[Contamination of Organophosphorus Pesticides Residue in Fresh Vegetables and Related Health Risk Assessment in Changchun, China].

This study aims to investigate the concentrations of organophosphorus pesticides (OPs) in fresh vegetables. A total of Z14 samples from seven types of vegetables were collected from the suburb in Changchun City. The OPs were analyzed by gas chromatography coupled with flame photometric detector (GC-FPD). Target hazard quotients (THQ) were applied to estimate the potential health risk to inhabitants. Results showed that OPs concentrations exceeded the Maximum Residue Limit (MRL) in more than 23. 4% samples, and were not detected in only 7. 9% samples. Detection rates of OPs was as follow in the decreased order: diazinon (82. 2%) > phorate (45. 8%) > dimethoate (29. 4%) > parathion-methyl (27. 6%) > omethoate (23. 8%) > dichlorvos (22. 9%) > fenitrothion (21%) > fenthion (18. 7%) > parathion (18. 2%) > methamidophos (17. 3%) > malathion (12. 1%). The percentages above MRL for leaves were higher than for non-leafy vegetables. The order of percentages of OPs above MRL was as follows: green onion (82. 5%) > radish (37. 5%) > red pepper (17. 2%) > Chinese vegetable (14. 3%) > cucumber (3. 2%) > eggplant (2. 9%) > tomato (0%). 49. 5% vegetables samples showed more than one OP. The average target hazard quotients (ave THQ) were all less than one and the average Hazard Index (ave HI) was 0. 462, so that inhabitants who expose average OP levels may not experience adverse health effects.

[Effects of elevated atmospheric CO2 concentration and nitrogen addition on the growth of Calamagrostis angustifolia in Sanjiang Plain freshwater marsh].

By using open top chamber, an experiment with two levels of atmospheric CO2 concentration (350 and 700 micromol x mol(-1)) and three levels of nitrogen supply (0, 5, and 15 g N x m(-2)) was conducted to investigate the effects of elevated atmospheric CO2 and nitrogen supply on the growth of Calamagrostis angustifolia in the freshwater marsh of Sanjiang Plain. Under elevated atmospheric CO2 concentration, the phenophase of C. angustifolia advanced. Jointing stage was advanced by 1-2 d, and maturity stage was advanced by 3 d. Elevated atmospheric CO2 promoted the tillering of C. angustifolia, with the increment of tiller number under 0, 5, and 15 g x m(-2) of nitrogen supply being 8.2% (P < 0.05), 8.4% (P < 0.05), and 5.5% (P > 0.05), respectively. Elevated atmospheric CO2 also promoted the aboveground biomass at jointing and heading stages, the increment being 12.4% and 20.9% (P < 0.05), respectively, and increased the belowground biomass at later growth stages, with the increment at dough stage and maturity stage being 20.5% and 20.9% (P < 0.05), respectively. The responses of C. angustifolia biomass to elevated atmospheric CO2 concentration depended on nitrogen supply level. Under sufficient nitrogen supply, the promotion effect of elevated atmospheric CO2 concentration on the biomass of C. angustifolia was higher.

[Spatial distribution and environmental risk of As and Pb from street dust in non-ferrous metals smelting areas].

ArcGIS analysis was applied to study the content level and the spatial distribution characteristics of As and Pb in street dust of Huludao city. Geoaccumulation Indexes and Potential Ecological Risk Index technique were applied to assess the ecological risk of As and Ph. The average contents of As and Pb were 33.10 mg x kg(-1) and 533.2 mg x kg(-1), which was 4 and 25 times as high as the background value respectively. The trends for Pb and As were similar with higher concentrations near Huludao Zinc Plant (HZP). The ecological risk of As and Pb contamination in street dust were serious, and the accumulation of Pb in street dust was higher than the As.

[Effects of simulated soil warming on the growth and physiological characters of Deyeuxia angustifolia].

