The impact of agronomic inputs on selected physicochemical features and their relationships with heavy metals levels in surface sediment and water in sugarcane farms in Nzoia,Kenya

Sugarcane farming is the most important cash crop cultivation activity in the Lake Victoria basin of Kenya practised in an area covering approximately 114,000 Ha in total. For better yields, various agronomic inputs including fertilizers and herbicides have been used intensively in the farms, causing serious concerns about their potential impacts on the aquatic ecosystems within the lake basin. In this study, the physicochemical features of surface sediment and water including pH, total organic carbon contents and heavy metal (Cd, Cu, Zn, Pb and Cr) loads in River Kuywa and in runoff canals in sugarcane farms in Nzoia nucleus estate within the lake basin were determined to assess the effects of agronomic activities including agronomic inputs in the form of nitrogenous fertilizers [urea and diammonium phosphate (DAP)], herbicides and sewage sludge used in farming on their levels. The results indicated significant differences (p ≤ 0.05) in the heavy metal levels in sediment and water samples taken before and after the farms, respectively, indicating a positive impact on the concentration levels. The canal water and sediment samples’ heavy metal levels were also significantly higher than those of the river samples showing that the influent sugarcane farm canal waters transfer these contaminants into River Kuywa. Although the levels of these parameters were significantly higher in the canals than in the controls obtained from outside the sugarcane farms, the heavy metal levels in soil samples from within the farms with similar agronomic activities did not differ significantly among the various plots. The turbidity, electrical conductivity, temperature, water and soil pH and total organic carbon values in samples obtained within the sugarcane farms showed significant seasonal variations and differed significantly from the values in the controls showing a significant negative impact of agronomic inputs on water quality.     

Major element composition of stratospheric micrometeorites

Abstract— The elemental compositions of 200 interplanetary dust particles (IDPs) collected in the stratosphere have been determined by energy dispersive X-ray (EDX) analysis. The results reasonably define the normal compositional range of chondritic interplanetary dust particles averaging 10 micrometers in size, and constitute a database for comparison with individual IDPs, meteorites, and spacecraft data from comets and asteroids. The average elemental composition of all IDPs analyzed is most similar to that of CI chondrites, but the data show that there are small yet discernable differences between mean IDP composition and the CI norm. Individual particles were classified into broad morphological groups, and the two major groups show unambiguous compositional differences. The “porous” group is a close match to bulk CI abundances, but the “smooth” group has systematic Ca and Mg depletions, and contains stoichiometric “excess” oxygen consistent with the presence of hydrous phases. Similar depletions of Ca and Mg in CI and CM matrix have been attributed to leaching, and by analogy we suggest that particles in the smooth group have also been processed by aqueous alteration. The occurrence of carbonates, magnetite framboids, and layer silicates provides additional evidence that at least a significant number of the smooth-class IDPs have been substantially processed by aqueous activity. The presence or absence of aqueous modification in members of a particle sub-class is an important clue to the origin. Although it cannot be proven, we hypothesize that extensive aqueous activity only occurs in asteroids and that, accordingly, the smooth class of IDPs has an asteroidal origin. If both comets and asteroids are major sources of interplanetary dust, then by default the porous particles are inferred to be dominated by cometary material.     

UH cosmic rays and solar system material: The elements just beyond iron

The origin of the elements from Cu to As in the UH (ultra-heavy) cosmic rays is investigated and related to current concepts of the nucleosynthesis of solar system material. The charge spectrum of the UH cosmic rays in the interval 29Z60 is studied via a fully developed propagation calculation for source abundances given by solar system material, ther-process, the massive-star core helium-burnings-process, and explosive carbon burning. None of these sources considered individually can explain the cosmic ray observations. However a combination of material produced in ther-process, the core helium-burnings-process and in explosive carbon burning provides a good representation of the experimental data. The cosmic-rayr-process is found to differ from solar systemr-process events by an underproduction of the low-massr-process peaks relative to theA195 peak. The large cosmicray abundance forZ=40–44 may be due to anr-process fission component, but this explanation is by no means certain. Improved cosmic-ray data, especially for Zn–Sr, can provide limits to the various source contributions. The model described here gives a consistent picture for the origin of both the cosmic rays and the solar system elements just beyond iron, and adds additional evidence for the importance of massive stars as a site of nucleosynthesis and the birthplace of the cosmic rays.Enrico Fermi Institute.     

