Heavy metal pollution in intertidal sediments from Quanzhou Bay, China

The concentrations of eight heavy metals （Cu, Zn, Pb, Cd, Cr, Ni, Hg, and As） in the intertidal surface sediments from Quanzhou Bay were determined to evaluate their levels and spatial distribution due to urbanization and economic development of Quanzhou region, southeast China. The ranges of the measured concentrations in the sediments are as follows： 24.8-119.7 mg/kg for Cu, 105.5-241.9 mg/kg for Zn, 34.3-100. 9 mg/kg for Pb, 0.28-0. 89 mg/kg for Cd, 51.1-121.7 mg/kg for Cr, 16.1-45.7 mg/kg for Ni, 0.17-0.74 mg/kg for Hg, and 17.7-30.2 mg/kg for As. The overall average concentrations of above metals exceed the primary standard criteria but meet the secondary standard criteria of the Chinese National Standard of Marine Sediment Quality. Several contents of Cu and Hg exceed the secondary standard criteria at some stations. The results of geoaccumulation index （Igeo） show that Cd causes strong pollution in most of the study area. There are no significant correlations among most of these heavy metals, indicating they have different anthropogenic and natural sources. Some locations present severe pollution by heavy metals depending on the sources, of which sewage outlets, aquatic breeding, and commercial ports are the main sources of contaminants to the area.     

Validation of an agricultural non-point source （AGNPS） pollution model for a catchment in the Jiulong River watershed, China

This study tested and evaluated the agricultural non-point source(AGNPS)model for the Wuchuan catchment, a typical agricultural area in the Jiulong River watershed, Fujian Province. China. The AGNPS model was calibrated and validated for the study area with observed data onten storms. Thedata on eight stormsin 2002 were used for calibration while data on two stormswere used for validation of the model. Considering the lack of water quality data over a long-term series, a novel method, comparing an internal nested catchment with its surrounding catchment, was used to supplement the less long-term series data. Dual calibration and validation of the AGNPS model was obtained by this comparison. The results indicate that the correlation coefficients were 0. 99 and 0. 98 for runoff, 0. 94 and 0. 95 forthe peak runoff rate of the large catchment and the small catchment, respectively, and 0. 76 forthe sediment of the small catchment only. Each pair of correlation coefficients is homogeneous for the same event for the two catchments. With the exception of the sediment yield and particulate phosphorus, the peak nmofr rate and other nutrients were well predicted. Sensitivity analysis showed that the Soil Conservation Service curve number and rainfall quantity were the most sensitive parameters, which resulted in high output variations. Erosivitv and other parameters had little influence on the hydrological and quality outputs.     

Characterization of the Songhua River sediments and evaluation of their adsorption behavior for nitrobenzene

The explosion at a plant of the Jilin Petrochemical Corporation on 13 November,2005,and the spill of an estimated 100 t of toxic substances (nitrobenzene as the main component) into the Songhua River received worldwide attention.This study has focused on the adsorption behavior of nitrobenzene that spilled onto sediments along the Songhua River,which was one of the efforts to evaluate the fate of nitrobenzene after the spillage event.The organic carbon contents of these sediments along the Songhua River ...     

Repeatability,Sensitivity, and Uncertainty Analyses of the BANCS Model Developed to Predict Annual Streambank Erosion Rates

Accelerated streambank erosion caused by channel instability can be the leading cause of sediment impairment of streams. Obtaining accurate streambank erosion rates for sediment budgeting and prioritizing mitigation efforts can be difficult and costly. One approach to quantifying streambank erosion rates is through the development and implementation of an empirically derived “Bank Assessment for Non‐point Source Consequences of Sediment” (BANCS) model. This study aims to improve the BANCS model application by evaluating repeatability between users and identifying sensitive and/or uncertain model inputs. Statistical analysis of streambank evaluations conducted by 10 different individuals suggests the implementation of the BANCS model may not be repeatable. This finding may be due to sensitive model inputs, such as streambank height and near‐bank stress level prediction method selection, and/or uncertain model inputs, such as bank material identification and the associated adjustment of erosion potential. Furthermore, it was found assessing streambanks as a group by obtaining a measure of central tendency from individual evaluations, as well as obtaining a higher level of training, may improve model implementation precision. Application of these suggestions may result in improved prediction of streambank erosion rates utilizing the BANCS model methodology.     

