共查询到20条相似文献，搜索用时 46 毫秒
1.
大气湿沉降向太湖水生生态系统输送氮的初步估算 总被引：30，自引：3，他引：27
测定和分析了2002年7月至2003年6月太湖周边地区太湖站、拖山岛、东山站、无锡、苏州、湖州、常州等7个站点大气降水化学组成,计算了水气界面TN、NH4 -N、NO3--N、T1N、TON的湿沉降率。结果表明,大气降水的TN浓度变化范围为2.06±0.30(常州)-3.71±0.43(拖山岛),太湖流域大气降水已呈富营养化水质的特征;大气降水TN、NH4 -N、NO3--N、TIN、TON的年均湿沉降率分别为2806.75kg/km2、1458.81kg/km2、631.67kg/km2、2090.48kg/km2和716.28kg/km2;每年由湿沉降直接进入太湖水体的TN约为6562.2t,NH4 -N为3410.7t,NO3--N为1476.8t,TIN为4887.5t,TON为1674.7t;TN占入湖河道年输入污染物总量的13.6%.大气湿沉降中,TIN对TN的贡献比较大,平均约占TN的78.78%.TIN的湿沉降率具有季节性分布,夏季高,春季次之,冬秋季低。这种现象无疑对太湖水体的蓝藻爆发和富营养化具有潜在的促进作用. 相似文献
2.
3.
大布苏湖地貌——沉积类型与湖泊演化 总被引：2，自引：1，他引：2
大布苏湖地处松嫩平原南部，是一个封闭的构造断湖，湖区山貌类型复杂，沉积环境独具特色，根据地形面的分层和特征，结合^14C测年，确定大布苏湖形成于晚更新世晚期，湖泊形成的早期，曾经历了深湖的发育阶段，全新世以来，湖面波动式下降，并有两次规模较大的扩张和收缩时期，形成了两个完整的湖进、湖退沉积旋回、晚全新世以来，气候干燥，风力作用活跃，湖面明显萎缩，形成我国东部地区极为罕见的盐湖。 相似文献
4.
J. Kubiak 《洁净——土壤、空气、水》1983,11(4):439-447
The Pomeranian Bay in the south-western part of the Baltic sea has an area of 4300 km2 and a volume of 51.4 km3 and contains a fresh-water inflow of 17.3 km3/a from a catchment area of 137,220 km2. There were evaluated 18 investigations of specific dates at 14 stations in the years 1976 … 1978: 229 … 235 hydrochemical measurements and 75 phytoplankton investigations. It can be demonstrated by multiple regression analyses that the nutrient concentrations are mainly determined by the fresh-water inflow and the mixing ratios, phytoplankton having a secondary effect. Of the nutrients mainly ammonium influences the phytoplankton development and the oxygen production, the full utilization of the nitrogen stock being limited by an N/P ratio of 48 in the surface water and of 41 in the bottom water layers. Obviously, a limitation of the primary production is out of the question due to the high turnover rates of phosphorus. The N/P ratio is also a clear evidence of the great influence of the inflowing nitrate-rich freshwater on the nutrient situation of the bay. 相似文献
5.
广州麓湖大气多环芳烃的干湿沉降 总被引：6，自引：2，他引：6
以广州麓湖为小型城市湖泊的代表,对大气中多环芳烃的颗粒态沉降进行了连续一年的采样与分析. 结果表明,年均颗粒态多环芳烃的沉降通量为0.47mg/( m2·a). 全年直接由大气输入到麓湖的颗粒态多环芳烃总量约为0.1kg. 不同季节相比,夏季多环芳烃的沉降通量略高于秋季,而冬春季最高. 对比大气总悬浮颗粒物中多环芳烃的组成发现,当降雨量增大时,沉降颗粒物中多环芳烃的组成逐渐趋近于大气总悬浮物中多环芳烃的组成. 广州地区雨热同期、干冷咸至的季风气候特点,以及由此导致的大气颗粒物粒径变化和PAHs的气-粒分配变化,与大气PAHs污染程度一起,共同控制着沉降颗粒物中PAHs相对组成的季节变化. 相似文献
6.
