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1.
Effect of temperature on phosphorus sorption to sediments from shallow eutrophic lakes 总被引:3,自引:0,他引:3
Lidong HuangLili Fu Chongwei JinGerty Gielen Xianyong LinHailong Wang Yongsong Zhang 《Ecological Engineering》2011,37(10):1515-1522
The availability of phosphorus (P) in lakes is dependent on the sorption characteristics of the underlying sediments. Temperature is a crucial factor affecting the P sorption in sediments. The objective of this study was to evaluate the effect of temperature on sorption of P by sediments from two eutrophic lakes. The study was carried out using short-term batch experiments at 4, 20 and 30 °C. Phosphorus sorption kinetics, isotherms, fractionation and desorption were investigated. The P sorption was dependent on sediment type and temperature (p < 0.001). The Mei sediments showed a higher sorption rate and sorption capacity than Hua sediments. The P sorption kinetics were best described by a pseudo second order model (R2 > 0.97). Activation energies derived from the kinetics rate constant indicated that P sorption onto the two sediments was controlled by a diffusion process. For both sediments, Freundlich model fit the P sorption isotherms well and the calculated apparent sorption heat was 6.37 kJ mol−1 for Mei sediments and 8.67 kJ mol−1 for Hua sediments. This indicated that P sorption onto both sediments was endothermic. Adding P significantly increased the soluble and loosely bound P (S/L-P), aluminum-bound P (Al-P) and iron-bound P (Fe-P) (p < 0.05). The amount of Al-P and Fe-P was markedly higher at 30 °C than at 4 °C (p < 0.05). Subsequent P desorption indicated that adsorbed P was highly labile, in particular for Hua sediment. The degree of P mobility that occurred during sediment sorption was inversely related to the temperature at the time of sorption. A significant relationship (R2 = 0.978) between phosphorus sorption maximum and oxalate-extractable Fe and Al at different temperatures reflects that the amorphous contents of Fe and Al are responsible for the temperature effect on P sorption. 相似文献
2.
Sediment‐phosphorus dynamics can shift aquatic ecology and cause downstream legacy effects after wildfire in large river systems
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Monica B. Emelko Micheal Stone Uldis Silins Don Allin Adrian L. Collins Chris H. S. Williams Amanda M. Martens Kevin D. Bladon 《Global Change Biology》2016,22(3):1168-1184
Global increases in the occurrence of large, severe wildfires in forested watersheds threaten drinking water supplies and aquatic ecology. Wildfire effects on water quality, particularly nutrient levels and forms, can be significant. The longevity and downstream propagation of these effects as well as the geochemical mechanisms regulating them remain largely undocumented at larger river basin scales. Here, phosphorus (P) speciation and sorption behavior of suspended sediment were examined in two river basins impacted by a severe wildfire in southern Alberta, Canada. Fine‐grained suspended sediments (<125 μm) were sampled continuously during ice‐free conditions over a two‐year period (2009–2010), 6 and 7 years after the wildfire. Suspended sediment samples were collected from upstream reference (unburned) river reaches, multiple tributaries within the burned areas, and from reaches downstream of the burned areas, in the Crowsnest and Castle River basins. Total particulate phosphorus (TPP) and particulate phosphorus forms (nonapatite inorganic P, apatite P, organic P), and the equilibrium phosphorus concentration (EPC0) of suspended sediment were assessed. Concentrations of TPP and the EPC0 were significantly higher downstream of wildfire‐impacted areas compared to reference (unburned) upstream river reaches. Sediments from the burned tributary inputs contained higher levels of bioavailable particulate P (NAIP) – these effects were also observed downstream at larger river basin scales. The release of bioavailable P from postfire, P‐enriched fine sediment is a key mechanism causing these effects in gravel‐bed rivers at larger basin scales. Wildfire‐associated increases in NAIP and the EPC0 persisted 6 and 7 years after wildfire. Accordingly, this work demonstrated that fine sediment in gravel‐bed rivers is a significant, long‐term source of in‐stream bioavailable P that contributes to a legacy of wildfire impacts on downstream water quality, aquatic ecology, and drinking water treatability. 相似文献
3.
