共查询到20条相似文献,搜索用时 31 毫秒
1.
For the last 20 years, human–wildlife conflicts have been rapidly increasing in towns. Although people want “greener” cities,
the expansion of disliked species causes problems that are difficult to manage and to reduce. The complexity of the numerous
factors involved in these human–wildlife relations needs the development of a comprehensive tool for urban planners. Today,
with the development of computers and geographical information systems, it is easier to analyze and combine different spatial
data as methods used for the management of risks in studies of natural hazards. Here we present a method for assessing and
mapping the risk in cases of human–wildlife conflict. An application to starling management in a town in western France will
show the efficiency of our methods to combine information given by a network of experts and to highlight higher risk sites.
The map of risk provides a spatial result useful for comprehension, communication between people and agencies, and public
education. 相似文献
2.
Construction of six large dams and reservoirs on the Missouri River over the last 50–75 years has resulted in major landscape
changes and alterations in flow patterns, with implications for riparian forests dominated by plains cottonwood (Populus deltoides). We quantified changes in land cover from 1892–1950s and the 1950s–2006 and the current extent and age structure of cottonwood
forests on seven segments (two reservoir and five remnant floodplain) comprising 1127 km (53 %) of the unchannelized upper
two-thirds of the Missouri River. Riparian forest area declined by 49 %; grassland 61 %; shrubland 52 %; and sandbar habitat
96 %; while agricultural cropland increased six-fold and river/reservoir surface area doubled from 1892 to 2006. Net rates
of erosion and accretion declined between the 1892–1950s and 1950s–2006 periods. Accretion exceeded erosion on remnant floodplain
segments, resulting in declines in active channel width, particularly in 1950s–2006. Across all study segments in 2006, most
cottonwood stands (67 %) were >50 years old, 22 % were 25–50 years old, and only 10 % were <25 years old. Among stands <50 years
old, the higher proportion of 25–50 year old stands represents recruitment that accompanied initial post-dam channel narrowing;
while declines in sandbar and shrubland area and the low proportion of stands <25 years old suggest declines in geomorphic
dynamism and limited recruitment under recent river management. Future conservation and restoration efforts should focus both
on limiting further loss of remnant cottonwood stands and developing approaches to restore river dynamics and cottonwood recruitment
processes. 相似文献
3.
Posttreatment Tree Mortality After Forest Ecological Restoration,Arizona, United States 总被引:1,自引:0,他引:1
Pine–oak forests are of high ecological importance worldwide, but many are threatened by uncharacteristically severe wildfire.
Forest restoration treatments, including the reintroduction of a surface fire regime, are intended to decrease fire hazard
and emulate historic ecosystem structure and function. Restoration has recently received much management attention and short-term
study, but little is known about longer-term ecosystem responses. We remeasured a replicated experimental restoration site
in the southwestern United States 5 years after treatments. Basal area, tree density, and canopy cover decreased in the treated
units at a faster rate than in controls. Delayed mortality, not evident right after treatment, decreased density modestly
(13% in treated units and 10% in controls) but disproportionately affected large trees (“large” ponderosa pines were those
with diameter at breast height [dbh] ≥37.5 cm; other species dbh ≥20 cm). In treated units, 10.9 large trees ha–1 died, whereas 6.2 trees ha–1 died in control units. Compared with reference conditions, the experimental blocks remained higher in pine density and, in
three of the four blocks, in basal area. Pine trees grew significantly faster in treated units than in controls, enough to
reach the reference level of basal area in 6 years. Although mortality of large trees is a concern, the treated units have
vigorous growth and low density, indicating that they will be relatively resistant to future drought and fire events. Similar
treatments may be beneficial in many areas of the United States and in related pine-oak ecosystems elsewhere. 相似文献
4.
Kyle A. Young 《Environmental management》2000,26(2):131-144
Oncorhynchus sp.), regional governments now restrict timber harvest in riparian forests. I summarize and assess the riparian zone management
guidelines of the states of California, Oregon, and Washington (USA) and the province of British Columbia (Canada). Only Oregon
and British Columbia protect fish-bearing streams with “no-harvest” zones, and only the wider (20–50 m) no-harvest zones for
larger fish-bearing streams in British Columbia are likely to maintain near-natural linkages between riparian and stream ecosystems.
