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1.
Methodological Development of an Index of Coastal Water Quality: Application in a Tourist Area 总被引:2,自引:0,他引:2
With the aim of obtaining an index of coastal water quality, a methodological procedure based on numerical classification and discriminant analysis is presented. The procedure was applied to nutrient data (ammonia, nitrite, nitrate, and phosphate) analyzed along the coastal waters of a Spanish tourist area. Using numerical classification, three levels of nutrient loading were revealed, characterizing oligotrophic, mesotrophic, and potentially eutrophic waters. Discriminant analysis was shown to be an effective methodological tool in the discrimination between trophic groups. For every group, the discriminant procedure generated the centroids. The centroids representing oligotrophic and potentially eutrophic conditions were used to establish the two extremes of the continuum of mesotrophic conditions in these coastal waters: Standardizing values from -1 to 1, the centroids for oligotrophic and potentially eutrophic waters yielded an interval that defined the range of mesotrophic conditions. This interval is proposed as a water quality index. The ability of the coastal water quality index to successfully predict mesotrophic conditions was proved with random samples. 相似文献
2.
Nine similarity indices based on phytoplankton community structure were examined for their sensitivity to assess different
levels of eutrophication. Two phytoplankton data sets, one from an open coastal system and one from a semi-enclosed gulf,
associated with different nutrient dynamics and circulation patterns were used for evaluating the indices. The results have
shown that similarity indices, measuring interspecific association and resemblance of phytoplankton communities between enriched
areas and control sites, were effective for detecting spatial and temporal dissimilarities in coastal marine ecosystems. The
structure of the oligotrophic habitat as a potential source of ambiguity for the results was discussed, whereas the validity
ranges and the potential applicability of this method were deemed to be dependent on the size of the fraction of the common
species among the samples, and the similarity of the classification patterns resulted from this subcategory and those extracted
from the overall community data. Furthermore, the study provides a new technique based on the use of the “Box and Whisker
Plot” designed to distinguish opportunistic and rare phytoplanktonic species. The similarity indices, applied solely to the
dominant species abundance, were more sensitive to resolve eutrophic, mesotrophic and oligotrophic conditions. This procedure
can be proposed as an effective methodology for water characterization and can also be used as a qualitative tracer for detecting
renewal processes of coastal marine ecosystems. 相似文献
3.
Jan‐Tai Kuo Wen‐Cheng Liu Ruey‐Tyng Lin Wu‐Seng Lung Ming‐Der Yang Chou‐Ping Yang Show‐Chyuan Chu 《Journal of the American Water Resources Association》2003,39(3):671-687
ABSTRACT: Field data collected from the Feitsui Reservoir in Taiwan indicate that the water is at a stage between mesotrophic and eutrophic. Recent measurements such as total phosphorus, chlorophyll a and Secchi depth levels suggest that the water quality has been declining. A two‐dimensional, laterally averaged, finite difference hydrodynamic and water quality model was used to simulate the water quality in the Feitsui Reservoir in an effort to determine sound water quality management strategies. The model was calibrated and verified using data collected in 1996 and 1997. The calibrated model was used to simulate algal biomass (in terms of chlorophyll a) levels under various wasteload reduction scenarios. Model results show that 50 percent reduction of the total phosphorus load will improve the existing water quality, shifting the trophic status from eutrophic/mesotrophic to oligotrophic. The modeling effort has yielded valuable information that can be used by decision makers for the evaluation of different management strategies of reducing watershed nutrient loads. 相似文献
4.
