共查询到6条相似文献,搜索用时 8 毫秒
1.
Clare Paton-Walsh Stephen R. Wilson Travis Naylor David W. T. Griffith O. T. Denmead 《Environmental Modeling and Assessment》2011,16(5):441-452
The Great Barrier Reef World Heritage Area contains highly sensitive ecosystems that are threatened by the effects of anthropogenic
activity including eutrophication. The nearby sugarcane plantations of tropical north Queensland are fertilised annually and
there has been ongoing concern about the magnitude of the loss of applied nitrogen to the environment. Previous studies have
considered the potential of rainwater run-off to deposit reactive nitrogen species into rivers and ultimately into the Great
Barrier Reef Lagoon, but have neglected the possibility of transport via the atmosphere. This paper reports the results of
a modelling study commissioned by Australia’s National Heritage Trust aimed at assessing whether or not atmospheric deposition
of reactive nitrogen from Queensland’s sugarcane plantations posed a potential threat to the Great Barrier Reef Lagoon. Atmospheric
dispersion modelling was undertaken using The Air Pollution Model, developed by Australia’s Commonwealth Scientific and Industrial
Research Organisation. Despite the predominance of onshore southeasterly winds, the dispersion model results indicate that
9% of the time during the sugarcane fertilization season (in the modeled years 2001–2006) the meteorological conditions resulted
in emissions from the coastal regions of north Queensland being transported out over the ocean around the Great Barrier Reef.
The results suggest that there may be a greater efficiency for transport out over the reef during October than for November
and December. For the 2 months that exhibited the greatest potential for transport of coastal pollution to the Great Barrier
Reef, the modeled deposition of nitrogen oxides (NOX) into the Great Barrier Reef lagoon was less than 1% of the total emissions from the sugarcane plantations, but was not zero.
Our model has a simple chemical scheme that does not cover the full chemistry of all reactive nitrogen compounds and so the
results are only indicative of the potential levels of deposition. Nevertheless, our study shows that small amounts of NOX that originate from sugarcane fertilization may be transported and dry deposited into the Great Barrier Reef lagoon. Other
pathways not included in the modeling scheme may provide a more efficient transport mechanism. Whilst modern practices for
the application of fertilizer to sugarcane plantations have drastically reduced emissions, the potential efficiency of transport
of pollutants via the atmosphere may be of concern for other more highly polluting agricultural industries. 相似文献
2.
Lirman D Gracias NR Gintert BE Gleason AC Reid RP Negahdaripour S Kramer P 《Environmental monitoring and assessment》2007,125(1-3):59-73
The recent decline in the condition of coral reef communities worldwide has fueled the need to develop innovative assessment
tools to document coral abundance and distribution rapidly and effectively. While most monitoring programs rely primarily
on data collected in situ by trained divers, digital photographs and video are used increasingly to extract ecological indicators, provide a permanent
visual record of reef condition, and reduce the time that divers spend underwater. In this study, we describe the development
and application of a video-based reef survey methodology based on an algorithm for image registration and the estimation of
image motion and camera trajectory. This technology was used to construct two-dimensional, spatially accurate, high-resolution
mosaics of the reef benthos at a scale of up to 400 m2. The mosaics were analyzed to estimate the size and percent cover of reef organisms and these ecological indicators of reef
condition were compared to similar measurements collected by divers to evaluate the potential of the mosaics as monitoring
tools. The ecological indicators collected by trained divers compared favorably with those measured directly from the video
mosaics. Five out of the eight categories chosen (hard corals, octocorals, Palythoa, algal turf, and sand) showed no significant differences in percent cover based on survey method. Moreover, no significant
differences based on survey method were found in the size of coral colonies. Lastly, the capability to extract the same reef
location from mosaics collected at different times proved to be an important tool for documenting change in coral abundance
as the removal of even small colonies (<10 cm in diameter) was easily documented. The two-dimensional video mosaics constructed
in this study can provide repeatable, accurate measurements on the reef-plot scale that can complement measurements on the
colony-scale made by divers and surveys conducted at regional scales using remote sensing tools. 相似文献
3.
The consistency of visual assessment of tree defoliation, which represents the most widely used indicator for tree condition, has frequently been in the focus of scientific criticism. Thus, the objective of the present study was to examine the consistency of the defoliation data from the annual national training courses for the forest condition survey in Germany from 1992 to 2012. Defoliation assessments were carried out in stands of beech (Fagus sylvatica), oak (Quercus robur and Quercus petraea), Norway spruce (Picea abies), and pine (Pinus sylvestris). Among the observer teams, the absolute deviation from the observer mean of all years was ±4.4 % defoliation and the standard deviation of defoliation was ±5.5 %. On average, 94 % of the assessments were located within the ±10 % interval of deviation from the mean. Tree species-specific differences did not occur when all years were considered. A trend towards increasing consistency was observed from 1992 to 2012, in particular for oak and spruce. The deviation of defoliation assessments depended non-linearly on the level of defoliation with highest deviations at intermediate defoliations. In spite of high correlations and agreements among observers, systematic errors were determined in nearly every year. However, within-observer variances were higher than between-observer variances. The present study applied a three-way evaluation approach for the assessment of consistency and demonstrated that the visual defoliation assessment at the national training courses in general produced consistent data within Germany from 1992 to 2012. 相似文献
4.
根据等速采样原理,探讨在标准状态下,采样体积的计算公式.当气温在0℃以下采样时,略去累计流量计、流量计前压力表、流量计前温度表,即不再用上述仪表测得参数求算采样体积,实现了冬季采样又简化了设备的结构. 相似文献
5.
The results of underwater visual fish censuses (UVC) could be affected by fish changing their behavior in response to the snorkeler or diver conducting the survey. We used an underwater video camera to assess how fish abundance, family richness, and community composition were affected by the presence of snorkelers (n?=?12) and self-contained underwater breathing apparatus (SCUBA) divers (n?=?6) on a coral reef in Thailand. The total number of families, abundance of some fish families, and overall species composition showed significant differences before and during snorkeling disturbances. We did not detect significant and consistent changes to these parameters in the presence of a SCUBA diver; however, this could be a result of lower statistical power. We suggest that the use of a stationary video camera may help cross-check data that is collected through UVC to assess the true family composition and document the presence of rare and easily disturbed species. 相似文献