Hydrogeochemical characterization of fluoride rich groundwater of Wailpalli watershed, Nalgonda District, Andhra Pradesh, India

The groundwater of Nalgonda district is well known for its very high fluoride content for the past five decades. Many researchers have contributed their scientific knowledge to unravel causes for fluoride enrichment of groundwater. In the present paper, an attempt has been made to relate the high fluoride content in the groundwater to hydrogeochemical characterization of the water in a fracture hard rock terrain—the Wailpally watershed. Groundwater samples collected from all the major geomorphic units in pre- and post-monsoon seasons were analyzed for its major ion constituents such as Ca^2?+?, Mg^2?+?, Na^?+?, K^?+?, CO $_{3}^{-}$ , HCO $_{3}^{-}$ , Cl^???, SO $_{4}^{-2}$ , NO $_{3}^{-}$ , and F^???. The groundwaters in the watershed have the average fluoride content of 2.79 mg/l in pre-monsoon and 2.83 mg/l in post-monsoon. Fluoride concentration in groundwater does not show perceptible change neither with time nor in space. The ionic dominance pattern is in the order of Na^?+? > Ca^2?+??> Mg^2?+??> K^??? among cations and HCO $_{3}^{-}\:\,>$ Cl^????> SO $_{4}^{-2} >$ NO $_{3}^{-} >$ F^??? among anions in pre-monsoon. In post-monsoon, Mg replaces Ca^2?+? and NO $_{3}^{-}$ takes the place of SO $_{4}^{-2}$ . The Modified Piper diagram reflect that the water belong to Ca^?+?2–Mg^?+?2–HCO $_{3}^{-}$ to Na^?+?–HCO $_{3}^{-}$ facies. Negative chloralkali indices in both the seasons prove that ion exchange between Na^?+? and K^?+? in aquatic solution took place with Ca^?+?2 and Mg^?+?2 of host rock. The interpretation of plots for different major ions and molar ratios suggest that weathering of silicate rocks and water–rock interaction is responsible for major ion chemistry of groundwater in Wailpally watershed. Chemical characteristics and evolution of this fluoride-contaminated groundwater is akin to normal waters of other hard rock terrain; hence, it can be concluded that aquifer material play an important role in the contribution of fluoride in to the accompanying water. High fluoride content in groundwater can be attributed to the continuous water–rock interaction during the process of percolation with fluorite-bearing country rocks under arid, low precipitation, and high evapotranspiration conditions.     

Effects of drill cuttings discharge on meiofauna communities of a shelf break site in the southwest Atlantic

The present study investigates the effects of drill cutting discharges on the structure of meiofauna communities in an area of the shelf break at Campos Basin, Southeast Brazil. Drilling activities were operated, in a first phase, with water-based fluid and, in a second phase, with synthetic fluid paraffin-based (NAF-III). A total of 135 samples taken at a pre-drilling situation (MS1) and two post-drilling moments (MS2 and MS3—3 and 22 months post-drilling, respectively) were analyzed. Effects on meiofauna were dependent on two main factors: 1—the impact received during drilling operation, if water-based or synthetic/water-based drilling fluid and 2—the background state, if it already presented signs of previous drilling activities or not. Based on univariate and multivariate analysis, there were evidences that the most affected area after drilling was those under the influence of synthetic-based fluid and that already had signs of previous drillings activities. The region impacted only by water-based fluid was less affected and the only one that completely recovered after 22 months. Nematodes and copepods had different responses to the impact. While copepods flourish in the impacted area and recovered 22 months after drilling, nematodes were adversely affected shortly after drilling and the community structure only recovered where hydrocarbons had been depleted.     

