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1.
Michael G Webb Robert Woodfield 《Journal of Environmental Economics and Management》1981,8(3):272-286
Trade effluent discharges to public sewers in England and Wales are controlled by two policy instruments, a charge and a standard. The charge is probably the nearest thing to a pollution tax currently existing in the United Kingdom. The basis of the charge is explained and the impact of these controls on dischargers examined. The relationship between optimal trade effluent charges and capacity at collective sewage works is developed. An empirical study of the effects of the charges on dischargers is presented. 相似文献
2.
Zicong Zhao Jing Yang Zigeng Zhang Sheping Wang Zhiqiang Zhang Jinsuo Lu 《Frontiers of Environmental Science & Engineering》2022,16(6):75
3.
Muhammad Wasim Shahrukh Shoaib N. M. Mubarak Inamuddin Abdullah M. Asiri 《Environmental Chemistry Letters》2018,16(3):861-879
Deterioration of buried metal pipes due to corrosive soil environment is a major issue worlwide. Although failures of buried pipe due to corrosive soil is an old problem, yet such failures are still uncontrollable even with the application of advanced corrosion protection technologies. Therefore, understanding factors causing corrosion of buried pipes is necessary. This article reviews factors causing corrosion of buried pipes in soils. Factors include moisture content, soil resistivity, pH, dissolved oxygen, temperature and microbial activity. Moreover, we discuss the influence of manufacturing method and the comparison of corrosion behaviour of cast iron, ductile and mild steel pipes. We found that corrosion rate of pipes increases with moisture contents up to the critical moisture value. Although pH affects corrosion, there is no relationship between corrosion and pH and the corrosion rates of buried pipes are inversely proportional to soil resistivity. Soils containing more organic matter show high resistivity. Dissolved oxygen in soil develops differential cell which accelerates corrosion of metallic pipe. Different types of bacteria present in soil develop biofilms on metallic pipes, which deteriorates pipes with time. 相似文献
4.
Comprehensive health condition assessment on partial sewers in a southern Chinese city based on fuzzy mathematic methods 总被引:1,自引:0,他引:1
Lili GAN Jiane ZUO Yajiao WANG Thong Soon LOW Kaijun WANG 《Frontiers of Environmental Science & Engineering》2014,8(1):144-150
A self-developed sewer health assessment system using the fuzzy comprehensive evaluation and analytical hierarchy process was applied to give a comprehensive health condition evaluation on part of the local sewers in a southern Chinese city based on the sewer video data collected by a sewer inspection closed circuit television (CCTV) robot. Aside from the overall condition evaluation, the structure, function, and stability status of the sewer were also analyzed using the method. A comprehensive index H was proposed to give the overall health condition of pipes with different defects, and Ht, Hs, and If were used to quantify the defects affecting the tightness, stability, and function of the pipe, respectively. Results show that 48% of the inspected pipes were in good condition (0〈H〈0.25), and about 33% of the sewer pipes analyzed were categorized to be at severe or urgent condition levels (H 〉 0.5), although most of the pipes were installed only within five years. Frequent sedimentation affects the function of the sewer, and deformation and joint damage affect the structure of the sewer. 相似文献
5.
Transient dynamics of pelagic producer-grazer systems in a gradient of nutrients and mixing depths 总被引:1,自引:0,他引:1
Phytoplankton-grazer dynamics are often characterized by long transients relative to the length of the growing season. Using a phytoplankton-grazer model parameterized for Daphnia pulex with either flexible or fixed algal carbon:nutrient stoichiometry, we explored how nutrient and light supply (the latter by varying depth of the mixed water column) affect the transient dynamics of the system starting from low densities. The system goes through an initial oscillation across nearly the entire light-nutrient supply space. With flexible (but not with fixed) algal stoichiometry, duration of the initial algal peak, timing and duration of the subsequent grazer peak, and timing of the algal minimum are consistently accelerated by nutrient enrichment but decelerated by light enrichment (decreasing mixing depth) over the range of intermediate to shallow mixing depths. These contrasting effects of nutrient vs. light enrichment are consequences of their opposing influences on food quality (algal nutrient content): algal productivity and food quality are positively related along a nutrient gradient but inversely related along a light gradient. Light enrichment therefore slows down grazer growth relative to algal growth, decelerating oscillatory dynamics; nutrient enrichment has opposite effects. We manipulated nutrient supply and mixing depth in a field enclosure experiment. The experimental results were qualitatively much more consistent with the flexible than with the fixed stoichiometry model. Nutrient enrichment increased Daphnia peak biomass, decreased algal minimum biomass, decreased the seston C:P ratio, and accelerated transient oscillatory dynamics. Light enrichment (decreasing mixing depth) produced the opposite patterns, except that Daphnia peak biomass increased monotonously with light enrichment, too. Thus, while the model predicts the possibility of the "paradox of energy enrichment" (a decrease in grazer biomass with light enrichment) at high light and low nutrient supply, this phenomenon did not occur in our experiment. 相似文献
6.
