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1.
This study was undertaken to investigate patterns of pyrite accumulation found in aJuncus roemerianus tidal marsh of north Florida. We speculate that the pattern of pyrite accumulation was caused mainly by the distribution of roots. Sediment cores from living stands (LS), dead stands (DS), and recently killed stands (RKS) were collected and analyzed for dissolved organic carbon (DOC), sulfate, chloride, Cr(II)-reducible sulfide, and biomass of roots and rhizomes. Living roots were distributed mainly in the upper 16 cm and concentrated 4–10 cm below the sediment surface. Pyrite accumulations were significantly different among the three types of sediment cores in the upper 16 cm sediment and follow the descending order of DS (615 μmol cm?3)>RKS (547 μmol cm?3)>LS (368 μmol cm?3). Between 20 cm and 30 cm, pyrite contents approached values of 40 μmol cm?3 and 55 μmol cm?3 in all sediment cores. The degree of pyritization approaches 92–94% between 14 cm and 20 cm where pyrite accumulation was probably limited by available iron. Root distribution also affected the redistribution of iron through iron sulfide formation. Sulfate depletion in the upper 16 cm was higher in RKS (79.3 μmol cm?3) than DS (49.1 μmol cm?3). No significant sulfate depletion was found in LS. Sulfate reduction under DS was likely limited by the readily available substrates. Root distribution had a major influence on pyrite accumulation and sulfate reduction of the marsh, and its effects need to be addressed in studies of wetland sulfur dynamics.  相似文献   

2.
《Applied Geochemistry》2006,21(4):547-562
Reducing the concentration of dissolved organic C (DOC) in water is one of the main challenges in the process of artificial groundwater recharge. At the Tuusula waterworks in southern Finland, surface water is artificially recharged into an esker by pond infiltration and an equal amount of groundwater is daily pumped from the aquifer. This groundwater study was conducted to consider the role of redox processes in the decomposition of DOC. The isotopic composition of dissolved inorganic C (δ13CDIC) in the recharged water was used as a tracer for redox reactions. The isotopic composition of O and H in water was determined in order to calculate mixing ratios between the local groundwater and the infiltrated surface water. Three distinct processes in the reduction of the DOC content were traced using isotopic methods and concentration analyses of DIC and DOC: (1) the decomposition of DOC, (2) adsorption of DOC on mineral matter, and (3) the dilution of artificially recharged water by mixing with local groundwater. The largest decrease (44%) in the DOC content occurred during the early stage of subsurface flow, within 350 m of the infiltration ponds. The reduction of DOC was accompanied by an equal increase in DIC and a significant drop in δ13CDIC. This change is attributed to the oxidative decomposition of DOC. A further 23% decrease in DOC is attributed to adsorption and a final drop of 14% to dilution with local groundwater.  相似文献   

3.
Deadwood is an indicator that addresses many parameters of naturalness and is becoming a general reference for natural forests. If there are enough of the different kinds of deadwood in a forest, then it is likely to be properly natural. Also, it is a practical indicator, representing the health and biodiversity of forests. The aim of this research was to find out how much deadwood should be present in different developmental stages in a natural forest as a reference. For this purpose, a natural forest ecosystem in Mazandaran province, north of Iran, which is located in Noshahr, was selected. Species, diameter and height of all (living and dead) trees in each area were assessed. Then, developmental stages were determined, and their map was produced. The amount of deadwood was determined in different stages. Results showed that all three stages (initial, optimal and decay stage) could be recognized in the studied beech stands. Deadwood rate varied and greatest volume and number of it occurred in decay and initial stages, respectively. The frequency and volume of deadwood depend on the pattern of natural disturbance, developmental stages and stand structure. The amount of deadwood within managed forests is open to debate and requires detailed knowledge about beech stands in local conditions. So, based on these results in natural forests of beech in north of Iran, deadwood volume between 4.9 and 54.3 m3 ha?1 or 1.1–9.6 % of total volume of wood could be considered as a reasonable amount and each developmental stage must be different.  相似文献   