All four jurisdictions protect most streams with “management zones” of variable width, in which timber harvest activities
are restricted. All the management zone guidelines permit the harvest of the largest conifers from riparian forests and will,
if applied over a series of timber harvest rotations (60–80 years), result in the continued removal of potential sources of
large woody debris from the region's watersheds. All four jurisdictions require additional protection for streams and watersheds
that are severely degraded or (in the United States) contain threatened or endangered species. The governments of the PNW
have taken a “manage until degraded, then protect” approach to riparian forest management that is unlikely to maintain or
restore the full suite of riparian-stream linkages necessary for lotic ecosystems to function naturally at the stream, watershed,
basin, or regional scale. 相似文献
5.
Degradation of warmwater streams in agricultural landscapes is a pervasive problem, and reports of restoration effectiveness
based on monitoring data are rare. Described is the outcome of rehabilitation of two deeply incised, unstable sand-and-gravel-bed
streams. Channel networks of both watersheds were treated using standard erosion control measures, and aquatic habitats within
1-km-long reaches of each stream were further treated by addition of instream structures and planting woody vegetation on
banks (“habitat rehabilitation”). Fish and their habitats were sampled semiannually during 1–2 years before rehabilitation,
3–4 years after rehabilitation, and 10–11 years after rehabilitation. Reaches with only erosion control measures located upstream
from the habitat measure reaches and in similar streams in adjacent watersheds were sampled concurrently. Sediment concentrations
declined steeply throughout both watersheds, with means ≥40% lower during the post-rehabilitation period than before. Physical
effects of habitat rehabilitation were persistent through time, with pool habitat availability much higher in rehabilitated
reaches than elsewhere. Fish community structure responded with major shifts in relative species abundance: as pool habitats
increased after rehabilitation, small-bodied generalists and opportunists declined as certain piscivores and larger-bodied
species such as centrarchids and catostomids increased. Reaches without habitat rehabilitation were significantly shallower,
and fish populations there were similar to the rehabilitated reaches prior to treatment. These findings are applicable to
incised, warmwater streams draining agricultural watersheds similar to those we studied. Rehabilitation of warmwater stream
ecosystems is possible with current knowledge, but a major shift in stream corridor management strategies will be needed to
reverse ongoing degradation trends. Apparently, conventional channel erosion controls without instream habitat measures are
ineffective tools for ecosystem restoration in incised, warmwater streams of the Southeastern U.S., even if applied at the
watershed scale and accompanied by significant reductions in suspended sediment concentration. 相似文献
6.
Observations on above ground litter decomposition and nutrient release in alpine ecosystem of the Himalaya were carried out.
Monthly variation was observed for above ground litter crop and it was higher in the protected sites (PR) when compared with
unprotected sites (UNPR). Turnover rate (TR) and time (TT) was also higher in PR sites and it corresponded to maximum net
accumulation of standing dead and litter biomass. This resulted into low litter disappearance and therefore, low nutrient
fluxes as well. Comparatively, potassium content was a maximum followed by N and OC in above ground crop of litter with significant
variation among the sites (P < 0.001 and 0.005, respectively). It was observed that only 9–12% litter of various categories was decomposed annually at
the rate of 0.1–0.13%. Overall, decomposition process was a maximum during active growth season and only 13.2–16.2% of total
litter was decomposed during the winter months (December–March). Release of OC and NPK to soil organic matter through the
decomposition of various litter types was also observed and the pattern of release was similar to that of disappearance channel.
All these parameters are reported and possible reasons are described in the present paper. 相似文献
7.
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
8.
