The Influence of the Niagara River on Contaminant Burdens of Lake Ontario Biota

Top predator and forage fish species, netplankton (> 153 μm), zooplankton, and benthic macroinvertebrates from Lake Erie and Lake Ontario were analyzed for whole body levels of trace metals and organic contaminants. Comparison of contaminant concentrations in similar aquatic food chains from both lakes indicated that levels of PCB, DDT, mirex, and mercury are significantly greater (P <0.05) in the biota of Lake Ontario. The Niagara River, the single largest tributary to Lake Ontario, was confirmed as a major source of organic contaminants and trace metals. Organic contaminants are adsorbed to the particulate load of the river and dispersed throughout Lake Ontario by the circulating currents. There was no significant regional difference (P<0.05) in the degree of contaminant accumulation by the pelagic food chain of Lake Ontario. Conversely, both inorganic and organic contaminant levels in the demersal amphipod, Pontoporeia affinis, were significantly different (P<0.05) between the eastern and western basins of Lake Ontario. The uptake and concentration of contaminants at the sediment-water interface is suggested as a possible mechanism to explain this observed difference.     

Lake Ontario Sediments as Indicators of the Niagara River as a Primary Source of Contaminants

Past studies on the distribution of mercury, PCB, and mirex in the surficial bottom sediments of Lake Ontario have clearly indicated the significance of the Niagara River as a major source of contaminants to the lake. The distributions have further indicated the net transport of sediment-bound materials in the lake which has assisted in the general understanding of the occurrence of contaminants at many trophic levels in the Lake Ontario ecosystem. Mean concentrations of a number of elements in suspended solids centrifuged from the Niagara River in 1974 further indicated that the river is also a major source for chromium, cadmium, vanadium, and arsenic, and a lesser though significant source of lead, copper, and nickel.     

Downflux of Sediment,Organic Matter,and Phosphorus in the Niagara River Area of Lake Ontario

Vertical arrays of sediment traps were installed near the mouth of the Niagara River and at nearshore and offshore sites. Surveys of temperature, turbidity, and conductivity were used to establish that the traps nearest the river mouth were under the river outflow plume. A single offshore array in 1980 indicated downfluxes of 1-2 g · m^?2 · d^?1 of dry matter in the mid-water column. These fluxes were similar to those of small lakes but much higher fluxes were found near the bottom of Lake Ontario. More extensive work in 1981 confirmed the presence of a near-bottom nepheloid layer and the effect it has on increasing downflux extimates. Sediment traps near shore and at the river mouth caught substantially more material at all depths than did traps at the offshore stations. Downfluxes of phosphorus and sediment were consistent with independent estimates of loading and retention.     

Compartmental Distribution of Organochlorine Contaminants in the Niagara River and the Western Basin of Lake Ontario

Ten chlorobenzenes, hexachlorobutadiene, and PCBs were measured in Niagara River water and suspended solids, and in western Lake Ontario sediments and benthic fauna. High levels of these contaminants were found on all fractions of the river suspended solids, but the larger particles contained much higher concentrations than the smaller particles. A portion of the CBs, HCBD, and PCBs present in the lake sediments was available to benthic organisms. A trend toward greater bioaccumulation for compounds having higher octanol-water partition coefficients was observed at all trophic levels.     

Chlorinated Organic Contaminants in Water and Suspended Sediments of the Lower Niagara River

Suspended sediment and raw water samples have been collected and analyzed for organochlorines and PCBs from a fixed location in the lower Niagara River at Niagara-on-the-Lake approximately weekly since 1979. Eight of the 19 organochlorine compounds measured were detected in more than 50% of the water samples analyzed, while 11 of the 19 compounds were detected in more than 50% of the suspended sediments collected at Niagara-on-the-Lake. Of the 10 chlorobenzene isomers measured, the one with the greatest usage (1, 4-dichloro) occurs in largest concentrations in the suspended sediments at Niagara-on-the-Lake. Other chlorobenzene isomers commonly occurring in suspended sediments are 1, 2 and 1, 3 dichloro, 1, 2, 4-trichloro, 1,2, 3, 4-tetrachloro, pentachloro, and hexachloro. All isomers of chlorobenzene occurred in more than 70% of the suspended sediment samples collected. Total loadings to Lake Ontario calculated from these data indicate that PCB loadings are about twice as high as previously reported, while mirex and total DDT hate decreased slightly. Although concentrations of contaminants in suspended sediments are usually higher than those measured in water samples, they are responsible for only about 40% of the total loadings for PCBs, DDT, and HCB, and significantly less for other organochlorine contaminants. Therefore, the data indicate that, to estimate total contaminant loadings, the water fraction must be sampled. Lake Erie is not the major source of such organic contaminants as PCBs and chlorobenzenes because contaminant levels in Lake Erie bottom sediments are 10 times lower for PCBs and 20 times lower for chlorobenzenes than in Niagara-on-the-Lake suspended sediments.     