By using improved heating cables, a field experiment was conducted to study the effects of 1 degrees C-30 degrees C soil warming on the growth and physiological characters of Deyeuxia angustifolia. Soil warming obviously promoted the growth of D. angustifolia. Under flooded condition, the plant height increased by 18.2%, leaf area increased by 37.32%, root volume increased by 24.67%, total root absorbing area increased by 60% , and tillers number increased by 25.81%; under unflooded condition, the plant height increased by 12.09%, leaf area increased by 32.9%, root volume increased by 36.26%, total root absorbing area increased by 37.47%, and tillers number increased by 32.77%. The responses of D. angustifolia physiological indices to soil warming were more obvious under flooded than under un-flooded condition. Under flooded condition, the total chlorophyll content and root soluble protein content increased by 9.8% and 23.88%, while the leaf soluble protein and soluble carbon contents and root soluble carbon content decreased by 25.02%, 22.92%, and 35.23%, respectively. 1 degrees C-30 degrees C soil warming promoted the growth of D. angustifolia, but the responses of its physiological characters to the soil warming varied with water conditions.

[Seasonal changes of potassium, calcium and magnesium contents and accumulation in Calamagrostis angustifolia in Sanjiang Plain].

From May to October 2004, the seasonal changes of K, Ca, and Mg contents and accumulation in Calamagrostis angustifolia, the dominant species in the typical meadow and marsh meadow communities of Sanjiang Plain, were studied. There was a greater difference in the seasonal changes of K, Ca, and Mg contents in different parts of typical meadow C. angustifolia (TMC) and marsh meadow C. angustifolia (MMC). The K content in aboveground parts of the two communities had an overall decreasing trend, according with linear model K = A + B(t), the Ca content had a smaller change in stem but an overall increasing trend in leaf and vagina, being accorded with parabola model Ca = A +B1t + B2t2 and exponential growth model Ca = Aexp(t/B1) + B2, respectively, while the Mg content had the greatest change in stem but changed relatively smoothly in leaf and vagina. The differences of K, Ca, and Mg contents in different parts of TMC and MMC were obvious. The K content in aboveground parts of TMC was generally higher than that of MMC, while the Ca and Mg contents in the root and vagina of MMC were higher than those of TMC. The K, Ca, and Mg storage and accumulation in different parts of TMC and MMC also differed. Root had the greatest K, Ca, and Mg storage, occupying 63.82 +/- 23.19%, 78.68 +/- 15.44%, and 76.48 +/- 19.06% of the total storage in TMC and 85.23 +/- 9.20%, 93.51 +/- 3.46%, and 92.39 +/- 3.22% in MMC, respectively. The aboveground parts of TMC had a higher storage of K, Ca and Mg than those of MMC, while the root was in adverse. Such a difference was mainly due to ecological characteristics of C. angustifolia and its habitat conditions.

[Spatial variation of heavy metals contamination in the soil and vegetables of Huludao City].

Hg, Pb, Cd, Zn, and Cu concentrations in the soil, vegetables and crop of Huludao city were investigated. The Hg, Pb, Cd, Zn, and Cu concentrations in soils of the smelting areas are 1.422, 443.1, 60.94, 4084, and 247.8 mg x kg(-1), thus 6.092, 3195, 341.7, 35 157, and 1 557 mg x kg(-1) for the maximal concentrations, respectively. Spatial distribution maps of heavy metals concentrations in top soils in Huludao City were separately laid out by using Kriging. Heavy metals spatial distribution patterns in soils show that Ph, Cd, Zn, Cu emissions from Huludao Zinc Plant are the main pollution sources of heavy metals to the top soils in Huludao City, but Hg emission from Huludao Zinc Plant and chlor-alkali industry is the main pollution source of mercury to the top soils. Heavy metals concentrations in top soils decrease exponentially with distance from the zinc smelting area. Except Hg, the exponential equation could be better to fit the variety forother heavy metals. Heavy metals in vegetable and crop cultivated around Huludao Zinc Plant are higher than from markets, suggests that heavy metals affect the local soil and crops seriously.