Effects of Anthropogenic Estrogens Nonylphenol and 17α‐Ethinylestradiol in Aquatic Model Ecosystems

Microcosm tests were conducted to investigate the effects of the estrogenic substances nonylphenol (NP) and 17α‐ethinylestradiol (EE) on aquatic ecosystems. Maximum concentrations of 9 to 120 μg L^—1 NP resp. 49 to 724 ng L^—1 EE were induced by controlled release. The controlled release method allows the establishment of a continuous concentration course. The microcosms proved to run robustly with abiotic conditions close to natural. They developed biocenosis with similar characteristics as in natural ecosystems and, considering their given level of complexity, they can be used to describe possible risks for the environment. Both tested chemicals unveiled the potential to affect the plankton communities in the tested concentration range. NP exposure caused a reduction of Cladocera and Copepoda abundances and disturbed the phytoplankton structure. A NOEC_community of 30 μg L^—1 was calculated. In the first EE study, a flood in the lake where the microcosm water was collected caused additional stress and thereby a high variability, both between the microcosms and in each microcosm over time. Probably therefore the only effect found was a reduction of Copepoda abundance. In a second EE study Cladocera and Copepoda abundances were reduced, from which the phytoplankton benefited. Although a final interpretation is difficult for results of microcosm tests, there are indications that the found effects of EE and perhaps also NP may be caused at least partially by endocrine disruptive activity.     

Implications of radiolarian assemblages for the late Quaternary Paleoceanography of the eastern equatorial Pacific

The distribution of radiolarian assemblages identified by Q-mode factor analysis of radiolarian microfossils in surface sediments from low latitudes in the Pacific Ocean reflects their associations with surface water masses. Downcore fluctuations of these radiolarian assemblages at two sites, RC10-65 and V19–29, indicate changes in circulation in the eastern equatorial Pacific during the past 500,000 yr. Surface-water radiolarian assemblages characteristic of zonal flow have dominated siliceous sedimentation in the eastern equatorial Pacific, except during times of intense upwelling which can occur along the coast of Peru and in the Equatorial Undercurrent. Fluctuations in the importance of this upwelling have not been consistent with glacial/interglacial changes in ice volume throughout the late Quaternary. Intensification of upwelling in the equatorial divergence, however, has consistently coincided with increases in ice volume in the past 500,000 yr. The times at which changes in the nature of the relationship between upwelling and ice volume occur (approximately 240,000 and 380,000 yr B.P.) roughly coincide with times of observed changes in other proxy indicators of oceanographic conditions in the Pacific and Indian oceans.     

Zur Anchimetamorphose permo-skythischer Sedimentgesteine im westlichen Drauzug,Kärnten — Osttirol (Österreich)

Zusammenfassung An 86 Proben permo-skythischer bis kretazischer Sedimentgesteine des westlichen Drauzuges wurden Metamorphosestudien vorgenommen. Es wurde die Illit-Kristallinität (IK) ermittelt und zusätzlich an Kluftquarzen von 9 Lokalitäten auch die Gas- und Flüssigkeitseinschlüsse untersucht.Die ermittelten IK-Werte belegen eine anchizonale Metamorphose der postvariszischen Sedimente. Diese Prägung ist im Nordteil des Drauzuges signifikant intensiver als im Südteil dieses Bereiches und kann bis in die Raibler Schichten nachgewiesen werden.Die Fluidzusammensetzung der ältesten Einschlußgeneration in den Kluftquarzen besteht aus einer wässerigen Kochsalzlösung. Es konnten weder CO₂, höhere Kohlenwasserstoffe noch Methan in den Einschlüssen festgestellt werden. Diese Fluidzusammensetzung weist in das Wasserfeld der höhergradigen Anchizone. Die PT-Bedingungen der im westlichen Drauzug wirksamen alpidischen Metamorphose lassen sich aufgrund dieser Ergebnisse in Anlehnung an das Modell der Fluidentwicklung in den Externbereichen der Schweizer Alpen bei einer Mindesttemperatur von 270°C und einem minimalen Druck von 1500 bis 2000 bar festlegen (entsprechend einer Gesteinsüberlagerung von 5500 bis 7500 Meter). Dies stimmt mit den Daten der Illit-Kristallinität gut überein.

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Summary The illite-crystallinity index (IC) of some Permo-Scythian to Cretaceous sediments of the western Drauzug had been investigated. In addition, the fluid inclusions of quartz crystals from crosscutting clefts of 9 localities were analyzed.The IC-values indicate an anchizonal metamorphism of the postvariscic sediments. The data also show that metamorphism is of lower intensity in the southern than in the northern part of the Drauzug. In that area the metamorphism is traceable upward into the Carnian Raibler Schichten.The earliest fluid inclusions in cleft quartz consist of a saline water. Neither CO₂, methane nor higher hydrocarbons could be detected. This fluid composition is indicative of the water field of the highgrade anchizone. This implies that a minimum temperature of 270 °C and a minimum pressure of 1500 to 2000 bar were reached during the alpidic metamorphism in the western Drauzug. This corresponds to an estimated overburden of 5500 to 7500 meters. These estimates are in fairly good agreement with our IC-data.

