The distribution of suspended matter in the Dutch coastal zone

Results are presented of suspended matter observations taken at bi-weekly intervals during the period 1975–1983, in a strip 70 km wide along the Dutch coast. The average distribution showed a (weak) minimum zone located north of Noordwijk at a distance of about 30 km from and parallel to the Dutch coast, between the salinity maximum and the coast. Variability was large between different years, seasons and individual cruises. A clear seasonal cycle emerged from the observed suspended-matter patterns: in winter a pronounced minimum existed, while in summer generally a monotonically decreasing concentration was measured, to open-sea values much lower than in winter. This seasonal cycle may be explained by a combination of variation in wind, river discharge and the activity of suspended-matter sources. The Flemish Banks and Channel waters are the main sources supplying suspended matter to the Dutch coastal area. Especially the varying transport through the Strait of Dover, large in winter, small in summer, determines the seasonal variation in the total amount of suspended matter. The existence of a localized turbidity minimum is tied to relatively large discharges from the Rhine and associated steep salinity gradients, also occurring mainly in winter and early spring. A simple model of cross-shore density-driven circulation shows the possible influence of the strong salinity gradients on the sedimentation of suspended matter. Particles with a settling rate comparable to the vertical velocity component of the circulation are forced to move offshore until they reach an area they sink out of the surface layer. The strength of this circulation is determined by the cross-shore density gradient due to the inflow of fresh water from the Rhine-Meuse estuary.     

Elementary composition of suspended particulate matter in the North Sea

The concentrations of the elements Al, Si, Ti, Fe, Mn, Ca, Mg, K, Cu, Zn, Cr, Pb, Ni, Cd, V and of particulate organic carbon (POC) were determined in 210 samples of suspended matter collected at 119 stations in the North Sea in January-February 1980. The distribution of these 15 elements and POC in the suspended matter in the North Sea was studied, as well as their relation with total suspended matter concentrations and salinity. The interrelationships between these elements were found to differ in different regions of the North Sea, which is related to the origin of the suspended material and the degree of mixing. A cluster analysis including all determined elements at all stations showed that the suspended matter in the North Sea consists of three clearly separated, specific types. One type was found in the northern part of the North Sea, the second in the southern part of the North Sea, while the third type was mainly observed in the Norwegian Channel, Skagerrak and eastern English Channel.The observed distributions are in agreement with what is known on the dispersal and deposition of suspended matter in the North Sea. Material from the southern North Sea hardly reaches the central and northern North Sea and the northern parts of the Norwegian Channel. The distribution of Mn is very strongly related to the accumulation of Mn in the top layers of finegrained bottom sediments and to the resuspension of Mn-enriched particles.     

流沙湾悬浮物数量动态变化规律的初步研究

在流沙湾设置9个观测站,对透明度和悬浮物数量动态变化规律进行了研究,结果表明：海湾水温周年平均值为26.4 ℃,变化范围为19.0～31.9 ℃;水域透明度年平均值为133.3 cm,变化范围为50～240 cm;悬浮物含量变化在9.12～29.90 mg/L之间,平均为18.70 mg/L。水域悬浮物含量有较明显的月变化规律（P＜0.05）,总的变化趋势是年水体悬浮物浓度呈先升高后降低的折线起伏变化分布。悬浮物含量多数观测站最高值出现在5月份,其平均值为26.81 mg/L。水体悬浮物数量的水平分布表现为5号站、6号站和9号站含量较高,1号站、3号站和8号站含量较低,即沿岸观测站高于航道与湾口。     

Minor and major elements in suspended matter in the Rhine and Meuse rivers and estuary

Suspended sediment in the Rhine-Meuse estuary contained as little as one third of the trace metal content of the river-borne suspended matter. It is shown that the strong seawardly decreasing gradient in the trace metal content of the suspended particulate matter is not due to desorption processes, but can be explained simply by the mixing of river-borne and marine-derived suspended sediments.     

