Nitrogen loads to New Zealand aquatic receiving environments: comparison with regulatory criteria     

Ton H. Snelder  Amy L. Whitehead  Caroline Fraser  Scott T. Larned  Marc Schallenberg 《新西兰海洋与淡水研究杂志》2020,54(3):527-550

ABSTRACT

There is concern about the deteriorating nutrient status of aquatic receiving environments in New Zealand. We estimated the amount by which current nitrogen (N) concentrations and loads exceed criteria in rivers, lakes and estuaries nationally. Criteria corresponded to national ‘bottom-line’ (i.e. minimal) environmental objectives set by government policy. Three metrics were evaluated: (1) degree of compliance describes the current TN loads in receiving environments relative to criteria; (2) catchment N status describes the acceptability of catchment N loads compared to criteria; and (3) excess load indicates the amount by which the N load exceeds the maximum allowable load (kg yr^?1). Non-compliance with N criteria was broadly distributed nationally particularly in low-elevation catchments. Catchments with unacceptable N status constituted at least 31% of New Zealand’s land area, which corresponds to at least 43% of the country’s agricultural land. The national excess load was estimated to be at least 19.1 Gg yr^?1. We are 97.5% confident that estimated excess loads exceed zero for nine of 15 regions and for the nation as a whole. The analyses provide a strategic assessment of where reductions in N emissions are required to achieve the minimal national objectives.  相似文献   

Model Simulations of Carbon Sequestration in the Northwest Pacific by Direct Injection     

Katsumi?MatsumotoEmail author  Bryan?K.?Mignone 《Journal of Oceanography》2005,61(4):747-760

The direct disposal of CO₂ into the ocean interior represents a possible means to help mitigate rising levels of atmospheric CO₂. Here, we use three different versions of an ocean general circulation model (OGCM) to simulate the direct injection of liquid CO₂ near Tokyo. Our results confirm that direct injection can sequester large amounts of CO₂ from the atmosphere when disposal is made at sufficient depth (80–100% of the carbon injected at 3000 m remains in the ocean after 500 years) but show that the calculated efficiency is rather sensitive to the choice of physical model. Moreover, we show, for the first time in an OGCM and under a reasonable set of economic assumptions, that sequestration effectiveness is quite high for even shallow injections. However, the severe acidification that accompanies injection and the impossibility of effectively monitoring injected plumes argue against the large-scale viability of this technology. Our coarse-grid models show that injection at the rate of 0.1 Pg-C/yr lowers pH near the site of injection by as much as 0.7–1.0 pH-unit. Such pH anomalies would be much larger in more finely gridded models (and in reality) and have potential to severely harm deep-sea organisms. We also show that, after several hundred years, one would effectively need to survey the entire ocean in order to accurately verify the inventory of injected carbon. These results suggest that while retention may be sufficient to justify disposal costs, other practical problems will limit or at best delay widespread deployment of this technology.  相似文献   

Sensitivity of CFCs and Anthropogenic CO2 Uptake in a North Pacific GCM to Mixing Parameterization and Surface Forcing     

Akio Ishida  Kisaburo Nakata  Shigeaki Aoki  Hiroshi Kutsukake  Michio J. Kishi  Masahisa Kubota 《Journal of Oceanography》2001,57(4):433-450