4.
The present study explores the effect of salinity and dissolved organic carbon (DOC) gradients on the stability and reactivity of titanium dioxide nanoparticle (TiO2-NP) agglomerates in ambient water from the Lagoon of Venice and their possible effect on nauplii sampled at the same locations. In all ambient water samples, TiO2-NPs formed rapidly micrometre-sized agglomerates. The increase in the salinity and concomitant decrease in DOC content induced the formation of larger agglomerates, with z-average hydrodynamic diameter increasing with TiO2-NP concentration and exposure duration. Under the studied conditions, ζ-potential exhibited negative values. In line with agglomeration results, enhancement of the salinity and lower DOC resulted in less negative ζ-potential with close to 0 values in the dispersions of 100 mg L?1 TiO2-NPs in sea water. Two-hour exposure to micrometre-sized agglomerates of TiO2-NPs resulted in an increase in the fluorescence of propidium iodide (PI) stained nauplii in comparison with unexposed controls, but had no effect at 24-h exposure. The increase in nauplii-associated PI fluorescence was more noticeable in dispersions containing 100 mg L?1 than those containing 10 mg L?1 TiO2-NPs, suggesting membrane permeability alteration in a concentration-dependent manner. However, the PI staining results have to be interpreted with caution because of the possible dye binding to the nauplii surface without penetration of cellular membrane. The effect of TiO2-NPs on nauplii was more pronounced at higher salinity and decreased with increasing DOC concentrations at 2 h, while no trends were found at 24-h exposure, as well as exposure to 100 mg L?1 TiO2-NPs.  相似文献   

5.
Dissolved organic carbon (DOC) is a key component involved in metal displacement in soils. In this study, we investigated the concentration profiles of soil-borne DOC, Cu and Zn at various irrigation rates with synthetic rain water under quasi steady-state conditions, using repacked soil columns with a metal-polluted topsoil and two unpolluted subsoils. Soil solution was collected using suction cups installed at centimeter intervals over depth. In the topsoil the concentrations of DOC, dissolved metals (Zn and Cu), major cations (Ca2+ and Mg2+) and anions ( and ) increased with depth. In the subsoil, the Cu and Zn concentrations dropped to background levels within 2 cm. All compounds were much faster mobilized in the first 4 cm than in the rest of the topsoil. DOC and Cu concentrations were higher at higher flow rates for a given depth, whereas the concentrations of the other ions decreased with increasing flow rate. The decomposition of soil organic matter resulted in the formation of DOC, , and and was the main driver of the system. Regression analysis indicated that Cu mobilization was governed by DOC, whereas Zn mobilization was primarily determined by Ca and to a lesser extent by DOC. Labile Zn and Cu2+ concentrations were well predicted by the NICA-Donnan model. The results highlight the value of high-resolution in-situ measurements of DOC and metal mobilization in soil profiles.  相似文献   

6.
δ13CPDB compositions for 39 samples of dissolved organic carbon (DOC) from the Gulf of Mexico-Caribbean Sea-Atlantic Ocean system, the South Pacific and Ross Sea are reported. Deep water values are similar with a mean of ?21.8%. attesting to the homogeneity of the oceanic DOC pool. In Antarctic waters, a 5%. difference between DOC and particulate organic carbon (POC), with POC having values similar to modern plankton (δ13CPDB approx ?27%.) supports the idea of the transient nature of POC as compared to DOC.Total, lipid, acid hydrolyzed, amino acid and residue fractions of POC are about 5, 3, 7, 5 and 3%. respectively, more negative in 2000 m water as compared to surface water samples from the Gulf of Mexico.  相似文献   