Vertical distribution of suspended particulate matter in the Zaire river,estuary and plume

Light transmission and hydrographic data were measured in situ simultaneously in the Zaire river estuary and on the shelf off the river extending to the Angola Basin. Profiles of light transmission indicate that the majority of the particles derived from the river are transported offshore into the Angola Basin through deep waters under the surface plume. The Zaire river is associated with a submarine canyon which extends well into the Zaire estuary and cuts across the shelf. Bottom nepheloid layers were well developed along the canyon axis. The sediments along the canyon axis were mostly sands, and thus the submarine canyon appears to provide an efficient transport route of fine-grained material to the Angola Basin across the shelf.The surface plume is so highly stratified that vertical mixing appears very limited across the plume boundary, and downward transport of suspended particles must be accomplished by particle settling. Profiles containing small-scale layers of turbid water under the surface plume are considered indications of settling particles from the surface river plume.     

Distribution,organic content and particle size of suspended matter in the north sea

Data on suspended matter concentrations and the organic content of the suspended matter for January 1980 showed a division in the North Sea between the southern North Sea (high suspended matter concentrations, but relatively low organic content) and the central and northern North Sea (low suspended matter concentrations, but relatively high organic content). The Skagerrak, which receives suspended matter from the southern as well as from the central and northern North Sea, took up an intermediate position.In summer suspended matter concentrations were lower than in winter but more variable, in concentration as well as in organic content, because of admixtures of particulate matter from primary production. On deposition of the suspended matter, a considerable part of the organic matter was apparently lost (in the order of 75% or more), resulting in low organic-matter concentrations of fine-grained bottom deposits.Particle-size distributions followed two main types: one (A) with a sharp peak at 30 to 100 μm, and one (B) bell-shaped with a peak at 5 to 15 μm. Type A occurred in deeper water and consisted of particles with a high organic-matter content, type B occurred in shallow areas and consisted of particles with a low organic-matter content. The suspended particles were mainly microflocs of mineral particles and organic matter. The mineral particles of both types were predominantly of 2 to 5 μm size, which was determined after oxidation of the organic matter. It is concluded that particles of type-B distributions are regularly exchanged with the bottom through deposition and resuspension, which results in low organic-matter contents and prevents the microflocs reaching large sizes. Paricles of type-A distributions, on the contrary, can reach much larger sizes, because mostly they remain in suspension and do not lose organic matter, so that they do not easily fall apart.     

In situ distribution of suspended matter during the tidal cycle in the elbe estuary

In situ size of suspended particles was measured with an underwater photographic system in the Elbe estuary. The data from the measurements at a stationary position indicate that the formation of large flocs took place at low current velocities and that the size distributions varied with the tidal cycle as a consequence of flocculation, deposition and resuspension processes.Flocculation of suspended particles in the estuary is interpreted as a dynamic process: the size of flocs changes with time and their distribution depends on the rates of aggregation and disaggregation of the particles. This is related to physical factors of which turbulence and differential particle settling play key roles in producing large flocs. Fluid shear is responsible for disaggregation of large flocs. Salinity and the organic content of particles may affect flocculation processes with respect to the particle cohesive interaction, but they have no critical effect on the variation of floc size during the tidal cycle in the estuary.     

The control of trace metal concentrations in coastal seawater through partition onto suspended particulate matter

The distribution of total metal concentration between dissolved and particulate phases in coastal seawater has been examined as a function of suspended particulate matter (SPM) loading. Partition between dissolved and particulate phases, as defined by a distribution coefficient, is demonstrated to be an important control on the concentration in each phase. The possible impact of anthropogenic inputs on trends in coastal water concentrations are contrasted for waters with a high (Netherlands), and a low (U.K.), SPM loading. For a given increase in input trends will be more readily detected in areas with a slow SPM loading. It is concluded that trends in coastal seawater concentrations will only become apparent after river inputs have dramatically increased. Monitoring coastal water concentrations of dissolved and particulate phase trace metals is not therefore likely to be a sufficiently sensitive technique to detect trends.     

