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1.
We examined the effects of dredged material disposal on benthic macroinvertebrates in Galveston Bay, Texas, USA, while investigating the utility of estimating secondary production with estimation methods that have less rigorous data requirements than most classical techniques. Production estimates were compared to estimates of benthic consumption by blue crabs, shrimp, and epibenthic fish. There was no evidence that dredged material disposal had a detrimental impact on benthic production; however, production was low throughout the entire bay the year following dredged material disposal, which may have obscured an assessment of the impact of disposal. In fact, disposal sites yielded both the highest production estimates and species richness in both the upper and lower bay areas 2 yr after disposal. Of the five estimation methods used, two that incorporated environmental parameters (temperature and depth) yielded similar and moderate results, ranging from 1.1 g ash-free dry weight m2 yr1 to 26.9 g ash-free dry weight (AFDW) m?2 yr?1 over the 4 yr studied. Daily food ration estimates applied to fishery-independent trawl-survey data yielded overall benthic consumption estimates ranging from 1.1 g AFDW m?2 to 1.7 g AFDW m?2. A second method of estimating consumption, which used transfer efficiency estimates and annual fisheries statistics produced slightly lower benthic consumption estimates (0.72–1.13 g AFDW m?2). The average consumption estimate exceeded benthic production in the upper bay in one of the 4 yr for which benthic production was estimated. In years with high benthic production, the estimated benthic food requirement of epibenthic predators was roughly 10–15% of benthic production. Variation in annual benthic production estimates was two to three times greater than the variation in consumption estimates.  相似文献   

2.
The purpose of this study was to quantify the dry mass of dredged material involved in each stage of typical clamshell dredging and ocean disposal activities in order to identify and quantify “losses” of dredged material Turbidity plumes generated at dredging sites were also observed Approximately 2% of the dredged material was lost at the dredging site Of this quantity 61% was due to the dredging itself and 38% was due to intentional barge overflow Approximately 3 7% of the dredged material was lost at the Mud Dump Site during disposal Total loss of dredged material during these clamshell dredging and ocean disposal operations was calculated to be 5 6% Observations revealed that turbidity plumes were local features which traveled along the bottom for several hundred feet These plumes only persisted while dredging was occuring, and ambient conditions were established within a relatively short time after dredging ceased  相似文献   

3.
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4.
The Port of New York/New Jersey is naturally shallow, and therefore dredging is required to maintain depths necessary for navigation. About six million cubic yards of material must be dredged annually to maintain navigation channels and berthing areas. Opportunities for disposal of dredged materials in the metropolitan region are limited. The existing ocean disposal site that has, until recently, received the majority of dredged materials is nearing capacity. Under the new, more stringent, guidance for ocean disposal, a large percentage of the dredged material is not considered acceptable for ocean disposal because of contamination. This paper explores nondredging alternatives to reduce the volume of materials to be dredged, thus reducing the disposal volume. These alternatives include short-term options (e.g., reprofiling operations, in which sediments from high spots in berths are dragged to depressions in lower spots) and long-term sedimentation minimization options (e.g., subsurface berms or air bubblers deployed around berths and interpier areas). These methods require an understanding of sedimentation/circulation patterns of the harbor as a whole and the local area in which the specific methodology may be employed.  相似文献   

5.
The objective of this study was to determine if the placement of dredged material on sediment-starved back barrier marshes in southeastern North Carolina could offset submergence without negatively affecting function. Clean sediment was placed in thickness from 0 to 10 cm, on deteriorated and non-deteriorated marsh plots. Original stem densities were greater, in non-deteriorated plots (256 stems m−2) compared to deteriorated sites (149 stems m−2). By the second growing season (after sediment additions), stem densities in the deteriorated plots (308 stems m−2) approached levels in the non-deteriorated plots (336 stems m−2). Sediment additions to, both nos-deteriorated and deteriorated plots resulted in a higher redox potential with plots receiving the most sediment exhibiting the highest Eh values. In deteriorated plots, placement of dredged material had the greatest effect on plant density, but also affected soil oxidation-reduction potential and sediment deposition (or mobility). Following sediment placement, substrate texture and composition incrementally returned to prefill conditions due to a combination of bioturbation and sedimentation. Where infaunal differences occurred, they were generally less abundant in deteriorated plots, but responses to sediment addition were variable. Sediment addition had little effect on the non-deteriorated plots, suggesting that the disposal of certain types of dredged material in marshes may be useful to mitigate the effects of marsh degradation without adversely affecting non-deteriorating marsh.  相似文献   