底泥厌氧环境和光照对菹草萌发和幼苗生理的影响

通过向底泥中投加不同量的蔗糖使其发生厌氧反应以模拟不同程度的底泥厌氧环境，研究这种环境和光照强度对菹草石芽萌发和幼苗生理作用的影响。实验结果表明，底泥厌氧环境能显著降低菹草石芽的最终萌发率，且低光照会加剧这种趋势；尽管低光照不一定会提高最终的萌发率，但对提早石芽的萌发是有利的。在01%蔗糖投加处理中，幼苗的叶绿素和可溶性蛋白含量最高(平均为250和1928 mg/g FW)，其后随投加量的升高而降低，而游离氨基酸的含量却一直呈上升趋势，最高时达到024 mg/g FW ，但低光照却使它下降；可溶性糖含量基本不受底泥厌氧水平的影响，但随着光照减少而降低。随着厌氧水平的增加（从对照到05%蔗糖投加量），菹草的超氧物歧化酶(SOD)活性呈现上升趋势，但在10%蔗糖投加处理中活性降至最低；而过氧化物酶(POD)活性一直处于下降趋势。研究结论是：底泥厌氧对菹草石芽萌发影响显著，这种影响可能比低光照的限制作用还要重要。轻度的厌氧环境反而能促进菹草幼苗的生理代谢，但随厌氧水平的升高对碳氮平衡和其它生理活动产生不利影响。此外，底泥厌氧环境对菹草幼苗的抗氧化系统也有明显刺激作用。     

TRACE METALS IN SEDIMENT: SPATIAL TRENDS AND SORPTION PROCESSES1

ABSTRACT: Sediment bound trace metals are often examined for spatial trends such as downstream patterns or distance from a source. Spatial trends may indicate either differences in metal inputs, or, when considerable sediment variability exists, differences in sediment sorption processes. These two possibilities become important not only when sediment contamination is evaluated within an area, but also when regulatory agencies attempt to make equivalent among area decisions. Sediments from an urban watershed were examined for: (1) downstream trace metal trends and (2) sediment sorption relationships. Analyses determined that downstream trenda as related to metal inputs could not be recognized by analyzing the < 2mm (≤, sand) sediment size fraction. Conversely, the trace metal concentrations were found to be distinctly related to sediment characteristics. The watershed's metal concentrations are similar to those found in uncontaminated to slightly contaminated sediments in the United States.     

HYDROLOGIC EFFECTS OF TWO METHODS OF HARVESTING MATURE SOUTHERN PINE1

ABSTRACT: Hydrologic responses to logging with skidders and responses to logging with a cable yarder are compared. After a 23-year calibration with an undisturbed control catchment, mixed stands of shortleaf pine (Pinus echinata Mill.) and hardwoods were clearfelled on two small catchments in the hilly Coastal Plain of north Mississippi and observed for five years. Runoff increased 370 mm (skidded) and 116 mm (yarded) during the first year with 1876 mm of rainfall, and 234 mm (skidded) and 228 mm (yarded) during the second year when 1388 mm of precipitation equaled the calibration mean. Sediment concentrations for the yarded catchment during the first two years averaged 641 and 1,629 mg L^?1, respectively, and yields were 6,502 and 12,086 kg ha^?1. Compared to calibration means of 74 mg L^?1 and 142 kg ha^?1, these extreme values can be attributed largely to transport of sediment stored in the channel and to erosion of subsurface flow paths, which was exacerbated by high flow volumes. During the first year, the concentration (231 mg L^?1) and yield (2,827 kg ha^?1) for the control catchment also exceeded the calibration means. However, concentrations (134 mg L^?1) and yields (1,806 kg ha^?1) for the skidded catchment were about 40 percent lower than for the control catchment during the first year, and were higher than those for the control only during the second year. Because deep percolation was limited and because rainfall was unusually high, increases in flows and sediment concentrations and yields probably approximate maximum responses to clearcut harvesting in the uplands of the southern Coastal Plain.     