Distribution and particle size of suspended matter in the Southern Bight of the North sea and the Eastern channel

The distribution of suspended matter content in the Southern Bight is related to the resultant current pattern. Suspended matter is concentrated in the coastal waters and high concentrations occur where resultant currents of different directions meet near to the large gyres off the Belgian-Dutch coast and off East Anglia. Suspended matter is chiefly supplied to the Southern Bight from the Channel through Strait Dover-Calais (at least 8 to 11.5 × 10⁶, probably 11.5 to 15 × 10⁶tons·a⁻¹. Other sources are the rivers that enter the Southern Bight (ca 2 × 10⁶ tons·a⁻¹), coastal erosion (ca 0.3 × 10⁶ tons·a⁻¹), erosion of the sea floor (in the order of several million tons·a⁻¹) and the atmosphere (ca 0.5 × 10⁶ tons·a⁻¹). Supply from primary production is small (less than 1 × 10⁶ tons·a⁻¹). Total supply of suspended matter to the Southern Bight is 17.5 to 21.5 × 10⁶ tons·a⁻¹. The concentration of suspended matter in the coastal waters is probably related to a shoreward displacement of bottom water.Particle size determinations were made (with a Coulter Counter) during the winter in the absence of living plankton. Measurements were made directly after sampling or within several hours. In the Belgian-Dutch Coastal Water particle size is somewhat finer than in Strait Dover-Calais and in the central part of the Southern Bight (the “Channel Water”). In the English Coastal Water particle size is more variable. The bulk of the suspended particles has a diameter of 5 to 20 μm but there is a variable admixture of particles of 1 to 3 μm. Most size distributions are a mixture of two log-normal distributions. In the Belgian-Dutch coastal water, in the eastern Channel and in Strait Dover-Calais regularly approximately log-normal distributions are present. The size distributions reflect the multiple origin of the suspended material and the variable conditions of deposition, resuspension and aggregation.     

The role of small,low density particles on the partition of selected PCB congeners between water and suspended matter (North Sea area)

The dissolved and particulate suspended concentrations of five PCB congeners (with 3–7 chlorine atoms) in the Southern Bight (North Sea) are interpreted in terms of an equilibrium partitioning model. K_d values for riverine/coastal samples generally increase with chlorine number of the congeners (K_d = 10⁴–10⁶). Values are more than an order of magnitude larger at the low suspended matter concentrations offshore (< 1 mg·dm⁻³). This is interpreted in terms of the presence of different SPM fractions with different contents of PCB: a fraction consisting of low size/density particles carrying high contents of PCBs, dominates at low SPM concentrations. The contribution of particulate forms to the total PCB concentration per unit volume may, therefore, be significant even at low SPM concentrations.     

Desorption of metals from suspended material in the rhine estuary

Aliquots of suspended matter collected from Rhine river water were resuspended in distilled water, in diluted artificial sea water (1 : 1), in artificial sea water, and in ‘nitrate sea water’, respectively at pH's 7.5 and 8.0. The desorption of heavy metals into these solutions was calculated in relation to the concentrations as determined by extraction in 4 M hydrochloric acid. The heavy metal concentrations after resuspension and the relative desorption percentages were compared with calculated inorganic metal ion speciation. These comparisons, though quantitatively not quite satisfactory, demonstrated that complex formation is important in desorption processes during estuarine mixing. The order of decreasing desorption of metals into 1 : 1 diluted sea water and sea water in the experiments is : Cd > Zn > Mn > Ni > Co > Cu > Cr; fo for Fe and Pb no desorption was found.Analyses of samples collected at a tidal station at Hoek van Holland show that both suspended matter and filtered water are depleted in most heavy metals. Certainly, in this tidal area suspended matter and adsorbed and dissolved heavy metals do not show a conservative mixing behaviour. In order to correlate experimental results and field obsevartions, large scale flocculation and sedimentation of suspended matter must be accepted at an early stage of estuarine mixing. It is not certain whether this can be proved; future research should include more chemical indicators for testing these estuarine processes.     