7.
We investigated anaerobic ammonium oxidation (anammox) in continental shelf and slope sediments of the Irish and Celtic Seas by using anammox specific ladderane biomarker lipids. We used the presence of an intact ladderane phospholipid as a direct indicator for living anammox bacteria, and compared it with the abundance of ladderane core lipids derived from both living and dead bacterial biomass. All investigated sediments contained ladderane core lipids as well as the intact ladderane phospholipid, in agreement with 15N-labeling experiments, which revealed anammox activity at all sites. Ladderane core lipid and intact ladderane phospholipid concentrations were significantly correlated (R2 = 0.957 and 0.464, respectively) with anammox activity over the transect of the continental shelf and slope sediments. In the Irish Sea (50-100 m water depth) highest abundances of the intact ladderane phospholipid were found in the upper 2 cm of the sediment, indicating a zone of active anammox. A sharp decline further down-core suggested a strong decrease in anammox biomass and rapid degradation of the intact lipids. In comparison, ladderane core lipids were 1-2 orders of magnitude higher in concentration than the intact ladderane phospholipid and accumulated as dead cell remnants with depth. In the slope sediments of the Celtic Sea both ladderane core lipids and the intact ladderane phospholipid were found in sediments at water depths ranging from 500 to 2000 m. Here, anammox seemed to be active at greater depths of the sediment (>2 cm). Mean abundances of both intact and core ladderane lipids in whole sediment cores increased downslope, indicating an increasing importance of anammox in deeper slope sediments.  相似文献   

8.
Particulate organic carbon (POC), dissolved organic carbon (DOC), and plant pigments (chlorophylls and carotenoids) were measured approximately bimonthly from March 1992 to October 1993 in the Sabine-Neches estuary (Sabine Lake region), located on the Texas-Louisiana border. High freshwater inflow into this shallow turbid estuary results in the shortest hydraulic residence time (ca. 7 d) of all Texas estuaries (Baskaran et al. in press). Annual averages of chlorophyll-a (3.0 μg l?1) and particulate organic carbon (1.1 mg l?1) in the water column were extremely low in comparison to other shallow estuaries. The highest chlorophyll-a concentrations were observed in October 1993, in the mid and lower regions of the estuary, during the lowest river discharge. Zeaxanthin and fucoxanthin concentrations suggested that much of the chlorophyll-a during this low flow period was represented by cyanobacteria and diatoms that entered from the Gulf of Mexico. The range of DOC concentrations was generally high (4.4–20.9 mg l?1) and were significantly correlated with POC, but not with chlorophyll-a concentrations. When total suspended particulate (TSP) concentrations were below 20 to 30 mg l?1, there were significant increases in %POC and %PON of the TSP. The unusually high POC: chlorophyll-a ratios (highest value of 1423) suggested that much of the POC contained low concentrations of chlorophyll-a that had degraded during transport from wetlands in the Sabine and Neches rivers. Based on these data, this estuary can be characterized as a predominantly heterotrophic system, with low light penetrance, short particle-residence times, high DOC, and low inputs from autochthonous carbon sources.  相似文献   

9.
The supply of nutrients from surface and subsurface water flow into the root zone was measured in a developing barrier island marsh in Virginia. We hypothesize that high production of tall-formSpartina alterniflora in the lower intertidal zone is due to a greater nitrogen input supplied by a larger subsurface flux. Individual nitrogen inputs to the tall-form and short-formS. alterniflora root zones were calculated from water flow rates into the root zone and the nutrient concentration corresponding to the source of the flow. Total dissolved inorganic nitrogen (DIN) input (as ammonium and nitrate) was then calculated using a summation of the hourly nutrient inputs to the root zone over the entire tidal cycle based on hydrologic and nutrient data collected throughout the growing season (April–August) of 1993 and 1994. Additionally, horizontal water flow into the lower intertidal marsh was reduced experimentally to determine its effects on nutrient input and plant growth. Total ammonium (NH4 +) input to the tall-formS. alterniflora root zone (168 μmoles 6 h?1) was significantly greater relative to the short-form (45 μmoles 6 h?1) during flood tide. Total NH4 + input was not significantly different between growth forms during ebb tide, and total nitrate (NO3 ?) and total DIN input were not significantly different between growth forms during either tidal stage. During tidal flooding, vertical flow from below the root zone accounted for 71% and horizontal flow from the adjacent mudflat accounted for 19% of the total NH4 + input to the tall-formS. alterniflora root zone. Infiltration of flooding water accounted for 15% more of the total NO3 ? input relative to the total NH4 + input at both zones on flood tide. During ebb tide, vertical flow from below the root zone still accounted for the majority of NH4 + and NO3 ? input to both growth forms. After vertical flow, horizontal subsurface flow from upgradient accounted for the next largest percentages of NH4 + and NO3 ? input to both growth forms during ebb tide. After 2 yr of interrupted subsurface horizontal flow to the tall-formS. alterniflora root zone, height and nitrogen content of leaf tissue of treatment plants were only slightly, but significantly, lower than control plants. The results suggest that a dynamic supply of DIN (as influenced by subsurface water flows) is a more accurate depiction of nutrient supply to macrophytes in this developing marsh, relative to standing stock nutrient concentrations. The dynamic subsurface supply of DIN may play a role in spatial patterns of abovegroundS. alterniflora production, but determination of additional nitrogen inputs and the role of belowground production on nitrogen demand need to also be considered.  相似文献   

