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1.
1　Introduction　Theuseofnaturalresources ,includingthosebeingofseeminglymarginalvalue ,isanimportanthumanactivitydesignedtoincreasefoodproductionandin come .Inagriculture ,soilsmaybetoosalinetosup portprofitablecrophusbandry ,yetsuchsoilmaybeusedalternat…  相似文献   

2.
Improving knowledge on the ability of bioengineering structures made of willow cuttings to enhance efficient and sustainable sediment trapping in marly gullies in the Southern French Alps under a mountainous Mediterranean climate, to decreasesediment trapped per experiment, the mean annual values reached 0.25, 0.14 and 0.08 m3 yr-1 in experiments C, A and B, respectively. Maximum values for one structure reached 1.94 m3 per year in experiment C. The significance of the volumes ofsediment yield at their outlets, is a key issue today for the international scientific community working in geosciences and ecology. This study therefore aims to assess three real-size experiments(A, B and C) carried out between 2003 and 2013 in this environment. A total of 157 bioengineering structures using purple and white willow(Salix purpurea and Salix incana)cuttings – which have been shown to resprout and survive more than 2 years after their installation,corresponding to brush layers with brush mats on wooden sills(BLM), 1.2 m wide and 2 m long,installed on the floors of 33 experimental marly gullies, were monitored. The results showed that sediment trapping occurred upstream of the vegetation barriers from the 1 st year onwards.Considering the depth of sediment trapped per experiment, the mean annual values reached 11.2 cm yr-1 after 3 years in experiment A, 7.7 cm yr-1 after 2–4 years in experiment C and 5.1 cm yr-1 after 5 years in experiment B. Occasionally, BLMs showed that they could trap up to 16 and 15 cm yr-1 in experiments A and C, respectively. Considering the volumes oftrapped sediment and the sustainability of sediment trapping are discussed, and rules for bioengineering strategies are proposed.  相似文献   

3.
To understand the factors causing frequent outbreaks of harmful algae blooms in the Taihu Lake, China, we studied water quality and nutrient budget in Chinese mitten crab (Eriocheir sinensis) farm ponds in the eastern part of the lake from November 2007 to December 2009. We estimated the nitrogen (N), phosphorus (P), and chemical oxygen demand (COD) loads. Materials input and output ponds, water exchange, and applied management practices of 838.5-hm2 crab ponds were surveyed using questionnaires. Water quality of 12 ponds, which were located no more than 2 km from East Taihu Lake, were monitored. The results show that water quality in the crab ponds was better than reference data. Feeds, including corn seed, commercial feed, trash fish, and gastropod, were the major sources of N and P input in the crab ponds, contributing 88.7% and 94.9%, respectively. In total, 60.5% of N and 37.3% of P were sequestered by macrophytes, and only 15.7% and 8.5% of them were discharged as effluent. The net loads of N and P in effluent were 16.43 kg/hm2/cycle and 2.16 kg/hm2/cycle, respectively, while the COD load was -17.88 kg/hm2/cycle. This indicated that crab farming caused minor negative impact on the trophic status of the lake area, which was attenuated by macrophytes. However, wastewater purification is still necessary in crab faming.  相似文献   

4.
A three-dimensional advection-diffusion model coupled with the degradation process is established for describing the transport of chemical oxygen demand (COD). Comparison of the simulated distribution of COD at the surface in the Bohai Sea in August, 2001 with field observations, shows that the model simulates the dataset reasonably well. The Laizhou Bay, Bohai Bay, and Liaodong Bay were contaminated heavily near shore. Based on the optimal discharge flux method, the Environmental Capacity (EC) and allocate...  相似文献   