[Nitrogen accumulation and allocation in Calamagrostis angusifolia in different plant communities of Sanjiang Plain].

From May to October in 2004, the characteristics of nitrogen (N) accumulation and allocation in Calamagrostis angustifolia, the dominant species in the typical meadow and marsh meadow communities of Sanjiang Plain, were studied. The results showed that the total nitrogen (TN) content in the aboveground organs and litters of typical meadow C. angustifolia (TMC) and marsh meadow C. angustifolia (MMC) decreased during growth season, which could be described by exponential decay model (TN = Aexp (-t/B1) + B2, R2 > or = 0.94). The TN content in TMC and MMC roots fluctuated greatly, and a significant N accumulation period (15-30 d) was observed before the coming of growth midseason. The N accumulation amount and rate of different organs and litters had obvious seasonal changes, and their values of the aboveground organs were much higher for TMC than for MMC, while the values of the roots were in adverse. The N allocation ratio of different parts of TMC and MMC also had significant differences. Root was the important N storage, and the root N allocation ratio of TMC and MMC was (59.38 +/- 12.86)% and (84.58 +/- 3.38)%, respectively. Among the aboveground parts, leaf had the highest N allocation ratio, being (24.28 +/- 12.09)% for TMC and (8.18 +/- 3.32)% for MMC. The change patterns of the N allocation ratio of aboveground and underground parts were just in adverse, which reflected the osculation contact in N supplement aspect. The annual N absorption amount and maximum standing crop of TMC and MMC were 23.02, 36.30 g x m(-2), and 28.18, 51.43 g x m(-2), respectively. The N absorption coefficient and utilization coefficient of TMC were much higher than those of MMC (0.017 and 0.634 relative to 0.015 and 0.548, respectively), illustrating that TMC had higher capability of N absorption and utilization than MMC.

[Dynamic coupling of ecological supporting capability and socioeconomic development of west Jilin Province].

The coupling relations between ecological supporting capability [F(x)] and socioeconomic situation [F(y)] of west Jilin Province from 1986 to 2004 were analyzed by harmonious development model and scissor difference method. The results showed that in study period, the F(x) of west Jilin Province had a trend of decreasing first and slightly increasing then, while F(y) had an overall exponential increase. Influenced by natural and anthropogenic factors, both F(x) and F(y) had obvious vulnerability. The scissor difference cx between F(x) and F(y) declined from 4.93 degrees in 1986 to 0.28 degrees in 1996, and then increased to 12.30 degrees in 2004. During the period of 1995 -2004, west Jilin Province gradually changed its traditional manner, i.e., from increasing F(y) with the rapid degradation of F(x) to the harmonious development of both F(x) and F(y), and the coupling degree of F(x) and F(y) changed from elementary or critical inharmonious to barley or elementary harmonious. After 1995, the scissor difference alpha increased with higher velocity, and the harmonious degree C also fluctuated obviously, illustrating an intensive antagonism between F(x) and F(y). The study area was in the erupting period of various ecological problems, and at present, the high instability of elementary harmonious status still existed. Comparing with harmonious development model alone, its combination with scissor difference method could reveal the coupling relations of F(x) and F(y) from the perspectives of development status and changing rate. This combination could reflect not only the equilibrium status but also the conflict intensity between F(x) and F(y), and give more comprehensive and profound analysis on the coupling relations between F(x) and F(y).

[Effects of simulated nitrogen deposition on biomass of wetland plant and soil active carbon pool].

