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411.
An erosion control product made by shredding on-site woody materials was evaluated for mitigating erosion through a series of rainfall simulations. Tests were conducted on bare soil and soil with 30, 50, and 70% cover on a coarse and a fine-grained soil. Results indicated that the wood product known as wood shreds reduced runoff and soil loss from both soil types. Erosion mitigation ranged from 60 to nearly 100% depending on the soil type and amount of concentrated flow and wood shred cover. Wood shreds appear to be a viable alternative to agricultural straw. A wood shred cover of 50% appears optimal, but the appropriate coverage rate will depend on the amount of expected concentrated flow and soil type.  相似文献   
412.
In marine areas throughout the world where recreational boats are densely located, concentrations of copper in the water are being found to be in excess of government standards, due to the hull coatings used on these boats. Copper-based hull coatings are intended to be antifouling in that they retard the growth of algae, barnacles and tubeworms; but alternatives exist that can eliminate the harm that copper contamination does to marine organisms. A variety of policy options are available to mandate or provide economic incentives to switch to these less harmful alternatives. This paper puts forth a conceptual framework for thinking about how to design and evaluate alternative policies to transition to nontoxic boat hulls, drawing from the authors' experience designing a policy for use in San Diego Bay. Many of the issues raised are broadly applicable to environmental problems where the solution involves a large-scale replacement of durable consumer goods.  相似文献   
413.
Recreational uses of unsurfaced trails inevitably result in their degradation, with the type and extent of resource impact influenced by factors such as soil texture, topography, climate, trail design and maintenance, and type and amount of use. Of particular concern, the loss of soil through erosion is generally considered a significant and irreversible form of trail impact. This research investigated the influence of several use-related, environmental, and managerial factors on soil loss on recreational trails and roads at Big South Fork National River and Recreation Area, a unit of the U.S. National Park Service. Regression modeling revealed that trail position, trail slope alignment angle, grade, water drainage, and type of use are significant determinants of soil loss. The introduction of individual and groups of variables into a series of regression models provides improved understanding and insights regarding the relative influence of these variables, informing the selection of more effective trail management actions. Study results suggest that trail erosion can be minimized by avoiding “fall-line” alignments, steep grades, and valley-bottom alignments near streams, installing and maintaining adequate densities of tread drainage features, applying gravel to harden treads, and reducing horse and all-terrain vehicle use or restricting them to more resistant routes.  相似文献   
414.
This study addressed the hydrological processes of runoff and sedimentation, soil moisture content, and properties under the effect of different water harvesting techniques (treatments). The study was conducted at three sites, representing environmental condition gradients, located in the southern part of the West Bank. For each treatment, the study evaluated soil chemical and physical properties, soil moisture at 30 cm depth, surface runoff and sedimentation at each site. Results showed that runoff is reduced by 65–85% and sedimentation by 58–69% in stone terraces and semi-circle bunds compared to the control at the semi-humid site. In addition, stone terraces and contour ridges significantly reduced the amount of total runoff by 80% and 73%, respectively, at the arid site. Soil moisture content was significantly increased by water harvesting techniques compared to the control in all treatments at the three study sites. In addition, the difference between the control and the water harvesting structures were higher in the arid and semi-arid areas than in the semi-humid area. Soil and water conservation, via utilization of water harvesting structures, is an effective principle for reducing the negative impact of high runoff intensity and subsequently increasing soil moisture storage from rainfall. Jessour systems in the valley and stone terraces were effective in increasing soil moisture storage, prolonging the growing season for natural vegetation, and decreasing the amount of supplemental irrigation required for growing fruit trees.  相似文献   
415.
This study investigated the soil nematode community structure along the Yellow River in the Lanzhou area of China, and analyzed the impact of heavy metals (Cd, Pb, Cr, Cu, and Zn) and polycyclic aromatic hydrocarbons (PAHs) on the nematode community. Soil samples from five locations (named A–E), which were chosen for soil analysis, showed significant differences in their heavy metal content (p < 0.01), as well as in the variety of nematodes (up to 41 genera) and families (up to 20) that were present. The different samples also differed significantly in the total PAH content (p < 0.05), as well as the six types of PAH present. Sites A–C showed the most severe contamination with heavy metals and PAHs; these sites had the lowest abundance of fungivores and omnivore/predators, but the proportion of bacteriovores was the highest (p < 0.05). Site E, in contrast, showed only minor pollution with heavy metals and PAHs, and it contained the highest abundance of plant parasites (p < 0.05). Several nematode ecological indicators were found to correlate with concentration of soil pollutants at all the sites tested: the maturity index (MI, in addition to plant parasites), plant parasite index (PPI), ΣMI (including all the soil nematodes), Shannon-Wiener diversity index (H′′), and Wasilewska index (WI). Disturbance to the soil environment was more severe when MI, ΣMI, and H′ values were lower. The results of the study show that the abundance and structure of the soil nematode communities in the sampling locations were strongly influenced by levels of heavy metals and PAHs in the soil. They also show that the diversity index H′ and the maturity index can be valuable tools for assessing the impact of pollutants on nematodes.  相似文献   
416.
