic manures in combination with chemical fertilizers. It is showed that the percentage of mass of the soil macro-aggregates with long-term application of fertilizers with sizes of 5-2 mm is increased compared with that of the samples with no fertilizer. It is easier to form lager size soil macro-aggregates by the long-term application of organic manures in combination with chemical fertilizers. The contents of organic matters, total nitrogen and nitrate nitrogen are all higher after treatments with different combinations of fertilizers, while there is a little effect on the contents of ammoniate nitrogen. The contents of organic matters, total nitrogen in the grades of soil macro-aggregates from the plough layers of the treated farmland exhibited significant difference. Moreover, the contents of organic matters and total nitrogen in the soil macro-aggregates with the size of 1-0.25 mm is the highest in all treated soil samples. The contents of nitrate nitrogen in soil macro-aggregates increased with the increasing of soil macro-aggregate size except those applied with chemical fertilizer and lower amount of corn stover. The results of correlation analysis revealed that there exists a significantly positive correlation between the percentage of mass of soil macro-aggregates with the size of 5-2 mm and the contents of organic matters, total nitrogen and nitrate nitrogen in the soil samples. However, the correlation between the percentage of mass of soil macro-aggregates with the size of 1-0.25 rnm and the contents of total nitrogen and nitrate nitrogen is significantly negative.The study showed that the highest contributing rates of macro-aggregates fractions to soil fertility is from the soil macro-aggregates fraction with the size of 1-0.25 mm in most of the cases.

The enrichments of organic matter and total nitrogen in sediment as affected by relavant factors

Serious soil erosion has already resulted in degradation of the Loess Plateau of China. Soil erosion is commonly accompanied by extensive soil nutrient loss. Because of enrichment processes,sediment nutrient content is often higher than that of natural soil. The objective of this study is to determine the enrichments of organic matter and total nitrogen in sediment in hilly and gully loess areas on the Loess Plateau of China. Measurements of enrichment ratios (ER) of organic matter (EROM) and total nitrogen (ERTN) in sediment as affected by rainfall, slope gradient, tillage, and fertilization were made in the field under natural rainfall conditions. The results showed that the enrichment of clay in sediment resulted in the enrichment of organic matter (OM) and total nitrogen (TN) in sediment. The averages of sediment clay ER, EROM and ERTN for the various slope gradients were 1.77, 2.09 and 1.61, respectively. The soil erosive module was negatively correlated with EROM and ERTN. Our results indicate that measures to reduce soil erosion, i.e. reducing rainfall erosivity, decreasing soil slope gradient, decreasing fertilizer use, and using level trenches, may increase EROM and ERTN. Both quantity and quality of sediment yield should be considered when implementing erosion control measures.

Nitrogen and Organic Matter Mineralization in the Tunisian Cork Oak Forest: A Laboratory Study

The mineralization of the organic matter is a very important phenomenon which leads to the release of nutriments used by plants. The rate of transformation of the organic matter depends on several factors and parameters such as climatic factors and biological and physicochemical properties of the soil and the litter. In this study, we investigate the effect of the addition of litter of various species as well as the effect of soil moisture on mineralization of organic matter and on mineral nitrogen release in three soils sampled in three cork oak stands during a period of 41 days under the same laboratory conditions. Carbon mineralization was determined using CO2 respiration method, whereas the mineral nitrogen content was measured at the last day of incubation both in soil samples with added plant leaf material, and in control soil samples without addition under two treatments of moisture (40% and 80% WHC—water holding capacity). Our results show that the addition of leaf litter causes an increase in the microbial activity. Soils without addition were significantly different from the plant leaf added soils in respect to carbon mineralization at the end of the incubation period. Moreover, it is noted that the mineralization of carbon is more marked with moisture at 80% than that of 40%, contrary to that of the nitrogen, which is not influenced by the variation of moisture.