Following a massive wreck of guillemots (Uria aalge) in late winter and spring of 1993, we monitored the deposition and subsequent disappearance of 398 beachcast guillemot carcasses on two beaches in Resurrection Bay, Alaska, during a 100 day period. Deposition of carcasses declined logarithmically with time after the original event. Since fresh carcasses were more likely to be removed between counts than older carcasses, persistence rates increased logarithmically over time. Scavenging appeared to be the primary cause of carcass removal, followed by burial in beach debris and sand. Along-shore transport was negligible. We present an equation which estimates the number of carcasses deposited at time zero from beach surveys conducted some time later, using non-linear persistence rates that are a function of time. We use deposition rates to model the accumulation of beached carcasses, accounting for further deposition subsequent to the original event. Finally, we present a general method for extrapolating from a single count the number of carcasses cumulatively deposited on surveyed beaches, and discuss how our results can be used to assess the magnitude of mass seabird mortality events from beach surveys. 相似文献
7.
Elena Zanella Lucia Gurioli Roberto Lanza Roberto Sulpizio Manuela Bontempi 《Bulletin of Volcanology》2008,70(10):1237-1248
The deposition temperature of the pyroclastic density current (PDC) deposits emplaced during the AD 472 Pollena eruption (Somma-Vesuvius,
Italy) has been investigated using the thermal analysis of the magnetic remanence carried by lithic clasts embedded within
the deposits. A total of 310 lithic clasts were collected from all the PDC units in the Pollena stratigraphic succession,
at different distances from the inferred vent and at different stratigraphic levels. The temperature reached by each individual
clast during residence in the PDC was estimated through stepwise thermal demagnetization, with the values from all clasts
collected at each site being used to infer the deposition temperature (T
dep). Although the sedimentological features of these PDC deposits show some variation, the deposition temperature typically
falls in the range 300 to 320°C, with a maximum range of 260 to 360°C. The fairly uniform temperature observed in both the
dune bedded and massive deposits points to homogeneity in attainment of T
dep for the different deposits and suggests similarity in the depositional regime of the different PDCs and/or in heat transfer
to lithic fragments. Similarity in depositional regime was also favoured by the limited control exerted by topography on the
distribution of these PDCs, with the northern wall of the Somma caldera that did not act as a morphological barrier. As a
result the currents were capable of moving away from the vent, without topographic disturbances and, thus, significant variations
in the cooling regime. Because the Pollena eruption is considered similar to the maximum expected event at Somma-Vesuvius,
the characteristics of its deposits best simulate the likely maximum hazard for the Vesuvius region. In this regard, Pollena
produced hot, dilute PDCs which were able to travel up to 12 km from the vent maintaining high temperatures across this distance. 相似文献
8.
Hydrographic structure of the water column, dissolved nutrient concentrations and the distribution of suspended particulate matter were recorded from CDT measurements and Niskin bottles sampling on the continental slope of the Bay of Biscay and on the axis of Capbreton canyon. Ascorbate extraction was applied here for the first time on marine suspended particles to determine the content of reactive Fe- and Mn-oxides, and P associated with Fe-oxides. Hydrographic structure of the south-eastern part of the Bay of Biscay did not change during the last three decades. Particulate organic carbon (POC) contents dropped strongly with depth, showing that organic matter mineralization was efficient in the water column. Organic matter mineralized in the water column had a Redfield N:P ratio. POC percent of particles collected at depth were higher during a bloom period, suggesting that some new organic matter reached the bottom. Contents of Fe and Mn extracted with the ascorbate leaching solution showed that suspended particles originated from the Gironde estuary, one of the major sources of particles in the Bay of Biscay. Intermediate and deeper nepheloid layers occurred in the Capbreton canyon. Particles of nepheloid layers were enriched in Mn- and Fe-oxides because they originated from resuspension of surface sediment. 相似文献
9.
In this paper, we considered dense avalanches made of dry and cohesion-less snow as gravitational granular flows. We used an effective friction law derived from the recent progress on granular behaviour research to represent momentum loss. We formulated a simple erosion and deposition model where the eroded and deposited mass fluxes are estimated from the knowledge of the starting and stopping conditions on a given slope angle. We adopted the shallow water hypothesis and introduced the new formulation of erosion and deposition processes. We solved the equations thanks to an accurate finite volumes solver scheme, using a non-structured mesh. This allows an easy integration of defence structures and singularities. Each component of this model was tested using analytical solutions and experimental laboratory data. Finally, we used the February 1999 Taconnaz avalanche event to test this model on a real snow avalanche case. These tests gave promising results. 相似文献
10.