皂荚皂苷的絮凝脱色及膜分离纯化

为获得高纯度的皂荚皂苷,以乙醇提取皂荚果皮所得皂苷粗提液为原料,采用多种无机低分子絮凝剂和有机高分子絮凝剂处理皂苷粗提液。通过对比不同种类和不同加量的絮凝剂对皂苷纯化及脱色效果的影响,确定最佳的絮凝剂种类和加量;采用膜处理工艺进一步提高皂苷产品纯度。结果表明：最佳絮凝工艺为双氰胺-双氰胺甲醛或双氰胺-双氰胺铵盐絮凝剂,加量为1.5%,搅拌速度为80 r/min。经过10000 Da、2000 Da及500 Da 3种分子量的卷式膜处理后,喷雾干燥所得皂荚皂苷产品脱色率达到60%,含量从43%提高到78%以上。该研究结果絮凝脱色及膜处理工艺可用于较高纯度皂荚皂苷产品的生产,为企业综合开发利用皂荚资源提供基础。     

The importance of estuaries in life histories of flatfish species on the Southern Coast of Africa

This paper reviews the ecology of flatfish species associated with estuaries in southern Africa. Information from estuarine and coastal studies carried out in this region over the past 25 years indicates that only 4 of the 56 flatfish species occurring in the region utilize estuaries during part of their life histories. The suitability of estuaries and their role as nursery grounds for juvenile flatfish is assessed in terms of the proportion of the life cycle that each species spends within estuarine systems. Biological data on Pseudorhombus arsius, Bothus pantherinus, Heteromycteris capensis and Solea bleekeri extracted from broad based estuarine studies in the warm temperate and subtropical regions of southern Africa are presented in support of the thesis that in the absence of calm, shallow, turbid, marine shelf areas, juveniles of these species utilize estuaries as nursery grounds.     

Genetic variation for dry matter and nitrogen accumulation and translocation in two-rowed spring barley: I. Dry matter translocation

A 4-year field study was carried out to determine dry matter and nitrogen accumulation until anthesis and at grain filling period and dry matter translocation and utilization in grain filling of barley. Twenty two-rowed spring barley (Hordeum vulgare ssp. distichum L.) cultivars originated from different countries (Yugoslavia, Germany, Australia, the Czeck Republic, Netherlands, France and USA) were grown during 1995–1998 on a non-calcareous chernozem soil near Novi Sad (45° 20′N, 15° 51′E, 86 m asl). Dry matter and nitrogen accumulation depended on the cultivar and year. In a year with favorable weather conditions, 58% of dry matter was accumulated during pre-anthesis, while in a year with less favorable weather the amount was 48%. In the favorable year 91% and in unfavorable year 65% of nitrogen was accumulated until anthesis. The results indicated that the greater amount of dry matter and nitrogen accumulated before anthesis. Dry matter translocation efficiency depended on the cultivar and ranged from 3 to 16.4%, while the contribution of pre-anthesis assimilates to kernel varied from 4 to 24.2%. Cultivars that have been developed for the growing conditions of the area where the experimental site was located, i.e. adapted ones, did not use pre-anthesis dry matter for grain filling. High positive correlations (P<0.01) were found between biomass at anthesis and biological yield, dry matter translocation efficiency, contribution of translocated dry matter to grain yield, and total plant nitrogen at maturity. Accumulated nitrogen at anthesis was positively correlated (P<0.01) with growing degree–days until anthesis, dry matter at anthesis and dry matter translocation parameters. Heritability for the investigated characters was rather high, over 0.60.     

