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1.
Hydroelectric power is an important energy source to meet the growing demand for energy, and large amounts of water are consumed to generate this energy. Previous studies often assumed that the water footprint of hydroelectric power equaled the reservoir’s water footprint, but failed to allocate the reservoir water footprint among the many beneficiaries; dealing with this allocation remains a challenge. In this study, we developed a new approach to quantify the water footprint of hydroelectric power (WFh) by separating it from the reservoir water footprint (WF) using an allocation coefficient (ηh) based on the ratio of the benefits from hydroelectric power to the total ecosystem service benefits. We used this approach in a case study of the Three Gorges Reservoir, the world’s largest reservoir, which provides multiple ecosystem services. We found large differences between the WFh and the water footprint of per unit of hydroelectric production (PWFh) calculated using ηh and those calculated without this factor. From 2003 to 2012, ηh decreased sharply (from 0.76 in 2005 to 0.41 in 2012), which was due to the fact that large increases in the value of non-energy ecosystem services, and particularly flood control. In 2009, flood control replaced hydroelectricity as the largest ecosystem service of water from the Three Gorges Reservoir. Using our approach, WFh and PWFh averaged 331.0 × 106 m3 and 1.5 m3 GJ−1, respectively. However, these values would almost double without allocating water footprints among different reservoir ecosystem services. Thus, previous studies have overestimated the WFh and PWFh of reservoirs, especially for reservoirs that serve multiple purposes. Thus, the allocation coefficient should not be ignored when calculating the WF of a product or service.  相似文献   

2.
Biomonitoring methods based on macrophytes have been used mandatorily in the assessment of freshwaters since the implementation of the Water Framework Directive (WFD). The Macrophyte Index for Rivers (MIR) was developed in Poland for the monitoring of running waters under the WFD requirements. This index shows the degree of river degradation under the influence of water pollutants, especially nutrients. The aim of the present study was to determine the relationship between the MIR and various hydrochemical parameters using artificial neural networks (ANNs). Physico-chemical parameters of water (monthly results for the whole year), which were derived from 147 lowland river survey sites, all located in Poland, were applied to model the MIR values. Water quality variables were determined over three timeframes: the annual average; the average for the vegetation period; and the average for the summer period. Quality of the networks was assessed using coefficient of determination (R2), Nash-Sutcliffe efficiency (NSE) and root mean square error (RMSE). The best modeling quality was obtained for yearly average values of water quality parameters. The quality statistics were: R2 = 0.722, NSE = 0.721 and RMSE = 0.056 (training dataset); R2 = 0.555, NSE = 0.533 and RMSE = 0.101 (validation dataset); R2 = 0.650. NSE = 0.600 and RMSE = 0.089 (testing dataset). This indicates that macrophytes reflect the whole year impact of pollution, whereas summer.  相似文献   

3.
《Marine pollution bulletin》2013,77(1-2):417-419
This study aims to determine the concentrations of total coliforms and Escherichia coli (E. coli) in beach water, Teluk Kemang beach. This study was also aimed to determine relationship between total coliforms, E. coli and physicochemical parameters. As perceived health symptoms among beach visitors are rarely incorporated in beach water studies, this element was also assessed in this study. A total of eight water sampling points were selected randomly along Teluk Kemang beach. Total coliforms concentrations were found between 20 and 1940 cfu/100 ml. E. coli concentrations were between 0 and 90 cfu/100 ml. Significant correlations were found between total coliforms and E. coli with pH, temperature and oxidation reduction potential. Skin and eyes symptoms were the highest reported though in small numbers. Microbiological water quality in Teluk Kemang public beach was generally safe for recreational activities except sampling location near with sewage outfall.  相似文献   

4.
《Marine pollution bulletin》2012,64(5-12):528-534
The Salt-water River watershed is one of the major river watersheds in the Kaohsiung City, Taiwan. Water quality and sediment investigation results show that the river water contained high concentrations of organics and ammonia–nitrogen, and sediments contained high concentrations of heavy metals and organic contaminants. The main pollution sources were municipal and industrial wastewaters. Results from the enrichment factor (EF) and geo-accumulation index (Igeo) analyses imply that the sediments can be characterized as heavily polluted in regard to Cd, Cr, Pb, Zn, and Cu. The water quality analysis simulation program (WASP) model was applied for water quality evaluation and carrying capacity calculation. Modeling results show that the daily pollutant inputs were much higher than the calculated carrying capacity (1050 kg day−1 for biochemical oxygen demand and 420 kg day−1 for ammonia–nitrogen). The proposed watershed management strategies included river water dilution, intercepting sewer system construction and sediment dredging.  相似文献   