6.
Approximately 28,475 m3 of muddy sediments were dredged from a shoal in a South Carolina estuarine system and released near the surface at a nearby site having high tidal current velocities. Effects at the dredged sites included decreased macrofaunal abundance and changes in species composition. These effects appeared to be short term, with substantial recovery occurring within 3 months. Rapid recovery was primarily attributed to immigration through slumping of channel wall sediments similar to those dredged. Detrimental effects on benthic macrofauna in the area of open water disposal were minimal. Most differences noted in community structure between collection dates were attributed to sampling and seasonal variability. The absence of a major longterm disruption to the benthos in the disposal area was probably due to (1) strong tidal currents, which rapidly dispersed the moderate amount of mud sediments released; (2) surface disposal, permitting wider dispersal; and (3) disposal during late autumn, a period of low faunal recruitment.  相似文献   

7.
疏浚污泥的处理与处置是世界性的环保难题,资源化处理技术的研究有重要的工程应用价值。通过化学处理技术,在疏浚污泥中加入磷酸,将其中的重金属转变成难溶的金属磷酸盐固化在处理产物中,加入FeCl3试剂与水作用,改善处理后污泥的物理力学性质;通过热处理技术大大降低有机物的含量,使固体残留物无害化。研究了不同磷酸含量和不同FeCl3含量对其物理力学和热学性质的影响。试验结果表明,处理后的疏浚污泥污染物活动性降低,并有可能用作建筑材料。  相似文献   

8.
太湖疏浚底泥堆场黏土防渗层阻隔污染物的试验研究   总被引：1，自引：0，他引：1  
李涛  张志红  唐保荣 《岩土力学》2012,33(4):993-998
底泥疏浚是治理太湖污染的必要途径之一。限于目前国内的经济与技术条件以及疏浚底泥的数量巨大,太湖雪浪底泥堆场只能直接采用下部的天然黏性土层作为防渗层而不加任何处理。为了确保疏浚污染底泥在堆放期间不对周围环境和地下水造成污染,采用渗透与阻隔、静态吸附、动态土柱等试验测定和分析了黏土层对底泥中主要污染物（总氮、氨氮、硝氮、亚硝氮、总磷、化学耗氧量（COD））渗透和运移的阻隔能力,同时得到了可用于分析污染物在土层中运移和转化规律的一些重要参数。试验结果表明,雪浪堆场下部的黏土层对疏浚底泥中的主要污染物具有较强的吸附和阻隔能力。  相似文献   

9.
A dredged material disposal operation was monitored at a location in Lake Erie, 8 km offshore at Ashtabula, Ohio, in 1975. Approximately 200 sediment cores were collected from 12 experimental and 4 control locations before and after dredging and analyzed for the grain-size distribution and related heavy-metal content. The dredged sediments were similar to those from the lake bottom at the disposal and control sites. Because of this similarity, it was extremely difficult to distinguish between the dredged material and the lake bottom sediments without tagging the material with dyes or radioactive isotopes. A sequence consisting of a linear discriminant analysis followed by a univariate and multivariate analysis of variance was successfully applied to discriminate between the dredged and the original lake sediments. Results indicate that 4 months after the disposal operation some stations had returned to predisposal conditions, a probable result of currents stripping dredged material off the lake bottom. The analysis of variance indicated that the clay-size fraction was responsible for initial changes in the grain-size distribution. Storm induced scouring caused an eventual return of the grain-size distribution to predisposal conditions. In support of this observation, the concentrations of iron and zinc, which were statistically correlated to the clay size fraction, also exhibited the same trends.  相似文献   

