TBT toxicity on the marine microalga Nannochloropsis oculata

Commercial antifouling formulations containing TBT are the major source of organotin contamination in coastal waters. In view of the persisting TBT residues (13 ng Sn l⁻¹) in the coastal waters of South Korea, an attempt has been made to evaluate the growth response and biochemical composition of laboratory-cultured Nannochloropsis oculata to TBT toxicity. It is evident that the persisting concentration level of TBT is high enough to cause adverse effect on the microalgal species. The EC₅₀ (24 h) was found to be at 0.89 nM level of TBT for this marine eustigmatophyte N. oculata. Photosynthetic pigment content was significantly affected. At elevated TBT concentrations of 1.0 nM, especially pronounced changes in biochemical composition was found. TBT tolerance of N. oculata and its growth as well as biochemical responses are discussed.     

Experimental study on the effect of bottomless structure in front of a bottom outlet on a sediment flushing cone

One of the main problems in reservoirs is sedimentation which reduces the operating life of dams if a proper plan and analysis method are not in place.The techniques to manage sediment in reservoirs include several sustainable management techniques that route sediment through or around the reservoir.One of the main economical methods in arid and semi-arid regions is pressurized flushing using moderate drawdown of the water level of the reservoir to evacuate sediment deposited behind dams.In the current study,the effect of a new structure called a dendritic bottomless extended(DBE)outlet structure at three angles of 30°,45°,and 60°
on pressurized flushing efficiency was investigated.Consequently,45 experiments were designed for three discharge rates (Qo),three sediment levels(Hs),four types of structure,and a no-structure condition(reference test).The results indicated that the DBE structure with a 30°angle between the branches,a sedimentary dimensionless index of Hs/Do=4.59,and a flow dimensionless index of Qo=/√gD05=1:43(where g is the acceleration of gravity and Do is the diameter of the bottom outlet)lead to 10-fold increase in the sediment flushing cone dimensions and sediment removal efficiency compared to the results of the reference test.Finally,according to a statistical analysis of the results,a dimensionless equation for calculating the sediment flushing cone dimensions was developed for the tested sediment characteristics.     

TBT toxicity on the marine microalga Nannochloropsis oculata

Commercial antifouling formulations containing TBT are the major source of organotin contamination in coastal waters. In view of the persisting TBT residues (13 ng Sn l⁻¹) in the coastal waters of South Korea, an attempt has been made to evaluate the growth response and biochemical composition of laboratory-cultured Nannochloropsis oculata to TBT toxicity. It is evident that the persisting concentration level of TBT is high enough to cause adverse effect on the microalgal species. The EC₅₀ (24 h) was found to be at 0.89 nM level of TBT for this marine eustigmatophyte N. oculata. Photosynthetic pigment content was significantly affected. At elevated TBT concentrations of 1.0 nM, especially pronounced changes in biochemical composition was found. TBT tolerance of N. oculata and its growth as well as biochemical responses are discussed.     

The effect of forestry drainage operations on upland sediment yields: The results of a storm-based study

The effects of pre-afforestation open ditching on the sediment yield of an upland catchment in the Southern Pennines, England are described. Marked increases in the production of suspended sediment following ploughing caused major pollution of a local reservoir. Sediment supply prior to ditching was limited and easily exhausted, but afterwards remained plentiful, allowing sustained erosion during periods of storm runoff. Large volumes of sediment were carried into the reservoir during the winter of 1980–81. More recently, exhaustion of supplies of loose material in the ditches and revegetation have led to a lower rate of sediment output.     