Critical nutrient loads to prevent duckweed dominance loads in polder ditches were assessed using the eutrophication model
PCDitch. In this article the ecological target was set at 50% duckweed coverage. This may be very high for ditches with a
nature function, but is not unreasonable for ditches in agricultural areas, with upwelling nutrient rich groundwater, run-off
and drainage. Since the change from a ditch with submersed vegetation to duckweed coverage is often a sudden shift, the choice
of the amount of duckweed coverage does not influence the calculated loading very much. The main topic of this paper is to
present a method to calculate critical loads of nutrients when ecological targets have been set. Sediment type, residence
time and water depth influenced the critical loading rates. The calculated critical phosphorus load ranged from 1.8 to 10.2 g P m−2 year−1, while the calculated critical nitrogen load stretched from 12.1 to 43.8 g N m−2 year−1. The concentration ranges that were derived from the loading rate were 0.19–0.42 mg P l−1 and 1.3–3.3 mg N l−1. Since PCDitch does not distinguish between Lemna spp. and Azolla spp., no definite conclusions were drawn concerning the effects of nitrogen reduction. In a model situation a pristine ditch
was loaded with phosphorus, which resulted into complete duckweed coverage during summer within a few years. When reducing
the phosphorus load, it took 10 years before the original situation was reached again. Dredging would accelerate the process
of recovery significantly, because the water depth would increase and the phosphorus release from the sediments in summer
would decrease.
Received September 2003; accepted in revised form February 2005 相似文献
4.
S. Shukla D. GoswamiW.D. Graham A.W. HodgesM.C. Christman J.M. Knowles 《Ecological Engineering》2011,37(8):1158-1163
Ditch fencing and culvert cattle crossing Best Management Practice (BMP) was evaluated in this study with regard to phosphorus (P) and nitrogen (N) load reductions and economic feasibility in the Lake Okeechobee (LO) basin. The BMP was implemented at a 170 m section of a drainage ditch within a ranch in the LO basin and flow and concentration (N and P) data at the upstream and downstream of the ditch were collected for one pre-BMP (June-October, 2005) and three post-BMP (June-October, 2006-2008) periods. During the pre-BMP period, downstream total P (TP) load was 20% (67.0 kg) higher than the upstream, indicating the cattle crossing to be a source of P. Downstream loads of TP in 2006 and 2008 (post-BMP periods) became 26% (14.7 kg) and 11% (85.9 kg) lower than the upstream loads, respectively indicating that the BMP reduced the P loads. The site was a sink for N for all periods except the 2007. Unusual dry conditions during 2007 resulted in the addition of P and N at the BMP site, probably due to the release of P and N from soil and plants. Average of three post-BMP period load showed a 10% reduction of TP loads at the downstream (251.8 kg) compared to the upstream (281.0 kg) location. To consider potential P contributions from the soil and plant, two scenarios, conservative and liberal, were considered to estimate P load reductions due to the BMP. For the conservative scenario, P contribution from soil and plant was considered, while for liberal it was not. Reductions in P loads for conservative and liberal scenarios were 0.35 and 0.44 kg/day, respectively. Phosphorus removal cost for the conservative scenario was $12.61/kg of P, which is considerably less than the cost of other P reduction strategies in the basin. Overall, results show that the BMP can reduce P concentration and loads from ranches without causing adverse impact on cattle production. 相似文献
5.
MICHAEL J. VANNI WILLIAM H. RENWICK ANNA M. BOWLING MARTIN J. HORGAN ALAN D. CHRISTIAN 《Freshwater Biology》2011,56(5):791-811
1. Catchments export nutrients to aquatic ecosystems at rates and ratios that are strongly influenced by land use practices, and within aquatic ecosystems nutrients can be processed, retained, lost to the atmosphere, or exported downstream. The stoichiometry of carbon and nutrients can influence ecosystem services such as water quality, nutrient limitation, biodiversity, eutrophication and the sequestration of nutrients and carbon in sediments. However, we know little about how nutrient stoichiometry varies along the pathway from terrestrial landscapes through aquatic systems. 2. We studied the stoichiometry of nitrogen and phosphorus exported by three catchments of contrasting land use (forest versus agriculture) and in the water column and sediments of downstream reservoirs. We also related stoichiometry to phytoplankton nutrient limitation and the abundance of heterocystous cyanobacteria. 3. The total N : P of stream exports varied greatly among catchments and was 18, 54 and 140 (molar) in the forested, mixed‐use and agricultural catchment, respectively. Total N : P in the mixed layers of the lakes was less variable but ordered similarly: 35, 52 132 in the forested, mixed‐use and agricultural lake, respectively. In contrast, there was little variation among systems in the C : N and C : P ratios of catchment exports or in reservoir seston. 4. Phytoplankton in the forested lake were consistently N limited, those in the agricultural lake were consistently P limited, and those in the mixed‐use lake shifted seasonally from P‐ to N limitation, reflecting N : P supply ratios. Total phytoplankton and cyanobacteria biomass were highest in the agricultural lake, but heterocystous (potentially N fixing) cyanobacteria were most abundant in the forested lake, corresponding to low N : P ratios. 5. Despite large differences in catchment export and water column N : P ratios, the N : P of sediment burial (integrated over several decades) was very low and remarkably similar (4.3–7.3) across reservoirs. N and P budgets constructed for the agricultural reservoir suggested that denitrification could be a major loss of N, and may help explain the relatively low N : P of buried sediment. 6. Our results show congruence between the catchment export N : P, reservoir N : P, phytoplankton N versus P limitation and the dominance of heterocystous cyanobacteria. However, the N : P stoichiometry of sediments retained in the lakes was relatively insensitive to catchment stoichiometry, suggesting that a common set of biogeochemical processes constrains sediment N : P across lakes of contrasting catchment land use. 相似文献
6.