Deposition, mineralization, and storage of carbon and nitrogen in sediments of the far northern and northern Great Barrier Reef shelf 总被引：4，自引：0，他引：4
The flow of carbon and nitrogen in sediments of the far northern and northern sections of the Great Barrier Reef continental shelf was examined. Most of the organic carbon (81–94%) and total nitrogen (74–92%) depositing to the seabed was mineralized, with burial of carbon (6–19%) and nitrogen (8–20%) being proportionally less on this tropical shelf compared with other non-deltaic shelves. Differences in carbon and nitrogen mineralization among stations related best to water depth and proximity to river basins, with rates of mineralization based on net ∑CO2 production ranging from 17 to 39 ( mean=23) mmol C m−2 d−1. The overall ratio of O2:CO2 flux was 1.3, close to the Redfield ratio, implying that most organic matter mineralized was algal. Sulfate reduction was estimated to account for ≈30% (range: 6–62%), and denitrification for ≈5% (range: 2–13%), of total C mineralization; there was no measurable CH4 production. Discrepancies between ∑CO2 production across the sediment–water interface and sediment incubations suggest that as much as 5 mmol m−2 d−1 (≈25% of ∑CO2 flux) was involved in carbonate mineral formation. Most microbial activity was in the upper 20 cm of sediment. Rates of net NH4+ production ranged from 1.6 to 2.7 mmol N m−2 d−1, with highly variable N2 fixation rates contributing little to total N input. Ammonification and nitrification rates were sufficient to support rapid rates of denitrification (range: 0.1–12.4 mmol N m−2 d−1). On average, nearly 50% of total N input to the shelf sediment was denitrified. The average rates of sedimentation, mineralization, and burial of C and N were greater in the northern section of the shelf than in the far northern section, presumably due to higher rainfall and river discharge, as plankton production was similar between regions. The relative proportion of plankton primary production remineralized at the seafloor was in the range of 30–50% which is at the high end of the range found on other shelves. The highly reactive nature of these sediments is attributed to the deposition of high-quality organic material as well as to the shallowness of the shelf, warm temperatures year-round, and a variety of physical disturbances (cyclones, trawling) fostering physicochemical conditions favorable for maintaining rapid rates of microbial metabolism. The rapid and highly efficient recycling of nutrients on the inner and middle shelf may help to explain why the coral reefs on the outer shelf have remained unscathed from increased sediment delivery since European settlement. 相似文献
11.
Nitrogen uptake and denitrification in restored and unrestored streams in urban Maryland, USA 总被引：2，自引：0，他引：2
Carolyn A. Klocker Sujay S. Kaushal Peter M. Groffman Paul M. Mayer Raymond P. Morgan 《Aquatic Sciences - Research Across Boundaries》2009,71(4):411-424
There is growing interest in rates of nitrate uptake and denitrification in restored streams to better understand the effects
of restoration on nitrogen processing. This study quantified nitrate uptake in two restored and two unrestored streams in
Baltimore, Maryland, USA using nitrate additions, denitrification enzyme assays, and a 15N isotope tracer addition in one of the urban restored streams, Minebank Run. Restoration included either incorporation of
stormwater ponds below a storm drain and catch basins to attenuate flow or hydrologic “reconnection” of a stream channel to
its floodplain. Stream restoration was conducted for restoring aging sanitary and bridge infrastructure and introducing some
stormwater management in watersheds developed prior to current regulations. Denitrification potential in sediments was variable
across streams, whereas nitrate uptake length appeared to be significantly correlated to surface water velocity, which was
low in the restored streams during summer baseflow conditions. Uptake length of NO3
−–N in Minebank Run estimated by 15N tracer addition was 556 m. Whole stream denitrification rates in Minebank Run were 153 mg NO3
−–N m−2 day−1, and approximately 40% of the daily load of nitrate was estimated to be removed via denitrification over a distance of 220.5 m
in a stream reach designed to be hydrologically “connected” to its floodplain. Increased hydrologic residence time in Minebank
Run during baseflow likely influenced rates of whole stream denitrification, suggesting that hydrologic residence time may
be a key factor influencing N uptake and denitrification. Restoration approaches that increase hydrologic “connectivity” with
hyporheic sediments and increase hydrologic residence time may be useful for stimulating denitrification. More work is necessary,
however, to examine changes in denitrification rates in restored streams across different seasons, variable N loads, and in
response to the “flashy” hydrologic flow conditions during storms common in urban streams. 相似文献
12.