沉积物再悬浮对浮游动物群落结构影响的模拟实验

沉积物再悬浮是浅水湖泊的重要特征之一.通过模拟实验,比较不同再悬浮程度下浮游动物群落结构的变化,以探讨沉积物再悬浮对浮游动物的影响.结果显示,不同处理下总悬浮物与叶绿素a浓度差异显著.再悬浮组中枝角类简弧象鼻溞(Bosmina coregoni)、角突网纹溞(Ceriodaphnia cornuta)和轮虫占优势,而对照组中大型枝角类溞属(Daphniasp.)占优势,再悬浮使浮游动物群落组成趋于小型化.不同再悬浮条件下隆线溞(Daphnia carinata)、简弧象鼻溞(Bosmina coregoni)和轮虫的丰度差异显著,角突网纹溞(Ceriodaphnia cornuta)和桡足类丰度差异不显著.总悬浮物浓度与轮虫和简弧象鼻溞丰度显著正相关,与隆线溞丰度显著负相关,与其它浮游动物种群丰度无显著相关性.本研究显示,沉积物再悬浮是决定浮游动物群落结构变化的重要过程之一.     

Properties of fly ash as a marine sediment

Large quantities of waste fly-ash from coal-fired power stations are dumped in the sea, where the ash settles on the sea bed. The physical and chemical characteristics of the ash have been assessed in relation to the marine benthic environment. The material acts as a fine mud substrate, of low porosity and permeability, chemically analogous to natural mud, but with no organic content for faunistic exploitation.     

Fenton体系处理黑臭河道沉积物的效果初探

沉积物中有机质的削减是黑臭水体治理的关键.Fenton(Fe^2++H2O2)试剂在有机污染废水和土壤原位修复中的应用广泛且效果良好;Fenton试剂也能很好地去除黑臭水体中的色度和浊度,但其氧化沉积物有机质的研究未见报道.为探究Fenton试剂对黑臭水体沉积物的氧化效果,本研究通过室内模拟实验用Fenton氧化法对黑臭河道沉积物进行处理,考察氧化过程沉积物特征和性质的变化;分析覆水后沉积物中污染物的释放特征,并和H2O2体系(无Fe^2+)进行比较.结果表明:Fenton体系显著提高了沉积物与上覆水的氧化还原电位,对黑臭河道沉积物中的有机质具有很强的氧化效率.在温度为28℃、H2O2为20%Q(Q为体系中沉积物有机质完全矿化的理论H2O2用量)和Fe^2+∶H2O2(摩尔比)为0.5∶1时,反应1 d,酸挥发性硫化物去除率为70.13%,沉积物总有机碳减少了22.14%,总有机氮减少了87.60%,生成了较多的铵态氮和硝态氮;由于铁对磷的钝化,沉积物中溶解性反应磷含量大幅减少.H2O2体系的氧化速度较Fenton体系慢,覆水后对体系中的Eh提高不明显.值得注意的是,Fenton体系会降低上覆水的pH,释放较多的铵态氮.需要联合其他技术(如微生物法),强化水体中有机质和氨氮的降解,以取得理想的修复作用.     

The effect of forestry drainage operations on upland sediment yields: A case study

Forestry is generally considered to be a land use giving low sediment yields. However, in Britain most forestry is on land that requires extensive drainage, and it was found that the drainage of a small upland catchment resulted in sediment yields over the following five years equivalent to nearly half a century's load at pre-drainage rates. Subsequent sediment yields did not decline to pre-drainage levels, but remained about four times higher, as a result of erosion of the drains.     

The effect of properties of sediment type on the relationship between suspended sediment concentration and radiance

Abstract

A laboratory experiment was designed to determine the spectral characteristics of different types of sediment suspended in water in the visible and near infrared wavelengths (0.45–0.9 μm) using a four-channel radiometer. Field collected sediments were resuspended in water to produce different concentration levels for the measurement of radiance. Spectral measurements of turbid water showed a distinctive difference in the behaviour of radiance with change in the inorganic suspended sediment concentration and type. It was noted that the correlation between the suspended sediment concentration and the radiance varied with the mineral composition of the sediment. The clay minerals of low specific gravity had larger values of radiance than those from high specific gravity nonclay minerals. Based on the results obtained, it appears that an algorithm to estimate suspended sediment concentration can be developed from radiance.     