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Résumé Une étude du métamorphisme a été effectuée sur 86 échantillons de roches sédimentaires d'âge permo-scythien à crétacé, provenant de la partie ouest du Drauzug. On a déterminé la cristallinité de l'illite (IC) et étudié les inclusions fluides dans les cristaux de quartz des fentes alpines provenant de 9 localités.Les données IC montrent un métamorphisme anchizonal des sédiments post-varisques. Dans la partie nord du Drauzug ce phénomène est beaucoup plus intense que dans la partie sud où il peut être suivi jusqu'aux couches de Raibler.Les fluides les plus précoces des cristaux de quartz sont composés d'une solution aqueuse légèrement salée contenant moins de mole % de CH₄, de CO₂ ou d'autres gaz. Il n'a été trouvé, dans les inclusions, ni des hydrocarbures plus lourds que le méthane, ni du méthane. Cette composition de fluides est caractéristique pour l'anchizone supérieure et pour l'épizone inférieure. En se référant au modèle de l'évolution des inclusions fluides dans les parties externes des Alpes Suisses, une température minimale de 270 °C et une pression minimale de 1500–2000 bars peut être détérminée. Cette pression correspond à une surcharge de roches de 5500 à 7500 mètres. Ceci est en bon accord avec les données de IC.

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A comparative study of iron and manganese diagenesis in continental slope and deep sea basin sediments off Uruguay (SW Atlantic)

Pore water and solid phase from surface sediments of the continental slope off Uruguay and from the Argentine Basin (southwestern Atlantic) were investigated geochemically to ascribe characteristic early diagenetic reactions of iron and manganese. Solid-phase iron speciation was determined by extractions as well as by Mössbauer spectroscopy. Both methods showed good agreement ( <6% deviation) for total-Fe speciation. The proportion of easy reducible iron oxyhydroxide relative to total-Fe oxides decreased from the continental slope to the deep sea which is attributed to an increase in crystallinity during transport as well as to a general decrease of iron mobilization. The product of iron reoxidation is Fe oxyhydroxide which made up less than 5% of total Fe. In addition to this fraction, a proportion of smectite bound iron was found to be redox reactive. This fraction made up to 10% of total Fe in sediments of the Argentine Basin and was quantitatively extracted by 1?N HCl. The redox reactive Fe(+II) fraction of smectite was almost completely reoxidized within 24?h under air atmosphere and may therefore considerably contribute to iron redox cycling if bioturbation occurs. In the case of the slope sediments we found concurrent iron and manganese release to pore water. It is not clear whether this is caused by dissimilatory iron and manganese reduction at the same depth or dissimilatory iron reduction alone inducing Mn(+IV) reduction by (abiotic) reaction with released Fe²⁺. The Argentine Basin sediment showed a significant manganese solid-phase enrichment above the denitrification depth despite the absence of a distinct pore-water gradient of Mn. This implies a recent termination of manganese mobilization and thus a non-steady-state situation with respect to sedimentation or to organic carbon burial rate.     

Henry’s and non-Henry’s law behavior of Br in simple marine systems

Experimental studies for the partitioning of Br as a trace element between aqueous and solid solutions were carried out in simple marine systems. The evaporation experiments were performed at 25°C and 1 atm in the systems of halite (NaCl), sylvite (KCl), kainite (KMgClSO₄ · 2.75H₂O), carnallite (KMgCl₃ · 6H₂O), and bischofite (MgCl₂ · 6H₂O). The partition coefficients for the systems investigated are constant only at a restricted concentration range. For concentrations lower than 100 to 300 μg Br/g aqueous solutions, D_Br increases with decreasing concentrations. Various evaporation experiments indicate that this observation is not due to kinetic effects (evaporation rates). To find a link between the partition coefficient and the Henry’s law behavior, the activity coefficients of the trace components in the solid solutions were recalculated from the experimentally derived data. It can be shown from these calculations that constant activity coefficients or Henry’s law behavior is reached for higher mole fractions of the trace component in the solid solution in halite and sylvite and thus correspond to constant partition coefficients. For bischofite and carnallite, Henry’s law behavior is restricted to the lower mole fractions, where D_Br is not constant. This behavior is caused by the activity of the trace component in the aqueous solution, which is powered by the stoichiometric factor of this component in the Br-end-member solid solution. For halite, sylvite, and kainite, this factor equals 1 and is 2 for bischofite and 3 for carnallite. However, it is thus impossible to correlate Henry’s law behavior with constant partition coefficients for solid solution systems where the stoichiometric factor of the trace component is greater than 1.