A simulation study was made on the responses of biomass of Deyeuxia angustifolia and soil active carbon pool in Sanjiang Plain of Northeast China to simulated nitrogen deposition. Two water conditions (W1: non-flooded, W2: flooded) and four N treatments (equivalent to 0, 1, 3, 5 g N x m(-2) x a(-1) nitrogen deposition rate) were installed. The results showed that under effects of nitrogen deposition, the total biomass, above-ground biomass, and root biomass of D. angustifolia were higher than the control, and the increment of root biomass was the highest. Both the carbon content and its allocation proportion in D. angustifolia root increased significantly, while the carbon content in above-ground part decreased dramatically (P < 0.05). Nitrogen deposition also had significant effects on soil active carbon pools, and the contents of various fractions in the carbon pool were the highest in treatment 5 g N x m(-2) x a(-1). The responses of various fractions in soil active carbon pool to nitrogen deposition followed the sequence of carbohydrate carbon > labile carbon > dissolved organic carbon > microbial biomass carbon, and the interaction between nitrogen deposition and flooded water condition facilitated the release of soil active carbon. Regression analysis indicated that there were significant correlations between soil active carbon pools and plant indices of D. angustifolia. Nitrogen deposition could enhance the biomass of D. angustifoliat and soil active carbon content.

[Effects of simulated wetland water change on the decomposition and nitrogen dynamics of Calamagrostis angustifolia litter].

From May 2005 to September 2006, the potential effects of wetland water change on the decomposition and nitrogen (N) dynamics of the typical meadow Calamagrostis angustifolia (TMC) and marsh meadow C. angustifolia (MMC) litters were studied by litterbag technique in the typical depressional wetland in the Sanjiang Plain. In this study, the natural water gradient in the depressional wetland was applied to simulate the changes of wetland water conditions, and six decomposition sub-zones were laid in turn in the six communities, Carex pseudocuraica (PF), Carex lasiocarpa (MG), Carex meyeriana (WL), Marsh meadow C. angustifolia (XII), Typical meadow C. angustfolia (XI), and Island forest (DZL), along the water gradient. The results show that water condition has significant effects on the decomposition of litters. If the hydrous environment is formed in C. angustfolia wetland due to the change of precipitation pattern in the future, the litter weightless rates of TMC and MMC will increase 4.33%-16.76% and 24.84%-53.97%, the decomposition rates will increase 10.51%-32.73% and 77.85%-93.92%, and the 95% decomposition time will decrease 0.72-1.85 a and 3.67-4.05 a, respectively. The changes of N contents and N accumulation indices of TMC and MMC litters are relatively consistent, but the change patterns indifferent sub-zones are different. In general, the N in litters in DZL, XI, WL, MG and PF sub-zones show the alternant change characteristics of release and accumulation, but the release process is predominated. In contrast with that, the N in litters in XII sub-zone show release at all times. The C/N ratios have important regulation functions to the changes of N in litters in decomposition process. The estimation results show that the N standing crops of TMC and MMC litters are 12.75 g x m(-2) and 8.29 g x m(-2), and the N annual returning amounts are larger than 1.95 g x (m2 x a)(-1) and 2.25 g x (m2 x a)(-1), respectively. The studies of affecting factors indicate that temperature has promotion effects on the relative decomposition rates of litters, while water condition has restraint effects on them. Further analysis shows that the relative decomposition rates, to some extent, depend on the substrate quality of litters if the nutrient status of decomposition environment does not change greatly. In reverse, if the nutrient status of decomposition environment changes greatly, the relative decomposition rates, to some extent, depend on the supply status of nutrient in decomposition environment.

[Dynamics of initial decomposition of Calamagrostis angustifolia litter in Sanjiang Plain of China].

A 28-day leaching-decomposition experiment was conducted to study the effects of microbial activity and leaching on the initial decomposition of Calamagrostis angustifolia litters taken from the boggy meadow and meadow in Sanjiang Plain of China. The results showed that the mass loss of the litters at their initial decomposition stage accounted for 59% and 22% of yearly mass loss, respectively, and the remaining dry mass decreased significantly after 28-day decomposition. By the end of the experiment, the N content in the litters decreased by 32.65% and 24.55% , and P content decreased by 36.71% and 45.15%, respectively. The N and P contents in the litters treated with chloroform were higher than those of the control, but the difference was not significant. No significant difference was also observed in the N and P release from the litters to the leachates between the treatment of chloroform and CK, which indicated that the initial decomposition of the litters was mainly affected by leaching. There was no significant difference in the decomposition rate and nutrient loss rate between the two litters.