The Enhancement of Soil Fertility,Dry Matter Transport and Accumulation,Nitrogen Uptake and Yield in Rice via Green Manuring

Readily available chemical fertilizers have resulted in a decline in the use of organic manure(e.g.,green manures),a traditionally sustainable source of nutrients.Based on this,we applied urea at the rate of 270 kg ha−1 with and without green manure in order to assess nitrogen(N)productivity in a double rice cropping system in 2017.In particular,treatment combinations were as follows:winter fallow rice-rice(WF-R-R),milk vetch rice-rice(MV-R-R),oil-seed rape rice-rice(R-R-R)and potato crop rice-rice(P-R-R).Results revealed that green manure significantly(p≤0.05)improved the soil chemical properties and net soil organic carbon content increased by an average 117.47%,total nitrogen(N)by 28.41%,available N by 26.64%,total phosphorus(P)by 37.77%,available P by 20.48%and available potassium(K)by 33.10%than WF-R-R,however pH was reduced by 3.30%across the seasons.Similarly,net dry matter accumulation rate enhanced in green manure applied treatments and ranked in order:P-R-R>R-R-R>MV-R-R>WF-R-R.Furthermore,the total leaf dry matter transport(t ha−1)for the P-R-R in both seasons was significantly higher by an average 11.2%,7.2%and 36%than MV-R-R,R-R-R,and WF-R-R,respectively.In addition,net total nitrogen accumulation(kg ha−1)was found higher in green manure applied plots compared to the control.Yield and yield attributed traits were observed maximum in green manure applied plots,with treatments ranking as follows:P-R-R>R-R-R>MV-R-R>WF-R-R.Thus,results obtained highlight ability of green manure to sustainably improve soil quality and rice yield.

Distribution characteristics of SOM and nitrogen on the eastern slope of Gongga Mountain

The distribution of soil organic matter (SOM) and nitrogen on Gongga Mountain was studied in this paper. The results showed that the content of SOM and nitrogen (N) of A horizon had an ascending trend with the increase of the elevation. The vegetation types distributed higher than the mixed broad-leaved and coniferous forest have the irregular trends. In the transitional zone vegetation such as mixed trees and treeline, the content of SOM and N is higher than other vegetation types. The distribution of SOM and N of A horizon is dependent on the synthetic effect of climate and vegetation types. The vertical distribution of SOM and N in soil profiles has the similar trends for all kinds of vegetation types, i.e., the content of A horizon is higher than that of the B and C horizons, which is the same to the distribution of dead animal and plant in soil. The soil C:N is between 7 and 25, which is relatively low comparing to the appropriate C:N of 25-30. The ratio of soil carbon to nitrogen (C:N)increases with the increase of the elevation, but its vertical distribution in soil horizons varies with different vegetation types. The N exists in SOM mainly in the form of organic nitrogen, and the soil C:N correlates significantly with SOM.

Changes in Phosphorus Fractions and Nitrogen Forms During Composting of Pig Manure with Rice Straw

The study was conducted to reveal P fractions and N forms changing characters during composting of pig manure with rice straw.During composting,the NH 4 ＋-N concentration decreased and reached at a relatively low value（〈400 mg kg-1） in the final compost,while the NO 3--N concentration increased.Total N losses mainly occurred during thermophilic phase due to the high temperature,the high NH 4 ＋-N concentration and the increase of pH value.Labile inorganic P was dominated in the pig manure and initial compost mixture.During composting,the proportion of labile inorganic P of total extracted P decreased,while the proportion of Fe＋Al-bound P,Ca＋Mg-bound P and residual P increased.The evolutions of the proportion of labile inorganic P,Fe＋Al-bound P and Ca＋Mg-bound P were well correlated with the changes of pH value,organic matter and C/N ratio.Therefore,composting could increase the concentration of N and P and decrease the presence of NH 4 ＋-N and labile P fractions which might cause environmental issues following land application.

Improved speciation of dissolved organic nitrogen in natural waters: amide hydrolysis with fluorescence derivatization

The objective of this study was to improve primary-amine nitrogen (1°-N) quantification in dissolved organic matter (DOM) originating from natural waters where inorganic forms of N, which may cause analytical interference, are commonly encountered. Efforts were targeted at elucidating organic-N structural criteria influencing the response of organic amines to known colorimetric and fluorescent reagents and exploring the use of divalent metal-assisted amide hydrolysis in combination with fluorescence analyse...