5.
Soda lakes and pans represent saline ecosystems with unique chemical composition, occurring on all continents. The purpose of this study was to identify and characterise the main environmental gradients and trophic state that prevail in the soda pans (n = 84) of the Carpathian Basin in Central Europe. Underwater light conditions, dissolved organic matter, phosphorus and chlorophyll a were investigated in 84 pans during 2009–2010. Besides, water temperature was measured hourly with an automatic sensor throughout one year in a selected pan. The pans were very shallow (median depth: 15 cm), and their extremely high turbidity (Secchi depth median: 3 cm, min: 0.5 cm) was caused by high concentrations of inorganic suspended solids (median: 0.4 g L−1, max: 16 g L−1), which was the dominant (>50%) contributing factor to the vertical attenuation coefficient in 67 pans (80%). All pans were polyhumic (median DOC: 47 mg L−1), and total phosphorus concentration was also extremely high (median: 2 mg L−1, max: 32 mg L−1). The daily water temperature maximum (44 °C) and fluctuation maximum (28 °C) were extremely high during summertime. The combination of environmental boundaries: shallowness, daily water temperature fluctuation, intermittent hydroperiod, high turbidity, polyhumic organic carbon concentration, high alkalinity and hypertrophy represent a unique extreme aquatic ecosystem.  相似文献   

6.
The lake monitoring programme compliant with the Water Framework Directive has been implemented in Poland since 2007. Currently, the methods for three biological quality elements (BQEs): phytoplankton (the Phytoplankton Multimetric for Polish Lakes, PMPL), macrophytes (the Ecological State Macrophyte Index, ESMI) and phytobenthos (the Diatom Index for Lakes, IOJ) are officially applied and internationally intercalibrated. Based on the monitoring data from 256 lakes surveyed in 2010–2013 and assessed for all the three BQEs, we tested whether the assessment results obtained by the three biological methods were consistent and we searched for the causes of inconsistencies which we found. The lake classifications obtained from the PMPL and ESMI were highly consistent and the relationship between these metrics was relatively strong (R = 0.66, p < 0.001). Both metrics correlated equally strongly with water quality indicators. However, the PMPL and ESMI indicated systematic dissimilarities in the sensitivity to eutrophication between shallow and deep lakes. In shallow lakes, the alarming symptoms of macrophyte community deterioration (lower values of ESMI) occurred at lower nutrient and Chla concentrations and were accompanied by a better status of phytoplankton (higher values of PMPL) than in deep lakes that can be explained by a synergistic effect of inorganic suspended solids and algal growth on water transparency. As a consequence, the positions of phytoplankton and macrophytes as early warning indicators in the eutrophication gradient in shallow lakes were inverted compared to those in deep lakes. Compared to the PMPL and ESMI, the IOJ method gave the least stringent assessment results, with 22% of lakes failing to meet the environmental objectives. The relationships between IOJ and PMPL, and ESMI were relatively weak (R = 0.17, p = 0.008 and R = 0.17, p = 0.007, respectively). Moreover, the phytobenthos index IOJ correlated significantly more weakly with all the water quality indicators than either PMPL or ESMI did. The poor performance of the phytobenthos method in this study may suggest a limited indicator value of this BQE for lake assessment or inappropriate sampling design.  相似文献   