The translocation of phosphorus (P) from terrestrial landscapes to aquatic bodies is of concern due to the impact of elevated P on aquatic system functioning and integrity. Due to their common location in depressions within landscapes, wetlands, including so-called geographically isolated wetlands (GIWs), receive and process entrained P. The ability of depressional wetlands, or GIWs, to sequester P may vary by wetland type or by land use modality. In this study we quantified three measures of P sorption capacities for two common GIW types (i.e., emergent marsh and forested wetlands) in two different land use modalities (i.e., agricultural and least impacted land uses) across 55 sites in Florida, USA. The equilibrium P concentration (EPC0) averaged 6.42 ± 5.18 mg P L?1 (standard deviation reported throughout); and ranged from 0.01–27.18 mg P L?1; there were no differences between GIW type or land use modality, nor interaction effects. Significant differences in phosphorus buffering capacity (PBC) were found between GIW types and land use, but no interaction effects. Forested GIWs [average 306.64 ± 229.63 (mg P kg?1) (µg P L?1)?1], and GIWs in agricultural settings [average 269.95 ± 236.87 (mg P kg?1) (µg P L?1)?1] had the highest PBC values. The maximum sorption capacity (Smax) was found to only differ by type, with forested wetlands (1274.5 ± 1315.7 mg P kg?1) having over three times the capacity of emergent GIWs (417.5 ± 534.6 mg P kg?1). Classification trees suggested GIW soil parameters of bulk density, organic content, and concentrations of total P, H2O-extractable P, and HCl-extractable P were important to classifying GIW P-sorption metrics. We conclude that GIWs have high potential to retain P, but that the entrained P may be remobilized to the wetland water column depending on storm and groundwater input P concentrations. The relative hydrologic dis-connectivity of GIWs from other aquatic systems may provide sufficient retention time to retain elevated P within these systems, thereby providing an ecosystem service to downstream waters. 相似文献
7.
Reversibility of phosphorus sorption by ferruginous nodules 总被引:1,自引:0,他引:1
Ferruginous nodules sorb significant amounts of available soil and fertiliser phosphate. The effect of this sorption on phosphorus
availability of an agricultural soil was tested by sequential extraction and by exhaustive cropping with millet (Pennisetum typhoides) in a greenhouse trial following fertilisation of the original soil containing 70% nodules and of prepared samples containing
various mixes of separated soil fines and nodules. Phosphorus sorption maxima by the soil fines and nodules were 190 mg kg−1 and 380 mg kg−1 respectively. Samples of fines and nodules which had sorbed 110 and 194 mg kg−1 were submitted to 8 successive extractions with 0.01 M KCl, after which P desorption amounted to 117 mg kg−1 and 103 mg kg−1 respectively. Hysteresis between sorption and desorption was negligible for the soil fines and increased with increasing
nodule content of the samples. In the greenhouse experiment, P uptake at the first cropping was highest in the soil fines
at all levels of phosphorus applied. Subsequent croppings, however, showed higher P uptake in the concretionary soils. These
results indicate a higher initial P release from the soil fines with cropping followed by an earlier exhaustion of phosphorus.
At the end of the greenhouse experiment, yields were low in spite of the large quantities of P still remaining in the soils.