10.
The re-vegetation of soils contaminated by potentially harmful metals is generally considered a suitable option to reduce the metal dispersion in surrounding environments. A continuous flow experiment was conducted to quantitatively assess the effect of Italian ryegrass (Lolium multiflorum Lam.) root activity on the weathering of smithsonite (ZnCO3), a common Zn mineral. At the end of the experiment (10 days), the total amount of Zn released by smithsonite was increased by a factor of 2.25 in the presence of plants. This increase was due not only to plant uptake but also to the enhancement of the Zn release into leachates. The rate of Zn release from smithsonite to leachates was 2.9 × 10−4 μg g−1 s−1 and 1.5 × 10−4 μg g−1 s−1 in the presence and the absence of plants, respectively. The strong correlation (r = 0.95; p < 0.001) between concentrations of Zn and dissolved organic C (DOC) produced by the rhizosphere activity in leachates indicated that organic root exudates and secretions were closely involved in smithsonite weathering. Although the results are derived from laboratory study, and further in situ investigations over the long term are needed, they clearly highlighted that plants can enhance metal release into the environment by accelerating mineral weathering. Therefore, it is suggested that the ability of plants to alter metal phases in soils should be further taken into account when re-vegetation strategies are proposed for the rehabilitation of metal-polluted soils.  相似文献   

11.
Brazil has extensive sugar cane monocultures, which significantly alter hydrogeochemical material fluxes. We studied dissolved organic matter (OM) fluxes in the Manguaba lagoon-estuary system, which drains a sugar cane monoculture-dominated hinterland and discharges into the Atlantic coastal ocean. The OM fluxes into the lagoon originate from baseflow, field runoff and sugar cane factory effluents. In the study, dissolved organic carbon (DOC) concentration, δ13C DOC and UV absorbance were analysed along a freshwater-seawater salinity gradient that encompasses river (DOC 9-11 mg l−1, δ13C −22.2‰ to −25.5‰); lagoon (4-11 mg l−1, −20.5‰ to −24.8‰); estuary (3-9 mg l−1, −22.6‰ to −25.3‰) and coastal waters (1.64 mg l−1, −21‰) with different intra-seasonal runoff conditions. We used the carbon isotope data to quantify the sugar cane derived DOC. Where river water meets brackish lagoon water, substantial loss of DOC occurs during rainy conditions, when suspended sediment from eroded fields in the river is very high. During dry weather, at much lower suspension levels, DOC increases, however, presumably from addition of photolysed resuspended sedimentary OM. In the estuary, mixing of DOC is strictly conservative. Ca. 1/3 of riverine DOM discharged into the lagoon has a sugar cane source. Within the lagoon on avg. 20% of the bulk DOM is comprised of sugar cane DOM, whereas during heavy rainfall the amount increases to 31%, due to intensified drainage flow and soil erosion. In the estuary, 14-26% is of sugar cane origin. The sugar cane-derived component follows the mixing patterns of bulk DOM.  相似文献   

