Particle size distribution and pollutants in road-deposited sediments in different areas of Zhenjiang,China

An understanding of road-deposited sediment (RDS) characteristics on an impervious surface is essential to estimate pollutant washoff characteristics and to minimise the impacts of pollutants on the water environment. A total of 62 RDS samples were collected from four different land-use types (commercial, residential, intense traffic and riverside park) in Zhenjiang City, China. The samples were fractionated into seven grain-size classes and analysed for particle size distribution and concentrations of pollutants. The samples are found to consist predominantly of fine particles (60–80%, <250 μm). The maximum mean concentrations of zinc, lead and copper were 686.93, 589.19 and 158.16 mg/kg, respectively, with the highest metal concentrations found in samples from the intense traffic area. The maximum mean contents of organic matter (12.55%), nitrogen (6.31 mg/g) and phosphorus (5.15 mg/g) were found in samples from the commercial area. The concentrations of heavy metals were highest in the smallest particle size fraction analysed (63 μm). The organic matter and nitrogen content generally increased with decreasing particle sizes in the <500-μm particle size range. The results also revealed that most of the total nitrogen (TN) is attached to the finer sediments and that to effectively reduce TN loads in particulates, treatment facilities must be able to remove the finer particles (down to 125 μm for TN).     

Impacts of mussel dredging on sediment phosphorus dynamics in a eutrophic Danish fjord

Effects of mussel dredging on sediment metabolism (oxygen uptake and sulfate reduction rates) and phosphorus dynamics (flux across sediment-water interface and sequential extraction) were examined in Limfjorden (Denmark) during spring (May) and summer (August). Sediment samples were taken during mussel dredging and in addition an experimental simulation of the dredging was performed to investigate short-term changes in phosphorus (P) dynamics. Iron-bound P was reduced by up to 2/3 in the surface layer in the dredging track (from 31 to 8?mmol?P?m^?2), whereas the dissolved P-pools and less reactive particulate pools were not affected by dredging. Sediment oxygen consumption was enhanced immediately after dredging, but returned to the initial level after 4 days (20–40?mmol?m^?2?d^?1). The enhanced consumption was attributed to reoxidation of reduced compounds released during dredging. Sulfate reduction rates were high in the area (13–15?mmol?m^?2?d^?1) and sulfides competed with P for oxidized iron resulting in low iron-bound pools in the area (<4% of total P pools). Sulfate reduction rates were stimulated by the resuspension of sediments, especially in August, where a subsurface maximum was found, possibly due to a mixing of labile organic matter into these layers. In contrast sulfate reduction rates were reduced in the dredging track due to removal of labile organic matter from the surface layers. The loss of P during dredging was to some extent counteracted by regeneration of iron-bound P pools in the surface layers. The release of P due to mussel dredging was estimated to be in the same order of magnitude as the annual loading from the catchments and point sources to Limfjorden.     

强化生物除磷的机理模型研究进展

主要论述了以乙酸盐及葡萄糖作为基质的强化生物除磷的相关机理模型。当以乙酸盐为底物时．重点需要明确导致工艺中微生物代谢模式差异的原因及厌氧条件下还原力供给方式的问题;当以葡萄糖为底物时．主要需要解决厌氧条件下供能方式以及各种微生物之间的关系。某些抑制条件(如供氧不足)可能会促进强化生物除磷效果的实现。强化生物除磷各种机理的差异主要由所驯化的优势微生物种类及其代谢模式不同而造成的。     

镇江市金山湖沉积物磷元素分布特征研究

以镇江市金山湖为研究区域,于2019年1月（冬季）和2019年7月（夏季）采集了10个点位的表层沉积物样品,参照欧洲标准测试测量组织建立的沉积物磷形态分析方法（SMT）测定沉积物总磷（TP）、无机磷（IP）、有机磷（OP）、铁/铝-磷（Fe/Al-P）和钙-磷（Ca-P）质量分数,研究金山湖表层沉积物磷元素及其赋存形态的季节分布特征。结果表明,金山湖表层沉积物中TP质量分数在冬、夏季分别为727.39~1 073.70 mg/kg和700.90~1 002.17 mg/kg,处于中等污染水平;金山湖表层沉积物磷以IP为主,IP在TP中的占比在冬、夏季分别为68.58%~88.86%,73.09%~87.21%;除了Fe/Al-P以外,OP作为生物有效磷源,其冬、夏季质量分数分别为69.37~190.93 mg/kg和108.45~210.42 mg/kg;其平均值分别为129.01,160.15 mg/kg。金山湖冬、夏季沉积物各形态磷质量分数所占比例均表现为Ca-P>Fe/Al-P>OP,表明该研究区域沉积物以Ca-P占优势。金山湖表层沉积物pH值呈现弱碱性,通过Ca-P直接释放到上覆水中的磷较少,故金山湖沉积物磷元素的潜在风险较小。各形态磷的相关性分析结果发现,冬季沉积物TP与Fe/Al-P、IP呈极显著正相关（P<0.01）。夏季沉积物TP与IP、Fe/Al-P之间呈极显著正相关（P<0.01）,与Ca-P呈显著正相关（P<0.05）。此外,金山湖沉积物OP、Fe/Al-P以及Ca-P的来源不一致。pH值对沉积物IP会产生一定影响,而其余磷形态则受pH值的影响程度较小。     

Cost-Effective Control of Interdependent Water Pollutants

Excess nutrient loads to coastal waters lead to increased production of algae, which when decaying cause oxygen depletion in bottom sediments, which in turn leads to major changes in marine ecosystems. A cost-minimization model was investigated in which nitrogen and phosphorus were assumed to interact with respect to algae production. It was investigated under what conditions only a single nutrient should be decreased and when it is cost-effective to decrease both nutrients. The model was applied to the Baltic Proper, which is the largest of the seven major basins in the Baltic Sea. Results showed that the stringency of the environmental target, as well as assumptions regarding substitutability between nutrients, are important factors to determine the nutrient on which to focus. Uniform decrease rates for emissions are often used in international agreements, and the results of this model showed that the costs of making such proportional decreases could be substantial.     