HYDROLOGIC RESPONSES OF AN AGRICULTURAL WATERSHED TO VARIOUS HYDROLOGIC AND MANAGEMENT CONDITIONS1

ABSTRACT: The hydrologic responses from an agricultural watershed in southeast Nebraska were investigated under an array of physiographic, hydrologic, meteorologic, and management conditions. For analytical purposes, the hydrologic responses were narrowed to include only runoff and sediment yield. The study was performed by utilizing the ANSWERS (Areal Nonpoint Source Watershed Environment Response Simulation) hydrologic-simulation model. Results of this study indicate that, generally, nonstructural (agronomic) Best Management Practices (BMPs) have a more significant impact in controlling erosion and nonpoint-source pollution than structurally oriented BMPs. The percentage of reduction in average soil loss as a result of changing tilage systems from conventional to chisel plow was in the mid-40s. The corresponding percentages of reduction in sediment yield from the watershed under minimum tillage and no-till systems were in the mid-60s and mid-80s, respectively. The impact of these management strategies on runoff varied considerably. That is primarily based on the watershed's antecedent soil moisture condition, land use, and the growth stage of crops. Generally, an intense, short, thunderstorm type of rainfall event had more relative impact on runoff, and therefore sediment yield than a long, gentle, and steady event.     

Phosphorus export by runoff from agricultural field plots with different crop cover in Lake Taihu watershed

ＩｎｔｒｏｄｕｃｔｉｏｎＷａｔｅｒｅｕｔｒｏｐｈｉｃａｔｉｏｎｉｓｏｎｅｏｆｔｈｅｇｌｏｂａｌｅｎｖｉｒｏｎｍｅｎｔａｌｐｒｏｂｌｅｍｓ ,ａｎｄａｇｒｉｃｕｌｔｕｒａｌｎｏｎｐｏｉｎｔｓｏｕｒｃｅｐｏｌｌｕｔｉｏｎｈａｓｂｅｅｎｇｉｖｅｎｉｎｃｒｅａｓｅｄａｔｔｅｎｔｉｏｎ (Ｓｈａｒｐｌｅｙ ,1994 ;Ｈａｒｒｉｓ ,1995;Ｔｉｅｓｓｅｎ ,1995;Ｔｏｎｄｅｒｓｋｉ,1996;Ｄａｎｉｅｌ,1998) .Ｌａｋｅｅｕｔｒｏｐｈｉｃａｔｉｏｎｈａｓｂｅｅｎｉｄｅｎｔｉｆｉｅｄａｓａｃｒｉｔｉｃａｌｐｒｏｂｌｅｍｏｆｓｕｒ…     

沉积物再悬浮对沉水植物生长的影响研究

通过室内模拟实验,研究了沉积物再悬浮对苦草(Vallisneria natans)和马来眼子菜(Potomogeton malaianus)2种沉水植物生长的影响.为期10周的实验发现,有沉积物再悬浮的处理组中,苦草的生物量显著低于对照组中(没有沉积物再悬浮)苦草的生物量;同样,沉积物再悬浮对苦草的分蘖和块茎数也产生了明显的影响;马来眼子菜的生物量和分蘖数同样受到了沉积物再悬浮的影响,但影响程度小于苦草.因此,沉积物再悬浮对沉水植物的生长、繁殖具有的抑制作用,但这种作用因种类不同而有所差异.