5.
Ten clonal units of Carex pseudocuraica growing in four different microhabitats (perennial flooded ditch water, perennial flooded ditch sediment, seasonal flooded ditch sediment and perennial flooded soil) of the Sanjiang Plain, Northeast China, were collected randomly for phenotypic plasticity analysis. Iron content, chemical and physical properties of substrates and the total Fe of nine plant modules were measured as well. The results show that the performance of the C. pseudocuraica is affected by the microhabitat, with the greatest performance score in perennial flooded ditch water, and the lowest in perennial flooded soil. The biomass allocation indexes indicate that much more mass is allocated to stems and roots to expand colonization area. The distribution of the total Fe in plant modules appears as pyramids from the tip to the root, while marked differences are observed in the distribution proportion of stems, tillering nodes and roots that are allometrically growing. Iron transfer from substrates to the plant is mainly controlled by the substrate type. The differences of iron distribution and transfer in the plant in different microhabitats are attributed to the iron contents of the substrates as well as the phenotypic plasticity of the plant.  相似文献   

6.
Wetlands play a very important role in ecosystems. Qixinghe Wetland is a nature reserve area in northeastern China. In this paper, diatom communities and environmental qualities were investigated at eight sites in Qixinghe Wetland. This study was to examine diatom species patterns in relation to environmental variables in wetlands, and to use diatoms as indicators to water quality in wetlands and wetland classification. Diatoms were sampled in summers and autumns in 2002 and 2004, during which 180 taxa were identified. Environmental variations in pH, temperature, biochemical oxygen demand (BOD), and chemical oxygen demand (COD) were measured. The seasonal composition and abundance of diatoms changed greatly during the study period. The relationship between diatoms and chemical water quality was estimated statistically. Canonical correspondence analysis (CCA) with forward selection and Monte Carlo permutation tests revealed that all water environmental variables changed during the study period (P<0.05). Among all the parameters, variation in BOD among the sites was a very important determinant of species composition according to the CCA, and BOD decreased from 2002 to 2004. Our results suggest that the water quality had improved during the three-year period because of enhanced environmental protection with less human disturbance. We conclude that diatoms can be used to indicate water quality and habitat conditions in this wetland.  相似文献   

7.
Two modes of regulating the water quality of experimental ponds in indoor raceway culture of Litopenaeus vannamei were evaluated using simple water treatment facilities. A self-made water purifying net, aeration stone, composite microbe preparation, and Ceratophyllum demersum were placed in the experimental ponds and the culture water was circulated along the raceway inside the pond using a paddle wheel aerator. In addition, the water quality in the experimental pond was improved by draining effluent from the pipeline at the bottom of ponds 7 and 8 (mode I) and exchanging the circulating water in pond 10 (mode II) with the reservoir water in pond 9 using a pump and pipeline. The water quality in the experimental ponds was similar in response to regulation using mode I or mode II. Water quality parameters in the experimental ponds were controlled within a suitable range by simple facilities during culture period without using any chemical treatments. The rich content of dissolved oxygen was maintained by the circular flow and continuous aeration of the pond water. The respective average values of the main water parameters in experimental ponds 7 and 10 in response to regulation of the water quality using modes I and II were as follows: pH 8.17 and 7.99; DO 5.16 mg/L and 5.97 mg/L; CODMn 18.45 and 12.61 mg/L; TAN (NH3-N) 0.854 mg/L (0.087 mg/L) and 0.427 mg/L (0.012 mg/L); NO2-N 0.489 mg/L and 0.337 mg/L. Moreover, the average body length and body weight of harvested shrimp of pond 7 and pond 10 were 7.56 cm and 8.99 cm, 5.10 g and 8.33 g, respectively. Furthermore, the survival rate, average biomass yield and average condition factor of the shrimp harvested were 70% and 60%, 2.54 kg/m2 and 2.14 kg/m2, and 0.675 g/cm and 0.927 g/cm, respectively. Linear equations describing the relationship between body length and culture time and cubic or power functions describing the relationship between body weight and body length were obtained based on evaluation of the growth data of shrimps throughout the culture period.  相似文献   

8.
Historical records of metal inputs were studied by using a sediment core collected from a sand-rich mudflat in the Qinjiang River estuary, China. 210Pb chronology was used to reconstruct the fluxes of Hg, Cu, Pb, Zn, Cd, Cr and As to the core site during the last 86 years. Based on the constant initial concentration model, the sedimentation rates are 1.18 cm year-1 in the top 30 cm sandy layer and 0.92 cm year-1 in the muddy bottom layer. To compensate for grain-size and mineralogy effects on metal concentra-tions, aluminum was used as the normalizing element. The enrichment factors (EF) indicate that the natural inputs had prevailed up to the early 1980s. After this period, the intensity of human activities has resulted in continual increasing trend of metals towards the surface. Recent sediment samples from the Qinjiang River estuary are found moderately enriched by Cd (EF>1.5) and slightly enriched by other metals (EF<1.5). Considering that the drainage area of the Qinjiang River is mostly agricultural land, the increased Cd may be due to the usage of fertilizers and pesticides in agricultural activities and the combustion of fossil fuels.  相似文献   