Assessing the Effects of Nutrient Management in an Estuary Experiencing Climatic Change: The Neuse River Estuary, North Carolina

Eutrophication is a serious water quality problem in estuaries receiving increasing anthropogenic nutrient loads. Managers undertaking nutrient-reduction strategies aimed at controlling estuarine eutrophication are faced with the challenge that upstream freshwater segments often are phosphorus (P)-limited, whereas more saline downstream segments are nitrogen (N)-limited. Management also must consider climatic (hydrologic) variability, which affects nutrient delivery and processing. The interactive effects of selective nutrient input reductions and climatic perturbations were examined in the Neuse River Estuary (NRE), North Carolina, a shallow estuary with more than a 30-year history of accelerated nutrient loading and water quality decline. The NRE also has experienced a recent increase in Atlantic hurricanes and record flooding, which has affected hydrology and nutrient loadings. The authors examined the water quality consequences of selective nutrient (P but not N) reductions in the 1980s, followed by N reductions in the 1990s and an increase in hurricane frequency since the mid-1990s. Selective P reductions decreased upstream phytoplankton blooms, but increased downstream phytoplankton biomass. Storms modified these trends. In particular, upstream annual N and P concentrations have decreased during the elevated hurricane period. Increased flushing and scouring from storms and flooding appear to have enhanced nutrient retention capabilities of the NRE watershed. From a management perspective, one cannot rely on largely unpredictable changes in storm frequency and intensity to negate anthropogenic nutrient enrichment and eutrophication. To control eutrophication along the hydrologically variable freshwater–marine continuum, N and P reductions should be applied adaptively to reflect point-source–dominated drought and non–point-source–dominated flood conditions.     

Agricultural Land Use and Best Management Practices to Control Nonpoint Water Pollution

In recent years, improvements in point-source depuration technologies have highlighted the problems regarding agricultural nonpoint (diffuse) sources, and this issue has become highly relevant from the environmental point of view. The considerable extension of the areas responsible for this kind of pollution, together with the scarcity of funds available to local managers, make minimizing the impacts of nonpoint sources on a whole basin a virtually impossible task. This article presents the results of a study intended to pinpoint those agricultural areas, within a basin, that contribute most to water pollution, so that operations aimed at preventing and/or reducing this kind of pollution can be focused on them. With this aim, an innovative approach is presented that integrates a field-scale management model, a simple regression model, and a geographic information system (GIS). The Lake Vico basin, where recent studies highlighted a considerable increase in the trophic state, mainly caused by phosphorus (P) compounds deriving principally from the intensive cultivation of hazelnut trees in the lake basin, was chosen as the study site. Using the management model Groundwater Loading Effects of Agricultural Management Systems (GLEAMS), the consequences, in terms of sediment yield and phosphorus export, of hazelnut tree cultivation were estimated on different areas of the basin with and without the application of a best management practice (BMP) that consists of growing meadow under the trees. The GLEAMS results were successively extended to basin scale thanks to the application of a purposely designed regression model and of a GIS. The main conclusions can be summarized as follows: The effectiveness of the above-mentioned BMP is always greater for erosion reduction than for particulate P reduction, whatever the slope value considered; moreover, the effectiveness with reference to both particulate P and sediment yield production decreases as the slope increases. The proposed approach, being completely distributed, represents a considerable step ahead compared to the semidistributed or lumped approaches, which are traditionally employed in research into tools to support the decision-making process for land-use planning aimed at water pollution control.     

不同形态P对Cu、Zn、Cd联合生物毒性效应的影响

运用水潘趋光行为的抑制试验研究了水体中不同磷形态和重金属(Cu、Zn、Cd)共同存在时的联合生物毒性效应.结果表明,水体中重金属的生物毒性不仅取决于它们的种类和浓度,也与溶液中共存的P形态有关.重金属对水溞的生物毒性由强至弱依次为Cu2 ＞Zn2 ＞Cd2 ;当溶液中存在不同形态的P时,重金属的生物毒性发生了改变.中等P营养水平(TP为0.05mg·L-1)时,不同形态P的存在可显著降低Cu、Zn、Cd的生物毒性,在某种程度上减轻重金属对生物的伤害.不同形态P对重金属生物毒性的拮抗作用顺序为H2PO-4≈HPO24-＞PO34-.因此,重金属污染与富营养化双重胁迫水体的生物毒性,将可能因水体中P形态的不同而产生差异.     

不同水生植物富集氮磷能力的试验研究

研究了伊乐藻、菹草、微齿眼子菜、竹叶眼子菜、石菖蒲和水芹菜等水生植物在不同营养状态下体内富集N、P的能力。结果表明:植物体内氮磷浓度增加的趋势与所在水体中的氮磷去除效果相一致;挺水植物水芹菜和沉水植物微齿眼子菜吸收N、P的能力较强,可将这两种植物构成双层次群落结构用以修复太湖地区的富营养化水体。     

城市富营养湖泊沉积物中磷负荷及其释放对水质的影响

以南京玄武湖为研究对象,探讨了城市富营养湖泊沉积物中磷的分布、化学形态和负荷量:通过模拟实验深入研究了溶解氧、pH值、温度、扰动等环境因子对沉积物中磷的释放影响．进而得出磷释放速率．并对pH值影响作出校正,计算出沉积物中磷对湖水释放量,为玄武湖富营养化防治提供科学依据。