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1.
Measurements of transpiration from individual trees of Eucalyptus from plantations at four different sites in Karnataka, Southern India, are presented. These show large (as much as tenfold) differences in the transpiration between premonsoon and postmonsoon periods, a reflection of the effects of soil-moisture stress in the premonsoon periods. For trees with diameters at breast height (DBH) less than 10 cm the transpiration rate of individual trees is proportional to the square of the DBH. For trees which are not experiencing soil-water stress the daily transpiration rate of individual trees, q, is well represented by the relation: q = (6.6 ± 0.3)g (m3 day−1 where g (m2) is the tree basal area. On a unit ground area basis the transpiration rate, expressed as a depth per day is given by the relation: Et = (0.66 ± 0.03)G (mm day−1 where g(m2ha−1) is the total basal area per hectare. For all the sites studied, although there is evidence for the ‘mining’ of soil water as roots penetrate deeper depths in the soil each year, there is no evidence for direct abstraction from the water table.  相似文献   

2.
Xiao-Yan Li   《Journal of Hydrology》2002,260(1-4):151-160
Information regarding dew deposition on the stone-covered surface is scarce. The effects of gravel and sand mulches on dew condensation were studied during the late summer and fall of 1999 in the semiarid loess region of China. The results indicated that there were significant difference in daily dew amount between gravel mulch, sand mulch and dry loess soil (control). The average dew amount for gravel mulch was 0.071 mm d−1 with extreme 0.022 and 0.20 mm d−1. The average values for sand mulch and dry loess soil was 0.12 and 0.15 mm d−1, respectively. The minimum dew amount was 0.048 mm d−1 for sand mulch and 0.071 mm d−1 for dry loess soil, and the maximum dew amount was approximate 0.25 mm d−1 for both treatments. The results suggest that surface stone mulch can reduce dew deposition as compared to sand and dry loess soil.  相似文献   

3.
Playa systems are driven by evaporation processes, yet the mechanisms by which evaporation occurs through playa salt crusts are still poorly understood. In this study we examine playa evaporation as it relates to land surface energy fluxes, salt crust characteristics, groundwater and climate at the Salar de Atacama, a 3000 km2 playa in northern Chile containing a uniquely broad range of salt crust types. Land surface energy budget measurements were taken at eight representative sites on this playa during winter (August 2001) and summer (January 2002) seasons. Measured values of net all-wave radiation were highest at vegetated and rough halite crust sites and lowest over smooth, highly reflective salt crusts. Over most of the Salar de Atacama, net radiation was dissipated by means of soil and sensible heat fluxes. Dry salt crusts tended to heat and cool very quickly, whereas soil heating and cooling occurred more gradually at wetter vegetated sites. Sensible heating was strongly linked to wind patterns, with highest sensible heat fluxes occurring on summer days with strong afternoon winds. Very little energy available at the land surface was used to evaporate water. Eddy covariance measurements could only constrain evaporation rates to within 0.1 mm d−1, and some measured evaporation rates were less than this margin of uncertainty. Evaporation rates ranged from 0.1 to 1.1 mm d−1 in smooth salt crusts around the margin of the salar and from 0.4 to 2.8 mm d−1 in vegetated areas. No evaporation was detected from the rugged halite salt crust that covers the interior of the salar, though the depth to groundwater is less than 1 m in this area. These crusts therefore represent a previously unrecorded end member condition in which the salt crusts form a practically impermeable barrier to evaporation.  相似文献   

4.
Canopy interception and its evaporation into the atmosphere during irrigation or a rainfall event are important in irrigation scheduling, but are challenging to estimate using conventional methods. This study introduces a new approach to estimate the canopy interception from measurements of actual total evapotranspiration (ET) using eddy covariance and estimation of the transpiration from measurements of sap flow. The measurements were conducted over a small‐scale sprinkler‐irrigated cotton field before, during and after sprinkler irrigation. Evaporation and sap flow dynamics during irrigation show that the total ET during irrigation increased significantly because of the evaporation of free intercepted water while transpiration was suppressed almost completely. The difference between actual ET and transpiration (sap flow) during and immediately following irrigation (post irrigation) represents the total canopy evaporation while the canopy interception capacity was calculated as the difference between actual ET and transpiration (sap flow) during drying (post irrigation) following cessation of the irrigation. The canopy evaporation of cotton canopy was calculated as 0.8 mm, and the interception capacity was estimated to be 0.31 mm of water. The measurement uncertainty in both the non‐dimensional ET and non‐dimensional sap flow was shown to be very low. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