7.
The feasibility of a potential bioindicator based on functional groups of microzooplankton tintinnids for bioassessments of water quality status was studied during southwest monsoon (June to September) along the coastal waters of Kalpakkam, India during 2012–2015. The work highlights the following features (1) tintinnid community composed of 28 species belonging to 11 genera and 9 families, revealed significant differences among the four study sites (2) maximum numerical abundance (2224 ± 90 ind. l? 1) and species diversity (H′ = 2.66) of tintinnid were recorded towards Bay of Bengal whereas minimum abundance (720 ± 35 ind. l? 1) and diversity (H′ = 1.74) were encountered in the backwater sites, (3) multivariate analyses [RELATE, Biota-environment (BIOENV) and canonical analysis of principal coordinates (CAP)] reveal that chl a, nitrate and phosphate were the potential causative factors for tintinnid distribution. Based on the results, we suggest that tintinnids may be used as a potential bioindicator of water quality status in marine ecosystem.  相似文献   

8.
The study analyses the long-term biophysical and demographic changes in Dal lake, located in the heart of Srinagar city, Kashmir India, using a repository of historical, remote sensing, socio-economic and water quality data supported by the extensive field observations. The lake faces multiple pressures from the unplanned urbanization, high population growth, nutrient load from intensive agriculture and tourism. The data showed that the lake has shrunk from 31 km2 in 1859–24 km2 in 2013. Significant changes were observed in the land use and land cover (LULC) within the lake (1859–2013) and in the vicinity of the lake (1962–2013). Analysis of the demographic data indicates that the human population within the lake has shown more than double the national growth rate. Additionally, 7 important water quality parameters from 82 well distributed sites across the lake were analyzed and compared with the past data to determine the historical changes in the water quality from 1971 to 2014. The changes in the LULC and demography have adversely affected the pollution status of this pristine lake. Ortho-phosphate phosphorous concentration has increased from 16.75 μg L−1 in 1977–45.78 μg L−1 in 2014 and that of the nitrate-nitrogen from 365 μg L−1 to 557 μg L−1, indicating nutrient enrichment of the lake over the years. Built-up area within the lake has increased 40 times since 1859, which, together with the changes in the population and settlements, have led to the high discharge of untreated nutrient-rich sewage into the lake. Similarly the expansion of floating gardens within the lake and agriculture lands in the catchment has contributed to the increased nutrient load into the lake due to the increasing use of fertilizers. The information about the existing land cover, demography and water quality was integrated and analyzed in GIS environment to identify the trophic status of the lake. The analysis indicated that 32% of the lake falls under sever degradation, 48% under medium degradation while as 20% of the lake waters are relatively clean. It is believed that the results provide improved knowledge and insights about the lake health and causal factors of its degradation necessary for effectively restoring its ecological and hydrological functionality.  相似文献   

9.
Toxic and non-toxic Microcystis sp. are morphologically indistinguishable cyanobacteria that are increasingly posing health problems in fresh water systems by producing odours and/or toxins. Toxic Microcystis sp. produces toxicologically stable water soluble toxic compounds called microcystins (MCs) that have been associated with cases of aquatic life and wildlife poisoning and kills including some cases of human illnesses/deaths around the world. Thus, the need for rapid detection of toxic Microcystis sp. in surface water is imperatively a necessity for early mitigation purposes. Genomic DNA from potentially toxic Microcystis sp. comprises of ten microcystin synthetase (mcy) genes of which six major ones are directly involved in MCs biosynthesis. In Polymerase Chain Reaction (PCR) methodsmcy genes can be amplified from intracellular/extracellular genomic DNA using PCR primers. However, little is known about the limitations of sourcing genomic DNA templates from extracellular DNA dissolved in water. In this work, filtered water (0.45 μM) from a Microcystis infested Dam (South Africa) was re-filtered on 0.22 μM syringe filters followed by genomic DNA isolation and purification from micro-filtrates (9 mL). Six major mcy genes (mcyABCDEG) from the isolated DNA were amplified using newly designed as well as existing primers identified from literature. PCR products were separated by gel electrophoresis and visualized after staining with ethidium bromide. The limitation of using dissolved DNA for amplification of mcy genes was qualitatively studied by establishing the relationship between input DNA concentrations (10.0–0.001 ng/μL) and the formation of respective PCR products. The amplification of mcyA gene using new primers with as little as 0.001 ng/μL of DNA was possible. Other mcy gene sensitivities reached 0.1 ng/μL DNA dilution limits. These results demonstrated that with appropriately optimized PCR conditions the method can provide accurate cost-effective tools for rapid detection of toxic Microcystis sp. in water giving early information for water quality monitoring against MC producing cyanobacteria.  相似文献   