Tiga Neya Akwasi. A. Abunyewa Oble Neya Benewende J-B Zoungrana Kangbeni Dimobe Hypolite Tiendrebeogo John Magistro 《Environmental management》2020,65(2):203-211
Agroforestry plays an important role in climate mitigation through atmospheric carbon removal by photosynthetic activity of tree. However, the carbon sequestration potential of smallholder’s agroforestry’s parklands is not well documented in Burkina Faso. Therefore, agroforestry parkland of smallholders’ farmers in three climatic zones was studied. Thirty household farmlands in each climatic zone representing about 35 ha were selected on which systematic woody species inventory and dendrometry data collections were undertaken. Nondestructive method using fitted allometrics equations was used to compute carbon stock. Sustainability analysis of carbon sequestration potential was done using ]0–10], ]10–40], and ]40–110 cm] diameter class as long term, medium term, and short term, respectively. The balance between marketable carbon value and the trade-off from tree conservation of three major crops was also analyzed. The results revealed 24.71 ± 5.84 tCO2 ha−1, 28.35 ± 5.84 tCO2 ha−1, and 33.86 ± 5.84 tCO2 ha−1 in Ouahigouya, Sapouy, and Bouroum-Bouroum at p < 0.1 respectively. Long- and short-term carbon sequestration potential was attributed to Ouahigouya with 1.82 and 68.03%, respectively. With, the medium term analysis Sapouy came first with 71.71% of total amount of carbon. The marketable carbon value was less than trade-off value resulting in keeping trees and crop production. The balance analysis revealed that carbon payment system promoted by REDD+ initiative will be profitable and compensable to smallholder farmers effort to plant and keep tree when the tCO2 ha−1 price will be around US$ 4.00. By taking into account farmers’ interests and profitability on carbon market will be the most relevant incentive method to enhance carbon stock in agroforestry parkland. 相似文献
5.
ABSTRACT: Trophic classification of the Canadian nearshore waters of the Great Lakes is attempted using summer, surface water quality data for the early 1970's. A generalized Composite Trophic Index is developed using paired linear relationships for total phosphorus, chlorophyll a, and Secchi depth data for 66 defined nearshore regions. The chlorophyll a and total phosphorus relationship indicates that the nearshore waters contain a low chlorophyll a concentration for a given total phosphorus concentration than observed for the open waters of the Great Lakes or for smaller Canadian lakes. The most eutrophic nearshore regions occur in areas of relatively restricted circulation and/or high nutrient loadings. These include the Bay of Quinte, Toronto and Hamilton harbours, and portions of Lake We's Western Basin. Lakes Huron and Superior are generally oligotrophic, except for some embayments. Although nearshore water quality is highly variable, this apprach represents a reasonable compromise with respect to analytical complexity. The Composite Trophic Index removes biases introduced through the use of a single trophic state indicator and uniquely describes the nearshore water quality in terms generally comparable to other water bodies. 相似文献
6.
J. Shaun Dustin A. Woodruff Miller 《Journal of the American Water Resources Association》2001,37(4):887-898
ABSTRACT: Increased visitation at Grand Teton National Park (GTNP) has raised concerns about impacts on surface water in the park. The purposes of this study are to perform a benchmark trophic state survey for comparison to future evaluations and to identify possible areas of concern. Four watershed regions based on geographic and geologic features were delineated for study. Six Alpine lakes, six Moraine lakes, three Valley lakes, and two Colter Bay lakes are evaluated. Lakes were sampled for total phosphorus (TP), chlorophyll‐a, and transparency. The water quality, as defined by trophic state, in the park is generally good. Oligotrophic to mesotrophic conditions were found in the Alpine and Moraine lakes and mesotrophic to eutrophic conditions were found in the Colter Bay and Valley lakes. High inflow TP concentrations in the park's northeast side may be due to the presence of natural geologic phosphate from the Phosphoria Formation. 相似文献
7.
Paul D. Uttormark Mark L. Hutchins 《Journal of the American Water Resources Association》1980,16(3):494-500
ABSTRACT: Over the past several years, input/output models have been used increasingly as decisionmaking aids in the design of lake restoration activities because they provide an approximation of the link between nutrient influx and lake trophic status. To evaluate the applicability of these models as design tools, a study was conducted in which “before” and “after” data were obtained for 25 lakes which experienced reductions in nutrient inflow, and comparisons were made of observed and predicted changes in lake conditions. Three input/output models were used as predictive tools to describe lake response: those reported by Dillon and Rigler (1974) and by Vollenweider (1975, 1976). Based on described trophic states of oligotrophic, mesotrophic, and eutrophic, it was found that all three models yielded accurate predictions for at least 70 percent of the study lakes. The model of Vollenweider (1976) performed slightly better than the other two (80 percent correct) on the data set studied. 相似文献
8.