13.
Samples characterizing the horizontal distribution of bottom deposits of different types in the Upper Volga reservoirs were used to study the statistical relationship between the indicators of the potential and actual trophy of water bodies. These indicators are the amount of biogenic elements (the total nitrogen and phosphorus) and phyto-pigments (in the dry and wet masses of soil and in its organic fraction). The relationship between the above indicators for the channel deposits from the Upper Volga reservoirs and for the deposits in the lake hollows is found to he linear. 相似文献
14.
Nitrogen concentrations in various tektites and natural glasses have been measured using RNAA and are found to be almost constant at about 15 ppm. A terrestrial origin for tektite formation is favoured. 相似文献
15.
16.
放养前后鱼塘沉积物中氮、磷、有机质、色素的变化及环境意义 总被引：1，自引：0，他引：1
通过对针塘沉积物中营养盐,有机质及色素在放养前后的测试,对比分析了在人类活动（养殖）的影响下,由于鱼塘水体快速富营养化而引起底质上述指标的变化过程,其中快速沉积环境极有利于沉积色素的保存,具有较好的环境营养状况指示意义,同时有机质,色素和营养盐之间存在着密切的相关关系,这为利用色素方法研究短时间序列环境演变,尤其是在近代人类活动影响下的环境变化提供了一定的依据。 相似文献
17.
太湖流域望虞河西岸地区氮磷污染来源解析及控制对策 总被引：7，自引：2，他引：5
本文比较全面地调查了太湖流域望虞河西岸地区氮磷污染来源,结果表明:太湖流域望虞河西岸水体氮磷污染严重,氮磷污染物主要来源于生活污染,其氨氮、总氮、总磷排放量分别占总负荷量的60.2%、52.5%和52.9%.工业污染问题突出,纺织印染是污染物排放最大的工业行业.张家港市和江阴市为氮磷污染的主要贡献地.对区域环境容量进行了预测,并提出了氮磷污染削减目标,氨氮、总氮和总磷污染削减率分别达32.4%,51.8%和51.1%.最后,从加大污染综合治理力度、落实河道及生态修复工程、加强环境管理和监控等方面提出了望虞河西岸地区的氮磷污染控制对策. 相似文献
18.
19.
20.
— There is an increasing interest regarding the fate of nitrogenous compounds emitted from agricultural activities in the southeastern United States. Varying climate, topography and proximity to the Atlantic Ocean particularly complicates the problem. An increased understanding of the interaction of synoptic scale flow with mesoscale circulations would constitute a significant improvement in the assessment of regional scale transport and deposition potential. This knowledge is necessary to facilitate current and future modeling attempts in the region as well as for planning future monitoring sites to develop a cohesive regional policy for the abatement strategies. The eastern portion of North Carolina is used as a case example due to its high, localized emission of nitrogen compounds from agricultural waste. Three periods: July 2–7, 1998, October 5–11, 1998, and December 12–19, 1998, corresponding to three different seasons were studied. Surface wind and thermodynamic patterns were analyzed using surface observing stations and archived-model analysis results centered over eastern North Carolina. Diurnal and seasonal patterns were identified for dispersion and concentration values obtained using an air pollution transport and dispersion model. This mesoscale information was used to draw qualitative conclusions regarding the possible trends and deviations in the dynamic trajectories as well as the resulting near-surface concentrations and deposition potential in eastern North Carolina. Results show that highly variable seasonal and diurnal atmospheric circulations characterize the study domain. These variations can significantly impact the transport and fate of pollutants released in this region. Generally, summer provides the highest potential for localized deposition, while fall can provide opportunity for long-range transport. The results also suggest that mean climatological or seasonally averaged flow patterns may not be sufficient for analyzing the fate of the agricultural releases in this region. At the very least, mean and variance based analysis is required to capture the climatology of the dispersion and deposition patterns. These patterns in eastern North Carolina appear to be sensitive to the strength and location of air mass boundaries along the coastal plain, indicating diverse scale interactions affecting the variability and uncertainty in the regional pollutant transport. 相似文献