5.
Accurate estimation of the resistances to water vapor movement is a major difficulty in evaluating evaporation from soil. By including the temperature of a dry soil surface (the temperature of the surface of a dry soil column buried in the field), a method for estimating evaporation from soil is proposed. The necessary input variables for the suggested method are temperature, net radiation, and soil heat flux. There are three advantages of the proposed method over the conventional methods. First, soil surface resistance and aerodynamic resistance are not required. Second, the variables included are fewer. Third, measurement and analysis of the parameters involved are relatively easy. Sensitivity analysis shows that the suggested method is sensitive to temperatures. Test experiments were conducted in a sandy field, where a weighing lysimeter was installed. Evaporation from soil, together with the variables specified above, were measured. For temperatures measured by thermocouples, experimental results showed that the mean absolute error (MAE) for the daily evaporation over 22 days was 0.17 mm day−1. The regression between calculated and measured evaporation was highly significant (r2=0.89). Moreover, the intercept and slope of the regression equation were not significantly different from zero and unity, respectively, at the 0.05 probability level. Furthermore, by using the temperatures measured by infrared thermometers, the MAE between measured evaporation and estimated evaporation was 0.15 mm day−1. The regression between them was highly significant (r2=0.94). In addition, the intercept and slope of the regression equation were not significantly different from zero and unity, respectively, at the 0.05 probability level. These results show that evaporation calculated using the proposed method is in good agreement with lysimeter measured values. By comparing with the temperature difference method, it was shown that the suggested method estimated soil evaporation more accurately than the temperature difference method. Therefore, it is concluded that the proposed method is not only a simple way for application, but also an accurate way to estimate soil evaporation.  相似文献   

6.
Discharge of saline groundwater from Eucalyptus forests on a semi-arid floodplain was directly determined by first measuring transpiration rates from the forests, and then partitioning the transpiration flux into groundwater discharge and soil water depletion. This partitioning was achieved by identifying the source of the transpired water with naturally occurring stable isotopes of water. Transpiration rates were low, being about 0.3 mm day−1 from three E. largiflorens sites and up to 2 mm day−1 from an E. camaldulensis site. There was no significant variation in transpiration across seasons, indicating that transpiration was limited by environmental factors other than evaporative demand. Despite its salinity (electrical conductivities of 11–33 dS m−1), the groundwater was used by the forests at all sites and all times, and made up 100% of transpiration in more than half of the measurements, and 40–80% in the remainder. There was some consistency in water uptake patterns. E. camaldulensis tended to take up shallow soil water and groundwater simultaneously, as did trees at one of the E. largiflorens sites. At the driest sampling time, however, groundwater was the only source of water for trees at both of these sites. Trees at the remaining two E. largiflorens sites generally relied solely on the groundwater. The tree water source results indicate that groundwater discharge fluxes were between 40 and 100% of the transpiration fluxes at these sites. These groundwater discharge fluxes were small in terms of regional groundwater balances, but would be important in the salinisation of the soils. Additionally, uptake of water from the soil profile by the trees substantially increased groundwater discharge compared with discharge from the soils had they been bare of vegetation.  相似文献   

