Fractionation of Mn, Fe, Zn and Cu in Sediments of Khor Kalabsha, Lake Nasser, Egypt

Khor Kalabsha is the second largest Khor in Lake Nasser, which is a freshwater side-branch of the main lake. Chemical analysis of the samples indicates that calcium carbonate and organic matter content in the surface sediments average 17.8 and 3.07%, respectively. Moreover, manganese, iron, zinc and copper concentrations are lower in Khor Kalabsha than in other lakes of Egypt. It has been found that both oxides and residual forms constitute the major part of the measured elements in the study area, while manganese and iron play an important role in building up clay minerals. It is noted that both zinc and copper fractions are controlled by biological and biochemical processes.     

Chemistry, mineralogy and radioactivity in posidonia oceanica meadows from North-Western Sicily

This paper presents measurements of major, minor, metal trace elements and radionuclides in sediments and in Posidonia oceanica samples from north-western Sicily (Italy). The mineralogical and chemical composition of sediments were determined by X-ray diffraction and X-ray fluorescence techniques, respectively. A flame atomic absorption spectrophotometry was used to measure concentrations of Cu, Zn, Cd and Pb in P. oceanica samples and in sediments. Specific activities of selected radionuclides have been determined by high-resolution gamma spectrometry. Standard statistical analysis was used to assess correlations between different elements and different sample types.     

高原湿地剑湖湖滨带功能作用的定量研究

采用野外采样与室内分析的方法，从水质和底泥两个方面定量研究剑湖湖滨带的功能作用。结果表明，湖滨带在水质净化和拦截泥沙等方面效果显著，特别是对水中总氮与总磷的平均去除率分别高达66．28％和45．73％，其拦截作用表现为：迎水面的泥层厚度是背水面的1．5倍；底泥的各项指标（除pH值），湖滨带背水面均比迎水面高，速效磷和全氮的增加量最为明显，其含量分别是迎水面的3．30和2．61倍，这主要与湖滨植物带大量吸收入湖矿质营养用于自身生长，其残体在背水面沉积有关，从另一角度体现了湖滨带的吸附、净化功能。因此，要重视并保护湖滨带，从而使其功能得到有效发挥。     

攀枝花地区河流沉积物的重金属污染研究

攀枝花市是长江流域经济带上游区第一城，几十年的开发建设使该地区的经济、社会得到了飞速的发展，但同时也造成了一定的环境影响。采用地质累积指数评价了该区水系沉积物中的重金属污染状况，结果表明，水系沉积物中各元素的污染程度由高到低为：Ti、Cu、V、Pb、Zn、Cr、As；总体上看，各元素在攀钢采矿场、选矿厂、冶炼厂及尾矿坝等地的污染程度较高，表明该区水系沉积物中重金属和攀枝花地区金沙江水质的污染主要与该区钒钛磁铁矿的采、选、冶等矿业活动有关。该区应采取如下措施减轻环境影响：(1)加强矿区环境恢复和环境管理，确保区域资源、环境、经济、社会可持续发展；(2)加强城市环境监测，特别是重金属和其他微量元素污染的监测，进行城市生态环境安全预警。     

GRAZED STUBBLE HEIGHT AS A CRITERION FOR CONTROLLING SEDIMENT PRODUCTION FROM GRAZING LANDS1

ABSTRACT: Efforts by state and federal agencies to develop standards and guidelines for protecting and enhancing water quality on grazing lands have led to suggestions that grazed stubble height criteria could be used to determine when cattle should be removed from a specific pasture or grazing area. Until recently only indirect scientific evidence from agronomy and laboratory studies gave support to the stubble height concept. Consequently, a grazing study was initiated on a Montana ranch in 1997 to determine the reduction in overland sediment achieved by grazing a pasture to a predetermined stubble height. Treatments consisted of 7 cm (3 in) grazed, 7 cm (3 in) clipped or mowed, 15 cm (6 in) grazed; 15 cm (6 in) clipped and untreated or natural forage plant height. The five treatments were used in a two‐year trial spanning 1997 to 1999. At the conclusion of this study the magnitude of sediment production was related to the number of intense rain events during the March through June period rather than total precipitation. There was a significant year effect in terms of sediment accumulation (P < 0.01) but no year by treatment effect (P = 0.11). Even though a significant difference in sediment accumulation was detected between the shorter and taller stubble heights (P = 0.04) in both 1998 and 1999, the difference could not be explained by grazed stubble height alone. Close grazing (7 cm stubble) consistently ranked lowest in sediment production (P < 0.01) among all treatments, including the ungrazed control. These results suggest that changes in plant community structure and microtopographic caused by grazing influence sediment entrapment (retention) on hillslopes more than those caused by plant height.     