KEVIN M. BROWN R. MICHAEL ERWIN MILO E. RICHMOND P. A. BUCKLEY JOHN T. TANACREDI DAVE AVRIN 《Environmental management》2001,28(2):207-224
During the 1980s, the exponential growth of laughing gull (Larus atricilla) colonies, from 15 to about 7600 nests in 1990, in the Jamaica Bay Wildlife Refuge and a correlated increase in the bird-strike
rate at nearby John F. Kennedy International Airport (New York City) led to a controversy between wildlife and airport managers
over the elimination of the colonies. In this paper, we review data to evaluate if: (1) the colonies have increased the level
of risk to the flying public; (2) on-colony population control would reduce the presence of gulls, and subsequently bird strikes,
at the airport; and (3) all on-airport management alternatives have been adequately implemented. Since 1979, most (2987, 87%)
of the 3444 bird strikes (number of aircraft struck) were actually bird carcasses found near runways (cause of death unknown
but assumed to be bird strikes by definition). Of the 457 pilot-reported strikes (mean = 23 ± 6 aircraft/yr, N= 20 years), 78 (17%) involved laughing gulls. Since a gull-shooting program was initiated on airport property in 1991, over
50,000 adult laughing gulls have been killed and the number of reported bird strikes involving laughing gulls has declined
from 6.9 ± 2.9 (1983–1990) to 2.6 ± 1.3 (1991–1998) aircraft/yr; nongull reported bird strikes, however, have more than doubled
(6.4 ± 2.6, 1983–1990; 14.9 ± 5.1, 1991–1998). We found no evidence to indicate that on-colony management would yield a reduction
of bird strikes at Kennedy Airport. Dietary and mark–recapture studies suggest that 60%–90% of the laughing gulls collected
on-airport were either failed breeders and/or nonbreeding birds. We argue that the Jamaica Bay laughing gull colonies, the
only ones in New York State, should not be managed at least until all on-airport management alternatives have been properly
implemented and demonstrated to be ineffective at reducing bird strikes, including habitat alterations and increasing the
capability of the bird control unit to eliminate bird flocks on-airport using nonlethal bird dispersal techniques. Because
the gull-shooting program may be resulting in a nonsustainable regional population of laughing gulls (>30% decline), we also
recommend that attempts be made to initiate an experimental colony elsewhere on Long Island to determine if colony relocation
is a feasible management option. 相似文献
9.
C. Tara. Marshall Antoine Morin Robert H. Peters 《Journal of the American Water Resources Association》1988,24(5):1027-1034
ABSTRACT: Data from 56 north-temperate lakes and reservoirs are used to develop models predicting temporal variance as a function of the mean chlorophyll-a concentration. Trophy, as estimated by mean chlorophyll-a concentration, is shown to have little effect on the sampling effort required to achieve a pre-determined level of precision for lakes sampled year-round. Collecting ten observations results in a coefficient of variation that averaged 20 percent; collecting more than ten observations yields increasingly marginal improvements in precision. The same guidelines apply to mesotrophic or eutrophic lakes sampled in the summer, whereas oligotrophic lakes sampled in the summer require fewer observations to achieve the same level of precision. The bias resulting from collecting too few observations is minimized if five or more observations are collected. 相似文献
10.