Distributions and characteristics of water mass and chlorofluorocarbons (CFCs) in the North Pacific are investigated by using a General Circulation Model (GCM). The anthropogenic CO₂ uptake by the ocean is estimated with velocity fields derived from the GCM experiments. The sensitivity of the uptake to different diffusion parameterizations and different surface forcing used in the GCM is investigated by conducting the three GCM experiments; the diffusive processes are parameterized by horizontal and vertical eddy diffusion which is used in many previous models (RUN1), parameterized by isopycnal diffusion (RUN2), and isopycnal diffusion and perpetual winter forcing for surface temperature and salinity (RUN3). Realistic features for water masses and CFCs can be simulated by the isopycnal diffusion models. The horizontal and vertical diffusion model fails to simulate the salinity minimum and realistic penetration of CFCs into the ocean. The depth of the salinity minimum layer is better simulated under the winter forcing. The results suggest that both isopycnal parameterization and winter forcing are crucial for the model water masses and CFCs simulations. The oceanic uptake of anthropogenic CO₂ in RUN3 is about 19.8 GtC in 1990, which is larger by about 10% than that in RUN1 with horizontal and vertical diffusive parameterization. RUN3 well simulates the realistic water mass structure of the intermediate layer considered as a candidate of oceanic sink for anthropogenic CO₂. The results suggest that the previous models with horizontal and vertical diffusive parameterization may give the oceanic uptake of anthropogenic CO₂ underestimated. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Régimes des flux des matières solides en suspension au Cameroun: revue et synthèse à l’échelle des principaux écosystèmes; diversité climatique et actions anthropiques / Regimes of suspended sediment flux in Cameroon: review and synthesis for the main ecosystems; climatic diversity and anthropogenic activities     

《水文科学杂志》2013,58(1)

Abstract

Abstract Since the end of the 1950s, suspended matter measurements have been carried out in the streams and rivers of Cameroon. Despite the fact that these are often point measurements, they provide a framework for a global approach towards studying the regimes of suspended sediment transport in these rivers. The objective here is to assess the intensity of sediment transport and to determine the principal factors which influence it, according to the main climatic units. The influence of human activities is pointed out. It appears that steep slopes, population density, soil cultivation and cattle grazing are the essential factors. The sediment load in these rivers is increasing with latitude with 20–40 g m^-3 at the Equator, 80–100 g m^-3 in the transition zones and 150–160 g m^-3 in the dry tropical zones. The choice of drainage basin size for the characterisation of the rate of effective erosion is indispensable. In fact, in large drainage basins (5 × 10⁴ km²), there is an integration of heterogeneous geomorphological, phytogeographical, pedological and anthropogenic characteristics into average characteristics which do not show the influence of local conditions on sediment transport.  相似文献   

High‐resolution topography and anthropogenic feature extraction: testing geomorphometric parameters in floodplains          下载免费PDF全文

Giulia Sofia  Giancarlo Dalla Fontana  Paolo Tarolli 《水文研究》2014,28(4):2046-2061

In floodplains, anthropogenic features such as levees or road scarps, control and influence flows. An up‐to‐date and accurate digital data about these features are deeply needed for irrigation and flood mitigation purposes. Nowadays, LiDAR Digital Terrain Models (DTMs) covering large areas are available for public authorities, and there is a widespread interest in the application of such models for the automatic or semiautomatic recognition of features. The automatic recognition of levees and road scarps from these models can offer a quick and accurate method to improve topographic databases for large‐scale applications. In mountainous contexts, geomorphometric indicators derived from DTMs have been proven to be reliable for feasible applications, and the use of statistical operators as thresholds showed a high reliability to identify features. The goal of this research is to test if similar approaches can be feasible also in floodplains. Three different parameters are tested at different scales on LiDAR DTM. The boxplot is applied to identify an objective threshold for feature extraction, and a filtering procedure is proposed to improve the quality of the extractions. This analysis, in line with other works for different environments, underlined (1) how statistical parameters can offer an objective threshold to identify features with varying shapes, size and height; (2) that the effectiveness of topographic parameters to identify anthropogenic features is related to the dimension of the investigated areas. The analysis also showed that the shape of the investigated area has not much influence on the quality of the results. While the effectiveness of residual topography had already been proven, the proposed study underlined how the use of entropy can anyway provide good extractions, with an overall quality comparable to the one offered by residual topography, and with the only limitation that the extracted features are slightly wider than the investigated one. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Anthropogenic Aerosol Pollution over the Eastern Slope of the Tibetan Plateau     