Phosphorus fractionation showed that, of the P left in the soil after cropping 20% was in labile, 29% in Fe or Al-associated,
and 51% in low-availability forms. 相似文献
8.
The heavy use of fertilizers in agricultural lands can result in significant nitrate (NO3−) loadings to the aquatic environment. We hypothesized that biological denitrification in agricultural ditches and streams could be enhanced by adding elemental sulfur (So) to the sediment layer, where it could act as a biofilm support and electron donor. Using a bench-scale stream mesocosm with a bed of So granules, we explored NO3− removal fluxes as a function of the effluent NO3− concentrations. With effluent NO3− ranging from 0.5 mg N L−1 to 4.1 mg N L−1, NO3− removal fluxes ranged from 228 mg N m−2 d−1 to 708 mg N m−2 d−1. This is as much as 100 times higher than for agricultural drainage streams. Sulfate (SO42−) production was high due to aerobic sulfur oxidation. Molecular studies demonstrated that the So amendment selected for Thiobacillus species, and that no special inoculum was required for establishing a So-based autotrophic denitrifying community. Modeling studies suggested that denitrification was diffusion limited, and advective flow through the bed would greatly enhance NO3− removal fluxes. Our results indicate that amendment with So is an effective means to stimulate denitrification in a stream environment. To minimize SO42− production, it may be better to place So deeper in the sediment layer. 相似文献
9.
We evaluated the P sources (point, diffuse), through a nested watershed approach investigating the Blaise (607 km2), dominated by livestock farming, the Grand Morin (1202 km2), dominated by crop farming, and the Marne (12,762 km2), influenced by both agriculture and urbanization. Fertilizers account for the main P inputs (>60%) to the soils. An agricultural P surplus (0.5–8 kg P ha–1 year–1) contributes to P enrichment of the soil. The downstream urbanized zone is dominated by point sources (60%, mainly in dissolved forms), whereas in the upstream basin diffuse sources dominate (60%, mostly particulate). Among the diffuse sources (losses by forests, drainage and runoff), losses by runoff clearly dominate (>90%). P retention in the alluvial plain and the reservoir represents 15–30% of the total P inputs. Dissolved and particulate P fluxes at the outlet of the Marne are similar (340 and 319 tons of P year–1, respectively). The Blaise sub-basin receives P from point and diffuse sources in equal proportions, and retention is negligible. The Grand-Morin sub-basin, influenced by the urbanized zone receives, as does to the whole Marne basin, 60% of P inputs as point sources. The total particulate phosphorus in suspended sediments averaged 1.28 g P kg–1, of which about 60% are inorganic and 40% organic P. Particulate phosphorus exchangeable in 1 week and 1 year (32P isotopic method) accounts for between almost 26% and 54% of the particulate inorganic phosphorus in the suspended sediment and might represent an important source of dissolved P, possibly directly assimilated by the vegetation. 相似文献
10.
Patterns in substrate, canopy openness, tree species composition and structure were studied in a swamp forest in southeastern Brazil (Itirapina, SP), using a fine spatial scale (∼0.05 km2). Sixty quadrats of 10 m × 10 m were divided into three sample plots, located in the centre and at both ends of the forest remnant (upstream and downstream), encompassing different environmental conditions. In each quadrat we quantified and identified individuals with CBH (circumference at breast height) ≥ 10 cm, the chemical properties of the soil, the drainage (flooded area) and the percentage of canopy openness. We keep 5124 individuals distributed over 37 species and 25 families. The downstream site presented a lower frequency of flooding, canopy openness, species richness (15 species) and density of individuals. In the central site we found different patterns of drainage and light incidence, the greatest species richness (31 species) and density of individuals, but smaller trees both in height and in diameter. The upstream site was subject to higher frequency of flooding, with intermediate values for density and species richness (27 species). Floristic and structural variation between and within sites reflects the different environmental conditions related to substrate and canopy openness. However, a larger number of species were correlated with drainage pattern (21 species) rather than with canopy openness (14 species), suggesting that the main factor responsible for the spatial organization of the plant community in swamp forests is soil drainage. 相似文献
11.