Quantifying the Effect of Ecological Restoration on Soil Erosion in China’s Loess Plateau Region: An Application of the MMF Approach 总被引:5,自引:0,他引:5
Changbin Li Jiaguo Qi Zhaodong Feng Runsheng Yin Biyun Guo Feng Zhang Songbing Zou 《Environmental management》2010,45(3):476-487
Land degradation due to erosion is one of the most serious environmental problems in China. To reduce land degradation, the
government has taken a number of conservation and restoration measures, including the Sloping Land Conversion Program (SLCP),
which was launched in 1999. A logical question is whether these measures have reduced soil erosion at the regional level.
The objective of this article is to answer this question by assessing soil erosion dynamics in the Zuli River basin in the
Loess Plateau of China from 1999 to 2006. The MMF (Morgan, Morgan and Finney) model was used to simulate changes in runoff
and soil erosion over the period of time during which ecological restoration projects were implemented. Some model variables
were derived from remotely sensed images to provide improved land surface representation. With an overall accuracy rate of
0.67, our simulations show that increased ground vegetation cover, especially in forestlands and grasslands, has reduced soil
erosion by 38.8% on average from 1999 to 2006. During the same time period, however, the change in rainfall pattern has caused
a 13.1% ± 4.3% increase in soil erosion, resulting in a net 25.7% ± 8.5% reduction in soil erosion. This suggests that China’s
various ecological restoration efforts have been effective in reducing soil loss. 相似文献
11.
Crab samples, both male and female specie, were purchased from fishermen at the Ojo Rivers, Lagos, Nigeria. The samples separated
into abdomen, muscle tissue, and thorax were oven dried at 80°C for 3 days. The dried samples were then pulverized in a clean
acid-washed mortar and pestle. Approximately 1.00 g each of the pulverized samples was weighed and Zn, Cr, Pb, and Cd were
determined in the solution of the aqua regia digested samples by means of AAS (Buck Scientific 210 GVP model). The results
obtained showed Zn metal to be consistently higher in all the female parts compared to the male with values of 12.92 ± 3.65 μg/g
to 16.03 ± 1.08 μg/g and 9.33 ± 1.77 μg/g to 15.75 ± 1.02 μg/g, respectively. Mean values of 0.39 ± 0.09 μg/g and 0.22 ± 0.02 μg/g
cadmium were found in the abdomen and tissue of the male crab as against 0.35 ± 0.07 μg/g and 0.17 ± 0.07 μg/g in the female
crab. The tissues of both species have comparable value of chromium. Lead was below the detection limit of 0.05 μg/g in the
tissues of male crab but the female tissue contained 0.83 ± 0.13 μg/g and in other parts identified, lead was consistently
higher than the 2.00 μg/g permissible level of WHO in foods. A simple pair t-test did not demonstrate any significant difference in the distribution of metals between the male and female crabs. The
coefficient of variation (CV) calculated for each metal with respect to the studied parts showed Pb to be widely distributed
(56.23–89.54%) while Cr did not vary widely (4.17–8.20%). 相似文献
12.
Clifford A. Siegfried 《Journal of the American Water Resources Association》1982,18(4):613-620
Phosphorus loading from precipitation and more than a dozen tributaries of Big Beat Lake, Woman, was determined for the period from January to December 1978. Direct precipitation contributed 1120 kg·P·yr-1 (0.096 g P·m-2·yr-1) while tributary runoff contributed 21,560 kg for a total P loading of 1.84 g P·m-2 Rathbone creek, although accounting for only 4 percent of the hydro-logic input to Big Bear Lake, contributed >27 percent of the annual phosphorus load. Phosphorus loading increased with increased impervious geology and increased development. Nitrogen loading exhibited similar loading patterns. Big Beat Lake is currently eutrophic and is likely to remain eutrophic. Calculations based on Vollenweider's critical phosphorus loading concept indicated that tributary P-loading would have to be reduced by >95 percent to achieve mesotrophic conditions. The completion of Big Bear Dam created a “naturally” eutrophic re mix which dl require proper management to enhance its resource potential. 相似文献
13.