Forest certification is a mechanism involving the regulation of trade of forest products in order to protect forest resources
and improve forest management. Although China had a late start in adopting this process, the country has made good progress
in recent years. As of July 31, 2009, 17 forest management enterprises and more than one million hectares of forests in China
have been certified by the Forest Stewardship Council (FSC). Several major factors affect forest certification in China. The
first set is institutional in nature. Forest management in China is based on centralized national plans and therefore lacks
flexibility. A second factor is public awareness. The importance and value of forest certification are not widely understood
and thus consumers do not make informed choices regarding certified forest products. The third major factor is the cost of
certification. Together these factors have constrained the development of China’s forest certification efforts. However, the
process does have great potential. According to preliminary calculations, if 50% of China’s commercial forests were certified,
the economic cost of forest certification would range from US$0.66–86.63 million while the economic benefits for the forestry
business sector could exceed US$0.66–86.63 million while the economic benefits for the forestry
business sector could exceed US150 million. With continuing progress in forest management practices and the development of
international trade in forest products, it becomes important to improve the forest certification process in China. This can
be achieved by improving the forest management system, constructing and perfecting market access mechanisms for certificated
forest products, and increasing public awareness of environmental protection, forest certification, and their interrelationship. 相似文献
9.
Impact of industrial air pollutants on some biochemical parameters and yield in wheat and mustard plants 总被引:1,自引:0,他引:1
The present study was carried out to determine the impacts of SO2, NO
x
, SPM and RSPM, the most common air pollutants, generated mainly due to industries and vehicles, on some biochemical parameters
and yield in wheat and mustard plants during 2006. The concentration of SO2, NO
x
, SPM and RSPM was determined at the polluted sites across the seasons, which ranged between 14.29–18.10, 20.81–22.43, 483.65–500.85
and 160.67–171.18 μg m−3, respectively. The wheat and mustard plants grown at polluted sites showed significant reduction in chlorophyll ‘a’, chlorophyll ‘b’, total chlorophyll, carotenoid, ascorbic acid, pH, relative water content and yield. The data were further analyzed using
a two way ANOVA. It is concluded that the ambient air pollutants have a potential adverse impact on biochemical parameters,
which further leads to a reduction in the yield of wheat and mustard crops. 相似文献
10.
Section 404 wetland mitigation and permit success criteria in Pennsylvania,USA, 1986-1999 总被引:2,自引:1,他引:1
Twenty-three Section 404 permits in central Pennsylvania (covering a wetland age range of 1–14 years) were examined to determine
the type of mitigation wetland permitted, how the sites were built, and what success criteria were used for evaluation. Most
permits allowed for mitigation out-of-kind, either vegetatively or through hydrogeomorphic class. The mitigation process has
resulted in a shift from impacted wetlands dominated by woody species to less vegetated mitigation wetlands, a trend that
appears to be occurring nationwide. An estimate of the percent cover of emergent vegetation was the only success criterion
specified in the majority of permits. About 60% of the mitigation wetlands were judged as meeting their originally defined
success criteria, some after more than 10 years. The permit process appears to have resulted in a net gain of almost 0.05
ha of wetlands per mitigation project. However, due to the replacement of emergent, scrub–shrub, and forested wetlands with
open water ponds or uplands, mitigation practices probably led to a net loss of vegetated wetlands. 相似文献
11.
Fire occurrences and their sources were monitored in Emas National Park, Brazil (17°49′–18°28′S; 52°39′–53°10′W) from June
1995 to May 1999. The extent of burned area and weather conditions were registered. Forty-five fires were recorded and mapped
on a GIS during this study. Four fires occurred in the dry winter season (June–August; 7,942 ha burned), all caused by humans;
10 fires occurred in the seasonally transitional months (May and September) (33,386 ha burned); 31 fires occurred in the wet
season, of which 30 were caused by lightning inside the park (29,326 ha burned), and one started outside the park (866 ha
burned). Wet season lightning fires started in the open vegetation (wet field or grassy savanna) at a flat plateau, an area
that showed significantly higher fire incidence. On average, winter fires burned larger areas and spread more quickly, compared
to lightning fires, and fire suppression was necessary to extinguish them. Most lightning fires were patchy and extinguished
primarily by rain. Lightning fires in the wet season, previously considered unimportant episodes, were shown to be very frequent
and probably represent the natural fire pattern in the region. Lightning fires should be regarded as ecologically beneficial,
as they create natural barriers to the spread of winter fires. The present fire management in the park is based on the burning
of preventive firebreaks in the dry season and exclusion of any other fire. This policy does not take advantage of the beneficial
effects of the natural fire regime and may in fact reduce biodiversity. The results presented here stress the need for reevaluating
present policies and management procedures concerning fire in cerrado conservation areas. 相似文献
12.