Distribution and fate of anthropogenic nitrogen in the Calamagrostis angustifolia wetland ecosystem of Sanjiang Plain, Northeast China.

Wetlands are important for the protection of water quality of rivers and lakes, especially those adjacent to agricultural landscapes, by intercepting and removing nutrients in runoff. In this study, the 15N tracer technique was applied to study the distribution and fate of anthropogenic nitrogen (15N-fertilizer) in Calamagrostis angustifolia Kom wetland plant-soil microcosms to identify the main ecological effects of it. 15NH415NO3 solution (14.93 mg N/L, 20.28 at.%15N) was added to each microcosm of the first group, which was approximate to the current nitrogen concentration (CNC) of farm drainage, and 29.86 mg N/L 15NH415NO3 solution was added to another group, which was approximate to the double nitrogen concentration (DNC) of farm drainage, while no nitrogen (NN) was added to the third group. The results suggest that the input of anthropogenic nitrogen has positive effects on the biomass and total nitrogen content of plant, and the positive effects will be elevated as the increase of its input amount. The increase of 15N-fertilizer can also elevate its amounts and proportions in plant nitrogen. Soil nitrogen is still the main source of plant nitrogen, but its proportion will be reduced as the increase of 15N-fertilizer. The study of the fate of 15N-fertilizer indicates that, in CNC treatment, only a small proportion is water-dissolved (0.13 +/- 0.20%), a considerable proportion is soil-immobilized (17.02 +/- 8.62%), or plant-assimilated (23.70 +/- 0.92%), and most is lost by gaseous forms (59.15 +/- 8.35%). While in DNC treatment, about 0.09 +/- 0.15% is water-dissolved, 15.33 +/- 7.46% is soil-immobilized, 23.55 +/- 2.86% is plant-assimilated, and 61.01 +/- 5.59% is lost by gaseous forms. The double input of anthropogenic nitrogen can not elevate the proportions of plant-assimilation, soil-immobilization and water-dissolution, but it can enhance the gaseous losses.

[Effects of urbanization on supply and demand of regional ecological footprint].

Based on the time series of ecological footprint (EF) in Jilin Province from 1994 to 2003, the relationship models of EF, ecological budget, and EF intensity with urbanization level were established. The results showed that in Jilin Province, there existed significant correlations of EF, ecological budget, and EF intensity with urbanization level. Along with the development of urbanization, the EF in the Province increased from 1.59 hm2 x cap(-1) in 1994 to 2.23 hm2 x cap(-1) in 2003, which was mainly affected by the process of urbanization and the proportion of tertiary industry. The EFs of built-up land, pasture and fossil fuel land changed more markedly, among which, the EFs of pasture and fossil fuel land were mainly affected by domestic consumption, while that of built-up land was mainly affected by the GDP per capita and the proportion of tertiary industry. Owing to the increase of domestic consumption, the ecological deficit increased from 0.319 hm2 cap in 1994 to 0.923 hm2 cap(-1) in 2003. The changes in ecological budget of pasture and fossil fuel land were more remarkable. Under the effects of the optimization of economic structure and consumption structure, the EF intensity in the Province decreased from 4.14 hm2 x (10(4) Yuan)(-1) in 1994 to 2.35 hm2 (10(4) Yuan)(-1) in 2003, and there still had enough potential for the decrease. Through the optimization of economic structure and consumption structure, an ecological surplus and the balance between natural resources supply and demand in the Province could be achieved.

[Soil nitrogen net mineralization and nitrification in typical Calamagrostis angustifolia wetlands in Sanjiang Plain].