Rui JIA  Min LUO  Yuzhi LIU  Qingzhe ZHU  Shan HUA  Chuqiao WU  Tianbin SHAO 《大气科学进展》2019,(8):847-862

In this study, a combination of satellite observations and reanalysis datasets is used to analyze the spatiotemporal distribution, classification and source of pollutants over the eastern slope of the Tibetan Plateau(ESTP). The aerosol optical depth(AOD) over the ESTP is extremely large and even larger than some important industrialized regions and deserts. The main aerosol component over the ESTP is sulfate, followed by carbonaceous and dust aerosols. Local emissions related to human activity directly contribute to the accumulation of sulfate and carbonaceous aerosols over the Sichuan Basin. In addition, in spring, abundant carbonaceous aerosols emitted from forest, grassland and savanna fires in Southeast Asia can be transported by the prevailing southwesterly wind to southern China and the ESTP. The dust AOD over the ESTP peaks in spring because of the transport from the Taklimakan and Gobi deserts. Additionally, the high aerosol loading over the ESTP is also directly related to the meteorological background. Due to the special topography, the terrain-driven circulation can trap aerosols in the Sichuan Basin and these aerosols can climb along the ESTP due to the perennial updraft. The aerosol loading is lowest in summer because of effective wet deposition induced by the strong precipitation and better dispersion conditions due to the larger vertical temperature gradients and ascending air movement enhanced by the plateau heat pump effect. In contrast,the aerosol loading is greatest in winter. Abundant anthropogenic aerosols over the ESTP may generate some climatic and environmental risks and consequently greatly influence the downstream regions.  相似文献   

Statistical Analysis of the Relationships among Coronal Holes,Corotating Interaction Regions,and Geomagnetic Storms     

Yunhee Choi  Y.-J. Moon  Seonghwan Choi  Ji-Hye Baek  Sungsoo S. Kim  K.-S. Cho  G. S. Choe 《Solar physics》2009,254(2):311-323

We have examined the relationships among coronal holes (CHs), corotating interaction regions (CIRs), and geomagnetic storms in the period 1996?–?2003. We have identified 123 CIRs with forward and reverse shock or wave features in ACE and Wind data and have linked them to coronal holes shown in National Solar Observatory/Kitt Peak (NSO/KP) daily He i 10?830 Å maps considering the Sun?–?Earth transit time of the solar wind with the observed wind speed. A sample of 107 CH?–?CIR pairs is thus identified. We have examined the magnetic polarity, location, and area of the CHs as well as their association with geomagnetic storms (Dst≤?50 nT). For all pairs, the magnetic polarity of the CHs is found to be consistent with the sunward (or earthward) direction of the interplanetary magnetic fields (IMFs), which confirms the linkage between the CHs and the CIRs in the sample. Our statistical analysis shows that (1) the mean longitude of the center of CHs is about 8°E, (2) 74% of the CHs are located between 30°S and 30°N (i.e., mostly in the equatorial regions), (3) 46% of the CIRs are associated with geomagnetic storms, (4) the area of geoeffective coronal holes is found to be larger than 0.12% of the solar hemisphere area, and (5) the maximum convective electric field E _y in the solar wind is much more highly correlated with the Dst index than any other solar or interplanetary parameter. In addition, we found that there is also a semiannual variation of CIR-associated geomagnetic storms and discovered new tendencies as follows: For negative-polarity coronal holes, the percentage (59%; 16 out of 27 events) of CIRs associated with geomagnetic storms in the first half of the year is much larger than that (25%; 6 out of 24 events) in the second half of the year and the occurrence percentage (63%; 15 out of 24 events) of CIR-associated storms in the southern hemisphere is significantly larger than that (26%; 7 out of 27 events) in the northern hemisphere. Positive-polarity coronal holes exhibit an opposite tendency.  相似文献   

Estimates of anthropogenic CO<Subscript>2</Subscript> uptake in a global ocean model   总被引：2，自引：0，他引：2  