Theodore E. Endreny Gregory D. Jennings 《Journal of the American Water Resources Association》1999,35(2):363-377
ABSTRACT: Recent developments in water quality monitoring have generated interest in combining non-probability and probability data to improve water quality assessment. The Interagency Task Force on Water Quality Monitoring has taken the lead in exploring data combination possibilities. In this paper we take a developed statistical algorithm for combining the two data types and present an efficient process for implementing the desired data augmentation. In a case study simulated Environmental Protection Agency (EPA) Environmental Monitoring and Assessment Program (EMAP) probability data are combined with auxiliary monitoring station data. Auxiliary stations were identified on the STORET water quality database. The sampling frame is constructed using ARC/INFO and EPA's Reach File-3 (RF3) hydrography data. The procedures for locating auxiliary stations, constructing an EMAP-SWS sampling frame, simulating pollutant exposure, and combining EMAP and auxiliary stations were developed as a decision support system (DSS). In the case study with EMAP, the DSS was used to quantify the expected increases in estimate precision. The benefit of using auxiliary stations in EMAP estimates was measured as the decrease in standard error of the estimate. 相似文献
14.
Hatch L Clark C Merrick R Van Parijs S Ponirakis D Schwehr K Thompson M Wiley D 《Environmental management》2008,42(5):735-752
In 2006, we used the U.S. Coast Guard’s Automatic Identification System (AIS) to describe patterns of large commercial ship
traffic within a U.S. National Marine Sanctuary located off the coast of Massachusetts. We found that 541 large commercial
vessels transited the greater sanctuary 3413 times during the year. Cargo ships, tankers, and tug/tows constituted 78% of
the vessels and 82% of the total transits. Cargo ships, tankers, and cruise ships predominantly used the designated Boston
Traffic Separation Scheme, while tug/tow traffic was concentrated in the western and northern portions of the sanctuary. We
combined AIS data with low-frequency acoustic data from an array of nine autonomous recording units analyzed for 2 months
in 2006. Analysis of received sound levels (10–1000 Hz, root-mean-square pressure re 1 μPa ± SE) averaged 119.5 ± 0.3 dB at
high-traffic locations. High-traffic locations experienced double the acoustic power of less trafficked locations for the
majority of the time period analyzed. Average source level estimates (71–141 Hz, root-mean-square pressure re 1 μPa ± SE)
for individual vessels ranged from 158 ± 2 dB (research vessel) to 186 ± 2 dB (oil tanker). Tankers were estimated to contribute
2 times more acoustic power to the region than cargo ships, and more than 100 times more than research vessels. Our results
indicate that noise produced by large commercial vessels was at levels and within frequencies that warrant concern among managers
regarding the ability of endangered whales to maintain acoustic contact within greater sanctuary waters.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
15.
Surendra Suthar 《The Environmentalist》2008,28(2):76-84
The potential of the epigeic earthworm Eisenia fetida to stabilize sludge␣(generated from a distillation unit of the sugar industry) mixed with cow dung, in different proportions
i.e. 20% (T1), 40% (T2), 60% (T3) and 80% (T4) has been studied under laboratory conditions for 90 days. The␣ready vermicompost was evaluated for its’ different physico-chemical
parameters using standard methods. At the end of experiment, all vermibeds expressed a significant decrease in pH (7.8–19.2%)
organic C (8.5–25.8%) content, and an increase in total N (130.4–170.7%), available P (22.2–120.8%), exchangeable K (104.9–159.5%),
exchangeable Ca (49.1–118.1%), and exchangeable Mg (13.6–51.2%) content. Overall, earthworms could maximize decomposition
and mineralization efficiency in bedding with lower proportions of distillery sludge. DTPA extractable metal reduction in
substrate was recorded between the ranges of 12.5–38.8% for Zn, 5.9–30.4% for Fe, 4.7–38.2% for Mn and 4.5–42.1% for Cu. Maximum
values for the mean individual live weight (809.69 ± 20.09 mg) and maximum individual growth rate (mg wt. worm−1 day−1) (5.81 ± 0.18) of earthworms was noted in T1 treatment, whereas cocoon numbers (69.0 ± 7.94) and individual reproduction rate (cocoon worm−1 day−1) (0.046 ± 0.002) was highest in T2 treatment. Earthworm mortality tended to increase with increasing proportion of distillery sludge, and maximum mortality
in E. fetida was recorded for the T4 (45.0 ± 5.0) treatment. Results indicate that vermicomposting might be useful for managing the energy and nutrient rich distillery
sludge on a low-input basis. Products of this process can be used for sustainable land restoration practices. The feasibility
of worms to mitigate the toxicity of metals also reduces the possibility of soil contamination, which has been reported in
earlier studies during direct field application of industrial wastes. 相似文献
16.