Nitrogen removal in subsurface water by narrow buffer strips in the intensive farming landscape of the Po River watershed, Italy 总被引:1,自引:0,他引:1
Raffaella Balestrini Cristina AreseCarlo Andrea Delconte Alessandro LottiFranco Salerno 《Ecological Engineering》2011,37(2):148-157
In many countries buffer strips have become an important management tool widely accepted for controlling the diffuse pollution and supporting the development of more sustainable agriculture. However, there is the need to investigate their role in intensive farming systems where a realistic and shareable proposal to realize buffer strips can only foresee the use of a limited space. We evaluated the nitrogen buffering capacities of two narrow riparian strips (5-8 m) along irrigation ditches located in a typical flat agricultural watershed of the alluvial plain of the River Po (Northern Italy). Subsurface water level and nutrient concentrations were monitored along transects of piezometers installed from crop fields to ditches in two different areas. Spatial and temporal variation in water chemistry and hydrology were investigated to individuate the main processes (biological or physical) leading to groundwater nitrate depletion related to fertilization, pluviometric regime and seasonal variation. The results obtained indicate an elevated nitrate removal efficiency in both riparian areas. Compared to the high mean concentrations measured at the exit of the crop fields (10-90 mg l−1 N-NO3−), nitrate levels within riparian sites can be very low, completely disappearing below the ditches. The patterns of some chemical species (O2, SO42− and HCO3−) and the potential denitrification rates suggest that denitrification plays a predominant role in the N-NO3− depletion observed in the first few meters of the herbaceous strip. The key factors in the system are the elevated groundwater residence time and the effect of the evapotranspiration. The water uptake by woody vegetation affects the subsurface water to flow through the riparian zone and, at the same time, it contributes to completely remove the nitrate from the groundwater.Our findings also suggest the double role of riparian vegetation both in ecohydrological and biological terms. In fact the water uptake by trees affects the subsurface flow pattern and contributes to completely remove the nitrate in the riparian zone. 相似文献
12.
Concentration and transport of dissolved and suspended substances in the Orinoco River 总被引:11,自引:4,他引:7
The Orinoco River, which is hydrologically unregulated and has a minimally disturbed watershed, was sampled quantitatively
over a four-year interval. In conjunction with the sampling, a method was developed for quantifying statistical uncertainty
in the estimates of annual transport. The discharge-weighted mean concentration of total suspended solids in the Orinoco River
is 80 mg/l, which corresponds to total annual transport of 90 × 106 t/y, or, expressed per unit of watershed area, 960 kg/ha/y, of which 96% is inorganic. The mean for dissolved solids is 34
mg/l, of which 25 mg/l is inorganic. The total transport of inorganic material, with a small allowance for bedload, is 128
× 106 t/y, which corresponds to an erosion rate of 4 cm/1000 y. Concentrations of dissolved and suspended constituents derived
from rock weathering are very low because of dilution from high runoff (1190 mm/y), coverage of the southern part of the drainage
by shield rock, and minimal watershed disturbance. Seasonal patterns in dissolved and suspended constituents are repeated
with a high degree of consistency from one year to the next.
For most variables, relationships between transport and discharge are described adequately by a power function. There are
three categories of response to changing discharge: purging (exponent > 1: soluble organic fractions and all particulate fractions),
dilution (exponent 0–1: major ionic solids and silicon), and conservation (exponent < 0: nitrate, interannual). Variability
across seasons and across years is highest for the particulate constituents, but within this group variability is lower for
the organic than for the inorganic components. Major ions that originate primarily from the atmosphere have a higher seasonal
variability than major ions that originate primarily from weathering. Potassium and soluble silicon have the lowest variabilities.
Variability is much lower across years than across seasons for most constituents.
Because of high runoff per unit area, the Orinoco drainage has a high specific transport of organic carbon (72 kg/ha/y, 6.8
× 106 t/y, 1.6% of global river transport), even though the concentrations of organic carbon in the river are not exceptionally
high (mean, 4.4 mg/l dissolved, 1.4 mg/l particulate). Concentrations of ammonium (35 μg/l as N) and of nitrate (80 μg/l as
N) are high given the undisturbed nature of the watershed and the high amount of runoff. The high transport rate for total
nitrogen (5.7 kg/ha/y, 0.54 × 106 t/y, l.5% of global river transport) can be sustained only by high rates of nitrogen fixation within the watershed. Concentrations
of soluble phosphorus are within the range expected for undisturbed river systems (20 μg/l), but concentrations of particulate
phosphorus are low because the amounts of particulate matter are small and the phosphorus per unit weight of suspended matter
is low. Phosphorus transport (0.75 kg/ha/y) can be accounted for easily by weathering of the parent material, even within
the Guayana Shield, where weathering rates are lowest. Biological modification of nutrient and carbon fractions during transit
along the main stem are minimal. 相似文献
13.