10.
San Quintin Bay, Mexico, is a hypersaline coastal lagoon where the main external forcing of physical and biogeochemical processes is oceanic. Non-conservative fluxes of inorganic N (ΔDIN) and P (ΔDIP), and aspects of net ecosystem metabolism were studied in this lagoon during August 1995, August 1996, and February 1996, by following the LOICZ budgetary modeling approach. The whole-system water exchange time during summer (≈13 d) was shorter than in winter (≈26 d) as northwesterly winds enhancing mixing with the ocean are more intense during the spring-summer upwelling season. Whole-bay ΔDIP values of +0.2 to +0.3 mmol m?2 d?1 in August, and <+0.01 mmol m?2 d?1 in February indicate that the system is a net source of dissolved inorganic phosphorus (DIP). DIP fluxes from the Bay to the ocean during August are probably balanced by a net import of particulate organic matter between 1,000–1,300 × 103 mol C d?1, equivalent to a net ecosystem production (NEP) between ?24 and ?31 mmol C m?2 d?1. ΔDIN showed opposite trends in August 1995 and August 1996, with a net import of 13×103 mol N d?1 and a net export of 30× 103 mol N d?1, respectively. However, N fixation minus denitrification (“apparent denitrification”) estimates of ≈?4 mmol N m?2 d?1 in both periods indicate that San Quintin Bay is a net sink of nitrogen. Results from a 3-box model indicate that during summer Box C, adjacent to the ocean, contributed 70–80% of the excess DIP produced in the whole-system. This observation and high apparent denitrification values of ≈?7 mmol N m?2 d?1 at the entrance of the Bay, suggest that the net heterotrophic condition of San Quintin Bay in summer is largely determined by imports of labile phytoplanktonic carbon generated in the adjacent ocean during upwelling.A net flux of organic carbon of 30×106 mol C yr?1 was estimated from Box C, adjacent to the ocean, to Box B, locally known as Bahia Falsa, which is the area designated for oyster aquaculture in the lagoon. It is estimated that this net organic carbon supply is almost equivalent to the annual oyster food demand; our estimate is that oyster aquaculture in San Quintin Bay accounts for the vast majority of the net heterotrophy of Bahia Falsa.  相似文献   

11.
Modeling and simulation using GPS-X software for a packed bed up-flow anaerobic sludge blanket followed by a biological aerated filter were studied. Both treatment units were packed with a non-woven polyester fabric as a bio-bed. The system was operated at a hydraulic and organic loading rate of 9.65 m3/m2/d and 2.64 kg BOD5/m3/day. Verification of the experimental results and calibration of the model were carried out prior simulation and modeling. Variables under consideration were HLR, OLR, and surface area of the packing material. HLR and OLR are increased incrementally until the break through point has been achieved. The results obtained from modeling indicated that the treatment system has great potential to be used as an ideal and efficient option for high hydraulic and organic loading rates up to 19.29 m3/m2/d and 4.48 kg BOD5/m3/day. The model indicated that increasing the input HLR and OLR loads to the treatment system up to 50 % of the original values achieved removal efficiencies 98 % for TSS, 88 % for BOD5, and 85 % for COD. Moreover, increasing the HLR to four times the original value (38.59 m3/m2/d) reduced the efficiency of the treatment system to 50 % for COD and BOD5. However, the removal rates of TSS, TKN, and TP were not affected. Also, the modeling results indicated that increasing the surface area of the packing material increased the overall efficiency of the treatment system.  相似文献   

12.
Excavation of a 16-km water diversion tunnel from Northfield Mountain to Quabbin Reservoir in western Massachusetts may be undertaken from at least three shafts in addition to the outlet adit. This account is concerned with the disposal of spoil from the aqueduct. The rock formations are mainly gneiss and schist, with minor quartzite and amphibolite. Structurally the area is part of the Pelham dome and folds on its east side. The greatest impact on the environment would be dumping of the rock spoil in piles. The total volume would be about 215,000 m3. An underground power house, if decided upon, would add another 43,000 m3 of spoil. Some of the material could be used in the project itself, for instance as riprap along the spillway. None of the piles would be deeper than 6 m, their combined extent not exceeding 14 h. The smallest impact would result if off-site contractors were to take the material as fill or aggregate. The broken rock out of one shaft might be utilized in the realignment of a nearby highway. The sites are in hilly, rural woodland. Two are close to water and one overlooks an upland bog. Adverse effects of spoil disposal can be minimized by selecting areas that avoid slope instability and interference with natural drainage, as well as undue ecologic change. Special problems involve a site that is underlain by clay and a shaft likely to yield bedrock with sulfide minerals.  相似文献   

13.
The Poplar Island Dredged Material Placement Site in Talbot County, Maryland is proposed to be used for the restoration of Poplar Island and for the creation of desirable habitats lost through erosion of Poplar Island by the beneficial use of clean and uncontaminated dredged material from the Chesapeake Bay approach channels to the Port of Baltimore. The Poplar Island baseline environmental assessment studies included among others, seasonal water quality, benthic community, and benthic tissue contaminants, that were carried out by the Maryland Department of the Environment, in cooperation with the University of Maryland, from September 1995 to July 1996. The purpose of the study was to document the present-day levels of nutrients, trace metals, and organic contaminants in the area to establish a baseline against which subsequent levels and biological responses may be compared. The overall results of the study indicate that Poplar Island and vicinity areas are non-impacted in terms of water quality and benthic tissue contamination. The nutrient levels in the water column were below average for this region of Chesapeake Bay, while the trace metals and organic contamination in the benthic tissues were comparable to other sites within Chesapeake Bay that are not impacted by direct inputs. Concentrations were equivalent or lower than those found at Hart-Miller Island, a disposal facility outside Baltimore Harbor, Maryland containing dredged material.  相似文献   

