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A one-layer, two-dimensional computer model for the time-dependent, lakewide advective and diffusive transports as well as physical regeneration of total phosphorus in Lake Erie has been developed. It has 60 × 16 square grid cells of 6.67-km mesh size and uses a time step of 12 h. The model has been verified and found to be in reasonably good agreement with the Canada Centre for Inland Waters (CCIW) monitor cruise data for October, November, and December during which period there were high winds with high phosphorus concentrations being observed. Computed, daily averaged currents from a hydrodynamic model developed at CCIW are used for the transport terms and actual data for the lake boundary conditions. The physical regeneration is attributed to wave motions induced by wind. A formula is proposed which expresses the regenerated amount of total phosphorus in terms of wave orbital velocity and sediment mean grain size. A discussion is presented on the choice of the settling rate and the regeneration coefficient which produce satisfactory model results.

In 259 samples of the topmost 3 cm of sediment taken from Lake Erie in 1971, total mercury values ranged from 8 to 2929 ppb [Formula: see text]. The highest levels were in the Western basin adjacent to the Detroit River, the rest of the lake showing increasing concentration from the coarser sediments of the Inshore Zone and cross-lake moraine sills out into the basin muds. A quartz correction was applied to compensate for texture and dilution by an inert constituent. The distribution of quartz-corrected mercury confirmed that the Detroit River is the predominant source of industrial mercury to the Western basin with subsequent transport across the Central basin to final sink in the Eastern basin. Further possible inputs were indicated from Erie, Pennsylvania and Buffalo, New York. Analysis of suspended sediment in the Detroit River showed no change in concentration between 1970 and 1974 with a mean 1974 level of 1060 ppb. Mercury loading was estimated at 7.2 m.t./yr to the sediments of the Western basin. A relationship was observed between total mercury and organic carbon, showing two distinct regressions: ’A’ with lower organic-bound mercury, is taken to represent the levels related to industrial and natural loadings existing prior to the introduction of mercury cell chlor-alkali plants; ’B’ applicable to highly contaminated sediments, is believed to be indicative of loadings derived from the chlor-alkali industry.

The phosphorus in 48 surficial Lake Erie sediment samples was present in three major forms: phosphorus associated with apatite, nonapatite inorganic phosphorus (NAIP), and organic phosphorus. The apatite was of natural, detrital origin. It existed as particles ranging from fine sand to clay in size but mostly as silt-sized particles and was concentrated in nearshore sediments. Both NAIP and organic phosphorus was concentrated in fine-grained sediments accumulating in offshore depositional areas. NAIP was associated with amorphous hydrated ferric oxide in the oxidized microzone but was present as vivianite (Fe3(PO4)2∙8H2O) and possibly other forms also in the reduced zone. The organic phosphorus content of the sediment was closely related to organic carbon content. The phyllosilicate, organic matter, and reactive iron and manganese components of the sediments existed in intimate association.

A budget for phosphorus retention in Lake Erie during 1970 has been drawn up. Phosphorus associated with sand-sized particles (> 63 μm) was excluded. Retention of apatite phosphorus (AP) and nonapatite phosphorus (NAP) within each of the three basins of the lake (Western, Central, and Eastern) was estimated in each case by two independent methods. The two estimates of retention of total phosphorus within the entire lake agreed to within 9.5% of their mean. The estimates of AP retention within the Western basin also agreed well. However, the input–output balance estimates of AP retention in the Central basin and of NAP retention in the Western and Central basins greatly exceeded the corresponding sedimentation values, while in the Eastern basin this pattern was reversed. The AP discrepancy was attributed to unobserved transport of AP from the Central to the Eastern basin via nearshore currents past Long Point, while the NAP discrepancies were largely attributed to eastward movement of NAP through the lake within about 2 m of the lake bottom. The total amount of phosphorus retained within the lake in 1970 was 41,000 metric tons, or about 92% of input. AP of natural origin and inert nature accounted for approximately 44% of the total phosphorus retained. A reduction in anthropogenic phosphorus input of about 15,000 metric tons/yr, as called for in the Great Lakes Water Quality Agreement, will reduce present annual NAP loading to close to pre-1850 values.

On étudie l'influence des rejets de deux stations d'épuration sur la teneur des sédiments côtiers en phosphore, fer et carbone organique. Ces deux stations sont situées sur le littoral lémanique, l'une à Lausanne (Vidy), l'autre à Morges. La quantité de phosphore des sédiments situés dans la zone de rejet de Vidy excède dix fois la teneur naturelle. Les très fortes valeurs trouvées également pour le fer indiquent qu'une pattie du complexe ferro-phosphaté formé lors de l'épuration est relâchée avec les effluents. Les effets de la station de Morges sont moins marqués et ne sont pas visibles dans la distribution géographique du phosphore total dans les sédiments. En revanche, l'utilisation des rapports [fer extractible]/[phosphore non-apatite] et [carbone organique]/[phosphore organique] montre que les effluents de la station de Morges ont enrichi les sédiments côtiers en phosphore à presque deux fois la teneur naturelle. Ces rapports semblent être de meilleurs indicateurs de l'enrichissement des sédiments que les valeurs du P total.

Moment and graphic size parameters were computed on 420 surfical sediment samples from Lake Geneva (Switzerland). The sediment ranges from sand to clay-size and comprises a significant amount of precipitated silt-size calcite. Comparison of parameters shows that mean, sorting, and skewness may be estimated either by moment measures or by Folk and Ward's descriptors, without essential differences in interpretation. As for kurtosis, moment and graphic parameters provide different information, and both should be used separately as interpretive tools.