Quantification of the factors affecting phosphorus (P) loading to surface waters is important in assessing the contribution from agricultural activities to water quality. This study investigated the long-term impact of applications of P in poultry litter on the loadings of P and sediment to streams in two subbasins of the Illinois River Watershed. The influences of application rate and environmental characteristics were examined utilizing a transport model, a geographical information system (GIS), and 30 years of daily weather data. Simulated runoff and sediment concentrations of P increased linearly with poultry litter application rate. Most P loadings to streams were in the dissolved form, as overall sediment transport was low, particularly in areas with excellent stands of forage. Because only pasturelands received poultry litter and the initial concentrations of P in the soils in the forested areas were low, the forested areas contributed little runoff and sediment P to streams. Areas of high P loadings coincided with soils having high Curve Numbers (CN) and poor internal drainage. Therefore, subbasins of the watershed containing a greater proportion of pasture and soils with poor drainage characteristics have higher loading rates to streams. Predicted runoff, sediment, and P loadings in both subbasins were highly variable. 相似文献
14.
In this study we compared the biodiversity of five waterbody types (ditches, lakes, ponds, rivers and streams) within an agricultural
study area in lowland England to assess their relative contribution to the plant and macroinvertebrate species richness and
rarity of the region. We used a Geographical Information System (GIS) to compare the catchment areas and landuse composition
for each of these waterbody types to assess the feasibility of deintensifying land to levels identified in the literature
as acceptable for aquatic biota. Ponds supported the highest number of species and had the highest index of species rarity
across the study area. Catchment areas associated with the different waterbody types differed significantly, with rivers having
the largest average catchment sizes and ponds the smallest. The important contribution made to regional aquatic biodiversity
by small waterbodies and in particular ponds, combined with their characteristically small catchment areas, means that they
are amongst the most valuable, and potentially amongst the easiest, of waterbody types to protect. Given the limited area
of land that may be available for the protection of aquatic biodiversity in agricultural landscapes, the deintensification
of such small catchments (which can be termed microcatchments) could be an important addition to the measures used to protect
aquatic biodiversity, enabling ‘pockets’ of high aquatic biodiversity to occur within working agricultural landscapes.
Guest editors: R. Céréghino, J. Biggs, B. Oertli & S. Declerck
The ecology of European ponds: defining the characteristics of a neglected freshwater habitat 相似文献
15.
Phosphorus release from cyanobacterial blooms in Meiliang Bay of Lake Taihu, China 总被引:11,自引:0,他引:11
Xiaoming ChuaiWei Ding Xiaofeng ChenXiaolin Wang Aijun MiaoBeidou Xi Lianshen HeLiuyan Yang 《Ecological Engineering》2011,37(6):842-849
To investigate the relationship between cyanobacterial density and phosphorus release into a lake aquatic environment, in situ experiments with 2.5 L microcosms were conducted in Meiliang Bay, located in the northern part of Lake Taihu, China. The effects of different environmental factors on phosphorus release and the ways changes of water quality indexes are involved in phosphorus release were further examined. It was found that total dissolved phosphorus (TDP) concentration kept to low levels (around 0.488 mg L−1) in the microcosm with the low cyanobacterial density (8.85 × 107 cell L−1) throughout the experimental period, whereas first-order kinetics of TDP release was observed in microcosms with intermediate (7.60 × 108 cell L−1) and high cyanobacterial density (3.65 × 109 cell L−1). Accordingly their TDP release rate constants were both approximately 0.8930 d−1 in the latter two treatments. The dissolved inorganic phosphorus (DIP) concentrations also increased with the increase of cyanobacterial density in 4 days. However, the DIP decreased from 35.52 mg L−1 on day 4 to 6.72 mg L−1 on day 6 in microcosm with the high cyanobacterial density during the experiments. Temperature could remarkably improve phosphorus release, while disturbance and illumination had negative effects on it. In addition, both TDP and DIP concentrations were positively correlated with electronic conductivity, salinity and total dissolved solid, but negatively correlated to chlorophyll-a and cyanobacterial density when cyanobacterial density was more than 7.60 × 108 cell L−1. Thus, more phosphorus can be released from cyanobacterial blooms at higher cyanobacterial densities in Meiliang Bay, which is also determined by high temperature. Higher dissolved phosphorus concentration in cyanobacteria-dominated lakes (regions) is mainly due to the decomposition of cyanobacteria during the outbreak of cyanobacterial bloom in Lake Taihu, especially in Meiliang Bay. 相似文献
16.