7.
In order to establish a reliable chronology for lacustrine sediments of the Frickenhauser See (central Germany) different dating methods have been applied. A total of 17 AMS 14C dates, all within the last 2000 years, were supplemented with 137Cs/210Pb dating and varve counting of the uppermost sediments (131 years). The age–depth model for the Frickenhauser See has to cope with highly variable sedimentation rates and overlapping probability distributions of calibrated 14C dates. The uncertainty of calibrated 14C dates could be considerably reduced by including the stratigraphic relationship of the dated samples, the age information derived from short-lived isotopes and varve counting as well as an upper and lower limit of realistic sedimentation rates as ‘a priori’ information in the calibration procedure. Sets of possible age combinations obtained by repeated sampling from the modified probability distributions were used to calculate continuous age–depth relationships based on monotonic smoothing splines. The obtained age–depth model for the sediment record of the Frickenhauser See represents the average of over 16,000 such model runs and suggests a drastic increase in sedimentation rates from around 1–2 mm a−1 (200–1000 AD) to over 25 mm a−1 for the period between 1100 and 1300 AD. From then on, sedimentation rates exhibit relatively stable values around 3–9 mm a−1. ‘Conventional’ age–depth models such as general polynomial regression or cubic splines either do not include the obtained age-information in a satisfying manner (the model being too “stiff”) or exhibit “swings” causing age-reversals in the model. Although the age–depth relationships obtained for monotonic smoothing splines and mixed-effect regression are generally very similar, they differ in their respective sedimentation rates as well as in their uncertainties. Mixed-effect regression resulted in much higher sedimentation rates of more than 37 mm a−1. These results suggest that monotonic smoothing splines give better control of the age–depth model characteristics and are well suited in situations, where the integrity of 14C dates is high, i.e. the dated material represents the age of the respective layer.  相似文献   

8.
Hydraulic properties of deeply weathered basement rocks and variably weathered sedimentary materials were measured by pumping and slug-test methods. Results from over 200 bores in 13 catchments, and eight pumping-test sites across the eastern and central wheatbelt of Western Australia were analysed. Measurements were made in each of the major lithological units, and emphasis placed on a ubiquitous basal saprolite aquifer. Comparisons were made between alternative drilling and analytical procedures to determine the most appropriate methods of investigation.

Aquifers with an average hydraulic conductivity of 0.55 m day−1 occur in variably weathered Cainozoic sediments and poorly weathered saprolite grits (0.57 m day−1). These aquifers are separated by an aquitard (0.065 m day−1) comprising the mottled and pallid zones of the deeply weathered profile. Locally higher values of hydraulic conductivity occur in the saprolite aquifer, although after prolonged periods of pumping the values decrease until they are similar to those obtained from the slug-test methods. Hydraulic conductivities measured in bores drilled with rotary auger rigs were approximately an order of magnitude lower than those measured in the same material with bores drilled by the rotary air-blast method.

Wheatbelt aquifers range from predominantly unconfined (Cainozoic sediments), to confined (saprolite grit aquifer). The poorly weathered saprolite grit aquifer has moderate to high transmissivities (4–50 m2 day−1) and is capable of producing from less than 5 to over 230 kl day−1 of ground water, which is often of a quality suitable for livestock. Yields are influenced by the variability in the permeability of isovolumetrically weathered materials from which the aquifer is derived.

The overlying aquitard has a low transmissivity (< 1 m2 day−1), especially when deeply weathered, indurated and silicified. The transmissivity of the variably weathered sedimentary materials ranges from less than 0.5 m2 day−1 to over 10 m2 day−1, depending on the texture of the materials and their position within the landscape. Higher transmissivity zones may occur as discrete layers of coarser textured materials. The salinity of the saprolite and sedimentary aquifers ranges from less than 2000 mgl−1 to greater than 250000 mgl−1 (total dissolved solids; TDS), depending on position within the landscape. Secondary soil salinization develops when groundwater discharge occurs from either saprolite or sedimentary aquifers.  相似文献   


9.
Morton's complementary relationship areal evapotranspiration (CRAE) model was originally designed to provide regional estimates of monthly evapotranspiration. Often, however, hydrologists and others require estimates of evapotranspiration for field-sized land units under a specific land use, for shorter intervals of time. This paper examines CRAE with respect to the algorithms used to describe different terms and its applicability to reduced spatial and temporal scales.

Daily estimates by CRAE of atmospheric radiation fluxes during the summer months are compared with monitored values. It is shown that errors in estimation of the extra-terrestrial flux, the transmittancy of clouds to short-wave radiation, the surface albedo and the net long-wave flux result in standard deviations of the difference between ‘modelled’ and ‘measured’ net all-wave radiation for 1-, 5- and 10-day periods of 2.58, 1.8 and 1.50 MJm−2 day−1 respectively.

The assumption in CRAE that the vapour transfer coefficient is independent of wind speed may lead to appreciable error in computing evapotranspiration. A procedure for incorporating a wind correction factor is described and the improvement in estimating regional evaporation is illustrated.