Long-Term Variability in Bioassessments: A Twenty-Year Study from Two Northern California Streams 总被引:2,自引:2,他引:0
Long-term variability of bioassessments has not been well evaluated. We analyzed a 20-year data set (1984–2003) from four
sites in two northern California streams to examine the variability of bioassessment indices (two multivariate RIVPACS-type
O/E scores and one multimetric index of biotic integrity, IBI), as well as eight metrics. All sites were sampled in spring;
one site was also sampled in summer. Variability among years was high for most metrics (coefficients of variation, CVs ranging
from 16% to 246% in spring) but lower for indices (CVs of 22–26% for the IBI and 21–32% for O/E scores in spring), which resulted
in inconsistent assessments of biological condition. Variance components analysis showed that the time component explained
variability in all metrics and indices, ranging from 5% to 35% of total variance explained. The site component was large (i.e.,
>40%) for some metrics (e.g., EPT richness), but nearly absent from others (e.g., Diptera richness). Seasonal analysis at
one site showed that variability among seasons was small for some metrics or indices (e.g., Coleoptera richness), but large
for others (e.g., EPT richness, O/E scores). Climatic variables did not show consistent trends across all metrics, although
several were related to the El Ni?o Southern Oscillation Index at some sites. Bioassessments should incorporate temporal variability
during index calibration or include climatic variability as predictive variables to improve accuracy and precision. In addition,
these approaches may help managers anticipate alterations in reference streams caused by global climate change and high climatic
variability. 相似文献
13.
Ana M. Nobre 《Environmental management》2009,44(1):185-204
An adaptation of the Drivers-Pressure-State-Impact-Response methodology is presented in this work. The differential DPSIR
(ΔDPSIR) was developed to evaluate impacts on the coastal environment and as a tool for integrated ecosystem management. The
aim of the ΔDPSIR is to provide scientifically-based information required by managers and decision-makers to evaluate previously
adopted policies, as well as future response scenarios. The innovation of the present approach is to provide an explicit link
between ecological and economic information related to the use and management of a coastal ecosystem within a specific timeframe.
The application of ΔDPSIR is illustrated through an analysis of developments in a Southwest European coastal lagoon between
1985 and 1995. The value of economic activities dependent on the lagoon suffered a significant reduction (ca. −60%) over that
period, mainly due to a decrease in bivalve production. During that decade the pressures from the catchment area were managed
(ca. 176 million Euros), mainly through the building of waste water treatment plants. Notwithstanding this, the ecosystem
state worsened with respect to abnormal clam mortalities due to a parasite infection and to benthic eutrophication symptoms
in specific problematic areas. The negative economic impacts during the decade were estimated between −565 and −315 million
Euros, of which 9–49% represent the cost of environmental externalities. Evaluation of these past events indicates that future
management actions should focus on reducing the limitation on local clam seeds, which should result in positive impacts to
both the local socio-economy and biodiversity. 相似文献
14.
In relation to fluoride in ground water, dental fluorosis is studied in seven villages, viz., Nasipur, Vabanandapur, and Deshnabagram
under Nalhati I block and Kamdebpur, Chalk Atla, Nowapara, and Junitpur under Rampurhat II block, of Birbhum district, West
Bengal, India. Water samples (N = 70) were collected from the tube wells of the mentioned villages in the months of December 2010 to February 2011 and analyzed
for fluoride and other water parameters. The study result revealed that the fluoride levels of almost all the water samples
(95.7%) were higher than 1.5 mg/L, with mean values of 3.15 and 3.83 mg/L in Nalhati I block and Rampurhat II block, respectively.