Toshikazu Kizuka Hiroyuki Yamada Masao Yazawa Hoi-Hoon Chung 《Landscape and Ecological Engineering》2008,4(1):27-37
Concomitant with farmland development in the Ishikari Peatland of northern Japan, deterioration of water chemistry has become
increasingly evident at mire pools there. Using spatial analysis methods with a geographic information system and a statistical
methodology, this study examined the effects of agricultural land use on the pool water chemistry. A water chemistry survey
of several pools showed that nitrogen, phosphorus, and suspended-solid concentrations were remarkably higher than those in
pools that had been undisturbed or less-disturbed by land-use development. Principal component analysis (PCA) was conducted
to summarize water chemistry variables. Correlation analysis was conducted between the principal component (PC) scores and
land-use variables to clarify land-use effects. Results of the PCA showed that the water chemistry variances were accounted
for by the first two PCs: PC1 included farmland subsurface drainage containing nitrogen, specifically nitrate, and mineral
ions; PC2 included farmland surface drainage containing soil particles and ammonium nitrogen. These PC scores were also affected
by the number of inflow ditches and the total area of farmland located within the drainage catchment of inflow ditches leading
to the pools. Results suggest that farmland subsurface and surface drainage water flowing into the pools degraded the water
chemistry. The extent of the effects of drainage water depended on agricultural practices such as fertilizer application and
paddy-field puddling (i.e., mechanical homogenization of water-saturated soil). Accordingly, water chemistry of the study
pools was affected by agricultural practices and by the amount of farmland in the drainage basin, engendering eutrophication,
and the deterioration of water chemistry. Therefore, preservation of water chemistry necessitates changes in agricultural
practices, such as improving fertilizer application methods, along with measures related to land-use planning such as changing
the drainage ditches’ flow direction. 相似文献
17.
Drainage ditching at the catchment scale affects water quality and macrophyte occurrence in Swedish lakes 总被引:1,自引:0,他引:1
FRAUKE ECKE 《Freshwater Biology》2009,54(1):119-126
1. We have limited knowledge of the effects of land use in general and of drainage ditching in particular on macrophyte communities in lakes. I quantified catchment land use, including drainage ditching, as well as water quality and the number of macrophyte species in 17 Swedish lakes in summer 2005. 2. Land use within 1 km of the studied lakes was analysed in a geographic information system. The following variables were included: areas of forests, mires, agricultural land and urbanization, length of drainage ditches (classified according to the use of the land they drained), and shortest distance from lake to an urban area. To extract and analyse general trends in the data sets, redundancy analysis was used. 3. Water quality was explained mainly by three land‐use related variables: the lengths of agricultural, forest and mire ditches. The length of agricultural ditches was positively correlated with lake water conductivity, total dissolved solids, Ca, N and total organic carbon (TOC). The lengths of forest and mire ditches were positively correlated with lake water characteristics, especially TOC. 4. The number of species representing different macrophyte life forms was explained by three environmental variables: conductivity, and lengths of forest and agricultural ditches. The numbers of isoetids, nymphaeids, elodeids and total obligate hydrophytes were negatively correlated with length of forest ditches. In contrast, the number of lemnids and helophytes was positively correlated with conductivity and length of agricultural ditches. Furthermore, the number of isoetids was exponentially related (negatively) to lengths of agricultural and forest ditches, indicating a threshold response to drainage ditch length. 5. The results suggest that effects on water quality and macrophyte communities result from drainage ditching in the lake catchments rather than from land use itself. Given the total area of drainage‐ditched land worldwide (millions of ha in Scandinavia alone), drainage ditching should be considered when evaluating environmental impacts on lake water quality and macrophyte occurrence and when determining reference conditions for catchment land use. 相似文献
18.