Distribution of Hydrocarbons and Chlorinated Hydrocarbons in Various Phases of the Detroit River

Concentrations of several chlorohydrocarbons, polychlorinated biphenyls, and polynuclear aromatic hydrocarbons in the Detroit River were measured. For purposes of this study, the river ecosystem was divided into six phases or compartments: sediments, pore water in the sediments, suspended solids, subsurface water, surface microlayer, and air. Significant amounts of the above mentioned compounds occur in all of these compartments except air (for which our detection was relatively insensitive). The sediments contained over 99% of the chlorinated compounds. The polynuclear aromatic hydrocarbons were distributed between the subsurface water and the sediments.     

Sedimentology and Geochemistry of Recent Sediments off the Mouth of the Niagara River,Lake Ontario

Sediment thickness and bathymetric characteristics were derived from echo sounding, side scan sonar, and shallow seismic reflection recordings. Sediment samples were analyzed for particle size, major and trace elements, and for benthic organisms. The Niagara Bar has been separated into Inner and Outer Bar deposits and it is proposed that the Outer Bar was formed during an earlier, lower stage of Lake Ontario. Both deposits appear to be largely derived from reworked, local, shoreline materials. Trace element analyses indicate that the surficial sediments (prior to the 1972 Great Lakes Water Quality Agreement) were moderately enriched in Cd, Cr, Cu, Pb, and Zn, and greatly enriched in Hg. Normalized distributions of trace elements in the bar sediments show the presence of distinct dispersal patterns. These dispersals indicate that some of the suspended load passes out of the main outflow channel, across the bar, and toward west and north northwest directions. Particle-size and geochemical characteristics of the off-shore sediments indicate that they differ significantly from marginal facies and imply that local variations in the forms and type of peripheral inputs to the lake have little influence on deep basin deposits.     

Recent Sediment Stratigraphy and Geotechnical Characteristics of Foreset and Bottomset Beds of the Niagara Bar

Forest beds of the Niagara Bar are composed of fine sands and sandy silts. Their thickness is uncertain, but probably 6 to 8 m have accumulated on the upper slope since the last low water stage in Lake Ontario. The maximum thickness of these beds occurs near the foot of the outer slope (water depths 80 to 90 m) where accumulation exceed 20 m north of the present river mouth, and 10 to 12 m to the northwest. The bottomset beds of fine silt and silty clay thin rapidly offshore and decrease to as little as 0.5 m, at about 5 km northwest of the Outer Bar. There is a fining upward lithology in many cores, and this is consistent with continuing deposition under rising water levels. Geotechnical measurements indicate that bottomset and lower foreset beds have low undrained shear strengths (typically less than 4 kPa) and high water contents. Upper foreset beds, of coarser composition, have somewhat higher, undrained shear strengths (20 to 90 kPa, and greater) and much lower water contents. The steepest parts of the Outer Bar lie between 20 and 60 m water depth, where slope angles vary between 2 and 10°; maximum local values reach 14 to 15°. Despite the presence of gas in sediments of the lower foreset beds the slope shows no evidence of slumping.     

Identification and Determination of Trace Organic Substances in Sediment Cores from the Western Basin of Lake Ontario

A study was carried out to identify and to determine organic chemicals in sediment from the western basin of Lake Ontario, particularly in the fine-grained sediments near the mouth of the Niagara River. Sediment cores were obtained at five sampling stations, and samples were extracted by the base/neutral and acid method designed by US Environmental Protection Agency for extraction of water samples. The identification of organic compounds in the base/neutral sediment extract was carried out by GC/MS techniques. The major classes of investigated contaminants were aromatics, polynuclear aromatics, alkylated polynuclear aromatics, alkylated benzenes, phthalates, methyl esters of fatty acids, olefins, aldehydes, chlorobenzenes, and benzoates. In addition, all sediment samples were analysed for 2,3,7,8-tetrachloro dibenzo-p-dioxin. In the surface sediments, the abundance of contaminants decreased with the distance from the Niagara River mouth toward the north-west. However, high concentrations of most of the detected organics were present in sediment at the station located east of the River mouth.     