Comparisons of evapotranspiration estimates by CRAE and measurements obtained from soil moisture and precipitation observations in the semi-arid, cold-climate Prairie region of western Canada demonstrate that the assumptions that the soil heat flux and storage terms are negligible, lead to large overestimation by the model during periods of soil thaw.  相似文献   


10.
During two successive growing seasons meteorological measurements were made in a pearl millet field in the Sahel to investigate the evaporation process in relation to crop growth. The evaporation was measured by eddy correlation and simulated using the Shuttleworth Wallace (SW) model [Q. J. R. Meteorol. Soc. 111 (1985) 839–855]. To take sun height and multi-layer scattering into account a radiation balance model was formulated. The model indicates that partitioning of the net radiation between the vegetation and the soil may be estimated (r2=0.94) from the fraction of diffuse radiation, the leaf area index and an attenuation coefficient, but that the attenuation coefficient may not be similar in different locations. To solve the SW-model with respect to the soil resistance an iterative solution was employed with the total evaporation estimated from the Bowen-ratio calculated from eddy correlation measurements. The procedure made it possible to derive stable estimates of soil resistance at soil evaporation rates down to 25 W m−2. The soil resistance was found to be in accordance with evaporation through a dry surface layer. The SW-model indicates, that advection of sensible heat from the dry soil to the plants, increases transpiration considerably. This will cause management techniques, such as mulching and dry farming, aimed at reducing soil evaporation to be less effective than might be anticipated. The effects of raising the leaf area index to improve the microclimate is discussed in relation to management of the available water and crop security.  相似文献   

11.
An eddy covariance (EC) station was deployed at Solfatara crater, Italy, June 8–25, 2001 to assess if EC could reliably monitor CO2 fluxes continuously at this site. Deployment at six different locations within the crater allowed areas of focused gas venting to be variably included in the measured flux. Turbulent (EC) fluxes calculated in 30-min averages varied between 950 and 4460 g CO2 m−2 d−1; the highest measurements were made downwind of degassing pools. Comparing turbulent fluxes with chamber measurements of surface fluxes using footprint models in diffuse degassing regions yielded an average difference of 0% (±4%), indicating that EC measurements are representative of surface fluxes at this volcanic site. Similar comparisons made downwind of degassing pools yielded emission rates from 12 to 27 t CO2 d−1 for these features. Reliable EC measurements (i.e. measurements with sufficient and stationary turbulence) were obtained primarily during daytime hours (08:00 and 20:00 local time) when the wind speed exceeded 2 m s−1. Daily average EC fluxes varied by ±50% and variations were likely correlated to changes in atmospheric pressure. Variations in CO2 emissions due to volcanic processes at depth would have to be on the same order of magnitude as the measured diurnal variability in order to be useful in predicting volcanic hazard. First-order models of magma emplacement suggest that emissions could exceed this rate for reasonable assumptions of magma movement. EC therefore provides a useful method of monitoring volcanic hazard at Solfatara. Further, EC can monitor significantly larger areas than can be monitored by previous methods.  相似文献   

12.
Evaporation and infiltration were compared for tropical rainforest and pasture, near to Manaus, Brazil from October 1990 to February 1992 using measurements of soil water storage over a depth of 2 m. The soil is a clayey oxisol of low water available capacity. In both of the dry seasons studied, the maximum change in soil water storage in the forest was 154 mm and in the pasture it was 131 and 112 mm. Similar behaviour of the soil water reservoir below forest and pasture in the wet season implied that differences in evaporation and drainage were small. In the dry season, soil water storage behaviour in the upper metre of the soil was similar but there were marked differences in the second metre. The pasture took up little water from below 1.5 m but the forest appeared to utilise all of the available water in the 2 m profile in both seasons.

The water balance of the 2 m profile showed that the pasture evaporation rate was equal to that of the forest until storage had decreased 80 mm from the maximum. There was then a decline in pasture evaporation rate to 1.2 mm day−1 as the storage decreased by a further 50 mm. In contrast, the forest uptake rate remained above 3.5 mm day−1 until storage had decreased 140 mm from the maximum (within 15 mm of the extraction limit), before declining abruptly to less than 1.5 mm day−1. There was strong evidence that the forest was able to abstract water from depths greater than 3.6 m.