10.
Lakes Chivero and Manyame are amongst Zimbabwe’s most polluted inland water bodies. MEdium Resolution Imaging Spectrometry level 1b full resolution imagery for 2011 and 2012 were used to derive chlorophyll-a (chl_a) and phycocyanin (blue-green algae) concentrations using a semi-empirical band ratio model; total suspended matter (TSM) concentrations were derived from the MERIS processor. In-situ measured chl_a was used to validate the remotely sensed values. Results indicate that remote sensing measurements are comparable with in situ measurements. A strong positive correlation (R2 = 0.91; MAE = 2.75 mg/m3 (8.5%)) and p < 0.01 (highly significant)) between measured and modeled chl_a concentrations was obtained. Relationships between optically active water constituents were assessed. Measured chl_a correlated well with MERIS modeled phycocyanin (PC) concentration (R2 = 0.9458; p < 0.01 (highly significant)) whilst chl_a and TSM gave (R2 = 0.7344; p < 0.05 (significant)). Modeled TSM and PC concentrations manifested a good relationship with each other (R2 = 9047; p < 0.001 (very highly significant)). We conclude that remote sensing data allow simultaneous retrieval of different water quality parameters as well as providing near real time and space results that can be used by water managers and policy makers to monitor water bodies.  相似文献   

11.
In Malawi, shallow wells constitute the most important water sources for domestic purposes. However, increasing human population coupled with poor sanitation and infrastructure is undermining the quality of shallow well water. An assessment of microbial and geochemical quality of shallow well water in high-density areas of Zolozolo, Ching’ambo and Chiputula in Mzuzu City, Northern Malawi, has been carried out. The study aimed at characterising domestic water sources, identifying possible sources of water contamination and determining levels of microbial and chemical contamination. Arc-view GIS was used to map the water sources. A questionnaire survey was carried out to elicit information on characteristics of drinking water sources. Water samples were collected from quasi-randomly selected shallow wells and analysed for microbial and chemical parameters using standard methods. HCA, performed using R-programme, was used to group sampled sites according to their bio-physicochemical characteristics. Compliance of the water with MBS/WHO water quality guidelines was determined. The WQI was computed to turn multifaceted data obtained from laboratory analyses into simple information that is comprehensible and useable by the public to assess overall quality of water at a specific water points. The GW-chart was used to show hydrogeochemical water types from each sampled site. Microbial analysis revealed that water from 96.3% of shallow wells recorded faecal coliforms ranging from 129 to 920 cfu per 100 ml which were significantly higher than the Malawi Standards and WHO thresholds. In general, shallow well water is of low mineralisation (EC range 80–500 μS cm−1), with hydrogeochemical facies dominated by Ca–HCO3, which evolves to Ca–Cl water type. The shallow well water registered a WQI range of 50.16–66.04%, with a medium WQ rating. This suggested that the water obtained from the shallow wells is unsuitable for direct human consumption. It was observed that 100% of the shallow wells were at risk of pollution from onsite sanitation because of their proximity to sanitary facilities. It was strongly recommended that onsite treatment interventions have to be mobilised and initiated to protect the households from further possible consequences of using the water.  相似文献   

12.
Excessive macrophyte biomass and cyanobacterial blooms associated with eutrophication and possibly exotic fish frequently compromise freshwater systems. In this study, 20 large (∼3.2 m3), replicated enclosures were used to investigate the effects of piscivorous Australian bass (Macquaria novemaculeata), planktivorous gambusia (Gambusia holbrooki (Girard)), benthivorous carp (Cyprinus carpio), and macrophyte removal on water quality, as well as trophic interactions within the enclosures. Fish effects on reservoir water quality were carp > gambusia > bass. Cryptomonads spp. (54,083 cells/mL) and Anabaena spp. (47,983 cells/mL) increased significantly (63 and 23 fold, respectively) in carp enclosures, possibly because of physiological adaptation to low light, high turbidity, total phosphorus concentrations (TP) and low TN: TP ratios (N-limitation); a consequence of carp benthic grazing. Carp and gambusia caused an unconventional shift from smaller to medium sized zooplankton (e.g. Boeckella sp., Bosmina meridionalis), possibly a result of copepod nauplius grazing. In the subtropical system studied, fish-induced nutrient recycling appears more important to the outcome of bio-manipulation than grazing impacts. Macrophyte harvesting unexpectedly decreased phytoplankton biomass linked to declines in Euglenophyta and diatoms (Asterionella spp.). Cyanophyta (Oscillatoriales spp./Anabaena spp.) increased in response to macrophyte harvesting and was consistent with findings on European lakes that Cyanophyta abundance tends to be higher in the absence of macrophytes. Results indicate exotic fish removal, nutrient loading control and macrophyte conservation is important in these aquatic systems to maintain high water quality.  相似文献   

