ABSTRACT: Intensive cropping systems based on mechanical movement of soil have induced land degradation in most agricultural areas due to soil erosion and soil fertility losses. Thus, farmers have been increasing fertilization rates to maintain an economically competitive crop yield. This practice has resulted in water quality degradation and lake eutrophication in many agricultural watersheds. Research was conducted in the Patzcuaro watershed in central Mexico to develop appropriate technology that prevents nonpoint source pollution from fertilizers. Organic matter (OM) and nitrogen (N) losses in runoff and nitrate (NO3‐N) percolation in Andisols with corn under conventional till (CT) and no‐till (NT) treatments using variable percentages of crop residue as soil cover were investigated for steep‐slope agriculture. USLE type runoff plots were used to collect water runoff, while suction tubes with porous caps at 30, 60, and 90 cm depth were used to sample soil water solutes for NO3‐N analyses. Results indicated a significant reduction of N and OM losses in runoff as residue cover increased in the NT treatments. Inorganic N in runoff was 25 kg/ha for NT without residue cover (NT‐0) and 6 kg/ha for the NT with 100 percent residue cover (NT‐100). Organic matter losses in runoff were 157 and 24 kg/ha for the NT‐0 and NT‐100 treatments, respectively. Nitrate‐N percolation was evident in CT and NT with 100 percent residue cover (NT‐100). However, NT‐100 had higher NO3‐N concentration at the root zone, suggesting the possibility of reducing fertilization rates with the use of NT treatments. 相似文献
ABSTRACT: Recent research that couples climate change scenarios based on general circulation models (GCM) with Great Lakes hydrologic models has indicated that average water levels are projected to decline in the future. This paper outlines a methodology to assess the potential impact of declining water levels on Great Lakes waterfront communities, using the Lake Huron shoreline at Goderich, Ontario, as an example. The methodology utilizes a geographic information system (GIS) to combine topographic and bathymetric datasets. A digital elevation surface is used to model projected shoreline change for 2050 using water level scenarios. An arbitrary scenario, based on a 1 m decline from February 2001 lake levels, is also modeled. By creating a series of shoreline scenarios, a range of impact and cost scenarios are generated for the Goderich Harbor and adjacent marinas. Additional harbor and marina dredging could cost as much as CDN $7.6 million. Lake freighters may experience a 30 percent loss in vessel capacity. The methodology is used to provide initial estimates of the potential impacts of climate change that can be readily updated as more robust climate change scenarios become available and is adaptable for use in other Great Lakes coastal communities. 相似文献
The applications of chlorine have been broadly used in many industrial products, such as bleaching agents, synthetic rubbers, plastics, disinfectants, iron chlorides, fire refractory materials, insecticides, and anti-freezers, etc. According to the Taiwan Environmental Protection Administration (TEPA), more than 30 thousand tons were used in the year 2000. In addition, there were more than 12 reported incidents from 2000 to 2003—mostly on using chlorine as disinfectants (five) and as process agents (four).
This study investigated 15 chlorine operation plants in central Taiwan. These chlorine usages included bleaching agents, disinfectants, iron chloride, synthesizing rubber plastics, and others. Thirteen plants were located in the industrial parks and two were in or near residential zones. The consequence analysis were used three different methods to analyze the worst-case scenarios (WCSs) and alternative release case scenarios (ACSs) in order to compare impact zones for applying various active and passive mitigation systems, such as confined space, scrubber, water-spray, and so no. For two plants in or near residential zones, multi-layers mitigation systems and operation limits should be implemented in order to enforce more stringent protection measures. However, there was no specific regulation for chlorine plants operated at different locations, such as industrial parks or residential zones. In order to reduce chemical accidents and their impacts on public safety, our results suggest that source mitigation/management and warning systems should be adopted simultaneously. 相似文献
Pesticide users, natural resource managers, regulators, government agencies and many others are concerned about the off-site
impact of pesticides on the environment. Systematic methods of the assessment of potential risk of pesticides to environmental
components can serve as valuable tools in decision making and policy formulation. Simple risk indicators have been developed
which cover a range of scenarios such as toxicity to organisms, health of farm workers, consumer health, and residues in harvested
produce. The authors have developed a software package named Pesticide Impact Rating Index (PIRI) that outputs an improved
pesticide risk indicator for water quality. PIRI is a standalone, user-friendly, platform-independent program. It can be used
to (i) rank pesticides in terms of their relative pollution potential to groundwater or surface water, and (ii) to compare
different land uses in a catchment or at a regional scale in terms of their relative impact on water quality. It is based
on pesticides use; the pathway through which the pesticides are released to the water resources (drift, runoff, erosion, leaching)
and the value of the water resources threatened. Each component is quantified using pesticide characteristics (including toxicity
to organisms at different trophic levels, i.e. fish, daphnia, algae, etc.), environmental and site conditions (e.g. organic
carbon content of soil, water input, slope of land, soil loss, recharge rate, depth of water table, etc.). This paper describes
two case studies of the application of PIRI in Australia. The comparison of the risk assessment by PIRI on these revealed
that PIRI correctly estimated the pollution potential of pesticides in greater than 80% of cases. A GIS version of PIRI is
described in a companion paper in this volume.
An erratum to this article is available at . 相似文献
The East Usambara Mountains, recognized as one of the 25 most important biodiversity hot spots in the world, have a high degree
of species diversity and endemism that is threatened by increasing human pressure on resources. Traditional slash and burn
cultivation in the area is no longer sustainable. However, it is possible to maintain land productivity, decrease land degradation,
and improve rural people’s livelihood by ameliorating cultivation methods. Improved agroforestry seems to be a very convincing
and suitable method for buffer zones of conservation areas. Farmers could receive a reasonable net income from their farm
with little investment in terms of time, capital, and labor. By increasing the diversity and production of already existing
cultivations, the pressure on natural forests can be diminished. The present study shows a significant gap between traditional
cultivation methods and improved agroforestry systems in socio-economic terms. Improved agroforestry systems provide approximately
double income per capita in comparison to traditional methods. More intensified cash crop cultivation in the highlands of
the East Usambara also results in double income compared to that in the lowlands. However, people are sensitive to risks of
changing farming practices. Encouraging farmers to apply better land management and practice sustainable cultivation of cash
crops in combination with multipurpose trees would be relevant in improving their economic situation in the relatively short
term. The markets of most cash crops are already available. Improved agroforestry methods could ameliorate the living conditions
of the local population and protect the natural reserves from human disturbance. 相似文献