9.
Stormwater runoff in rural townships has a high potential for water quality impairment but little information is available on strormwater runoff pollution from rural townships.To investigate the characteristics of runoff pollution in a rural township,a catchment(2.32 ha) in Linshan Township,Sichuan,China was selected to examine runoff and quality parameters including precipitation,flow rate,and total nitrogen(TN),dissolved nitrogen(DN),total phosphorus(TP),dissolved phosphorus(DP),particulate phosphorus(PP),chemical oxygen demand(COD) and suspended solid(SS) in 12 rainfall events occurring between June 2006 and July 2007.Results show that the annual pollutant loads were 47.17 kg ha-1 for TN,6.64 kg ha-1 for TP,1186 kg ha-1 for COD,and 4297 kg ha-1 for SS.DN and PP were the main forms of nitrogen and phosphorus in stormwater runoff.TP,COD and SS showed medium mass first flushes,in which nearly 40% of the total pollutant masses were transported by the first 30% of total flow volume.The peak of pollutant concentration appeared before the peak of runoff due to the first flush of accumulative pollutants in impervious areas and drainage ditches.The EMC values of TN,TP,DN and PP were negatively correlated to the maximum rainfall intensity,precipitation,total flow volume,and runoff duration(P<0.05,n=12),while EMC of COD and SS were not related to any rainfall characteristics.The FF30(FF,First Flush) for TN,TP,COD and SS were positively correlated to the maximum rainfall intensity(P<0.05,n=12),and TP was also positively correlated to the average rainfall intensity(P<0.05,n=12),indicating that the magnitude of first flush increased with the rainfall intensity in the Linshan Township.  相似文献   

10.
The distribution characteristics of methyl mercury in Rana chensinensis and water, sediment and soil in gold-mining areas of the upper reaches of the Songhua River, China were studied by field sampling and laboratory testing. The results show that the methyl mercury contents in water, sediment and soil in gold-mining areas are much higher than those in the control site, indicating that gold-mining activities intensify the methyl mercury pollution in the study area. Methyl mercury contents are in a descending order of sediment > soil > water in the environment, and in a descending order of brain > viscera > muscle > skin in Rana chensinensis. There are significant correlation between methyl mercury contents in Rana chensinensis and those in water and sediment. In particular, the methyl mercury content in the skin of Rana chensinensis is positively correlated with those in water and sediment in spring. Therefore, skin is one of main intake pathways for methyl mercury due to its high permeability.  相似文献   

11.
It is well known that acid-volatile sulfide （AVS） plays an important role in influencing the toxicity of divalent cationic metals within anoxic sediments. In studying sediment core samples collected from tidal flats within the Jiaozhou Bay, China, we found that the AVS concentration gradually increases with depth and decreases from high tidal flat to low tidal flat areas. We evaluated the chemical activity and bioavailability of heavy metals in the tidal flat based on the molar ratio of simultaneously extracted metals （SEM） and AVS. The value of SEM/AVS is generally less than 1 in this area except for the surface layer, which suggests that the heavy metals only have chemical activity in the surface layer. SEM is most highly concentrated at the boundary of the redox layer SEM have similar depth distributions throughout the tidal flat. The aeration of low tidal flat sediment indicates that SEM gradually move to deeper sites via interstitial water.  相似文献   