Spatial variability of soil water storage was significantly greater beneath the pasture than beneath the forest, particularly following rainfall events in the dry season. This was largely the result of redistribution of rainfall as local surface runoff. There was no evidence of redistribution or runoff in the forest.  相似文献   


13.
A soil-water flux sensor was developed, which determines the flux value from the difference between downstream and upstream temperatures at some distances from an artificial heat source. It can detect flux values ranging from several mm hr.−1 to as small as 0.01 mm hr.−1. Design and calibration of the sensor are described.

The sensor was applied to the field studies of transfer processes in a surface soil, including rainwater infiltration, upward soil-water flow during evapotranspiration, and their effects on the water table level. Cl− accumulation in the surface soil is discussed on the basis of upward water flux and Cl− content observed.  相似文献   


14.
Evaporation of intercepted rain by a canopy is an important component of evapotranspiration, particularly in the humid boreal forest, which is subject to frequent precipitation and where conifers have a large surface water storage capacity. Unfortunately, our knowledge of interception processes for this type of environment is limited by the many challenges associated with experimental monitoring of the canopy water balance. The objective of this study is to observe and estimate canopy storage capacity and wet canopy evaporation at the sub-daily and seasonal time scales in a humid boreal forest. This study relies on field-based estimates of rainfall interception and evapotranspiration partitioning at the Montmorency Forest, Québec, Canada (mean annual precipitation: 1600 mm, mean annual evapotranspiration: 550 mm), in two balsam fir-white birch forest stands. Evapotranspiration was monitored using eddy covariance sensors and sap flow systems, whereas rainfall interception was measured using 12 sets of throughfall and six stemflow collectors randomly placed inside six 400-m2 plots. Changes in the amount of water stored on the canopy were also directly monitored using the stem compression method. The amount of water intercepted by the forest canopy was 11 ± 5% of the total rainfall during the snow-free (5 July–18 October) measurement periods of 2017 and 2018. The maximum canopy storage estimated from rainfall interception measurements was on average 1.6 ± 0.7 mm, though a higher value was found using the stem compression method (2.2 ± 1.6 mm). Taking the average of the two forest stands studied, evaporation of intercepted water represented 21 ± 8% of evapotranspiration, while the contribution of transpiration and understory evapotranspiration was 36 ± 9% and 18 ± 8%. The observations of each of the evapotranspiration terms underestimated the total evapotranspiration observed, so that 26 ± 12% of it was not attributed. These results highlight the importance to account for the evaporation of rain intercepted by humid boreal forests in hydrological models.  相似文献   

15.
Water-budget components and the vertical conductance were determined for Lowry (Sand Hill) Lake in north-central Florida, USA. In this type of lake, which interacts with both the surface-water and groundwater systems, the inflow components are precipitation, surface-water inflow, groundwater inflow, and direct runoff (i.e. overland flow), and the outflow components are evaporation, groundwater outflow, and surface-water outflow. In a lake and groundwater system that is typical of many karst lakes in Florida, a large part of the groundwater outflow occurs by means of vertical leakage through an underlying confining unit to a deeper, highly transmissive aquifer called the upper Floridan aquifer. The water-budget component that represents vertical leakage to the upper Floridan aquifer was calculated as a residual using the water-budget equation. For the 13 month period from August 1994 to August 1995, relative to the surface area of the lake, rainfall at Lowry Lake was 1.55 m yr−1, surficial aquifer inflow was 0.79 m yr−1, surface-water inflow was 1.92 m yr−1, and direct runoff was 0.01 m yr−1. Lake evaporation was 1.11 m yr−1, and surface-water outflow was 1.61 m yr−1. The lake stage increased 0.07 m yr−1, and the vertical leakage to the upper Floridan aquifer was 1.48 m yr−1. Surficial aquifer outflow from the lake was negligible. At Lowry Lake, vertical leakage is a major component of the water budget, comprising about 35% of the outflow during the study period. The vertical conductance (KV/b), a coefficient that represents the average of the vertical conductances of the hydrogeologic units between the bottom of a lake and the top of the upper Floridan aquifer, was determined to be 2.51 × 10−4 day−1 for Lowry Lake.  相似文献   