12.
《Applied Geochemistry》1993,8(5):483-493
Information regarding the origin, composition and transport of natural dissolved organic carbon (DOC) in groundwater is necessary to understand the transport of metals and organic pollutants, as well as for the use of14C in DOC as an isotopic groundwater dating method. Previous research in several groundwater systems has suggested soil organic C is the predominant source of high molecular weight DOC to the subsurface. Through the use of stable isotopes,14C and geochemical analyses, this study shows that significant concentrations of DOC and CH4 in a regional confined aquifer can be generated in situ from subsurface sedimentary organic sources. The DOC and CH4 produced is a combined result of degradation of buried peats and bacterial action, resulting in high DOC concentrations and strongly methanogenic conditions in the aquifer. The DOC and CH4 comprise, on average, nearly 50% of the total dissolved C pool in the central part of the aquifer. Methanogenic conditions complicate isotopic groundwater dating by the conventional dissolved inorganic carbon (DIC) method. Estimates of isotopic groundwater residence time using DOC14C data are proposed by the application of14C isotope and mass balance corrections.  相似文献   

13.
Isolation and chemical elucidation of dissolved and particulate polysaccharides in seawater were conducted. The water samples were collected in Mikawa Bay, Japan during a red tide bloom of the dinoflagellate, Prorocentrum minimum.Dissolved polysaccharides were concentrated from 5–101 of seawater with dialysis followed by separation by gel flitration, and isolation by ethanol precipitation. A heteropolysaccharide consisting of glucose, galactose, mannose, xylose, arabinose, fucose and rhamnose and a glucan were isolated from the polysaccharide component having a molecular weight more than 4,000 Dalton and were characterized by several chemical analyses. The heteropolysaccharide is a mucilaginous polysaccharide having a highly branched structure and a molecular weight of 104?5 × 106 Daltons and probably contains a sulfate half ester: the glucan is a polysaccharide with β-1,3- and 1,6-linkages (chrysolaminaran type). Concentrations of these were respectively ca. 20 and 67 μg l?1 at 1 m, and 2 and 26 μg l?1 at 6 m.A similar heteropolysaccharide was found in the boiling water extract of the particulate matter, while β-glucan was isolated in a much less purified form than the seawater β-glucan. In addition, a large amount of β-1,4 glucan was found in the strong alkali extract of the particulate matter, indicating that this glucan must be a cell wall polysaccharide derived from phytoplankton. These results strongly suggest that the heteropolysaccharide and chrysolaminaran type polysaccharide dissolved in seawater were derived from water soluble carbohydrates of phytoplankton through extracellular release or cell lysis.  相似文献   

14.
香根草固土护坡工程特性初步研究   总被引：2，自引：0，他引：2  
香根草的根系长度和抗拉力或强度都较大,单根的抗拉力或强度的平均值为12.4N或69.7MPa,而且群根效应显著,对边坡起着“活着的土钉”作用。深扎广布于坡体中的根系网,显著改善边坡土体的物理力学性质,明显提高边坡土体的强度及稳定性,可较大幅度地降低作用于护坡挡墙上的主动土压力强度(总主动土压力的减少值大于15%);浓密成丛的香根草可分散径流和减少径流量,有效降低降雨与径流对坡面的冲击力及侵蚀量,对坡面起到较好的防护作用;此外,光合作用强、速生快长的香根草及其发达根系网的吸收与蒸腾作用,可降低边坡土体中的含水量及孔隙水压力,增强土中吸力,进而提高边坡土体的强度,增强边坡的稳定性;穿扎广布于坡体土中的香根草根系网系统,类似“活性钢筋网”,与边坡体固结共同作用、融合胶结构成类似原位复合的重力墙,可较好地防止及控制边坡位移或失稳的发生。初步研究表明;香根草护坡的力学效果较为理想,且具有较强的经济效益及环境效益优势。  相似文献   

15.
Rhizoliths are defined as organosedimentary structures resulting in the preservation of roots of higher plants, or remains thereof, in mineral matter. They are abundant and characteristic features of Quaternary terrestrial carbonates (calcretes and aeolianites) from coastal regions of the western Mediterranean. Field and petrographic observations indicate that five basic types of rhizoliths can be recognized: (1) root moulds, which are tubular voids that outline positions of former, now decayed roots; (2) root casts, which are sediment- and/or cement-filled root moulds; (3) root tubules, which are cemented cylinders around root moulds; (4) rhizocretions s.s., which are pedodiagenetic mineral accumulations (here low magnesian calcite) around living or dead plant roots; and (5) root petrifactions, which are mineral impregnations or mineral replacements of organic matter whereby anatomical features of roots have been preserved partially or totally. Apart from rhizoliths themselves, roots of higher plants are responsible for the formation of numerous and characteristic features of pedogenetically affected terrestrial carbonates. Plant roots are responsible for, or contribute to, the formation of alveolar textures, in situ brecciation (rhizobrecciation) textures, horizontal sheet cracks, vertically elongate glaebules (concretionary soil structures) and micritization (rhizomicritization) within terrestrial carbonates. Rhizoliths, together with the above features, are products of pedodiagenesis. More significantly, rhizoliths and related features are indicators of palaeosols and hence of subaerial vadose environments in ancient (post-Silurian) successions.  相似文献   