12.
采用中心组合设计和响应曲面法研究温度(12~34℃)和盐度(0~26)对吉富品系尼罗罗非鱼(Oreochromis niloticus)幼鱼(体长4.20±0.10 cm,体质量2.42±0.15 g)肠道超氧化物歧化酶(Superoxide Dismutase,SOD)、过氧化氢酶(Catalane,CAT)的联合效应。结果表明:1)温度对吉富罗非鱼幼鱼肠道SOD和CAT活力的线性效应和累积效应均极显著(P<0.01);盐度对吉富罗非鱼幼鱼肠道SOD活力线性效应显著(P<0.05),累积效应极显著(P<0.01);盐度对吉富罗非鱼幼鱼肠道CAT活力线性效应不显著(P>0.05),累积效应极显著(P<0.01);温度和盐度对SOD活力的互作效应极显著(P<0.01),对CAT活力的互作效应不显著(P>0.05)。2)响应曲面法分析表明,随着温度和盐度的增大,两种抗氧化酶的活力均呈先减小后增大的趋势。3)建立两种抗氧化酶活力与温度、盐度间关系的模型方程(SOD:决定系数R2=0.992 9,预测决定系数R2Pred.=0.939 2,P<0.01;CAT:决定系数R2=0.948 5,预测决定系数R2Pred.=0.647 1,P<0.01),两模型方程可用于预测吉富罗非鱼幼鱼肠道SOD和CAT的活力。4)优化结果显示,温度为24.15℃,盐度为11.75时,SOD活力最小值为9.80 U/mg,CAT活力最小值为9.28 U/mg,满意度函数值高达0.961。  相似文献   

13.
We present a GIS-based habitat suitability index (HSI) model to identify suitable areas for Zostera marina L. restoration in the subtidal zone of Xiaoheishan Island. The controlling factors in the model, in order of importance, are Secchi depth, sediment composition, water temperature, salinity, current velocity, water depth and nutrient quality. Specific factor piecewise functions have been used to transform parameter values into normalized quality indexes. The weight of each factor was defined using expert knowledge and the analytic hierarchy process (AHP) method. All of the data thus obtained were interpolated using the inverse distance weighted (IDW) interpolation method to create maps for the entire region. In this study, the analysis of habitat suitability in the subtidal zone of Xiaoheishan Island was conducted for four seasons. According to the GIS-based HSI model, the optimal habitat of Zostera marina L. appears in spring, although habitat remains suitable all year round. On the whole, the optimum site for eelgrass restoration is located in the eastern region, followed by the western and southern regions. We believe that the GIS-based HSI model could be a promising tool to select sites for Zostera marina L. restoration and could also be applicable in other types of habitat evaluation.  相似文献   

14.
The distribution of sediment chloroplastic pigments (Chl-a, i.e. chlorophyll a and Pha-a, i.e. phaeophorbide a) in the Southern Yellow Sea of China was studied. Samples were collected from four cruises in January and June 2003, and January and June 2004. The results show that the vertical distribution of Chl-a and Pha-a in the sediment layers 0-2cm, 2-5cm and 5-8cm, follows a stable ratio, 5:3:2. The average ratio of Pha-a to Chl-a in sediment is 2.83. Spearman 2-tailed rank correlation analysis shows that Chl-a and Pha-a contents in each sediment layer have a highly significant correlation. The average contents of Chl-a and Pha-a in the sediment of the 0-8cm layer in the investigated area are 0.31 -0.47μgg-1 and 1.28-1.40 μgg-1 sediment (dry weight), respectively. The average Chl-a and Pha-a contents in sediment are higher in summer than in winter. ANOVA analysis shows that there is a highly significant variation among the Chl-a contents (P = 0.002 <0.01) of the four cruies, but this is not true for the case of Pha-a content (P = 0.766>0.05). The average Chl-a and Pha-a contents in the 2 sediment layers (0-2cm and 2-5cm) have significant or highly significant correlations with organic matter (OM), median diameter (Mdφ), silt plus clay percentage in the January 2003 cruise. In the June 2003 cruise, the average Chl-a content in the 3 sediment layers (0-2cm, 2-5cm, and 5-8cm) has a significant correlation with meiofauna biomass, and Pha-a content has highly significant correlations with water depth, bottom water temperature, OM and Mdφ The contents of Chl-a and Pha-a are lower than those in estuaries and intertidal areas, but close to those in the same area studied previously.  相似文献   