From June 2004 to July 2005, the dynamics of soil inorganic N pool and N net mineralization/nitrification rates in typical meadow Calamagrostis angustifolia wetland (TMCW) and marsh meadow C. angustifolia wetland (MMCW) in Sanjiang Plain were studied by top-closed PVC tube in situ incubation method, with the affecting factors and annual N net mineralization/nitrification investigated. The results showed that the soil inorganic N in the two wetlands had evident dynamic characteristics. The NH4(+) -N and NO3(-) -N contents were much higher in TMCW soil than in MMCW soil, and the soil N net mineralization/nitrification rates in the two wetlands presented significant fluctuations. Biological immobilization, denitrification, and abundant precipitation in rainy season were the main reasons inducing the N net mineralization/nitrification rates to be negative, and temperature, precipitation, soil organic matter content, soil C/N ratio and soil pH were the main factors resulting in the significant differences of soil inorganic N pool and N net mineralization/ nitrification rates between the two wetlands. The annual N net mineralization and nitrification and the percentage of nitrified N in mineralized N were much higher in TMCW soil than in MMCW soil, suggesting that TMCW soil was superior to MMCW soil in N availability and available N-maintaining capacity.

Nitrogen cycling of atmosphere-plant-soil system in the typical Calamagrostis angustifolia wetland in the Sanjiang Plain, northeast China.

The nitrogen (N) distribution and cycling of atmosphere-plant-soil system in the typical meadow Calamagrostis angustifolia wetland (TMCW) and marsh meadow Calamagrostis angustifolia wetland (MMCW) in the Sanjiang plain were studied by a compartment model. The results showed that the N wet deposition amount was 0.757 gN/(m2 x a), and total inorganic N (TIN) was the main body (0.640 gN/(m2 x a). The ammonia volatilization amounts of TMCW and MMCW soils in growing season were 0.635 and 0.687 gN/m2, and the denitrification gaseous lost amounts were 0.617 and 0.405 gN/m2, respectively. In plant subsystem, the N was mainly stored in root and litter. Soil organic N was the main N storage of the two plant-soil systems and the proportions of it were 93.98% and 92.16%, respectively. The calculation results of N turnovers among compartments of TMCW and MMCW showed that the uptake amounts of root were 23.02 and 28.18 gN/(m2 x a) and the values of aboveground were 11.31 and 6.08 gN/(m2 x a), the re-translocation amounts from aboveground to root were 5.96 and 2.70 gN/(m2 x a), the translocation amounts from aboveground living body to litter were 5.35 and 3.38 gN/(m2 x a), the translocation amounts from litter to soil were larger than 1.55 and 3.01 gN/(m2 x a), the translocation amounts from root to soil were 14.90 and 13.17 gN/(m2 x a), and the soil (0-15 cm) N net mineralization amounts were 1.94 and 0.55 gN/(m2 x a), respectively. The study of N balance indicated that the two plant-soil systems might be situated in the status of lacking N, and the status might induce the degradation of C. angustifolia wetland.

[Nitrification-denitrification and N2O emission of typical Calamagrostis angustifolia wetland soils in Sanjiang plain].