采用批实验研究了华北平原地下水中检出率较高的三氯乙烯和甲苯在沿污水河包气带不同深度土壤中的吸附情况。从3个地点分析结果来看,其中有机碳(OC)的质量分数均较低(最高为1.01%)。在河床和近河处土壤对甲苯和三氯乙烯的吸附总体上呈现出浅部土壤吸附性强的特点。在实验浓度范围内,土壤中无机矿物对有机污染物(特别是三氯乙烯)的表面吸附扮演了重要角色。土壤对甲苯的吸附表现出了强烈的非线性,而对三氯乙烯的吸附表现出了良好的线性关系。甲苯的吸附与土壤有机碳质量分数的关系要比三氯乙烯更密切,这说明了吸附作用过程与有机化合物的分子结构、疏水性等方面的性质也有关系。 相似文献
7.
Five municipal sewers with small flow rates (Manarola, Riomaggiore, Portovenere, Tellaro, Bocca di Magra) were studied using the Microtox® test and a bacterial luminescence bioassay in order to evaluate the water quality in these areas of the eastern Ligurian coast. The work was performed including chemical analysis, microbiological and ecotoxicological assays. Analyses were carried out on both the effluents and the water body close to the pipe discharge. None of the measured chemical parameters exceeded the permitted limits, both in the effluents and in the seawater samples, even if some slightly critical situations were highlighted by the Microtox® test on the effluents. On the other hand, the Microtox® appeared to be less effective than another ecotoxicological assay based on the luminescent fraction of epibacteria for the evaluation of seawater quality. The good water quality of the considered areas was assessed although a slightly worse condition was encountered in Bocca di Magra. 相似文献
8.
Environmental and Ecological Statistics - This paper introduces a time-varying parameter regression model for modeling, forecasting, and assessing inter-annual trends in daily snow depths. The... 相似文献
9.
I. Novaczek 《Marine Biology》1984,81(2):189-197
Ecklonia radiata (C. Ag.) J. Ag. growing in Goat Island Bay, New Zealand produced up to 6 kg dry weight of tissue m-2 yr-1 in dense populations at 7-m depth. Half this tissue and an unknown amount of exudates were sloughed or torn off. Tissue production at 15 m was 0.3 to 0.5 kg m-2 yr-1. At this depth the plants grew only half as fast as in shallow water and the population density was decreased. Approximately 20% by weight of tissue produced at 7 m and 10% of that at 15 m was reproductive tissue. At both depths the elongation rate and percentage of water in stipes varied with stipe size. Initial sorus formation was related to plant size and not to age. Seasonal fluctuations in growth rate, haptera formation, frond size and sporulation were delayed in plants in deeper water. 相似文献
10.
Cuttings of the marine phanerogam Posidonia oceanica (L.) Delile were collected and transplanted in January 1991 at four stations of different depths between 5 and 20 m in the underwater reserve at Monaco (1 ha in area). From January to July, samples of the transplants were collected to study the effect of depth on survival and on chlorophyll and carbohydrate concentrations. In the leaves, chlorophyll concentrations were significantly lower (1.00 mg g-1 dry wt) in cuttings taken from 5 m depth than in cuttings taken from 20 m (1.99 mg g-1). Transplantation of cuttings from 5 to 20 m or from 20 to 8 m did not significantly change the chlorophyll concentration in leaves for a period of 6 mo after transplantation. Cutting and transplantation result in stress, as indicated by a decrease in pigment concentration without change of depth. However, the carbohydrate concentration in rhizomes from 5 m (32 mg g-1 dry wt), is significantly higher than in material from 20 m (17 mg g-1). Cuttings transplanted from 5 to 20 m lost most of their carbohydrate reserves (reaching a minimum of 2.5 mg g-1 in May); cuttings transplanted from 20 to 8 m maintained higher reserves (with a minimum of 20 mg g-1 in June). This may explain why material transplanted from 5 to 20 m exhibited only 52% survival, while material transplanted from 20 to 8 m displayed 80 to 92% survival. Material taken from populations adapted to low light at 20 m is probably more resistant to transplantation stress, particularly when replanted at a higher light intensity in shallow water. 相似文献
11.