16.
In sparsely cropped farming systems in semi-arid tropics, rainfall partitioning can be complex due to various interactions between vertical and horizontal water flows, both in the atmosphere and in the soil. Despite this, quantifying the seasonal rainfall partitioning is essential, in order to identify options for increased yields. Results are presented on water flow components, based on field measurements and water balance modelling, for three years (1994–96) in a farmer's field cultivated with pearl millet [Pennisetum glaucum (L.) Br.] in the Sahel (Niger). Water balance modelling was carried out for three common infiltration categories: runoff producing surfaces, surfaces receiving inflow of runon water from upstream zones, and a reference surface with zero runoff and runon. Runoff was calculated to 25%–30% of annual rainfall (which ranged from 488 to 596 mm), from crust observations, rainfall, soil wetness data, and infiltration estimates. Inflow of runon was estimated from field observations to 8%–18% of annual rainfall. The parameters in the functions for soil surface and canopy resistances were calibrated with field measurements of soil evaporation, stomatal conductance and leaf area. The model estimates of soil water contents, which were validated against neutron probe measurements, showed a reasonable agreement with observed data, with a root mean square error (RMSE) of approximately 0.02 m3 m−3 for 0–160 cm soil depth. Estimated productive water flow as plant transpiration was low, amounting to 4%–9% of the available water for the non-fertilised crop and 7%–24% for the fertilised crop. Soil evaporation accounted for 31%–50% of the available water, and showed a low variation for the observed range of leaf area (LAI <1 m2 m−2). Deep percolation was high, amounting to 200–330 mm for the non-crusted surfaces, which exceeded soil evaporation losses, for 1994–95 with relatively high annual rainfall (517–596 mm). Even a year with lower rainfall (488 mm) and a distinct dry spell during flowering (1996), resulted in an estimated deep percolation of 160 mm for the non-fertilised crop. The crop did not benefit from the additional inflow of runon water, which was partitioned between soil water storage and deep percolation. The only exception to this was the fertilised crop in 1996, where runon somewhat compensated for the limited rainfall and the higher water demand as a result of a larger leaf area than the non-fertilised crop. The effects of rainfall erraticness, resulting in episodic droughts, explain why a crop that uses such a small proportion of the available water, in an environment with substantial deep percolation, still suffers from water scarcity. Application of small levels of phosphorus and nitrogen roughly doubled yields, from 380 to 620 kg ha−1, and plant transpiration, from 33 to 78 mm. Evapotranspirational water use efficiency (WUEET) was low, 6500–8300 m3 ton−1 grain for non-fertilised crop, which is an effect of the low on-farm yields and high non-productive water losses. The estimated seasonal rainfall partitioning indicates the possibility of quantifying vertical water flows in on-farm environments in the Sahel, despite the presence of surface overland flow.  相似文献   

17.
Portunid crabs Thalamita danae (carapace width: 46–56 mm) were exposed to low oxygen level (4.0 mg O2 l−1) and hypoxia (1.5 mg O2 l−1) for 6 h each day with three size classes (large: 15.0–19.9 mm, medium: 10.0–14.9 mm, small: 5.0–9.9 mm) of mussels Brachidontes variabilis offered as food. Consumption rate, prey size preference, and prey handling including breaking time, handling time, eating time and prey value, were studied during the time the crabs were exposed to reduced oxygen levels and results were compared with the crabs maintained at high oxygen level (8.0 mg O2 l−1) throughout the experiment. Consumption of mussels from all size classes was significantly higher at high oxygen level than at reduced oxygen levels. No mussel size preference was observed for crabs exposed to 4.0 or 8.0 mg O2 l−1 but those crabs exposed to 1.5 mg O2 l−1 preferred medium mussels. Both breaking time and handling time increased with mussel size but did not vary with oxygen level. Prey value of each mussel consumed (mg dry wt eaten crab−1 s−1) was calculated by dividing the estimated dry weight of the mussel by the observed handling time. Mean prey value varied significantly with mussel size, with values obtained for large mussels being higher than small mussels at 4.0 and 8.0 mg O2 l−1; the effect of oxygen level, however, was insignificant. In view of portunid crabs as major predators of mussels, results may help explain dominance of mussels in eutrophic harbours in Hong Kong.  相似文献   