16.
Organic matter is an important factor that cannot be neglected when considering global carbon cycle. New data including organic matter geochemistry at the small watershed scale are needed to elaborate more constrained carbon cycle and climatic models. The objectives are to estimate the DOC and DIC yields exported from small tropical watersheds and to give strong constraints on the carbon hydrodynamic of these systems. To answer these questions, we have studied the geochemistry of eleven small watersheds around Basse-Terre volcanic Island in the French West Indies during different hydrological regimes from 2006 to 2008 (i.e. low water level versus floods). We propose a complete set of carbon measurements, including DOC and DIC concentrations, δ13C data, and less commonly, some spectroscopic indicators of the nature of organic matter. The DOC/DIC ratio varies between 0.07 and 0.30 in low water level and between 0.25 and 1.97 during floods, indicating that organic matter is mainly exported during flood events. On the light of the isotopic composition of DOC, ranging from ? 32.8 to ? 26.2‰ during low water level and from ? 30.1 to ? 27.2‰ during floods, we demonstrate that export of organic carbon is mainly controlled by perennial saprolite groundwaters, except for flood events during which rivers are also strongly influenced by soil erosion. The mean annual yields ranged from 2.5 to 5.7 t km? 2 year? 1 for the DOC and from 4.8 to 19.6 t km? 2 year? 1 for the DIC and exhibit a non-linear relationship with slopes of watersheds. The flash floods explain around 60% of the annual DOC flux and between 25 and 45% of the DIC flux, highlighting the important role of these extreme meteorological events on global carbon export in small tropical volcanic islands. From a carbon mass balance point of view the exports of dissolved carbon from small volcanic islands are important and should be included in global organic carbon budgets.  相似文献   

17.
The investigation of hydrous boro(alumino)silicate melts and glasses with near infrared (NIR) spectroscopy revealed an important effect of boron on the water speciation. In the NIR spectra of B-bearing glasses new hydroxyl-related bands develop at the high frequency side of the 4500 cm−1 peak. In NaAlSi3O8 + B2O3 glasses this new peak is present as a shoulder at 4650 cm−1, and in NaAlSi3O8-NaBSi3O8 (Ab-Rd) glasses it appears as a resolved peak at 4710 cm−1. These bands increase with increasing boron concentration, suggesting that they are due to B-OH complexes. Furthermore, the variations in the NIR spectra indicate that with increasing B-content, but constant total water concentration, the amount of structurally bonded hydroxyl groups increases at the expense of molecular H2O. For example, at a total water concentration of 4 wt.%, pure Rd-glass contains ∼50% more water as hydroxyl groups than pure Ab-glass.In-situ NIR spectroscopy at high P and T using a hydrothermal diamond-anvil cell was used to gain information about the temperature dependence of the water speciation in NaBSi3O8 melts. The data demonstrate the conversion of molecular H2O to hydroxyl groups with increasing temperature. However, a fully quantitative evaluation of the high T spectra was hampered by problems with defining the correct baseline in the spectra. As an alternative approach annealing experiments on a Rd-glass containing 2.8 wt.% water were performed. The results confirm the conversion of H2O to OH groups with increasing T, but also suggest that the OH groups represented by the 4710 cm−1 peak (B-OH) participate much less in the conversion reaction compared to X-OH, represented by the 4500 cm−1 peak.  相似文献   