Statistical analyses of regional surface water quality in southeastern Ontario

Historical records from Ontario's Provincial Water Quality Monitoring Network (PWQMN) for rivers and streams were analyzed to assess the feasibility of mapping regional water quality patterns in southeastern Ontario which spans two major geologic zones, the Precambrian Shield and the St. Lawrence Lowlands, thus serving as a paradigm for much of Ontario. Despite biases toward the populated Lowlands and associated pollution problems, general spatial trends are evident via the analysis of intervariable relations, individual parameter maps and multivariate analysis. Using a robust algorithm designed to identify outliers and abstract underlying bivariate relations, a linear regional hardness-alkalinity relation was derived, where most anomalies proved to be mine drainage impacted sites. Regionally, multivariate ordination reveals that central tendencies of common indicators of ionic strength and nutrient richness correlate positively and that site clusters broadly reflect the transition from oligotrophic Shield waters to eutrophic conditions of heavily agricultural Lowland streams. Results suggest that on the Shield more precisely delineated aquatic regions may be realized by applying GIS to integrate river and synoptic lake survey data. Further synthesis with bedrock and surficial geology, physiography, pedology and other temporally invariant spatial attributes should yield regional patterns of background quality from which locally attainable water objectives might be defined. Additional synoptic surveys of sedimentary Lowland streams may be required as most available sites relflect anthropogenic pollution.     

The accumulation of metals and toxic effects in Nereis virens exposed to pulverised fuel ash

The marine polychaete worm Nereis virens was used to study the bioaccumulation patterns of metal exposures with pulverised fuel ash (PFA). Juvenile N. virens were exposed for 12 weeks to sediments comprised of 100% PFA, 50% PFA-50% clean sand, a reference sediment (contaminated harbour-dredged material) and a clean sand control. Mortality after the first 4 weeks was high at 32–45% in the four sediments. However, this declined to a few percent during the following 8 weeks. Growth expressed as biomass (wet weight) was reduced in bout PFA treatments and the reference sediment. Heavy metal accumulation in the tissues of N. virens was characterised as follows: a group of elements showed negligible to low accumulation (Cd, Cr, Ni, and Zn), As and Cu wich showed a definite, but moderate accumulation: and finally Se, which showed a low accumulation rate, where an uptake equilibrium was not reached after 9 weeks. It is concluded that acute toxic effects did not occur but a population of N. virens inhabiting a PFA dumping site could be affected by high Se concentrations.     

Relationship between phytoplankton cell size and the rate of orthophosphate uptake: in situ observations of an estuarine population

Orthophosphate uptake by a natural estuarine phytoplankton population was estimated using two methods: (1) ³²P uptake experiments in which filters of different pore sizes were used to separate plankton size-fractions; (2) ³³P autoradiography of phytoplankton cells. Results of the first method showed that plankton cells larger than 5 m were responsible for 2% of the total orthophosphate uptake rate. 98% of the total uptake rate occurred in plankton composed mostly of bacteria, which passed the 5 m screen and were retained by the 0.45 m pore-size filter. There was no orthophosphate absorption by particulates in a biologically inhibited control containing iodoacetic acid. Orthophosphate uptake rates of individual phytoplankton species were obtained using ³³P autoradiography. The sum of these individual rates was very close to the estimated rate of uptake by particulates larger than 5 m in the ³²P labelling experiment. Generally, smaller cells were found to have a faster uptake rate per m³ biomass than larger cells. Although the nannoplankton constituted only about 21% of the total algal biomass, the rate of phosphate uptake by the nannoplankton was 75% of the total phytoplankton uptake rate. Results of the plankton autoradiography showed that the phosphate uptake rate per unit biomass is a power function of the surface: volume ratio of a cell; the relationship is expressed by the equation Y=2x10^-11 X ^1.7, where Y is gP m^-3 h^-1 and X is the surface: volume ratio. These results lend support to the hypothesis that smaller cells have a competitive advantage by having faster nutrient uptake rates.     

