The impact of farming on river banks on water quality of the rivers

A study was carried out in a strip of a river in the dry and rainy seasons to assess the effect of farming along river banks on the quality of water in rivers. The results showed that there was an increase in the concentration of nitrate in the water downstream in both the rainy and dry seasons. In both rainy and dry seasons, the total nitrogen in the soil was highest (p<0.01) in the middle section. Significant seasonal differences (p<0.01) were observed for phosphate in water, being higher in the dry season. In the soil, the concentration of phosphate showed significant sectional differences (p<0.01) in the rainy season with the highest concentration observed in the lower section (1.74±0.01mg/l) and the least in the upper section (1.02±0.01g/l). However, in the dry season, the highest concentration was obtained in the middle section (1.69±0.01mg/l) and the least in the upper section (1.15±0.02 mg/l). The results suggest that the farms along the riverbanks have an impact on the water quality of the water in the river. It is therefore recommended that there should be close monitoring of the activities of the farms on riverbanks to minimise their impacts on the natural ecosystems that they interact with. Frequent monitoring of the water quality in the rivers relative to the farming estates should be done.     

Controlled source electrical methods for deep exploration

Application of controlled source electrical methods (CSEM) is impeded by natural field, electrification, geological, cultural, and topographic noise. Lateral resolution of parameters of adjacent steeply dipping bodies and vertical resolution of parameters of adjacent beds in a flatly dipping sequence are concerns with any CSEM method. Current channeling into a localized good conductor from a surrounding, overlying, or underlying conductor poses problems for the interpreter. A summary of the results of several recent experiments with CSEM techniques illustrates that with care and difficulty they can be used to depths on the order of 20 km. If measurements are made on a relatively uniform resistive surface, as can be found in glaciated Precambrian terranes, then either a grounded bipole or a loop source is acceptable. Most of the recent CSEM experiments were made over resistive Precambrian rocks and all were directed toward detecting a conductive layer near 20 km depth. For exploration beyond this depth, however, the MT/AMT method would seem to be preferred. The rationale behind this conclusion is largely contained in consideration of the ratio of signal to natural field noise. Where thick irregular surficial overburden of low resistivity occurs, two- and three-dimensional modeling is necessary to stripp off the effects of the shallow layers. This may not be possible for CSEM and then MT/AMT becomes the only alternative.     

Helium isotopic variations in volcanic rocks from Loihi Seamount and the Island of Hawaii

Helium isotopic ratios ranging from 20 to 32 times the atmospheric ³He/⁴He(R_A) have been observed in a suite of 15 basaltic glasses from the Loihi Seamount. These ratios, which are up to four times higher than those of MORB glasses and more than twice those of nearby Kilauea, are strongly suggestive of a primitive source of volatiles supplying this volcanism. The Loihi glasses measured span a broad compositional range, and the ³He/⁴He ratios were found to be generally lower for the alkali basalts than for the tholeiites. The component with a lower ³He/⁴He ratio appears to be associated with olivine xenocrysts, within which fluid inclusions are probably the carrier of contaminant helium. One Loihi sample has a much lower isotopic ratio (<5 R_A), but a combination of low He concentration, high vesicularity, and presence of cracks lined with clay minerals suggests that the low ratio is due to gas loss and contamination by atmospheric helium.Crushing and melting experiments show that for modest vesicularities (<5% by volume) the Loihi glasses obey a MORB-type partitioning trend, but at higher vesicularities the data show considerably more scatter due to volatile mobilization. The high vesicularities, low extrusion pressure and generally low helium concentrations are consistent with a considerable degree of degassing. Analyses of dunites, plus a correlation between total helium concentrations with xenocryst abundances also suggest that xenocrysts are a significant carrier of contaminating (low ³He/⁴He) helium.³He/⁴He ratios from samples of other Hawaiian volcanoes (Kilauea, Mauna Loa, Hualalai, and Mauna Kea) show a smooth decrease in ³He/⁴He with increasing volcano age and volume. We interpret this to be a synoptic picture of the time evolution of a hot-spot diapir: the earliest stage is characterized by primitive (> 30 R_A) helium with some (variable) component of lithospheric contamination added during “breakthrough”, while the later stages are characterized by a relaxation toward lithospheric ³He/⁴He ratios (～ 8 R_A) due to isolation of the diapir from the mantle below (as the plate moves on), and subsequent mining of the inherited helium and contamination from the surrounding lithosphere. The abrupt contrast in ³He/⁴He ratios between Kilauea and Loihi, despite their close proximity, is indicative of the small lateral extent of the plume.     