The fetch effect on aeolian sediment transport on a sandy beach: a case study from Magilligan Strand,Northern Ireland

Experiments were conducted on Magilligan Strand, Northern Ireland, to assess the influence of the fetch effect on aeolian sediment transport. During each experiment surface sediments were uniformly dry and unhindered by vegetation or debris. The leading edge of erodible material was well defined, with the limit of wave up‐rush demarcating the wet–dry boundary; the work was conducted during low tides. A number of electronic and integrating traps were utilised, with two ultrasonic anemometers used to measure wind direction and velocity at 1 Hz. The combination of 1^o direction data and trap locations resulted in a range of fetch distances, from 2 to 26 m. Data integrated over 15‐minute intervals (corresponding to the integrating trap data) revealed a distinct trend for all the experiments. An initial rapid increase in the transport rate occurred over a short distance (4–9 m). This maximum transport rate was maintained for a further 5–6 m before a steady decay in the flux followed, as fetch distance increased. A measured reduction in wind speed (6–8%) across the beach suggests a negative feedback mechanism may be responsible for the diminishing transport rate: the saltating grains induce energy dissipation, thus reducing the capability of the wind to maintain transport. For one experiment, the presence of compact sediment patches may also have contributed to the reduction of the transport rate. The decay trend calls into question the utility of the fetch effect as an important parameter in aeolian studies that seek to understand sediment budgets of the foredune‐beach zone. Copyright © 2016 John Wiley & Sons, Ltd.     

The effect of tides and storms on the sediment transport across a Dutch barrier island

Under natural conditions, barrier islands might grow vertically and migrate onshore under the influence of long‐term sea level rise. Sediment is transported onshore during storm‐induced overwash and inundation. However, on many Dutch Wadden Islands, dune openings are closed off by artificial sand‐drift dikes that prevent the influx of sediment during storms. It has been argued that creating openings in the dune row to allow regular flooding on barrier islands can have a positive effect on the sediment budget, but the dominant hydrodynamic processes and their influence on sediment transport during overwash and inundation are unknown. Here, we present an XBeach model study to investigate how sediment transport during overwash and inundation across the beach of a typical mesotidal Wadden Sea barrier island is influenced by wave, tide and storm surge conditions. Firstly, we validated the model XBeach with field data on waves and currents during island inundation. In general, the XBeach model performed well. Secondly, we studied the long‐term sediment transport across the barrier island. We distinguished six representative inundation classes, ranging from frequently occurring, low‐energy events to infrequent, high‐energy events, and simulated the hydrodynamics and sediment transport during these events. An analysis of the model simulations shows that larger storm events cause larger cross‐shore sediment transport, but the net sediment exchange during a storm levels off or even becomes smaller for the largest inundation classes because it is counteracted by larger mean water levels in the Wadden Sea that oppose or even reverse sediment transport during inundation. When taking into account the frequency of occurrence of storms we conclude that the cumulative effect of relatively mild storms on long‐term cross‐shore sediment transport is much larger than that of the large storm events. © 2017 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.     

The effect of a small vegetation dieback event on salt marsh sediment transport

Vegetation is a critical component of the ecogeomorphic feedbacks that allow a salt marsh to build soil and accrete vertically. Vegetation dieback can therefore have detrimental effects on marsh stability, especially under conditions of rising sea levels. Here, we report a variety of sediment transport measurements associated with an unexpected, natural dieback in a rapidly prograding marsh in the Altamaha River Estuary, Georgia. We find that vegetation mortality led to a significant loss in elevation at the dieback site as evidenced by measurements of vertical accretion, erosion, and surface topography compared to vegetated reference areas. Below-ground vegetation mortality led to reduced soil shear strength. The dieback site displayed an erosional, concave-up topographic profile, in contrast to the reference sites. At the location directly impacted by the dieback, there was a reduction in flood dominance of suspended sediment concentration. Our work illustrates how a vegetation disturbance can at least temporarily reverse the local trajectory of a prograding marsh and produce complex patterns of sediment transport. © 2018 John Wiley & Sons, Ltd.     