徐永福  李阳春 《大气科学进展》2009,26(2):265-274

A global ocean general circulation model (L30T63) is employed to study the uptake and distribution of anthropogenic CO₂ in the ocean. A subgrid-scale mixing scheme called GM90 is used in the model. There are two main GM90 parameters including isopycnal diffusivity and skew (thickness) diffusivity. Sensitivities of the ocean circulation and the redistribution of dissolved anthropogenic CO₂ to these two parameters are examined. Two runs estimate the global oceanic anthropogenic CO₂ uptake to be 1.64 and 1.73 Pg C yr^-1 for the 1990s, and that the global ocean contained 86.8 and 92.7 Pg C of anthropogenic CO₂ at the end of 1994, respectively. Both the total inventory and uptake from our model are smaller than the data-based estimates. In this presentation, the vertical distributions of anthropogenic CO₂ at three meridional sections are discussed and compared with the available data-based estimates. The inventory in the individual basins is also calculated. Use of large isopycnal diffusivity can generally improve the simulated results, including the exchange flux, the vertical distribution patterns, inventory, storage, etc. In terms of comparison of the vertical distributions and column inventory, we find that the total inventory in the Pacific Ocean obtained from our model is in good agreement with the data-based estimate, but a large difference exists in the Atlantic Ocean, particularly in the South Atlantic. The main reasons are weak vertical mixing and that our model generates small exchange fluxes of anthropogenic CO₂ in the Southern Ocean. Improvement in the simulation of the vertical transport and sea ice in the Southern Ocean is important in future work.  相似文献   

类似物研究和矿物学问题   总被引：1，自引：0，他引：1  

陈璋如 《矿物学报》2001,21(3):341-344

本文叙述了核废物地质处置研究领域中涉及天然和人为类似物研究中的一些矿物学问题。在自然界的天然玻璃、膨润土、晶质铀矿等分别作为高放废物玻璃固化体、高放废物处置库的缓冲／回填材料和乏燃料的天然类似物，考古遗址中的玻璃和青铜器文物作为人为类似物。通过这些天然非晶质结晶物质和人造制品的稳定性研究来预测未来10000－100000a间处置库中废物和缓冲／回填物质的变化，放射性核素迁移规律，为高放废物处置库的设计和建造提供重要科学依据，提高公众对高放废物安全处置的信心。  相似文献   

Mid-latitude winds in the mesosphere: a superposed epoch analysis over the geomagnetic storm times     

G. Ma  K. Igarashi  K. Hocke 《Journal of Atmospheric and Solar》2001,63(18):1075

This study aims at looking for the characteristic patterns of mesospheric wind over the geomagnetic storm times. For this purpose, the geomagnetic storms preceded by a sudden commencement (SSC) have been selected from January 1995 to April 1999. By using the onset of SSC as the timing mark, a superposed epoch analysis has been performed on the available neutral wind data measured with medium frequency (MF) radars at Yamagawa (31.2°N, 130.6°E) and Wakkanai (45.4°N, 141.7°E). In doing so, the length of time chosen for the superposed analysis is from 7 days before the SSC onset to 21 days after the onset; subsets of wind data are superimposed for summer and winter months, respectively. Then with harmonic analysis on the superposed winds the mean winds in both summer and winter months have been obtained. Concerning mean wind characteristics, some interesting details are the reversal heights of the summer zonal winds, which is 79–80 km at Yamagawa and 84 km at Wakkanai. Strong wavy structures with 2–4 days period are observed at both Yamagawa and Wakkanai in both summer and winter. As for storm effects, significant enhancement of eastward wind is found 5 days after SSC onset at both Yamagawa and Wakkanai in winter. Moreover, the northward wind turns southward at Wakkanai 2 days after the onset of SSC, and the southward wind lasts for several days thereafter. In summer months, the post-storm enhancement tends to be small and mainly in the eastward wind at both Yamagawa and Wakkanai.  相似文献