Dagmara Sirová Jakub Borovec Barbora Černá Eliška Rejmánková Lubomír Adamec Jaroslav Vrba 《Aquatic Botany》2009
We examined trap fluid of three aquatic carnivorous species of Utricularia (Lentibulariaceae) to assess the role of microbial community within their traps in plant nutrient acquisition. In the context of increasing trap age, we characterized microbial community composition using phospholipid fatty acid (PLFA) analysis and microscopy. Nutrient content in various fractions of the trap fluid was analyzed and the abundance of free-suspended bacteria estimated. The activities of extracellular phosphatase in the trap fluid were determined using fluorometry and the contribution of the microbial community to phosphatase production assessed by epifluorescence microscopy. The trap microbial community seems to be largely derived from Utricularia associated periphyton. PLFA analysis revealed that trap fluid contained all components of a complex microbial food web with bacteria forming more than 58% of the viable microbial biomass in the trap. Trap age seems to be the key factor in determining the patterns of microbial community development as well as enzyme production. The amount of nutrients increases with increasing trap age, and the total amounts of C, N, and P accumulated within traps during their lifetime are relatively large—of the order of 100 mg L−1 for C and N, and between 0.2 and 0.6 mg L−1 for P. A significant part of the nutrient pool is present in the dissolved form. Trap fluid stoichiometry (molar N:P ratios about 100) as well as the presence of nutrient limited microbial cells (molar N:P ratios 25–61) indicates the importance of phosphorus rather than nitrogen for the nutrition of Utricularia. Our findings support the hypothesis that mutualism, apart from the predator–prey interaction, is an important association in aquatic Utricularia traps and that the trap-associated microbial community may be of benefit to the rootless aquatic Utricularia species facing problems with P acquisition due to the loss of roots in their evolution. 相似文献
19.
Jacob L. Krans Karen D. Parfitt Patricia K. Rivlin 《Journal of insect physiology》2010,56(3):304-7885
The resting membrane potential (RMP) of most cells is not greatly influenced by the transmembrane calcium gradient because at rest, the membrane has very low permeability to calcium. We have observed, however, that the resting membrane potential of muscle cells in the larval bodywall of Drosophila melanogaster varies widely as the external calcium concentration is modified. The RMP depolarized as much as 21.8 mV/mM calcium at low concentrations, and on average, about 10 mV/mM across a range typical of neurophysiological investigations. The extent to which muscle RMP varies has important implications for the measurement of synaptic potentials as well. Two parameters of excitatory junctional potential (EJP) voltage were compared across a range of RMPs. EJP amplitude (ΔV) and peak voltage (maxima) change as a function of RMP; on average, a 10 mV change in RMP elicits a 4-5 mV change in EJP amplitude and peak voltage. The influence of the calcium gradient on resting and synaptic membrane potentials led us to investigate the endogenous ion concentrations of larval hemolymph. In addition to the major monovalent ions and calcium, we report the first voltammetric analysis of magnesium concentration in larval fruit fly hemolymph. 相似文献
20.
Phosphorus retention in lab and field-scale subsurface-flow wetlands treating plant nursery runoff 总被引:1,自引:0,他引:1
Sarah A. White Milton D. Taylor Joseph P. Albano Ted Whitwell Stephen J. Klaine 《Ecological Engineering》2011,37(12):1968-1976
Constructed wetland systems built to handle nutrient contaminants are often efficient at removing nitrogen, but ineffective at reducing phosphorus (P) loads. Incorporating a clay-based substrate can enhance P removal in subsurface-flow constructed wetland systems. We evaluated the potential of crushed brick, a recycled building product, and two particle sizes of a palygorskite–bentonite industrial mineral aggregate (calcined clay) to sorb P from simulated nutrient-rich plant nursery effluent. The three substrates were screened for P sorbing behavior using sorption, desorption, and equilibration experiments. We selected one substrate to evaluate in an 8-month field trial to compare field sorption capacity with laboratory sorption capacity. In the laboratory, coarse calcined clay average sorption capacity was 497 mg kg−1 and it sorbed the highest percentage of P supplied (76%), except at exposure concentrations >100 mg L−1 where the increased surface area of fine calcined clay augmented its P sorption capacity. Subsurface-flow mesocosms were filled with coarse calcined clay and exposed to a four and seven day hydraulic retention time treatment. Phosphorus export was reduced by 60 to 74% for both treatments until substrate P-binding sites began to saturate during month seven. During the eight month experiment, the four and seven day treatments fixed 1273 ± 22 mg kg−1 P and 937 ± 16 mg kg−1 P, respectively. Sequential extractions of the P saturated clay indicated that P could desorb slowly over time from various pools within the calcined clay; thus, if the calcined clay were recycled as a soil amendment, most P released would be slowly available for plant uptake and use. This study demonstrated the viability of using coarse calcined clay as a root bed substrate in subsurface-flow treatment wetlands remediating phosphorus from plant nursery runoff. 相似文献