The Great Lakes Hydrography Dataset: Consistent,Binational Watersheds for the Laurentian Great Lakes Basin 下载免费PDF全文
Danielle K. Forsyth Catherine M. Riseng Kevin E. Wehrly Lacey A. Mason John Gaiot Tom Hollenhorst Craig M. Johnston Conrad Wyrzykowski Gust Annis Chris Castiglione Kent Todd Mike Robertson Dana M. Infante Lizhu Wang James E. McKenna Gary Whelan 《Journal of the American Water Resources Association》2016,52(5):1068-1088
Ecosystem‐based management of the Laurentian Great Lakes, which spans both the United States and Canada, is hampered by the lack of consistent binational watersheds for the entire Basin. Using comparable data sources and consistent methods, we developed spatially equivalent watershed boundaries for the binational extent of the Basin to create the Great Lakes Hydrography Dataset (GLHD). The GLHD consists of 5,589 watersheds for the entire Basin, covering a total area of approximately 547,967 km2, or about twice the 247,003 km2 surface water area of the Great Lakes. The GLHD improves upon existing watershed efforts by delineating watersheds for the entire Basin using consistent methods; enhancing the precision of watershed delineation using recently developed flow direction grids that have been hydrologically enforced and vetted by provincial and federal water resource agencies; and increasing the accuracy of watershed boundaries by enforcing embayments, delineating watersheds on islands, and delineating watersheds for all tributaries draining to connecting channels. In addition, the GLHD is packaged in a publically available geodatabase that includes synthetic stream networks, reach catchments, watershed boundaries, a broad set of attribute data for each tributary, and metadata documenting methodology. The GLHD provides a common set of watersheds and associated hydrography data for the Basin that will enhance binational efforts to protect and restore the Great Lakes. 相似文献
17.
Surendra Suthar 《The Environmentalist》2007,27(3):329-335
Efforts have been made to convert the guar gum industrial waste into a value-added product, by employing a new earthworm species
for vermicomposting e.g. Perionyx sansibaricus (Perrier) (Megascolecidae), under laboratory conditions. Industrial lignocellulosic waste was amended with other organic
supplements (saw dust and cow dung); and three types of vermibeds were prepared: guar gum industrial waste + cow dung + saw
dust in 40: 30: 30 ratio (T1), guar gum industrial waste + cow dung + saw dust in 60: 20: 20 ratio (T2,), and guar gum industrial waste + cow dung + saw dust in 75: 15: 10 ratio (T3). As compared to initial concentrations, vermicomposts exhibited a decrease in organic C content (5.0–11.3%) and C:N ratio
(11.1–24.4%) and an increase in total N (18.4–22.8%), available P (39.7–92.4%), and exchangeable K (9.4–19.7%) contents, after
150 days of vermicomposting. A vermicomposting coefficient (VC) was used to compare of vermicomposting with the experimental control (composting). P. sansibaricus exhibited maximum value of mean individual live weight (742.8 ± 21.1 mg), biomass gain (442.94 ± 21.8 mg), growth rate (2.95 ± 0.15 mg
day−1), cocoon numbers (96.0 ± 5.1) and reproduction rate (cocoons worm−1 day−1) (0.034 ± 0.001) in T2 treatment. In T3 maximum mortality (30.0 ± 4.01 %) in earthworm population was observed. Overall, T2 vermibed appeared as an ideal substrate to manage guar gum industrial waste effectively. Vermicomposting can be proposed
as a low-input basis technology to convert industrial waste into value-added biofertilizer. 相似文献
18.