Dental fluorosis of 490 respondents was visually determined by a competent dentist using Dean’s index (DI) and the tooth surface
index of fluorosis (TSIF). According to the DI, the percentage of severely affected respondents was lowest in Chalk Atla (0%)
and highest in Deshnabagram (50%). The percentage of severely affected respondents was lowest in Kamdebpur and Chalk Atla
(0%) and highest in Nowapara (20%) according to the TSIF score. The age group 10–20 years showed the highest percentage of
severe DI (40.8%) and the age group 21–30 years showed the highest percentage of severe TSIF (22.51%) compared to the other
age groups in the study. The positive relationship between the fluoride level in water and the severity of dental fluorosis
has been proved statistically. The high mean score of dental fluorosis indicates that dental fluorosis is endemic throughout
the study area. 相似文献
15.
To investigate how the perceptions and behaviour of visitors to coral reefs are influenced by their prior experience and knowledge
of marine life, a questionnaire-based study was undertaken at sites in the Ras Mohammed National Park and at Sharm El Sheikh,
South Sinai, Egypt. It was evident that over the 10–20 years during which these reefs have deteriorated (mainly due to reef-flat
trampling), there have been interrelated shifts in the nature of visitors making use of them. First, there has been a shift
from experienced divers and snorkellers to inexperienced snorkellers and non-snorkellers with a poorer knowledge of reef biology.
Second, there has been a shift in the predominant nationalities of visitors, from German and British, through Italian, to
Russian. More recent user groups both stated and showed that they had less experience of snorkelling; they also showed less
knowledge of marine life and less interest in learning about it. Visitor perceptions of both the state of the marine life
on the reefs and the acceptability of current visitor numbers also varied between groups. More recent visitor groups and visitors
with less knowledge were more satisfied with reef health. In general, however, visitor perceptions of reef health did not
correlate well with actual reef conditions, probably because more experienced visitors preferred less impacted sites with
which they were nevertheless less satisfied than inexperienced visitors at heavily impacted sites. More recent visitor groups
were also less bothered by crowding on the shore or in the water. Consequently, the apparent “social carrying capacity” of
sites seems to be increasing to a level well above the likely “ecological carrying capacity”. 相似文献
16.
This study examined the relative influence of nutrients (nitrogen and phosphorus) and habitat on algal biomass in five agricultural
regions of the United States. Sites were selected to capture a range of nutrient conditions, with 136 sites distributed over
five study areas. Samples were collected in either 2003 or 2004, and analyzed for nutrients (nitrogen and phosphorous) and
algal biomass (chlorophyll a). Chlorophyll a was measured in three types of samples, fine-grained benthic material (CHLFG), coarse-grained stable substrate as in rock or wood (CHLCG), and water column (CHLS). Stream and riparian habitat were characterized at each site. TP ranged from 0.004–2.69 mg/l and TN from 0.15–21.5 mg/l,
with TN concentrations highest in Nebraska and Indiana streams and TP highest in Nebraska. Benthic algal biomass ranged from
0.47–615 mg/m2, with higher values generally associated with coarse-grained substrate. Seston chlorophyll ranged from 0.2–73.1 μg/l, with
highest concentrations in Nebraska. Regression models were developed to predict algal biomass as a function of TP and/or TN.
Seven models were statistically significant, six for TP and one for TN; r
2 values ranged from 0.03 to 0.44. No significant regression models could be developed for the two study areas in the Midwest.
Model performance increased when stream habitat variables were incorporated, with 12 significant models and an increase in
the r
2 values (0.16–0.54). Water temperature and percent riparian canopy cover were the most important physical variables in the
models. While models that predict algal chlorophyll a as a function of nutrients can be useful, model strength is commonly low due to the overriding influence of stream habitat.
Results from our study are presented in context of a nutrient-algal biomass conceptual model. 相似文献
17.