With intact soil core and by using acetylene inhibition method, this paper measured the N2O emission and denitrification rates of typical Calamagrostis angustifolia wetland soils in Sanjiang Plain, analyzed their relationships with environmental factors, and estimated the total amounts of N2O emission and denitrification loss. The results showed that meadow marsh soil and humus marsh soil had a similar change range of N2O emission rate (0.020-0.089 kg N x hm(2) x d(-1) and 0.012-0.033 kg N x hm(2) x d(-1), respectively), but the former had a much higher N2O emission rate than the latter, and the difference was significant (P < 0.05). As for denitrification rate, its change range was 0.024-0.127 kg N x hm(2) x d(-1) for meadow marsh soil and 0.021-0.043 kg N x hm(2) x d(-1) for humus marsh soil. Meadow marsh soil also had a higher denitrification rate than humus marsh soil, but the difference was not significant (P > 0.05). In meadow marsh soil, nitrification played an important role in N2O emission and nitrogen loss; while in humus marsh soil, denitrification was the main process inducing N2O emission and nitrogen loss. For these two soils, nitrogenous compounds were not the important factor affecting nitrification-denitrification. In meadow marsh soil, temperature had more evident effect, where nitrification-denitrification had a significant positive correlation with the soil temperature at the depths of 5 cm, 10 cm and 15 cm (P < 0.05). Soil moisture condition was another important factor inducing the difference of N2O emission and denitrification rates. In growth season, the amount of N2O emission and denitrification loss was 5.216 kg N x hm(-2) and 6.166 kg N x hm(-2) for meadow marsh soil, and 3.196 kg N x hm(-2) and 4.407 kg N x hm(-2) for humus marsh soil, respectively. In the denitrification productions of meadow marsh soil and humus marsh soil, the maximum value of N2O/N2 ratio was 5.49 and 3.76, respectively, indicating that the proportion of N2 in denitrification productions was higher in humus marsh soil than in meadow marsh soil, and the seasonal waterlogged condition could induce the decrease of N2O/N2 ratio.

[Phosphorus fractions under different land uses in Sanjiang plain].

Five land-uses type (soybean-filed, rice-field, abandoned cultivation, artificial forest, natural wetland) were obtained before planting and soil P fractions were determined by a modified Hedley fraction method. The result showed that the content of total P (TP) in natural wetland was higher than other soil. While the proportion of total inorganic P (TPi) in TP of farm land soil was higher than that of wetland. Adversely, the proportion of total organic P (TPo) was higher in wetland and least in rice-field. There was no obvious difference between that of abandoned field and artificial forest. The values of labile inorganic phosphorus (labile Pi) under different land-uses were similar. The contents of Resin-P and NaHCO3-Pi varied at a range of 32-36.3 mg x kg(-1) and 33.77-50.42 mg x kg(-1), respectively. The contents of NaOH-Pi and C.HCl-Pi in farmland were higher than those of wetland, especially in rice-field which was 152.4 mg x kg(-1). But for D.HCl-Pi, the content was higher in wetland with the value of 84.3 mg x kg(-1), and the contents of NaOH-Pi, C. HCl-Pi and D.HCl-Pi in abandoned field and artificial forest were in the middle of the above two land use patterns, which indicated that the restoration of soil P in abandoned farmland tended to approach the level of natural wetland. The value and percentage of Po was decreased greatly with the reclamation of wetland, and the decrease of C. HCl-Po was the most significant in all forms of organic P, and its values in soybean-filed and rice-field were only 25.96% and 19.26% of that in wetland. As the time went by the content of Po in abandoned arable land increased with very slow speed, which indicated that the restoration of wetland after reclamation would need a long time. The distribution of soil P in different P fractions has significant difference for the land-use change in Sanjiang plain.

[Dynamics of H2S and COS emission fluxes from Calamagrostis different calamagrostis angustifolia wetlands in Sanjiang Plain].

Using the static chamber and chromatogram method, H2S and COS emission fluxes from the mash meadow Calamagrostis angustifolia in Sanjiang Plain were measured during growth season(5-9 month), the results showed that the seasonal and diurnal variations of H2S and COS emission fluxes were obvious, the mean H2S and COS emission fluxes from the mash meadow Calamagrostis angustifolia were 0.34 microg x (m2 x h)(-1) and - 0.29 microg x (m2 x h)(-1) respectively, the Calamagrostis angustifolia wetlands were the sources for H2S and the sinks for COS during the growth time. The emission fluxes of H2S and COS were affected by the Calamagrostis angustifolia growth, and there were H2S emission peak and COS absorbed peak during the bloom growth time, meanwhile the integrative correlation of H2S and COS emission fluxes were observed.