18.
The clam Ruditapes decussatus L. was collected from Ria Formosa, Faro, southern Portugal, and exposed to a sublethal copper concentration of 0.01 mg l−1 for 20 days. Physiological measurements, respiration rates, clearance rates and absorption efficiency, were undertaken initially and after 2, 5, 9, 14 and 20 days and used to calculate Scope for Growth. Copper accumulation rate was calculated through the analysis of copper in the tissues at the same sampling times. The experiment showed two phases. Initially, copper was rapidly accumulated (1.95 μg Cu g−1 dw day−1 in the first 48 h), clearance rates declined markedly (lowest value 13.5% of control) and respiration rates increased (116% of control), resulting in a rapid decline of Scope for Growth, which showed a negative value after 5 days. In the second phase, (from day 9 on), the rate of copper uptake declined to 0.55 μg Cu g−1 day−1 and physiological responses were more stable. After 20 days, copper concentration in the tissues was 38.4 μg Cu g−1 dw (bioconcentration factor 3840). Clearance rates were 50% of control rates and respiration rates were still high, 145% of control rates. Therefore, Scope for Growth and performance of the clams was still greatly affected (ca. 23% of the control values), indicating that though animals partially recovered through detoxifying mechanisms, excess copper caused sustained impairment of physiological functions. This experiment confirms that the physiological energetics approach and the integrated Scope for Growth measurement is a sensitive methodology to detect deviations from normal performance and assess stress at environmental realistic copper concentrations.  相似文献   

19.
Organochlorine contaminants including 12 polychlorinated biphenyl (PCB) congeners and 18 insecticides were determined in water, pore water and sediments of the Jiulong River Estuary and Western Xiamen Sea, China. The results showed that the levels of the total PCBs ranged from non-detectable to 1500 ng l−1 in water, from 209 to 3870 ng l−1 in pore water, and from 2.78 to 14.8 ng g−1 dry weight in sediments. Total organochlorine insecticide concentrations were from below the limit of detection to 2480 ng l−1 in water, from 267 to 33400 ng l−1 in pore water, and from 4.22 to 46.3 ng g−1 dry weight in sediments. Concentrations of PCBs and insecticides in pore water were significantly higher than those in surface water, due to the high affinity of these hydrophobic compounds for sediment phase. The PCB congeners with the highest concentrations were CB153, CB180 and CB194, which together accounted for 68–87% of total PCBs in water, pore water and sediment. Among the hexachlorocyclohexane (HCH) compounds, beta-HCH was found to be a major isomer. Analysis of 1,1,1-trichloro-2,2-bis-chlorophenyl-ethane (DDT) and its metabolites showed that 1,1-dichloro-2[o-chlorophenyl]-2[p-chlorophenyl]-ethylene (DDE) was dominant in the group. In comparison to a 1998 study in the Western Xiamen Sea, levels of organochlorines were enhanced due probably to recent inputs and changes in sediments.  相似文献   

20.
In 1995–1998, Han 11 km terrestrial surge of Kuannersuit Glacier, an outlet glacier of the largest ice cap on Disko Island, West Greenland, affected the catchment dramatically. In order to estimate solute fluxes and provenances, bulk meltwaters were sampled at the main subglacial outlet during the initial part of the quiescent phase. The hydrochemistry is significantly influenced by a subglacial basaltic weathering regime with absence of carbonate minerals. The results show that marine and aerosol derived solutes have minimal contribution to the total ion content, whereas sequestration of atmospheric CO2 associated with carbonation of Ca-rich feldspar and reactive volcanic glass is more dominant than previously reported from glacierized catchments. Application of a sampling strategy dividing water samples into four groups to determine the content of dissolved HCO3− and CO32− shows that the cationic equivalent weathering rate range is 683–860 Σmeq+ m−2 a−1 and solute flux ranges between 76 and 98 t km−2 a−1. The crustal denudation rate is estimated to 26 t km−2 a−1, and the transient CO2 drawdown amounts to 8500–13700 kg C km−2 a−1.  相似文献   

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