To exploit resources in their environment, odontocete cetaceans have evolved sophisticated diving abilities to allow effective
foraging. However, data on the diving behaviour and underwater foraging behaviour remains limited. This study made use of
echolocation clicks and other calls to study the diving behaviour of bottlenose dolphins. Dolphins used the full water column
and consistently dived to depths of around 50 m, close to the seabed. However, the majority of their time appeared to be spent
within the surface layers of the water column. In addition, by localising calls that have been associated with prey capture
events (Janik, Proc R Soc Lond Ser B 267:923–927, 2000a), it appeared that certain forms of feeding behaviour occurred primarily
at depths of between 20 and 30 m. Furthermore, data on the depth of clicks made before and after these feeding calls suggested
that during the minute before the calls, dolphins were consistently diving from the surface to depths close to the seabed,
and were subsequently returning to the surface after the calls. This passive acoustic technique proved an accurate method
for studying the depth distribution of dolphin vocalisations. By exploiting the natural sounds made by these wild odontocetes,
this investigation provided a previously unavailable perspective on the the 3D nature of bottlenose dolphins foraging behaviour.
It confirmed that while the dolphins spent the majority of time close to the surface, the full water column was exploited
during foraging events. 相似文献
12.
K. L. Smith Jr 《Marine Biology》1983,72(3):249-256
Metabolism of two abundant echinoderm species constituting 99.6% of the epibenthic megafauna in the Santa Catalina Basin, off southern California, USA was measured at 1 300 m during the 1979 “Bathyal Expedition”. Specimens of the ophiuroid Ophiophthalmus normani and the holothurian Scotoplanes globosa, collected by the submersible “Alvin”, were individually placed in respirometers, and measured in situ for O2 consumption and ammonium excretion rates. For O. normani, weight-specific O2 consumption rates decreased with increasing weight and were of comparable magnitude to rates of deep-sea and shallow-water ophiuroids; excretion rates were highly variable. Population O2 consumption and excretion rates for O. normani (estimated from size-frequency distribution, abundance, and rate regression equations) were 1 129.28 μl O2 m-2 h-1 and 27.30 nmol NH 4 + m-2 h-1. Weight-specific O2 consumption and ammonium excretion rates of S. globosa decreased with increasing weight and were of comparable magnitude to rases of shallow-water holothurians. Population O2 constimption and excretion rates of S. globosa were 1.38 μl O2 m-2 h-1 and 4.86 nmol NH 4 + m-2 h-1. Combined population O2 consumption rates for O. normani and S. globosa are of comparable magnitude to that of the sediment community and plankton in the benthic boundary layer (sediment and overlying 50 m water column) of the Santa Catalina Basin. 相似文献
13.
Morphological characteristics, growth and carbohydrate storage dynamics of Typha angustifolia in relation to water depth were investigated. The study was based on observations carried out in two stands, namely Akigase and Teganuma, for two growth seasons. The latter stand was about two times deeper than the former. Teganuma stands exhibited significantly higher number of thick shoots compared to those of Akigase. Conversely, the difference in shoot heights between the two stands was insignificant. The same was true for rhizome lengths. Rhizome diameters were significantly bigger for Teganuma compared to Akigase. Furthermore, both the above and belowground biomass were significantly higher for Teganuma compared to those of Akigase. Teganuma stands allocated 55% of the total biomass to the aboveground parts, while Akigase stands allocated 60%. Similarly, Teganuma exhibited significantly higher stocks of total non-structural carbohydrates (TNC) compared to Akigase. The higher number of thick shoots and the relatively bigger rhizome diameters in Teganuma are seemingly important tolerance strategies in maintaining effective aeration into the rhizosphere, by reducing internal resistance. In addition, the higher TNC stocks and biomass help not only to enhance survival under anoxia for longer durations, they also provide firm substrate anchorage in the deeper Teganuma stands. 相似文献
14.