13.
The main objective of this study was to characterize the ecological conditions that prevail after the application of chicken, cow and pig manure. Three treatments, chicken, cow, pig manure and a control were assigned to aquadams in a completely randomized design and each treatment was replicated three times. The aquadams were fertilized 2 weeks before the fish were stocked. One hundred Oreochromis mossambicus (mean weight ±40 g) were stocked in each aquadam. Water physico-chemical parameters (temperature, dissolved oxygen, pH, electrical conductivity, salinity, turbidity, ammonia, nitrite, total alkalinity as calcium carbonate, and phosphorus) were determined once a week for the duration of the experiment. Zooplankton and phytoplankton in the different treatments were enumerated once every 2 weeks. The relationship between phytoplankton communities and the water physico-chemical parameters were evaluated using canonical correspondence analysis (CCA). The CCA indicated that the physico-chemical variables which best explain the distribution of phytoplankton were carbonate alkalinity, pH, phosphate, potassium, nitrogen and dissolved oxygen. Phytoplankton abundance was highest in chicken manure because the optimum nutrient conditions for the growth of phytoplankton were found in this treatment. Zooplankton abundance was also highest in the chicken manure treatment. The control was associated with one phytoplankton taxa, Chlorella. The numerical contribution of the different food items in the stomachs of O. mossambicus was determined. The diet of O. mossambicus was dominated by phytoplankton particularly Microcystis species. Total coliforms and Escherichia coli were used to assess the microbiological quality of the water in the different manure treatments. Chicken manure had the lowest total coliform and E. coli count. However, chicken manure had the highest Bacillus count. The implications of the microbial load in the chicken, cow and pig manure are discussed.  相似文献   

14.
In this study, remediation results of trace metals in natural water and treated water using three functionalized nanofiber mats of cellulose and chitosan are reported. The nanofiber materials, packed in mini-columns, were employed for the remediation of five toxic trace metals (Cd, Pb, Cu, Cr and Ni) from natural water samples. Trace metals in real water samples were undetectable as the concentrations were lower than the instrument’s detection limits of 0.27 × 10−3 (Cd) and 4.2 × 10−2 (Pb) μg mL−1, respectively. However, after percolation through the functionalised biosorbents in cartridges, detectability of the metal ions was enhanced. The starting volume of the natural water sample was 100 mL, which was passed through a column containing the nanofibers sorbent and the retained metals eluted with 5 mL of 2.0 M nitric acid. The eluate was analyzed for metals concentrations. An enrichment factor of 20 for the metals was realized as a result of the pre-concentration procedure applied to handle the determination of the metals at trace levels. The order of remediation of the studied metals using the nanofibers was as follows: chitosan/PAM-g-furan-2,5-dione < cellulose-g-furan-2,5-dione < cellulose-g-oxolane-2,5-dione. The modified biopolymer nanofibers were able to adsorb trace metals from the river water and treated water, thereby confirming their capability of water purification. These materials are proposed as useful tools and innovative approach for improving the quality of drinking for those consumers in small scale households.  相似文献   