Diel activity cycles of two Chesapeake Bay fishes,the striped blenny (Chasmodes bosquianus) and the oyster toadfish (Opsanus tau)

Diel activity cycles of toadfish and striped blennies were identified in the laboratory by means of mechanoelectric detector units. Data for both species were collected over 72-h periods. Daytime and nighttime activity rates were compared statistically. In addition, five 3-h segments (3 during the day and 2 at night) were selected for statistical comparison. both species are more active at night than during the day. The toadfish appears to be more strictly nocturnal than does the blenny, with the peak in its activity occurring in the 3-h segment following dusk. Blenny activity increases throughout the night, reaching a peak during the 3-h segment before dawn. It then ebbs to a low in the afternoon.     

Changes in climate and levels of lake Michigan: shoreline impacts at Chicago

This study concerns effects along the Illinois shoreline resulting from the record-low levels of Lake Michigan during 1964–65, and the potential impacts of future low water levels at Chicago resulting from potential climate changes. The low lake levels of the 1960s did not cause major impacts at Chicago when they occurred. The two major impacts discerned (damage to shoreline protection structures and the encroachment of structures onto areas too close to the lake) resulted from a sequence of low-water levels followed by high-water levels a few years later. Climate scenarios, derived from general circulation models (GCMs) and extreme historical precipitation values, were used in a basin hydrologic model to determine potential future lake levels. Possible impacts were then estimated by 29 lakeshore experts. If the average lake level were reduced 1.0 m during the next 50 yr, shoreline impacts would not be severe and cost about $ 100 million. Many of the adjustment costs could be offset by normal maintenance and replacement costs. If the average lake level was reduced more than 1.5 m during the next 50 yr, very sizable economic impacts would occur, costing between $3 and $35 billion (1988 dollars). Some of the adjustment cost could be offset by normal replacement costs, particularly if a master plan for changing affected facilities were implemented in advance. The type of climate change and degree of lakelevel change will greatly affect the severity of the effects at Chicago.     

Te and Se mineralogy of the high-sulfidation Kochbulak and Kairagach epithermal gold telluride deposits (Kurama Ridge, Middle Tien Shan, Uzbekistan)

Summary The Late Paleozoic Kochbulak and Kairagach deposits are located on the northern slope of the Kurama Ridge, Middle Tien Shan, in the same volcanic structure and the same ore-forming system. Au–Ag–Cu–Bi–Te–Se mineralization is confined to veins and dissemination zones accompanied by quartz-sericite wall-rock alteration. The tellurides, calaverite, altaite, hessite, and tetradymite are widespread at both deposits; at Kairagach selenides and sulfoselenides of Bi and Pb are common, while at Kochbulak Bi and Pb telluroselenides and sulfotelluroselenides are typical. The paragenetic sequence of telluride assemblages are similar for both deposits and change from calaverite + altaite + native Au to sylvanite + Bi tellurides + native Te, Bi tellurides + native Au, and, finally, to Au + Ag tellurides with time. These mineralogical changes are accompanied by an increase in the Ag content of native gold that correlates with a decrease in temperature, fTe₂ and fO₂ and an increase in pH.     

Pompeii Damaged by Volcaniclastic Debris Flows Triggered Centuries Prior to the 79 A.D. Vesuvius Eruption

This study records that Pompeii, long before its final devastation by the 79 A.D. Vesuvius eruption in southern Italy, was damaged by several mass gravity flows. Composition of the deposits indicates that they were derived from volcaniclastic cover of carbonate highlands positioned 14 km NE of the city. Stratigraphic and petrologic analyses of sections in excavations and drill cores in and near Pompeii record the presence of three downslope‐directed debris flows dated between 8th and 2nd century B.C. Some of these deposits were channelized via a stream bed that once extended from high reliefs to Pompeii. It is proposed that one of these events may have been partially responsible for urban decline during the 4th century B.C. These mass flows are interpreted as having been triggered primarily by intense rains in a manner similar to those that have occurred and destroyed towns in this region during the past 50 years. Our investigation shows that Pompeii and adjacent areas in the past, much as in recent time, have likely been most frequently susceptible to episodic damage by avalanches and mass flows of volcaniclastic material resulting from hydrological effects rather than from volcanic events, earthquake tremors, and societal disruptions such as wars.