226Ra chronology of a coastal marine sediment

Unsupported²²⁶Ra (t₁₂ = 1620years) in marine sediments can provide a basis for measuring rates of accumulation of the order of centimeters per thousand years. The excess radium apparently enters the sediments incorporated in phytoplankton. The sensitivity of the method depends upon the initial value of the unsupported²²⁶Ra and of the value of²³⁰Th, a parent of²²⁶Ra, in the sedimentary components.²²⁶Ra dating was applied to a sediment taken from the slope of the San Clemente Basin in the Southern California coastal region. Rates of sedimentation over two half-lives of the nuclide were found to be either 5.2 or 5.3 cm/1000 years depending upon which of two models for the geochronology is used. One model assumes that the²³⁰Th brings to the deposit an amount of²²⁶Ra in equilibrium with it. The other is based upon the growth of the²²⁶Ra from the²³⁰Th in the sedimentary components.^238+239Pu and²¹⁰Pb levels in the upper strata indicated sedimentation rates of the order of 100–500 cm/1000 years, i.e. much faster accumulations. We suggest these derived rates are spurious and reflect bioturbative activities of surface-living organisms.     

Detoxification of hazardous dust with marine sediment

Hazardous electric arc furnace dust containing dioxins/furans and heavy metals is blended with harbor sediment, fired at 950–1100 °C to prepare lightweight aggregates. Dust addition can lower the sintering temperature by about 100 °C, as compared to a typical industrial process. After firing at 950 °C and 1050 °C, more than 99.85% of dioxins/furans originally present in the dust have been removed and/or destructed in the mix containing a dust/sediment ratio of 50:100. The heavy metals leached from all fired mixes are far below Taiwan EPA legal limits. The particle density of the lightweight aggregates always decreases with increasing firing temperature. Greater addition of the dust results in a considerably lower particle density (mostly <2.0 g cm⁻³) fired at 1050 °C and 1100 °C. However, firing at temperatures lower than 1050 °C produces no successful bloating, leading to a denser particle density (>2.0 g cm⁻³) that is typical of bricks.     

The effect of marine colloids on the growth of photosysthetic bacteria

Marine colloids could be an important source of nitrogen for bacteria and photoplankton. But elevated concentration of colloids may stimulate algal growth and lead to red tides in coastal waters. The effects of colloidal organic carbon (COC) concentration on the growth of photosysthetic bacteria (PSB) were investigated under different colloidal treatments in the laboratory. The PSB growth was inversely proportional to COC concentration and was restricted by high-molecular-weight (HMW) colloids (>10 KDa) in treatments with non-nutrient or just inorganic nutrient with low COC concentration (5 μMC). However, the PBS growth was enhanced in the presence of HMW colloids in the treatment with inorganic nutrient and high COC (127 and 255 μMC) or with both inorganic nutrient and low-molecular-weight organic matter. Both bacteria number and bacteria growth ratio increased significantly when the concentration of COC was 5 μMC. Our results suggest that marine colloids can be utilized by bacteria and might regulate primary productivity in coastal waters.     

Magnetic characteristics of sediment grains concurrently contaminated with TBT and metals near a shipyard in Busan,Korea

Bottom sediments near shipyards are often susceptible to receiving accidental spills of TBT and metals or their degradation products from hull scraping of antifouling system paints applied prior to 2008, when the AFS Convention 2001 was not in force. We investigated TBT and metal contamination of sediments near the shipyards of a small marina located in Busan, Korea and found that they were highly contaminated with TBT, Cu, and Zn. To better understand the environmental impacts and to make an optimal remediation plan, we characterized individual antifouling fragments in terms of metal and TBT contents, magnetic properties, and grain-size. Coarse-sized individual antifouling fragments exhibited simultaneously high levels of TBT, metals and high magnetic susceptibility, and appeared to be a major source of pollution in the sediment. Therefore, magnetic separation in combination with size-separation appears to be a cost-effective remediation method to remove the TBT and metals from contaminated shipyard sediments.     