15.
A field observation was carried out in the Changjiang （Yangtze） River Estuary from May 19 to 26, 2003. A total of 29 stations, including 2 anchored stations, were occupied through almost the whole salinity gradient. Based on the observation data, biogeochemistry of chemical oxygen demand （COD） was examined. Spatial distribution pattern of COD shows that it decreased downstream. The COD concentration varied generally within a narrow range of 1.24-1.60 mg/L in the zone around the river mouth, beyond which it decreased rapidly to 0.20 mg/L. In the mixed water zone, the fluctuation in COD was smaller at 2 m above the bottom layer than at the surface layer in 48 h. In the seawater zone, the 48-h fluctuation at the surface was the largest, followed by that of 5 m below the surface and 2 m above the bottom layers in a range of from 2.50 to 0.55 mg/L. Freshwater discharge was the dominant source of COD in the estuary. The average COD beyond the river mouth was 2.7 mg/L, which accorded with the Chinese seawater quality Grade I. Relationships between dissolved oxygen and biogeochemical parameters such as suspended particulate matter, dissolved organic matter and chlorophyll-a were also discussed.  相似文献   

16.
Broodstock of Verasper moseri (Jordan and Gilbert) aged 3–4 years old were selected, and reinforced cultivation was conducted to promote maturation under controlled water temperature and photoperiod conditions. Fertilized eggs were obtained by artificial fertilization, and the development of embryos, larvae and juveniles was observed continuously. The results showed that the fertilized eggs of V. moseri were spherical, with transparent yolk and homogeneous bioplasm, and had no oil globule inside. The average diameter of the eggs was 1.77±0.02 mm. The eggs of V. moseri were buoyant in water with salinity above 35. The cleavage type was typical discoidal. Young pigment cells appeared when olfactory plates began to form. Hatching occurred at 187 h after fertilization at a water temperature of 8.5°C. The newly hatched larvae, floating on the water surface, were transparent with an average total length of 4.69±0.15 mm. During the cultivation period, when the water temperature was raised from 9 to 14.5°C, 4-day old larvae showed more melanophores on the body surface, making the larvae gray in color. The pectoral fins began to develop, which enabled the larvae to swim horizontally and in a lively manner. On days 7–8, the digestive duct formed. The yolk sac was small and black. The yolk sac was absorbed on day 11. Larvae took food actively, and body length and body height clearly increased. The rudiments of dorsal and anal fin pterygiophores were discernible and caudal fin ray elements formed on day 19. On day 24, the larval notochord flexed upwards, and the rays of unpaired fins began to differentiate. Pigment cells converged on the dorsal and anal fin rays, and the mastoid teeth on the mandible appeared. On day 29, the left eyes of juveniles began to move upwards. Depigmentation began in some juveniles and they became sandy brown in color on day 37. Most juveniles began to settle on the bottom of the tank. The left eyes of juveniles migrated completely to the right side on day 50, when the average body length attained 2.5±0.18 cm, and juveniles accomplished metamorphosis to young. The embryonic and larval characters of several flounder species are compared.  相似文献   

17.
This paper presents a paleoflood study to determine the flood frequency of the Changjiang River, based on core cj0702, taken from the Changjiang River subaqueous delta. We identified flood deposits by means of high-resolution grain-size variation, sensitive population, geochemical indexes and magnetic susceptibility. The core covers a time span of 120 years by 210 Pb dating and was sampled at 1–2 cm intervals. Grain size, geochemical elements, and physical parameters were analyzed. The results indicate that the sediment of the core is mainly composed of silt and clay, as well as groups of interbedded silt, clay silt, and clay. Vertically, the grain size pattern was controlled by seasonal variations in water discharge and by the sediment input in winter from the abandoned Huanghe River delta. River flooding caused extreme values in all our measured parameters. We identified more than 20 flood events that occurred since 1887 using the physical parameter analysis method. The environmentally sensitive component of sediment grain size(14.32–96.39 μm) contribution30%, Zr/Rb ratio1.5, and magnetic susceptibility16 were selected as the criteria for flood identification generally. We also found that floods that had taken place in the upstream, midstream, or downstream parts of the river were clearly identified by these indexes while the large-scale floods that covered the whole drainage area did not leave clear indications in the sediment record. This study for identification of flood events is of great significance for understanding hyperpycnal current sedimentation as well as for forecasting of floods.  相似文献   