Soil microbial populations can fluctuate in response to environmental changes and, therefore, are often used as biological indicators of soil quality. Soil chemical and physical parameters can also be used as indicators because they can vary in response to different management strategies. A long-term field trial was conducted to study the effects of different tillage systems (NT: no tillage, DH: disc harrow, and MP: moldboard plough), P fertilization (diammonium phosphate), and cattle grazing (in terms of crop residue consumption) in maize (Zea mays L.), sunflower (Heliantus annuus L.), and soybean (Glycine max L.) on soil biological, chemical, and physical parameters. The field trial was conducted for four crop years (2000/2001, 2001/2002, 2002/2003, and 2003/2004). Soil populations of Actinomycetes, Trichoderma spp., and Gliocladium spp. were 49% higher under conservation tillage systems, in soil amended with diammonium phosphate (DAP) and not previously grazed. Management practices also influenced soil chemical parameters, especially organic matter content and total N, which were 10% and 55% higher under NT than under MP. Aggregate stability was 61% higher in NT than in MP, 15% higher in P-fertilized soil, and also 9% higher in not grazed strips, bulk density being 12% lower in NT systems compared with MP. DAP application and the absence of grazing also reduced bulk density (3%). Using conservation tillage systems, fertilizing crops with DAP, and avoiding grazing contribute to soil health preservation and enhanced crop production.  相似文献   
417.
There is growing concern that recreational shoreline angling activity may negatively impact littoral and riparian habitats independent of any direct or indirect influences of fish harvest or fishing mortality through mechanisms such as disturbance (e.g., trampling, erosion) and pollution (e.g., littering). We sampled a suite of aquatic and terrestrial variables (i.e., water quality, aquatic and terrestrial macrophytes, soil compaction, anthropogenic refuse) at 14 high shoreline angling-activity sites (identified by way of interviews with conservation officers and angling clubs) within an urban area (Ottawa, Canada). For each high angling-activity site, a nearby corresponding low angling-activity site was sampled for comparison. We found that the percentage of barren area and soil compaction were greater in areas of high angling activity compared with areas that experienced relatively low angling activity. In addition, terrestrial and aquatic macrophyte density, height, and diversity were lower at high angling-activity sites. Angling- and non-angling-related litter was present in large quantities at each of the high angling-activity sites, and comparatively little litter was found at low angling-activity sites. Collectively, these findings indicate that shoreline angling does alter the riparian environment, contributing to pollution and environmental degradation in areas of high angling intensity. With growing interest in providing urban angling opportunities and in response to increasing interest in developing protected areas and parks, a better understanding of the ecologic impacts of shoreline angling is necessary to address multiuser conflicts, to develop angler outreach and educational materials, and to optimize management of angling effort to maintain ecologic integrity of riparian and aquatic ecosystems.  相似文献   
418.
岳喜云 《四川环境》2009,28(3):11-13
本文采用改进的BCR三步连续提取法对河北某食道癌高发地土壤中钙、镁进行了形态分析及提取序列的研究。实验表明:该地区土壤中镁主要以残渣态形式存在(占总量的83.66%-88.36%),钙则受提取序列的影响很大,在第一提取序列中,以酸溶态为主(74.11%-83.38%);第二提取序列中,以有机物结合态为主(78.12%-97.17%);第三、四提取序列中,以氧化物结合态为主(87.49%-103%)。提取剂的加入顺序明显影响到钙的各个形态的真实含量。  相似文献   
419.
A soil sampling intercomparison exercise for the ALMERA network   总被引:1,自引:0,他引:1  
Soil sampling and analysis for radionuclides after an accidental or routine release is a key factor for the dose calculation to members of the public, and for the establishment of possible countermeasures. The IAEA organized for selected laboratories of the ALMERA (Analytical Laboratories for the Measurement of Environmental Radioactivity) network a Soil Sampling Intercomparison Exercise (IAEA/SIE/01) with the objective of comparing soil sampling procedures used by different laboratories. The ALMERA network is a world-wide network of analytical laboratories located in IAEA member states capable of providing reliable and timely analysis of environmental samples in the event of an accidental or intentional release of radioactivity. Ten ALMERA laboratories were selected to participate in the sampling exercise. The soil sampling intercomparison exercise took place in November 2005 in an agricultural area qualified as a “reference site”, aimed at assessing the uncertainties associated with soil sampling in agricultural, semi-natural, urban and contaminated environments and suitable for performing sampling intercomparison. In this paper, the laboratories sampling performance were evaluated.  相似文献   
420.
This study reports on the effect of microwave radiation for inactivation of Ascaris lumbricoides eggs in 25 g of soil compared to ultraviolet irradiation and ozone expose. Microwave radiation at 700 W with 14% water content (w/w) achieved approximately 2.5 log inactivation of eggs in soil within 60 s. On the other hand, UV irradiation at 3 mW cm−2 with and without shaking soil for 3600 s achieved approximately 0.32 and 0.01 log inactivation of eggs, respectively. In ozone treatment, 0.13 log inactivation of eggs was achieved with 5.8 ± 0.7 mg L−1 of dissolved ozone dose for 30 min in a continuous diffusion reactor. In addition, the inactivation of eggs by three disinfection techniques was conducted in water in order to compare the inactivation efficiency of eggs in soil. The inactivation efficiency of microwave radiation was found to be no significant difference between in soil and water. However, the inactivation efficiency of UV irradiation was significantly increased in water while in ozone expose there was no significant difference between in soil and water. Microwave treatment thus proved to be the most efficient method in controlling A. lumbricoides eggs in soil.  相似文献   
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