Soil organic matter dynamics and losses in manured maize-based forage systems

Soil organic matter (SOM) produces positive effects on multiple soil properties. Increasing its level also provides an opportunity to reduce atmospheric concentration of carbon dioxide (CO₂). Recycling animal manure and returning crop residue are among the main practices to enhance organic carbon (C) stock in arable croplands. This study analysed data of soil organic carbon (SOC) stocks from a medium-term field trial (established in 1992) through a Hénin–Dupuis-based equation to determine the proportion of different organic materials retained in the soil as SOM.The treatments included in the experiment simulated different typical management techniques and implied the application to the soil of various organic materials, i.e. cattle slurry, cattle farmyard manure, maize straw, root, maize and ley stubble. Soil organic carbon and total nitrogen (N) (Kjeldhal N) were measured in the 0–30 cm layer during spring 1999 and spring 2003. The relationship between SOC and N stocks measured in 1999 and 2003 and the annual additions of C and N was described by the Hénin–Dupuis-based equation, assuming the presence of two C and N pools (stable and fresh).Our results showed that the application of farmyard manure, slurry and maize straw induced higher C and N content compared to the application of urea without return of crop residue. The different levels of urea application did not produce any significant difference in C and N soil content.We found that approximately 2% of SOC is lost to the atmosphere annually. Furthermore, the amount of C and N retained in the soil each year varied by organic materials: 46% C and 44% N with farmyard manure, 26% C and 11% N with slurry, 28% C and 10% N with root and 6% C with maize straw and ley stubble.These results were used to inform an estimate of C lost or removed to/from atmosphere following manure application and crop residue return for the compilation of greenhouse gas inventories. We found that the most C conservative management is the production and spreading of farmyard manure and that increasing amounts of mineral N fertilizer did not affect the C sequestration extent.     

大豆光谱反射率与地上干物重对数回归分析

摘要：研究目的：从统计学角度分析地上部干物重与叶片反射光谱特征的定量关系;方法：通过对近红外和可见光波段光谱反射率的分析, 确立不同时期大豆地上部干物重的敏感波段,计算出相应的植被指数,并建立植被指数与大豆地上部干物质量预测模型;结果表明：通过RDVI（1005,510nm）植被指数建立对数模型,方程为：y = -295.83Ln(x) - 123.05;结论：此模型能较好的描述大豆合农60光谱反射率与干物重的关系。     

长期施肥对褐潮土氮、有机质动态变化的影响

通过北京昌平“国家褐潮土土壤肥力和肥料效益监测基地”的长期定位试验（1991-2003年）,研究了长期施肥条件下对褐潮土氮、有机质动态变化的影响。结果表明：氮磷钾化肥配施有机物料提高耕层土壤全氮的效果最为明显,配施有机肥和秸秆处理分别比不施肥增加21.11%和14.35%,明显高于单一施用化肥。长期单施氮肥,或氮磷配合,或氮磷钾配合也显著增加了土壤全氮含量,分别比对照增加10.03%,8.32%和8.40%,而磷钾配合降低了土壤全氮含量。土壤碱解氮含量仍然是氮磷钾配施有机肥或秸杆处理优于单施化肥,分别比对照增加34.97%和32.96%,长期单施氮肥,或氮磷配合,或氮钾配合,或氮磷钾配合,分别比对照增加17.26％,21.55%,23.83%和26.41%。配合施用有机肥处理耕层土壤有机质含量明显高于单施化肥处理;与不施肥比较,NPK＋秸秆以及NPK＋有机肥处理土壤有机质含量分别增加7.90％和14.56％,氮磷钾配合和氮磷配合分别比对照增加6.51％和5.89%,而单施氮肥仅增加2.56%。可见NPK平衡施用及其配施有机肥对增加土壤有机质含量具有重要作用。     

3种土壤有机碳含量的研究

为了研究土壤呼吸作用产生的CO2量,分别在校花房地、南区野生大豆地和瓦房店人造湿地采集9种不同利用方式的土壤进行了有机碳含量的测定和分析。结果表明：校花房冬小麦地平均有机质含量最高,达到了11.34g/kg,南区野生大豆地有机质含量为8.97g/kg,瓦房店人造湿地有机质含量最低为8.33g/kg。经过方差分析,校花房冬小麦地有机质含量极显著高于南区野生大豆地和瓦房店人造湿地的有机质含量;南区野生大豆地的有机质含量也极显著地高于瓦房店人造湿地的有机质含量。校花房的两期播种冬小麦的土壤有机质含量差异不显著。南区不施盐碱土的有机质含量极显著地高于施盐碱土的土壤有机质含量。瓦房店人造湿地的自然状态和芦苇的有机质含量极显著地高于对照、野生大豆地和水稻地的有机质含量。