14.
Bacterial activity in the near-field environment of radioactive waste disposal facilities in deep argillaceous rocks is currently under investigation. Bacterial development could be enhanced by the availability of low-molecular-weight organic acids (LMWOA) dissolved in the pore water of clayey rocks. This study firstly aimed at isolating and characterizing the LMWOA of the Toarcian argillite from the Tournemire Underground Research Laboratory (France, Aveyron). It also aimed at assessing the disturbing effects that could be induced by a disposal facility on the type and release of LMWOA (exposure to oxygen, alkaline pH, temperature increase). Under the experimental conditions investigated at 60 °C, the mean dissolved organic carbon (DOC) is about 15 mg L−1 with a LMWOA proportion of 35 %. The main LMWOA are composed of formate, fumarate, propionate, acetate, and lactate. DOC is mainly influenced by both temperature and pH increases, whereas the LMWOA type nature and release are more specifically affected by the exposure to oxygen.  相似文献   

15.
Air dispersion modeling by was recently conducted to predict the incremental ground level and inplant concentrations of toxic organic chemicals due to stack and fugitive emissions from Sama Jaya Free Industrial Zone (SJFIZ), Kuching, Sarawak, Malaysia. Simulations of organic air pollutants emitted from industrial facilities in SJFIZ from years 1996 to 2001 were carried out in September 2004 by members of Faculty of Engineering, Universiti Malaysia Sarawak (UNIMAS). The results indicated that there were negligible amount of maximum incremental ground level concentrations of less than 3×10?2 μg/m3 for 365-day average, and less than 18×10?2 μg/m3 for 24 h. average. For in-plant maximum incremental concentrations, it is found that the simulated results were much lower than TWA values, except xylene. The predicted in plant concentration of xylene was 119.21 (parts per million) ppm as compared to ACGIH TLV-TWA of 100 ppm approximately 19% higher than ACGIH recommended values. From this study, it was concluded that both nearby population and in plant workers were not potentially at risk to exposing organic chemicals far lower than the threshold limit levels set by ACGIH.  相似文献   

16.
The mineral water at Borjomi has been bottled since the 19th century. Currently, the production comes from the regulated artesian flow of 11 boreholes. The total yield is about 540 m3/day. The mineral water is of sodium, hydrogen carbonate and CO2 type with mineralization up to 7.5 g/l and a temperature up to 40°C. Long-term observation has enabled the history of the structure of the Borjomi mineral water to be reconstructed from the beginning of its exploitation until the present. The hydrogeological structure of the Borjomi locality is very complex, but on the regional scale it occupies a relatively small area. The hydraulically well-defined and closed structure allows a simple conceptual model for each of the three main sectors to be designed. These are, namely, the Central, the Vaschlovani and the Likani sectors. The long-term extraction limits are about 190 m3/day in the Central sector, 300 m3/day in the Vashlovani sector and 77 m3/ day in the Likani sector.  相似文献   

17.
We present a nitrogen cycle model for pre-industrial times based on an extensive literature database. The model consists of 18 reservoirs in the domains of the atmosphere, land, and ocean. The biotic reservoirs on land and in the ocean (N-fixing plants, non-N-fixing plants, and marine biota) interact with atmospheric N2 and dissolved inorganic nitrogen (DIN, consisting of N2, NO3 ?, and NH4 +) in the ocean and soil waters. Marine DIN is taken up by marine biota and transformed from ocean particulate organic matter to dissolved organic nitrogen and the ocean sediment. The atmosphere, the largest nitrogen reservoir, supplies N2 to the system by N fixation, deposition, and dissolution, and these input fluxes are balanced by denitrification and volatilization back to the atmosphere. The land and ocean domains are linked by river transport, which carries both dissolved and particulate nitrogen to the oceanic coastal zone. The isotope–mass balances of the N reservoirs are calculated from the isotopic composition of the reservoirs and the fractionation factors accompanying the fluxes between the reservoirs based on reported values from different natural conditions. The model sensitivity was tested for different biouptake rates and was run with various human perturbations, including fertilization, nitrous oxide emissions, population-related sewage disposal, land-use changes, and temperature-dependent rate kinetics. The new N mass–isotope cycle model provides the basis for assessment of the impact of artificial fertilization between 1700 and 2050. The perturbation experiments in this study suggest that land-use change is the key factor altering the N mass cycle since industrialization.  相似文献   