Organic diagenesis in sediment and its impact on the adsorption of bisphenol A and nonylphenol onto marine sediment

Hydrophobic organic contaminants in marine water are mostly adsorbed onto (partitioned into) sediment organic matter (SOM). To study the impact of SOM diagenesis on sediment adsorption properties, artificial sediment with rich SOM content was incubated for more than 120 days. The sediment was sampled every week, and batch sediment adsorption tests were conducted with bisphenol A (BPA) and nonylphenol (NP) as the model pollutants. The results show that the amount of organic matter loaded in the sediment decreased by nearly 80% during incubation. For the incubated sediment, the BPA partition coefficient, K_d, decreased whereas the organic normalized partition coefficient, K_oc, more than doubled. The experiments with NP show an even greater increase in K_oc. Organic matter diagenesis shows a profound effect on the adsorption behavior of sediment, as the SOM residue has an increasing affinity and partition capacity for organic contaminants.     

Organic diagenesis in sediment and its impact on the adsorption of bisphenol A and nonylphenol onto marine sediment

Hydrophobic organic contaminants in marine water are mostly adsorbed onto (partitioned into) sediment organic matter (SOM). To study the impact of SOM diagenesis on sediment adsorption properties, artificial sediment with rich SOM content was incubated for more than 120 days. The sediment was sampled every week, and batch sediment adsorption tests were conducted with bisphenol A (BPA) and nonylphenol (NP) as the model pollutants. The results show that the amount of organic matter loaded in the sediment decreased by nearly 80% during incubation. For the incubated sediment, the BPA partition coefficient, Kd, decreased whereas the organic normalized partition coefficient, Koc, more than doubled. The experiments with NP show an even greater increase in Koc. Organic matter diagenesis shows a profound effect on the adsorption behavior of sediment, as the SOM residue has an increasing affinity and partition capacity for organic contaminants.     

表面流湿地沉积物再悬浮及其对湿地净化效果的影响

选取典型表面流人工湿地——盐龙湖人工湿地为研究对象,通过对沉积物理化性质分析,湿地系统水动力模拟,风场与悬浮物(SS)再悬浮浓度关系的拟合及全年再悬浮对湿地净化效果的影响估算,探索表面流湿地沉积物在动力条件下的再悬浮特征及此过程中营养物质的再悬浮量.结果显示:0.3～0.5 m水深沉积物的理论起动流速在18.54～22.62cm/s之间,模拟得到湿地运行过程中水体流速最大值为1.62 cm/s,会远小于理论起动流速值,因此湿地内部流动产生的底部扰动难以形成湿地底泥的大规模再悬浮现象.但湿地内部仍存在一定的底泥再悬浮效应,风场扰动是主要影响因素,风场作用受植物影响显著,萌发期(3-4月)和收割期(11月-次年2月)再悬浮贡献量大于生长期(5-8月)与成熟期(9-10月),并且当风速4 m/s时再悬浮浓度明显增加.再悬浮浓度与运行水深也有关,0.3 m水深SS再悬浮浓度分别高出0.4 m和0.5 m水深12.48%和18.67%;高锰酸盐指数(CODMn)分别高出12.61%和19.52%;总氮(TN)分别高出248.12%和341.94%;总磷(TP)分别高出35.53%和43.48%.全年SS、CODMn、TN和TP再悬浮量分别达到2.8、0.47、0.15和0.011 kg/m2.     

The effect of forestry drainage operations on upland sediment yields: A study of two peat-covered catchments

The suspended sediment yields of two adjacent, paired, catchments on blanket peat in mid-Wales were compared before and after preafforestation drainage works. Catchment A was ploughed whilst an adjacent catchment (B) was left unploughed. After eight months Catchment B was also ploughed. The ploughing strategy in both catchments was designed to minimize sediment loss. However, suspended sediment loss increased 2·5 times following ploughing in Catchment A, whilst no such increase occurred at this time in Catchment B. Subsequently, suspended sediment yields in Catchment B increased 4·8 times after it was ploughed. Organic sediment was lost mainly from furrow sides, and erosion pins showed maximum ground recession in summer, due to peat wastage. Summer desiccation prepared sediment for transport, and organic suspended sediment loads were highest in the autumn. Sediment loads were limited by vegetation colonization and some reduction in sediment loss was due to the presence of unploughed strips adjacent to stream courses.