Accumulation of bacterial cells on a transparent electrode was controlled by applying an alternating potential. Live and
dead cells on a transparent electrode can be distinguished as blue and red cells, by staining with two fluorescent dyes, propidium
iodide (PI) and 4′, 6-diamidino- 2-phenylindole dihydrochloride (DAPI) and propidium iodide (PI), respectively. Cells of
the gram-negative marine bacterium, Vibrio alginolyticus attached to an indium/tin oxide (ITO) electrode were killed by applying a potential of 1.1 V versus saturated calomel electrode
in seawater. By applying –0.4 V, 73% of the cells on the ITO electrode were desorbed in 10 min. Changes in pH and generation
of chlorine were not observed after applying potentials in the range of –0.4∼1.2 V. After 21 h of immersion in V. alginolyticus cell suspension with the application of an alternating potential of 1.1 and –0.4 V, cells on the electrode were completely
killed and the cell number decreased to 20% of that of no potential. Elution of indium and tin was not observed after 10 days
application of alternating potential.
Received: 11 August 1998 / Accepted: 30 September 1998 相似文献
19.
The regional-scale importance of an aquatic stressor depends both on its regional extent (i.e., how widespread it is) and
on the severity of its effects in ecosystems where it is found. Sample surveys, such as those developed by the U.S. Environmental
Protection Agency’s Environmental Monitoring and Assessment Program (EMAP), are designed to estimate and compare the extents,
throughout a large region, of elevated conditions for various aquatic stressors. In this article, we propose relative risk
as a complementary measure of the severity of each stressor’s effect on a response variable that characterizes aquatic ecological
condition. Specifically, relative risk measures the strength of association between stressor and response variables that can
be classified as either “good” (i.e., reference) or “poor” (i.e., different from reference). We present formulae for estimating
relative risk and its confidence interval, adapted for the unequal sample inclusion probabilities employed in EMAP surveys.
For a recent EMAP survey of streams in five Mid-Atlantic states, we estimated the relative extents of eight stressors as well
as their relative risks to aquatic macroinvertebrate assemblages, with assemblage condition measured by an index of biotic
integrity (IBI). For example, a measure of excess sedimentation had a relative risk of 1.60 for macroinvertebrate IBI, with
the meaning that poor IBI conditions were 1.6 times more likely to be found in streams having poor conditions of sedimentation
than in streams having good sedimentation conditions. We show how stressor extent and relative risk estimates, viewed together,
offer a compact and comprehensive assessment of the relative importances of multiple stressors. 相似文献
20.
The impact of anthropogenic activities on the fluctuation of nutrients along the Densu River and its tributaries was studied.
High concentrations of nutrients were observed in the study area but the river was found to be circumneutral and fresh with
pH ranging between 6.54 and 7.84. The levels of NH4
+–N ranged between 0.21 and 2.1 mg L−1 with mean concentration of 1.19 ± 0.02 mg L−1 while that of nitrate is between 0.13 and 5.21 mg L−1 with a mean concentration of 2.07 ± 0.01 mg L−1. The levels of PO4
3−–P fluctuated within the range 0.54 and 1.04 mg L−1 with a mean of 0.84 ± 0.01 mg L−1. The Densu River Basin was also found to be with organic matter with depleted dissolved oxygen. The river recorded high BOD
values ranging from 6.91 to 18.8 mg L−1. Concentration of nutrients and organic pollutants increased as a consequence of anthropogenic inputs particularly from domestic,
agricultural and municipal sources. The highly impaired sites were those located close to the urbanized, agricultural and
high-density residential areas. The relatively high concentration of nitrate and phosphate in the river indicated that it
was quite eutrophic. 相似文献