Diel trophic interactions between vertically-migrating zooplankton and their fish predators in an eelgrass community

Diel changes in the composition of crustacean zooplankton and the diets of fish predators from an intertidal eelgrass flat were monitored concurrently. The zooplankton is characterized by two major components. The obligate zooplankters (holoplanktonic calanoid copepods and meroplanktonic decapod larvae) appear to exhibit vertical migration, being present in higher densities near the surface of the water column at night. The facultative zooplankton (amphipods and ostracods) are benthic during the day, but move up into the water column at night. Planktivorous midwaterdwelling fish consume calanoid copepods and decapod larvae during the day and cease feeding or switch their diet to amphipods at night. Benthic-dwelling fish consume some amphipods during both day and night. The factors important in prey selection by fish and the functional significance of vertical migration in both components of the zooplankton are discussed in the light of the changing patterns of fish predation.This paper is Publication No. 183 in the Ministry for Conservation of Victoria, Environmental Studies Series.     

Continuous plankton records: The occurrence of apostome ciliates (Protozoa) on Euphausiacea in the North Atlantic Ocean and North Sea

The phoronts (resting cysts) of apostome ciliates have been recorded on Euphausia hemigibba, E. krohni, Meganyctiphanes norvegica, Nematoscelis megalops, Nyctiphanes couchi, Thysanoessa gregaria, T. inermis, T. longicaudata and T. raschi taken in the Continuous Plankton Recorder Survey of the North Atlantic Ocean and the North Sea. Variations in the percentage of host euphausiids infested by apostomes have been studied in relation to species, geography, body size and season. The percentage infestation was found to be related mainly to the body size of the hosts. The apostomes are believed to be species that develop either in the exuviae discarded exoskeletons or corpses of the euphausiids, or in the digestive systems of predators of the euphausiids.     

Possible strategy for the survival of marine bacteria under starvation conditions

A population of a psychrophilic marine vibrio (Ant-300) suspended at a low cell density in natural seawater (SW) or artificial seawater (ASW) showed an initial 200-fold increase in cell numbers. Ant-300 suspended in ASW at various densities showed a magnified initial increase in numbers as well as increased longevity as the population density decreased. The magnitude of the initial increase and the viability of the cells after 7 weeks continued incubation were the same whether the cells were suspended in SW, ASW amended with amino acids, or organic-free ASW. Continued incubation (long-term starvation) of a culture of Ant-300 at low cell densities in ASW showed that after 70 weeks over 15 times the orginal number of cells were still viable. When compared to the starvation survival of other bacceria, Ant-300 exceeds the longest reported starvation survival by at least 2.5 times. Our data indicate that Ant-300 is especially adapted for survival at low nutrient concentrations and low population densities due to a sustained increase in cell numbers that may represent a species survival mechanism for marine bacteria.Technical Paper No. 4493, Oregon Agricultural Experiment Station.     

Aspects of osmotic and lonic regulation in two Baltic teleosts: Effects of salinity on blood and urine composition

Hydromineral regulation was studied by examining the response to different environmental salinities in two Baltic brackish-water (BW) teleosts—a species of marine ancestry, Myoxocephalus scorpius (L.), and a glacial relict, M. quadricornis (L.). M. scorpius tolerated fresh water (FW) and M. quadricornis sea water (SW) for only about 24 h, but the survival time of M. scorpius in SW and M. quadricornis in FW was one to several weeks. M. scorpius seems able to balance plasma ionic concentrations in salinities down to about 2 to 3. Death of M. scorpius in FW was associated with partial haemolysis, increased volume of red blood cells (RBC), increased plasma K⁺ concentration, and decreased concentrations of Na⁺, Cl^- and Mg²⁺ in plasma and, to a lesser extent, in urine. Death of M. quadricornis in SW was associated with increased plasma osmolality, and Na⁺, Cl^- and Mg²⁺ concentrations, but the renal excretion of ions approached that generally found in marine teleosts. In most cases, RBC volume followed the changes in plasma osmolality or Na⁺ and Cl^- concentrations. Both species showed an ability to increase tubular Mg²⁺ secretion much over that needed in BW, and increased secretion was associated with high urine Cl^- concentration. M. quadricornis, but not M. scorpius, reabsorbed Na⁺ effectively in SW also. Differences between Oceanic and Baltic specimens of M. scorpius are discussed.