Synchronous Changes of Nitrogen and Carbon Isotopic Ratios and Nannoplankton Assemblage in Marine Sediments off Peru at 250 ka: A Role of Phytoplankton in Primary Ocean Productivity

We report the mechanism controlling changes of δ15Norg and δ13Corg values of marine organic matter, based on the change of calcareous nannoplankton assemblage during the last 500,000 years in core samples from ODP Hole 846B off Peru in the equatorial Pacific Ocean. The δ15Norg values fluctuate in a range from 2.1‰ to 6.7‰, giving an abrupt increase since about 250 ka with the averages of 3.8‰ and 5.0‰ during the older and younger periods, respectively. The δ13Corg values change in a range from ?23.5‰ to ?20.1‰ in an inverse correlation with δ15Norg values, describing an increase of average values at 250 ka as well as those of δ15Norg values. The total organic carbon content also shows averages of 0.6% and 0.3% during the younger and older periods, respectively. The numerical increase of deep dwelling species (Florisphaera profunda) of calcareous nannoplankton during the younger period in comparison with the older period indicates that these chemical and isotopic jumps synchronized with nannoplankton assemblage changes in marine sediments are caused by activity of deep dwellers in photic zone more stratified by an abrupt decline of trade wind strength on this sea area since about 250 ka. A study coupling δ15Norg and δ13Corg values and nannoplankton assemblage can be a useful method for evaluating the extent of stratification of photic zone and the roles of surface and deep dwellers of phytoplankton in producing primary organic matter.

The characteristics and significance of pure nitrogen fluid inclusions in Xikuangshan copper deposit,Dongchuan,Yunnan of China

Nitrogen is an important gas-phase element in geological fluid,and normally hosted in mineralizing fluid,in which the content is very low.Nearly 100% mol pure nitrogen inclusion was discovered in copper-bearing quartz vein from Xikuangshan copper deposit,Dongchuan,Yunnan Province in this research.It is between 3 and 5 μm,in shape of ellipse,occurring in group or independence without obvious orientation,and co-existed with primary gas-liquid inclusions.Inclusion analysis by using laser Raman spectroscopy shows its composition is dominated by nitrogen with minor H2O.High concentration of N2 may be the necessary and sufficient condition for forming this kind of inclusion.It is suggested that there are two genesis modes of pure N2 inclusion in the deposit,oxida-tion-devolativation of mantle matter and trap of metasomatic fluid in organic matter decomposition in Luoxue For-mation dolomite.In conclusion,pure N2 inclusion hardly presents in the ore-forming fluids,which providing a new evidence for the genesis of Xikuangshan type copper deposit.

Influencing factors and significance of organic and inorganic nitrogen isotopic compositions in lacustrine sedimentary rocks

Comprehensive nitrogen biogeochemical cycle has been reconstructed for representative lacustrine organic-rich sedimentary rock in China,namely the Triassic Yanchang Formation(YF,199–230 Ma)in Ordos and the Cretaceous Qingshankou Formation(QF,86–92 Ma)in Songliao basins,by evaluating the organic and inorganic nitrogen isotopic compositions rather than only organic or bulk nitrogen isotopic compositions.The results indicate that the nitrogen isotope values of bulk rock(δ^(15)N_(bulk))in the non-metamorphic stage are significantly different from that of kerogen,which challenge the conceptual framework of sedimentary nitrogen isotope interpretation.Theδ^(15)N_(bulk)from the YF and QF were lower than their respective the nitrogen isotope values of kerogen(δ^(15)N_(ker)),with offsets up to5.1‰,which have the inverse relationship for the metamorphosed rock.Thermal evolution did not significantly modify the d15N of bulk rock and kerogen.The d15N of sediments from the YF(δ^(15)N_(bulk),1.6‰–5.6‰)were lower than that of rock from the QF(δ^(15)N_(bulk),10.2‰–15.3‰).The nitrogen isotope values of silicate incorporated nitrogen(δ^(15)N_(sil))were slightly lower than those of the d15Nker in the YF and obviously lower for the QF.The fact that different nitrogen cycles occur in the YF and QF due to the different depositional redox conditions leads to different isotopic results.The YF water environment dominated by oxic conditions is not conducive to the occurrence of denitrification and anammox,and no abundant N2 loss leads to the relatively lightδ^(15)N_(bulk).In the stratified water for the QF,redox transition zone promotes denitrification and anammox,resulting in the heavyδ^(15)N_(bulk)of rock and promotes the DNRA,resulting in heavyδ^(15)N_(ker)and lowδ^(15)N_(sil).