18.
Transport of dissolved organic carbon (DOC) in four river systems in different physiographic regions of the United States was related to link magnitude by a power function, log Y = ?0.84 + 1.24 log X. Multiple linear regression indicated that discharge, watershed area, and link magnitude explained almost all variation in DOC transport. For purposes of ecosystem comparison, link magnitude appeared superior to other classification systems, such as stream order.In two of the river systems, the largest fraction of DOC was transported in the spring. A third has a winter transport maximum; the last had bimodal spring and fall maxima.Streams transporting similar total amounts of DOC may vary widely in DOC concentration (mg. 1?1). Particulate organic matter concentration was not simply related to that of DOC.Ranges and means of DOC concentration, mean DOC: POC ratios, annual load of transported DOC as well as annual watershed DOC output were tabulated for 45 streams and rivers, representing a broad range of stream systems and physiographic regions. Mean DOC concentration for these 45 waterways ranged from 0.7 to 28 mg. 1?1. The very low DOC values are found in undisturbed streams; many of the higher values are associated with larger streams influenced by human activities. Most DOC outputs fell within the range 0.21–5.42 metric tons. km?2.yr?1; mean DOC:POC ranged between 0.09 and 70.A comparison was made among several biomes of the ratio of experted DOC to watershed gross and net primary production. DOC, while playing a major role in aquatic ecosystem organic budgets, appears to be of little significance in the nutrient balance of watersheds.  相似文献   

19.
Emet Stream is one of the most important branches of Uluabat Lake (Ramsar area) and also one of Turkey’s most important river systems. In addition to the geologic structure of the basin, Harmancik Chromium Mines are one of the most important inorganic pollution sources for the basin and also for Uluabat Lake. In the present study, water, sediment and fish (Squalius cii, Capoeta tinca and Barbus oligolepis) samples were collected seasonally from eight stations (one of them was on the Kinik Stream where the Harmancik Chromium Mines is located on and one of them was on the Dursunbey Stream) on the Emet Stream Basin. Some limnological parameters (pH, conductivity and total hardness) in water and Cr, Ca, Mg, Ni and Mn levels in biotic (muscle, gill, liver and kidney tissues of fishes) and abiotic (water and sediment) components of basin were determined to evaluate the effects of Harmancik Chromium Mines on the system. Cluster Analysis, Factor Analysis, Pearson Correlation Index, One Way Anova Tests, Scatter dot Comparing and Matrix plot Distribution Diagrams were applied to the results in order to estimate the data properly. Water samples were evaluated according to the water quality criteria for Turkey and sediment samples were evaluated according to the sediment quality criteria. According to data obtained, statistically significance differences were identified between Kinik and Emet Streams according to Cr and Ni accumulations in water and sediment. Chromium levels of Kinik Stream were extremely higher an average of 153 times for water and 10 times for sediment than uncontaminated stations. Water and sediment quality of Emet Stream were decreasing after falling the Kinik Stream and increasing after falling the Dursunbey Stream. It was also determined that, the amount of chromium in muscle tissues of three fish species were much higher than the limit value of 0.15 mg kg?1 that FAO identified.  相似文献   

20.
Effect of soil salinity on physico-chemical and biological properties renders the salt-affected soils unsuitable for soil microbial processes and growth of the crop plants. Soil aggregation around roots of the plants is a function of the bacterial exo-polysaccharides (EPS), however, such a role of the EPS-producing bacteria in the saline environments has rarely been investigated. Pot experiments were conducted to observe the effects of inoculating six strains of EPS-producing bacteria on growth of primary (seminal) roots and its relationship with saccharides, cations (Ca2+, Na+, K+) contents and mass of rhizosheath soils of roots of the wheat plants grown in a salt-affected soil. A strong positive relationship of RS with different root growth parameters indicated that an integrated influence of various biotic and abiotic RS factors would have controlled and promoted growth of roots of the inoculated wheat plants. The increase in root growth in turn could help inoculated wheat plants to withstand the negative effects of soil salinity through an enhanced soil water uptake, a restricted Na+ influx in the plants and the accelerated soil microbial process involved in cycling and availability of the soil nutrients to the plants. It was concluded that inoculation of the EPS-producing would be a valuable tool for amelioration and increasing crop productivity of the salt-affected soils.  相似文献   

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