Spatial analysis of habitat selection by Sitka black-tailed deer in Southeast Alaska,USA 总被引:1,自引:0,他引:1
We used a vector-based geographic information system (GIS) to examine habitat selection by radiocollared Sitka black-tailed
deer (Odocoileus hemionus sitkensis) in logged forests of southeast Alaska. Our main objective was to explain deer habitat selection relative to old-growth/clear-cut
edges and edge habitats at two different spatial scales. Deer home ranges contained higher percentages of recent clear-cuts
(50–69%) than the study area (37%;P<0.01) and had higher old-growth/clear-cut edge densities than expected by chance (P<0.01). Deer relocation points were closer to old-growth/clear-cut edges (average=135 m) than random points located within
each deer's relocation area (average=168 m;P=0.05). Likewise, deer relocations were closer to old-growth/clear-cut edges than points randomly located within old-growth
stands or recent clear-cuts (P<0.01). As the size of clear-cuts increased, both deer relocation density and the proportion of a clear-cut occupied by deer
home ranges decreased. Because old growth is important deer habitat and clear-cuts can produce deer forage for only 20–30
years after logging in southeast Alaska, deer management plans such as preserving entire watersheds and maintaining mixes
of old growth and recent clear-cut have been proposed. Our data suggest that deer need a diversity of habitats near each other
within their home ranges. 相似文献
18.
Hegetschweiler KT van Loon N Ryser A Rusterholz HP Baur B 《Environmental management》2009,43(2):299-310
Urban forests are popular recreation areas in Europe. Several of these temperate broad-leaved forests also have a high conservation
value due to sustainable management over many centuries. Recreational activities, particularly the use of fireplaces, can
cause extensive damage to soil, ground vegetation, shrubs, and trees. Firewood collection depletes woody debris, leading to
a loss of habitat for specialized organisms. We examined the effects of fireplace use on forest vegetation and the amount
of woody debris by comparing disturbed and control plots in suburban forests in northwestern Switzerland. At frequently used
fireplaces, we found reduced species densities in the ground vegetation and shrub layer and changes in plant species composition
due to human trampling within an area of 150–200 m2. Picnicking and grilling also reduced the height and changed the age structure of shrubs and young trees. The amount of woody
debris was lower in disturbed plots than in control plots. Pieces of wood with a diameter of 0.6–7.6 cm were preferentially
collected by fireplace users. The reduction in woody debris volume extended up to a distance of 16 m from the fire ring, covering
an area of 800 m2 at each picnic site. In order to preserve the ecological integrity of urban forests and to maintain their attractiveness
as important recreation areas, we suggest depositing logging residues to be used as firewood and to restrict visitor movements
near picnic sites. 相似文献
19.
Omotayo Rafiu Awofolu 《The Environmentalist》2006,26(4):285-293
Groundwater (well water) from a residential area within the vicinity of an industrial estate in Lagos, Nigeria were sampled
and analysed by Flame Atomic Absorption Spectroscopy for their heavy metals content. This was with a view of assessing the
quality of the water, which was being used for domestic activities, especially, drinking usually without treatment. Total
trace metal determination by mineral acid digestion of water samples was applied. This method proved to be better than an
extractive concentration technique in the quality assurance protocols with the recovery range being 90.7 ± 0.006–97.6 ± 0.003%.
Mean concentration of trace metals in water samples ranged from Fe: 0.05–0.47 mg l−1; Al: 0.1–1.54 mg l−1; Cu: 0.14–1.39 mg l−1; Zn: 0.04–0.43 mg l−1; Cd: trace–0.02 mg l−1; Pb: trace–0.03 mg l−1, Mn: 0.01–0.18 mg l−1 and Ni: 0.02–0.11 mg l−1. Physical parameters of water samples examined were within the drinking water safety limits except for conductivity. Results
generally indicate the presence of heavy metal constituents in groundwater samples. Detection of metals such as cadmium and
lead which have serious health implications above WHO and USEPA limits in drinking water gives cause for concern. 相似文献
20.
Poterium spinosum, competitive under conditions of overgrazing and fire, accounted for 70%–85% of the total plant cover in all sites, except
Santorini, where participation of spiny species was very low. In the recently abandoned sites, annuals accounted for 50%–60%
of the standing biomass, but constituted only a tiny fraction in those abandoned for 30 years or more. This was not paralleled
by any remarkable increase of the total plant cover. In fact, the yearly produced green biomass decreased with the years after
abandonment. The productivity of old fields abandoned for a long time is insufficient to support the grazing animals present.
This shortfall, given the animals' requirements, is most dramatic in Symi. The nonrecovering vegetation in the old fields
of these mountainous islands constitutes a severe environmental threat; remedial measures appear imperative. 相似文献