18.
A laboratory experiment was conducted to assess the bioaccumulation of Pb2+ and its effects on growth, morphology and pigment contents of Spirulina (Arthrospira) platensis. The specimen cultured in Zarrouk liquid medium was treated with various initial metal concentrations (0, 5, 10, 30, 50 and 100 μg mL−1). The growth of S. platensis was adversely affected by Pb2+ at high concentrations (30, 50 and 100 μg mL−1). However, at low concentrations (5 μg mL−1), Pb2+ could stimulate its growth slightly. The pigment contents (chlorophyll α and β carotene) were decreased in a dose-dependent manner. The highest reductions (67% and 53% respectively in chlorophyll α and β carotene) were observed in 100 μg mL−1 treatment group. The LC50 (96 h) of Pb2+ was measured as 75.34 μg mL−1. Apart from a few cases of filament breakages at elevated concentrations (50 and 100 μg mL−1), morphological abnormalities are not specific. Metal bioaccumulation increased with Pb2+ concentrations, but decreased with exposure time. The maximum accumulated amount was 188 mg g−1 dry weight. The bioconcentration factor (BCF) reached to a peak at day 2, followed by a gradual reduction for all the exposure concentrations. S. platensis is able to tolerate considerably high Pb2+ concentrations. Consequently it can be used as a potential species to remove heavy metal from contaminated waters.  相似文献   

19.
Myosin subfragment-1 was prepared from the myofibrils of bighead carp (Aristichthys nobilis). The myosin subfrag- ment-1 was proved to have the activity of tripolyphosphatase (TPPase) responding to the hydrolysis of sodium tripolyphosphate (STPP). The optimum temperature and pH for the TPPase of myosin subfragment-1 were 30℃ and pH 5.0, and at pH 8.0 the TPPase also showed a high activity. Mg2 was necessary to TPPase. The TPPase activity of myosin subfragment-1 was activated by Mg2 under low concentrations, but was inhibited when the concentration was over 17 mmolL-1. The TPPase activity was also affected by KCl. The optimum concentration of KCl for TPPase was 0.3 molL-1 under the condition of 17 mmolL-1 Mg2 . The TPPase activity was significantly inhibited by EDTA-Na2. Reagents such as KBr, KI and KIO3 could inhibit the TPPase effectively. K2Cr2O7 as well as KMnO7 and KNO3 exhibited weak inhibiting effects. The TPPase converted STPP to pyrophosphate (PP) and orthophosphate (Pi) stoichiometrically with a KM of 3.2 mmolL-1.  相似文献   

20.
The goal of the study was to examine the effect of stocking density on the water quality of culture area, as well as the growth, body composition and cortisol content of rainbow trout（Oncorhynchus mykiss）. Pen-reared trout were stocked in densities of 40, 60, 80 fish individuals m-3(4.6, 6.6, 8.6 kg m-3, SD1, SD2 and SD3 groups, respectively) for 300 days. Compared to the water from SD1 and SD2, that from SD3 exhibited significantly higher NH4+-N content and COD（chemical-oxygen-demand）, and a significant reduction of dissolved oxygen in day 180(40.6 kg m-3). Stocking density was significantly associated with body weight, standard length, VSI（viscerosomatic index）, CF（condition factor） and FC（food coefficient） in group SD3, particularly in day 240 and day 300(45 or 49.3 kg m-3). Increased crude fat and decreased crude protein were displayed in high density group when the density reached to 36 kg m-3. As a cumulative effect of density-related stress, VSI, CF, FC, moisture, and crude protein content varied over time in each density group（SD1, SD2, and SD3）. In summary, trout exhibited a better growth performance in low density(26.3 kg m-3) than those reared in high densities(36 and 45 kg m-3). The results indicate that rainbow trout（114.44 g ± 6.21 g, 19.69 cm ± 0.31 cm） initially stocked in 6.6 or 8.6 kg m-3 should be lightened to less than 36 kg m-3 after an intensive rearing for 240 days.  相似文献   

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