Element cycling in the dominant plant community in the Alpine tundra zone of Changbai Mountains, China.

Element cycling in the dominant plant communities including Rh. aureum, Rh. redowskianum and Vaccinium uliginosum in the Alpine tundra zone of Changbai Mountains in northeast China was studied. The results indicate that the amount of elements from litter decomposition was less than that of the plant uptake from soil, but that from plant uptake was higher than that in soil with mineralization process released. On the other hand, in the open system including precipitation input and soil leaching output, because of great number of elements from precipitation into the open system, the element cycling(except N, P) in the Alpine tundra ecosystem was in a dynamic balance. In this study, it was also found that different organ of plants had significant difference in accumulating elements. Ca, Mg, P and N were accumulated more obviously in leaves, while Fe was in roots. The degree of concentration of elements in different tissues of the same organ of the plants also was different, a higher concentration of Ca, Mg, P and N in mesophyll than in nerve but Fe was in a reversed order. The phenomenon indicates (1) a variety of biochemical functions of different elements, (2) the elements in mesophyll were with a shorter turnover period than those in nerve or fibre, but higher utilization rate for plant. Therefore, this study implies the significance of keeping element dynamic balance in the alpine tundra ecosystem of Changbai Mountains.

The long-term nutrient accumulation with respect to anthropogenic impacts in the sediments from two freshwater marshes (Xianghai Wetlands, Northeast China).

Sediment cores, representing a range of watershed characteristics and anthropogenic impacts, were collected from two freshwater marshes at the Xianghai wetlands (Ramsar site no. 548) in order to trace the historical variation of nutrient accumulation. Cores were (210)Pb- and (137)Cs-dated, and these data were used to calculate sedimentation rates and sediment accumulation rates. Ranges of dry mass accumulation rates and sedimentation rates were 0.27-0.96 g m(-2)yr(-1) and 0.27-0.90 cm yr(-1), respectively. The effect of human activities on increased sediment accumulation rates was observed. Nutrients (TOC, N, P, and S) in sediment were analyzed and nutrient concentration and accumulation were compared in two marshes with different hydrologic regime: an "open" marsh (E-0) and a partly "closed" marsh (F-0). Differences in physical and chemical characteristics between sediments of "open" and partly "closed" marsh were also observed. The "open" marsh sequestered much higher amounts of TOC (1.82%), N (981.1 mg kg(-1)), P (212.17 mg kg(-1)), and S (759.32 mg kg(-1)) than partly "closed" marsh (TOC: 0.32%, N: 415.35 mg kg(-1), P: 139.64 mg kg(-1), and S: 624.45 mg kg(-1)), and the "open" marsh indicated a rather large historical variability of TOC, N, P, and S inputs from alluvial deposits. Nutrient inputs (2.16-251.80 g TOC m(-2) yr(-1), 0.43-20.12 g N m(-2) yr(-1), 0.39-3.03 g P m(-2) yr(-1), 1.60-15.13 g S m(-2) yr(-1)) into the Xianghai wetlands of China are in the high range compared with reported nutrient accumulation rates for freshwater marshes in USA. The vertical variation, particularly for N, P, and S indicated the input history of the nutrients of the Xianghai wetlands developed in three periods--before 1950s, 1950-1980s, and after 1980s. The ratios between anthropogenic and natural inputs showed that the relative anthropogenic inputs of TOC, N, P, and S have been severalfold (TOC: 1.68-11.21, N: 0.47-3.67, P: 0.24-1.36, and S: 1.46-2.96) greater than values of their natural inputs after 1980s. The result is probably attributable, in part, to two decades of surface coal mining activities, urban sewage, and agriculture runoff within the upstream region of the Huolin River. Our findings suggest that the degree of anthropogenic disturbance within the surrounding watershed regulates wetland sediment, TOC, N, P, and S accumulation.