18.
The FEBEX experiment is a 1:1 simulation of a high level waste disposal facility in crystalline rock according to the Spanish radwaste disposal concept. This experiment has been performed in a gallery drilled in the underground laboratory Grimsel Test Site (Switzerland). Two boreholes parallel to the FEBEX drift were drilled 20 and 60 cm away from the granite–bentonite interface to provide data on potential bentonite–granite solutes transfer. Periodic sampling and analysis of the major ions showed: (a) the existence of solutes transfer from the bentonite porewater towards the granite groundwater, explaining the Cl− and Na+ contents of the latter; (b) that the concentration of the natural tracers coming into the granite groundwater from the bentonite porewater increased over time. This bentonite–granite solutes transfer was modelled in order to predict the increase in the Cl− and Na+ concentrations of the granite groundwater. The modelled results seem to confirm that the mechanism of solute migration in this scenario is that of diffusive transport. An effective diffusion coefficient of De = 5 × 10−11 m2/s was that which best fitted the data obtained.  相似文献   

19.
大变形黏土防渗层中的污染物迁移和转化规律研究   总被引：1，自引：0，他引：1  
李涛  刘利  丁洲祥 《岩土力学》2012,33(3):687-694
国内湖泊疏浚污染底泥堆场一般以较厚的黏土层作为主要防渗层,由于在上覆底泥作用下黏土层会发生较大的固结变形,因此,在研究黏土防渗层中的污染物运移和转化规律时,应该考虑土体变形的影响。基于Gibson一维大变形固结理论和饱和多孔介质中的污染物对流扩散方程,建立了二者耦合的可变形多孔介质中污染物的运移和转化模型,其中首次考虑了土体自重和生物降解作用的影响。利用所建立模型的数值解,研究了在可变形黏土防渗层中的污染物运移和转化规律,同时分析了模型中不同项和主要参数的作用和影响。研究结果表明,土体大变形对黏土防渗层中污染物的运移有着较复杂的影响,一方面土体变形会加速污染物的运移;另一方面土体固结带来的渗透性减小会增加污染物的穿透时间,二者的不同作用取决于众多的影响因素,如土层厚度和吸附作用等。研究结果对于评估天然黏土防渗层对污染物的阻隔作用有重要的指导意义。  相似文献   

20.
Mukherjee  Kasturi  Mondal  Debika 《GeoJournal》2022,87(4):931-949

Spatial equity in urban facilities or service distribution is considered as a critical determinant of the quality of urbanization. Spatial equity simply means the presence of adequate facilities and equal proximity. Many initiatives have mostly focused on one type of facility, obviating the holistic understanding of the equity of distribution of all basic facilities in cities. Moreover, the perceptions of the citizens in the process of planning are hardly considered. In this paper, an integrated facility-satisfaction index is presented to evaluate the balance between the distribution of facilities and the level of residents' satisfaction derived from those facilities. This method has taken all possible urban facilities and categorized them as educational, health, financial, recreation, and others. The per capita facility availability is calculated by incorporating the spatial distribution of urban facilities, the service range of facilities, population distribution, and weight. The proper weights have been given by employing the analytical hierarchy process (AHP). The satisfaction index has been derived from the citizens’ perception of each facility, marked on a 5-point Likert scale during the field survey. The paired-sample t-test demonstrated that there is a significant difference between the facility availability and satisfaction index at the significance level of 0.05. The application of the method is demonstrated in fast urbanizing Barasat city, West Bengal, India. Based on the degree of facility-satisfaction differences or correspondences, the entire region has been categorized into four zones viz. satisfied people with favorable facility availability, unsatisfied people with poor facility availability, unsatisfied people with relatively high facility availability, and satisfied people with relatively low facility availability. The pattern has been validated by identifying spatial clusters and spatial outliers of facility availability and satisfaction using local Moran’s I. This approach can help a city to distribute the facilities to satisfy the citizens of all corners which will help to overcome the constant problems of policy decisions without adequate and reliable information about the actual demand of the residents.

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