15.
Water level, sediment heterogeneity, and plant density are important factors that determine plant growth, distribution, and community structure. In the present study, we investigated the effects of these factors on the growth and root characteristics of Carex brevicuspis. We conducted an outdoor experiment to monitor biomass accumulation and allocation, relative root distribution mass ratio, longest root length, and total N and P contents of C. brevicuspis plants. We used a factorial design with two water levels (0 cm and −15 cm relative to the soil surface, named high and low water level treatments, respectively), three sediment types (sand/clay sediment with 0–15 cm of sand and 15–30 cm of clay; mixed sediment with 0–30 cm mixture of sand and clay with 1:1 volumw ratio; and clay/sand sediment with 0–15 cm of clay and 15–30 cm of sand), and three plant densities (88 plants per m2, 354 plants per m2, and 708 plants per m2). Biomass accumulation decreased with increasing plant density and was significantly higher in the low water level and the clay/sand sediment than in the high water level and the other two sediment types. The shoot:root ratio was markedly higher in the high water level than in the low water level and decreased with increasing plant density; further, in the high water level, it was significantly lower in the sand/clay sediment than in the other two sediment types. The relative root distribution mass ratio was markedly higher in the high water level treatments than in the low water level treatments. Further, in the high water level treatments, the relative root distribution mass ratio increased with increasing plant density in the clay/sand sediment and was lower in the sand/clay sediment than in the other two sediment types. The longest root length was significantly lower in the high water level than in the low water level and increased with increasing plant density in the sand/clay sediment in the high water level. Total N content in the plants was influenced only by sediment type; on the other hand, total P content was markedly higher in the high water level than in the low water level. Our data indicate that growth of C. brevicuspis was limited by higher water level, higher density and sand/clay sediment. Plants can increase shoot:root ratio and develop shallow root system to acclimate to high water level and thus could adjust shoot:root ratio and root characteristics, e.g. decrease their shoot:root ratio and allocating more root and increasing root length to the nutrient rich layer to acclimate to conditions of higher density and sediment heterogeneity.  相似文献   

16.
Metal pollutants in water poses great threats to living beings and hence requires to be monitored regularly to avoid loss of lives. Various analytical methods are available to monitor these pollutants in water and can be improved with time. Modelling of metal pollutants in any water system helps chemists, engineers and environmentalists to greatly understand the various chemical processes in such systems. Water samples were collected from waste water treatment plant and river from highlands close to its source all the way to the ocean as it passing through areas with high anthropogenic activities. Pre-concentration of pollutants in the samples was done through acid digestion and metal pollutants were analysed using inductively coupled plasma-optical emission spectra (ICP-OES) to determine the concentration levels. Metal concentrations ranged between 0.1356–0.4658 mg/L for Al; 0.0031–0.0050 mg/L for Co, 0.0019–0.0956 mg/L for Cr; 0.0028–0.3484 mg/L for Cu; 0.0489–0.3474 mg/L for Fe; 0.0033–0.0285 mg/L for Mn; 0.0056–0.0222 mg/L for Ni; 0.0265–0.4753 mg/L for Pb and 0.0052–0.5594 mg/L for Zn. Modelling work was performed using PHREEQC couple with Geochemist’s workbench (GWB) to determine speciation dynamics and bioavailability of these pollutants. Modelling thus adds value to analytical methods and hence a better complementary tool to laboratory-based experimental studies.  相似文献   

17.
The Cerro Prieto dam, a relatively small water reservoir in NE Mexico, is one of the main resources of potable water for Monterrey, a city with a population of about four million inhabitants. A high resolution seismic study using non-linear parametric sub-bottom echo-sounder SES-2000 was carried out in this water reservoir. High resolution acoustic data interpretation shows that the thickness of recent sediments due to siltation of the reservoir reaches 3.5-4.0 m. It shows a high recent sedimentation rate (1-2 up to 14 cm/ year). Based on the echo-sounder data, the first bathymetric map and a digital model of recent sediment thickness were designed. A significant (5-12%) difference between the volume capacity value used by National Commission of Water (CNA) and acoustic survey results was revealed. Differences between the CNA and acoustic data indicate storage losses from 12-17 up to 30 million cubic meters. The results obtained through study such as this one, could be useful to improve a water resources management.  相似文献   