根据塔里木河中游5个断面30眼地下水监测井和30个植物样地2006—2008年调查监测的数据,分析了输水堤防修建后地下水埋深、地下水质以及物种多样性的变化及其相互关系。结果表明:地下水埋深的空间变化表现为沿河道方向先增加后减小的趋势,在时间上则表现为,从2006年到2008年埋深呈逐渐增加的特点;地下水化学类型的变化,在空间上表现出沿着河道方向有由Cl-—SO42-—Na+—Mg2+向Cl-—Na+类型转变的趋势,在时间上,地下水矿化度逐渐增加。物种多样性总体上呈现增加变化,地下水位和水质对塔里木河中游物种多样性变化有着密切的关系,地下水埋深2.8~3.7 m,矿化度1.8~2.4 g·L-1水平下的多样性较高,随着地下水埋深的增大和矿化度的升高,物种多样性水平降低。 相似文献
15.
根据塔里木河中游5个断面30眼地下水监测井和30个植物样地2006—2008年调查监测的数据,分析了输水堤防修建后地下水埋深、地下水质以及物种多样性的变化及其相互关系。结果表明:地下水埋深的空间变化表现为沿河道方向先增加后减小的趋势,在时间上则表现为,从2006年到2008年埋深呈逐渐增加的特点;地下水化学类型的变化,在空间上表现出沿着河道方向有由Cl-—SO42-—Na+—Mg2+向Cl-—Na+类型转变的趋势,在时间上,地下水矿化度逐渐增加。物种多样性总体上呈现增加变化,地下水位和水质对塔里木河中游物种多样性变化有着密切的关系,地下水埋深2.8~3.7 m,矿化度1.8~2.4 g·L-1水平下的多样性较高,随着地下水埋深的增大和矿化度的升高,物种多样性水平降低。 相似文献
16.
Seasonal reproduction of the brachiopod Frieleia halli and the scaphopod Cadulus californicus at bathyal depths in the deep sea 总被引:1,自引:0,他引:1
F. J. Rokop 《Marine Biology》1977,43(3):237-246
Two benthic species of invertebrates from the physically seasonless bathyal depths of the San Diego Trough off southern california USA showed highly synchronous reproductive cycles. Although the common pattern in the deep-sea benthos seems to be year-round reproduction, these two species are exceptions. The brachiopod Frieleia halli Dall spawned between January and April (1971) and the scaphopod mollusc Cadulus californicus Pilsbry and Sharp in late summer between July and October. Furthermore, F. halli. has maintained a predictable annual gametogenic cycle for three years (1970–1972). Several factors are suggested as possibly important in synchronizing their reproductive cycles, but no single environmental cue can be conclusively demonstrated as a definite influence. 相似文献
17.
Weiying Li Yu Tian Jiping Chen Xinmin Wang Yu Zhou Nuo Shi 《Frontiers of Environmental Science & Engineering》2022,16(6):72
18.
Previous investigations indicate that scour around bridge piers is one of the most important factors for the failure of waterway bridges. Hence, it is essential to determine the accurate scour depth around the bridge piers. Most of the previous studies were based on scour around a single pier; however, in practice, new bridges are usually wide and then piers comprise two circular piers aligned in the flow direction that together support the loading of the structure. In this study, the effect on maximum scour depth of the spacing between two piers aligned in the flow direction was investigated experimentally under clear water scour conditions. The results show that the maximum scour depth at upstream of the front pier occurs when the spacing between the two piers is 2.5 times the diameter of the pier. Two semi empirical equations have been developed to predict the maximum scour depth at upstream of both front and rear piers as a function of the spacing between the piers, in terms of a pier-spacing factor. If the new equations for the pier-spacing factor are used with some of the existing equations for scour at a single pier, the predicted scouring depths are in good agreement with observed results. The S/M equation exhibited the best performance among the various equations tested and was recommended for use in prediction of the equilibrium scour depth. The findings of this study can be used to facilitate the positioning of piers when scouring is a design concern. 相似文献
19.
施用不同尿素对稻季不同层次土壤溶液中氮形态的影响 总被引:1,自引:0,他引:1
在太湖地区乌栅土上,利用大型原状土柱比较研究了不同尿素品种、施肥量(0、普通尿素150、300和包膜尿素100、150 kg·hm-2,以N计算)处理对稻季不同层次(30、65、80 cm)土壤氮素动态变化的影响.结果表明:所有处理渗漏水中NO3--N质量浓度均低于饮用水标准,常规施肥未显著增加氮的淋溶损失;各处理在不同层次土壤均发生反硝化作用;包膜尿素促进土壤反硝化强度,在65 cm和80 cm处尤为明显.施用包膜尿素可能增强浅层地下水的反硝化作用而降低水体NO3--N质量浓度.其影响机理及在对其它类型土壤上氮素淋失和反硝化的影响,值得进一步研究. 相似文献