Evidence of successful river spawning by lake trout (Salvelinus namaycush) in the Lower Niagara River,Lake Ontario

Restoration of a wild-produced lake trout Salvelinus namaycush population in Lake Ontario has not been successful despite the adult population often meeting or exceeding restoration targets. Lack of high-quality spawning habitat in Lake Ontario is suggested as one impediment to recruitment of wild lake trout, although the quantity and location of spawning habitat is poorly understood. If high-quality spawning habitat is limited in Lake Ontario, lake trout may be using uncommon spawning locations such as rivers. Anecdotal angler accounts point to the Niagara River as a lake trout spawning location. To better understand the potential of the Niagara River as a spawning location, egg and juvenile fish collections were conducted 12–14 river kilometers from the mouth of the Niagara River from 2010 to 2012; and mature female lake trout with surgically implanted acoustic tags were monitored from 2015 to 2019. Genetic analyses confirmed 60% of collected eggs and 93% of collected post-hatch juvenile fish in the Niagara River were lake trout. Tagged female lake trout returned to the Niagara River over consecutive years during the spawning season. The short duration of lake trout presence in the river (mean = 56 days/year) suggests female lake trout use the Niagara River primarily for spawning. Diversity in spawning locations may provide lake trout population’s resilience against environmental variability through a portfolio effect. Improved identification of riverine spawning locations, including their overall contribution to wild recruitment, may be a useful tool for managers to restore a wild-produced population of lake trout in Lake Ontario.     

Distribution of Major Elements and Metals in Sediment Cores from the Western Basin of Lake Ontario

An investigation was made of the relationship between the changes in metal concentrations in sediments with the distance from the Niagara River mouth and the chemical and physical characteristics of the sediments. Sediment cores were obtained at nine sampling stations in the western basin of Lake Ontario. In addition, surface sediment was collected at three stations on the Niagara Bar. Minerals present at all stations were silica, feldspars, illite/muscovite, chlorite, kaolinite, and calcite. Dolomite was found at some sampling stations as grains of 2 to 63 μm size. Significantly elevated concentrations of calcite (up to 20%) in the surface sediment (about 0 to 10 cm) at four sampling stations in the western basin and in the entire 25-cm sediment column at the Niagara River mouth indicated increased input of this mineral into Lake Ontario during the past 100 years. Furthermore, sediment concentration profiles of Zn, Pb, Cr, Cu, Ni, and especially Hg at all sampling stations indicated major transport of metals associated with the clay- and silt-size particles from the Niagara River into Lake Ontario (especially north-north-east and east of the river mouth). A significant decrease in Hg loading from the Niagara River during the past 20 years was also observed. Although smaller in magnitude, a similar decrease was found for Pb, Zn, Cr, Ni, and Cu loading. However, elevated Hg concentrations (up to 7 μg g～^l above background values) existed in the surface 10 cm of sediment at eight sampling stations.     

黄河下游排沙特性及其对径流需求量的分析

通过黄河下游特征水沙年及三门峡水库不同方式运行期间泥沙输入与输出的分析，排沙能力的对水沙条件依赖关系的分析，论述了黄河下游排沙特性，并对黄河排沙的径流需求量作了探讨，为黄河流域可持续发展工程建设，如南水北调供水规划、建立黄河流域水资源配置体系，提供科学依据。     

洪水期水库调水调沙与黄河下游河道排沙分析

从1973～1990年期间，选取了60个洪峰时段的实测资料，分析了黄河下游河道的泥沙淤积和排沙比，得出结论为，如果洪水期三门峡出库平均含沙量为100～200kg／m3时，出库洪峰流量在4000～5000m3／s之间，可把50％～80％左右0．025～0．05mm和0．05～0．1mm的两级中粗沙排入海里；洪水期出库平均含沙量为50～100kg／m3，出库洪峰流量为3500～4000m3／s左右时，可把50％～190％的0．025～0．05mm和0．05～0．1mm的两级中粗沙排入海里．     