Changes in Extractable Metal Concentrations During Storage of Surface Water Samples Containing Sediments1

ABSTRACT: Changes in metal concentrations during storage of acidified water samples were studied. Water samples with high concentrations of suspended sediment were collected from the Fraser River, British Columbia. These samples were analyzed for “extractable” metals, which are defined to be the dissolved metals plus those metals extracted from suspended sediment by dilute mineral acid. Concentrations of extractable Cu, Fe, Pb, Zn, Ni, Co, Mn, and Cd were determined over time. Metal concentrations in these water samples were not stable and showed significant increases throughout the storage period. These results suggest that the extractable metal technique is inappropriate for the analysis of water samples containing suspended sediment.     

沉积物和生物样品铜,铅测定的质量控制

通过测定方法选择，基础实验，空白值测定，精密和准确度控制有效地控制测定过程，保证测定数据准确，可靠，可比。     

DISCHARGE AND SUSPENDED SEDIMENT PATTERNS OF AN INTERMITTENT COLD DESERT STREAM1

Sage Creek in south‐central Wyoming is listed as impaired by the U.S. Environmental Protection Agency (USEPA) due to its sediment contribution to the North Platte River. Despite the magnitude of sediment impacts on streams, little research has been conducted to characterize patterns of sediment transport or to model suspended sediment concentration in many arid western U.S. streams. This study examined the relationship between stream discharge and suspended sediment concentration near the Sage Creek and North Platte River confluence from 1998 through 2003. The objectives were to determine patterns of stream discharge and suspended sediment concentration, produce a sediment prediction model, and compare sediment concentrations for the six‐year period. Stream discharge and suspended sediment transport responded rapidly to convective storms and spring runoff events. During the study period, events exceeding 0.23 m³/s accounted for 92 percent of the sediment load, which is believed to originate from erodible headwater uplands. Further analysis of these data indicates that time series modeling is superior to simple linear regression in predicting sediment concentration. Significant increases in suspended sediment concentration occurred in all years except 2003. This analysis suggests that a six‐year monitoring record was insufficient to factor out impacts from climate, geology, and historical sediment storage.     

Transformation of Particle-Bound Phosphorus at the Land–Sea Interface in a Danish Estuary

Danish rivers carry >50% of the phosphorus (P) transport as particulate P (PP). In five of six rivers sampled in November 1998 iron-bound P made up > 59% of PP and loosely adsorbed P ranged between 2% and 13%. This fraction could potentially be released in 14‰ seawater. The behaviour of dissolved and particulate P fractions was studied during seven month in a 2 km long estuary with low freshwater retention time and low tidal range. The river carried ∼10% of PP as loosely adsorbed P but increased concentrations of dissolved inorganic P (DIP) relative to the estuarine mixing line was only observed in the summer month with low freshwater flow and was more likely due to DIP release from the bottom sediment. Instead estuarine particles were always enriched with oxidized iron (ox.Fe) and iron-bound P as well as loosely adsorbed P and during May–September this coincided with increasing concentration of PP in estuary. We suggest that flocculation of ox.Fe and adsorption of DIP onto the particles with subsequent transport seawards is a major loss process for P during the summer month. During winter month where 85% of the run-off occurs the dominant process in the estuary is sedimentation of larger particles, however, a comparison of river particles with surface sediment clearly reveals that most PP is mobilized again from the bottom sediments.     

HYDROLOGIC EFFECTS OF CLEARCUTTING AND STRIPCUTTING LOBLOLLY PINE IN THE COASTAL PLAIN1

ABSTRACT: Harvesting 29-year-old loblolly pine (Pinus taeda L.) plantations on six small catchments in the Coastal Plain of west Tennessee caused variable but generally minor increases of storm-flow volumes during the four years following harvest. The increases were primarily associated with decreases of rainfall interception rather than with soil disturbance. Harvesting had no effect on stormflow volumes in six nearby catchments of 37-year-old loblolly pine to which the same treatments were applied. Postharvest increases of flow-weighted sediment concentrations averaged higher for the catchments with greater flows at both locations. During the fourth through eighth years after harvest, average sediment concentrations for harvested catchments at each location approximated closely the base rate of 62 mg L^-1 previously defined for undisturbed pine types. Thus, relatively minor postharvest increases of stormflow volumes in the six 29-year-old plantations and increases of sediment concentrations in all 12 catchments were limited to about four years. Nevertheless, because of potential channel erosion, the findings confirm the need to extend stream management zones well up into drainages with intermittent and ephemeral flows wherever water quality is a concern. Despite certain undesirable effects of logging (baring of mineral soil, decreased weight and depth of forest floor, increased soil bulk density), the results demonstrate the high resilience developed by pine planted on severely eroded sites in the southern Coastal Plain.