Carbon and nitrogen isotopes analysis and sources of organic matter in the upper reaches of the Chaobai River near Beijing,China

The carbon and nitrogen isotopes in the surface sediments,plants,and soil in the upper reaches of the Chaobai River have been researched.The results showed 27.75‰-21.58‰ and 1.32‰-6.74‰ for carbon and nitrogen isotopic ratios in the surface sediments,respectively.The sources of sedimentary organic matter in this area are soil organic matter,aquatic vascular plants,and riverine plankton,respectively,and a significant contributor to sediment in the Chaohe River,the Baihe River,and the Miyun Reservoir areas is soil organic matter.Furthermore,part of sedimentary organic matter in the Miyun Reservoir is attributed to the input from the Chaohe River and the Baihe River,the other is from C4 vegetation growing around individual point stations at the Miyun Reservoir.Compared with the situation in Hebei Province,the contribution of soil organic matter decreased significantly and river plankton and aquatic vascular plants increased significantly in Beijing municipal areas.This study reveals that the source of organic matter has a close relationship with the soil erosion.

Effect of dissolved organic matter on nitrate-nitrogen removal by anion exchange resin and kinetics studies

The effects of dissolved organic matter （DOM） on the removal of nitrate-nitrogen from the model contaminated water have been investigated utilizing the strong base anion exchange resins. With the increase of gallic acid concentration from 0 to 400 mg/L, the adsorption amount of nitrate-nitrogen on the commercial resins, including D201, Purolite A 300 （A300） and Purolite A 520E （A520E）, would significantly decrease. However, the presence of tannin acid has little impact on nitrate-nitrogen adsorption on them. Compared to D201 and A300 resins, A520E resin exhibited more preferable adsorption ability toward nitrate-nitrogen in the presence of competing organic molecules, such as gallic acid and tannin acid at greater levels in aqueous solution. Attractively, the equilibrium data showed that the adsorption isotherm of nitrate-nitrogen on A520E resin was in good agreement with Langmuir and Fretmdlich equations. The rate parameters for the intra particle diffusion have been estimated for the different initial concentrations. In batch adsorption processes, nitrate-nitrogen diffuse in porous adsorbent and rate process usually depends on t1/2 rather than the contact time. The pseudo first- and the second-order kinetic models fit better for nitrate-nitrogen adsorption onto A520E resin. The observations reported herein illustrated that A520E resin will be an excellent adsorbent for enhanced removal of nitrate-nitrogen from contaminated groundwater.

Resolving the influence of nitrogen abundances on sediment organic matter in macrophyte-dominated lakes, using fluorescence spectroscopy

A controlled experiment was designed to resolve the influence of nitrogen abundance on sediment organic matters in macrophyte-dominated lakes using fluorescence analysis.Macrophyte biomass showed coincident growth trends with time, but different variation rates with nitrogen treatment. All plant growth indexes with nitrogen addition（N, NH4Cl100, 200, 400 mg/kg, respectively） were lower than those of the control group. Four humiclike components, two autochthonous tryptophan-like components, and one autochthonous tyrosine-like component were identified using the parallel factor analysis model. The results suggested that the relative component changes of fluorescence in the colonized sediments were in direct relation to the change of root biomass with time. In the experiment, the root formation parameters of the plants studied were significantly affected by adding N in sediments, which may be related to the reason that the root growth was affected by N addition.Adding a low concentration of N to sediments can play a part in supplying nutrients to the plants. However, the intensive uptake of NH4^＋may result in an increase in the intracellular concentration of ammonia, which is highly toxic to the plant cells. Hence, our experiment results manifested that organic matter cycling in the macrophyte-dominated sediment was influenced by nitrogen enrichment through influencing vegetation and relevant microbial activity.