黄河禹潼河段近期冲淤特点及防洪形势分析

在对禹潼河段近期冲淤特点深入分析后指出：该河段近期河道淤积量尤其是主槽淤积量明显增加，滩槽高差减小，河槽排洪能力下降，已建工程防洪标准降低，工程临背差加大，险情频繁发生，防洪形势严峻。     

1997年黄河潼关河段清淤及洪水冲刷效果分析

１９９７年汛期黄河潼关站枯水水少，仅发生一次流量大于３０００ｍ＾３／ｓ的洪水，汛期水量５５．５３亿ｍ＾３，较多年平均值偏枯６９．３％，是１９２９年以来水文记载的最小值。洪水前，在潼关以下宽浅河段进行清淤疏浚，采用射流冲沙的方法，以冲为主，冲沙与扰流相结合进行作业，疏浚主河道中的浅滩，封堵串流汉道。清淤后，河势趋于规顺，浅滩段比降增大，水流相对集中，河道形态发生有利变化，增大了河道泄洪输沙能力。７月     

1855—1995年黄河下游山东河段河道冲淤厚度浅析

对山东黄河河道主槽、滩面冲淤情况计算分析表明，陶城铺以上河段１９３４－１９９５年在主槽淤积３．０－６．０ｍ，１８７５－１９９５年滩地淤积４．０－４．３ｍ；陶城铺－利津河段１８５５－１９９５年主槽淤积９．５－１４．３ｍ，１８７５－１９９５滩地淤积３．４－３．９ｍ；利津－渔洼河段１９６５－１９９５年主槽淤积１．３－３．０ｍ，１９６４－１９９５年滩地淤积０．３－０．７ｍ；渔洼以下河段１９７７－１９９５年     

黄河上游宁蒙河道冲淤变化分析

黄河上游来水沙地区分布不均匀，水沙异源。大型水库修库前，来沙多，宁蒙河道淤积，５０年代淤积尤为严重。青铜峡、刘家峡水库运用后，水库大量拦沙，宁蒙河道发生冲刷。龙羊峡，刘家峡水库联合运用后，汛期蓄水削峰，出库中小水流量历时加长，大流量出现机会大大减少，宁蒙河道重新调整，主要表现在；水流挟沙能力降低；河道淤积严重，水位升高，平滩流量减小；河势摆动加剧，滩岸坍塌严重；西柳沟高含沙洪水淤堵干流呈加重趋势。     

异源水沙对黄河上游兰州至头道拐河段悬移质泥沙冲淤的影响

由于自然地理条件的差异,黄河上游(兰州至头道拐河段,以下简称兰头河段)具有十分显著的水沙异源特征,这对于河道冲淤有深远影响。本文以实测资料为基础,建立冲淤量与异源水沙之间的定量关系,为减淤措施的确定提供参考。划分了3个水沙来源区,即兰州以上清水来源区、祖厉河和清水河多沙细沙来源区和十大孔兑多沙粗沙来源区。基于清水区的汛期来水量与多沙细沙区、多沙粗沙区来沙量的对比关系,提出了不同来源区水沙的耦合指标,这些指标反映了清水区汛期来水对多沙区高含沙洪水的稀释作用。建立了兰头河段的年冲淤量SL-T与不同来源水沙量之间的多元回归方程,并按半偏相关系数的大小估算出兰州站汛期径流量Qwh,L、兰州站年输沙量Qs,L、祖厉河和清水河年输沙量Qs,ZQ和十大孔兑年输沙量Qs,KD对于SL-T变化的贡献率,分别为39.6%,23.8%,14.0%和22.6%。兰州汛期径流量对于兰头河段冲淤的贡献率居第一,十大孔兑的贡献率超过多沙细沙区。两个多沙区来沙贡献率之和为36.6%,为干流来沙贡献率的1.41倍。建立了兰头河段河道冲淤量与不同来源区水沙耦合指标的关系,并计算出使该河段达到冲淤平衡的临界值。这一临界值对于冲淤调控有一定的应用意义。基于本研究的成果,提出了减淤对策:(1)改变龙羊峡水库现有运用方式来增大兰州站汛期径流量;(2)在祖厉河和清水河多沙细沙区加强水土保持,减少从多沙细沙区进入干流的泥沙量;(3)在十大孔兑多沙粗沙区加强水土保持和进行风沙治理,减少输入黄河的粗泥沙量。