18.
During the past two-three decades the water chemistry in southern Norway has recovered considerably from acidification. The biological response, however, has been more variable. Thus, it has become increasingly apparent that decades of acidification may have masked other restrictors to fish populations in this area. The current study compiles data on young brown trout (Salmo trutta) density and water chemistry from 16 sites in River Sira in southwestern Norway during 2003–2014. The water chemistry during late snowmelt period was highly dilute, having a median conductivity and Ca of 10.5 μS/cm and 0.42 mg/l, respectively (n = 208). The corresponding minimum values were 5.0 μS/cm and 0.15 mg/l. With a pH median value of 5.89, the water was only slightly acidic. No effect of pH on the density of young brown trout was found, suggesting that acidification is no longer a limiting factor. However, both conductivity in year n-1 and Ca in year n correlated significantly with the density of 1+ brown trout. Al in year n, and surprisingly Ca in year n-1, correlated negatively on their densities. We conclude that very dilute water chemistry during late snowmelt is a limiting factor for the recruitment of brown trout in the study river. This effect has probably existed in the past as well, but has been less apparent due to decades of severe acidification.  相似文献   

19.
The Chilean Patagonian fjords region (41–56°S) is characterized by highly complex geomorphology and hydrographic conditions, and strong seasonal and latitudinal patterns in precipitation, freshwater discharge, glacier coverage, and light regime; all of these directly affect biological production in the water column. In this study, we compiled published and new information on water column properties (primary production, nutrients) and surface sediment characteristics (biogenic opal, organic carbon, molar C/N, bulk sedimentary δ13Corg) from the Chilean Patagonian fjords between 41°S and 55°S, describing herein the latitudinal pattern of water column productivity and its imprint in the underlying sediments. Based on information collected at 188 water column and 118 sediment sampling sites, we grouped the Chilean fjords into four main zones: Inner Sea of Chiloé (41° to ～44°S), Northern Patagonia (44° to ～47°S), Central Patagonia (48–51°S), and Southern Patagonia (Magellan Strait region between 52° and 55°S). Primary production in the Chilean Patagonian fjords was the highest in spring–summer, reflecting the seasonal pattern of water column productivity. A clear north–south latitudinal pattern in primary production was observed, with the highest average spring and summer estimates in the Inner Sea of Chiloé (2427 and 5860 mg C m?2 d?1) and Northern Patagonia (1667 and 2616 mg C m?2 d?1). This pattern was closely related to the higher availability of nutrients, greater solar radiation, and extended photoperiod during the productive season in these two zones. The lowest spring value was found in Caleta Tortel, Central Patagonia (91 mg C m?2 d?1), a site heavily influenced by glacier meltwater and river discharge loaded with glacial sediments. Biogenic opal, an important constituent of the Chilean fjord surface sediments (SiOPAL ～1–13%), reproduced the general north–south pattern of primary production and was directly related to water column silicic acid concentrations. Surface sediments were also rich in organic carbon content and the highest values corresponded to locations far away from glacier influence, sites within fjords, and/or semi-enclosed and protected basins, reflecting both autochthonous (water column productivity) and allochthonous sources (contribution of terrestrial organic matter from fluvial input to the fjords). A gradient was observed from the more oceanic sites to the fjord heads (west–east) in terms of bulk sedimentary δ13Corg and C/N ratios; the more depleted (δ13Corg ?26‰) and higher C/N (23) values corresponded to areas close to rivers and glaciers. A comparison of the Chilean Patagonian fjords with other fjord systems in the world revealed high variability in primary production for all fjord systems as well as similar surface sediment geochemistry due to the mixing of marine and terrestrial organic carbon.  相似文献   

20.
Evapotranspiration (LE) is an important factor for monitoring crops, water requirements, and water consumption at local and regional scale. In this paper, we applied the semi-empirical model to estimate the daily latent heat flux (LEd = Rnd + A − B(Ts − Ta)). LEd has been estimated using satellite images (Thematic Mapper sensor) and a local dataset (incoming and outgoing short- and long-wave radiation) measured during three years. We first estimated the daily net Radiation (Rnd) from a linear equation derived from the instantaneous net Radiation (Rnd = CRni + D). Subsequently, coefficients A and B have been estimated for two different cover vegetations (pasture and soybean). For each vegetation cover, an error analysis combining Rnd, A, B, and surface and air temperatures has been calculated. Results showed that Rnd had good performance (nonbias and low RMSE). LEd errors for pasture and soybean were ±28 W m−2 and ±40 W m−2 respectively.  相似文献   

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