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At least 145 records · Page 8Linked to original sources
PubMed1989

Factors influencing rain splash dispersal of infective larvae of Ostertagia ostertagi (Trichostrongylidae) from cow pats to the surroundings.

Laboratory experiments were conducted to investigate rain splash dispersal of infective Ostertagia ostertagi larvae (L3) from cow pats to the surroundings during simulated rainfall. Simulated rainfall on dry cow pats resulted in dispersal of only very few L3. When cow pats were watered prior to the experiments, many infective larvae were stimulated to migrate up onto the surface of the pats, where they might be hit by water drops. When pre-watered pats were hit by falling drops, a considerable proportion of L3 was translocated. More than 90% of the translocated larvae were transported passively by splash droplets and only a minor part of the larvae migrated actively in water films or were transported passively by water run-off to the soil surrounding the pats. A reduction of the fall height of the simulated raindrops resulted in a significant reduction of the number of translocated L3. When cow pats were hit by drops of diameters between 2 and 5 mm, it was found that small raindrops were just as effective as large drops in splash dispersal of L3, provided the amount of rain was the same; but individual small drops were less effective in this respect than individual large drops. When splash droplets could travel freely, most of the splash-dispersed L3 were found within a horizontal distance of 90 cm from the pats; this applied for all sizes of drops. Most splash droplets carrying L3 were travelling within a vertical distance of 30 cm from the ground.

Animals↗
PubMed2004

The effects of temperature and artificial rain on the metabolism of American kestrels (Falco sparverius).

The effect of rainfall on the metabolism of birds is poorly understood. We measured the metabolism as rate of oxygen consumption (VO2) of four male and four female American kestrels (Falco sparverius) using open-circuit respirometry. We measured VO2 during the spring at ambient temperatures (Ta) of 5, 10, 15, and 25 degrees C in air without rainfall and with simulated rainfall of 2.5 (low rainfall) and 6.1 cm h(-1) (high rainfall). Kestrel metabolism was significantly higher when exposed to the two rainfall levels compared to no rainfall. However, kestrel metabolism was not significantly different at the two rainfall levels. Body temperature (Tb) was significantly lower under high rainfall compared to low rainfall. In addition, under both rainfall levels Tb decreased with decreasing Ta. Calculated thermal conductance was significantly higher in kestrels exposed to rain compared to no rainfall. Kestrels may use sleeking behavior at high rainfall levels to decrease water penetration of the plumage. Daily energy expenditure (DEE) of kestrels exposed to rain may increase markedly, and kestrel energetics may be further exacerbated by wind that often accompanies natural rainstorms.

Animals↗
PubMed2006

Effect of acid rain on building material of the El Tajín archaeological zone in Veracruz, Mexico.

Three limestone slabs (approx. 20 cm2 each) were extracted from the El Tajin archaeological zone in Veracruz, Mexico. X-ray diffraction analysis revealed three components: calcite (81.2%), quartz (17.9%) and feldspar (0.9%). Calcite content by x-ray diffraction analysis was slightly higher than that determined by chemical reaction between the limestone sample and nitric acid. The latter analysis, carried out in triplicate, yielded a calcite content of 77.1%. Mean water absorption, density and porosity of the limestone samples were also determined. Dissolution of limestone samples was investigated using an experimental rainfall simulation chamber, in which the stone samples were irrigated with artificial rain matching the pH and the ionic composition with 40 rainfall samples collected at El Tajin from August 18, 2002, to April 9, 2003. According to calcium and bicarbonate net concentrations found in the effluent of the chamber, a chemical mechanism by which limestone at El Tajin is dissolved by acid rain is proposed. A model used to investigate the air transport pathways corresponding to precipitation events at El Tajin shows that air parcels come mainly from the Gulf of Mexico, although no directional preference is evident for acidic vs. non-acidic events.

Acid Rain↗
PubMed2006

Fluorescent quenching method for determination of trace hydrogen peroxide in rain water.

A simple and sensitive fluorescent quenching method for the determination of trace hydrogen peroxide (H(2)O(2)) has been proposed to determine hydrogen peroxide in rain water sample. The method is based on the reaction of H(2)O(2) with 3,3'-diethyloxadicarbocyanine iodide (DI) to form a compound which has no fluorescence in acetate buffer solution (pH 3.09). The maximum emission wavelength of the system is located at 604 nm with excitation at 570 nm. Under the optimal conditions, the calibration graph was obtained between the quenched fluorescence intensity and hydrogen peroxide concentration in the range of 5.0 x 10(-7) to 9.0 x 10(-4) mol L(-1). The proposed method was applied to determine H(2)O(2) in rain water samples, and the result was satisfactory. The mechanism involved in the reaction was also studied.

Acetates↗
PubMed2006

Is acid rain impacting the Sudetic lakes?

The diatoms and Cladocera (Crustacea) remains from two lakes in the Sudets Mountains were analyzed to indicate an influence of acidification induced by anthropogenic factors during the last 150 years. The border area of the Czech Republic, Germany and Poland, the so-called "Black Triangle", has been strongly impacted by developed industry for several decades. The most visible effect of this process is the destruction of mountain forests in the region by acid rains. The diatom communities of Mały Staw and Wielki Staw show that acid rain has strongly affected water biota. Diatom-inferred pH reconstruction suggests major acidification during the last two decades. This process was controlled mainly by anthropogenic factors. Cladoceran records also presented changes of dominant taxa in this period and point to significant changes in living conditions. The discovery of a pH decrease during the last decade is contradictory to emissions data that suggest decrease in industrial pollution.

Acid Rain↗
PubMed2000

Acid rain, storm period chemistry and their potential impact on stream communities in Hong Kong.

Hong Kong experiences acid deposition, however, little is known about the potential impact upon aquatic ecosystems. In a small drainage basin observations reveal that despite acid rain runoff, both baseflow and stormflow, was close to neutral in terms of pH. During storm events chemical analysis reveals that calcium (Ca) concentrations tended to rise. It also appears that the input of acid rain may increase aluminium (Al) levels in the stream. Due to the increased levels of Ca and only slight changes in pH acid deposition may not be generating problems in this stream. The presence of mayflies reported elsewhere may further support the results of the chemical study.

Acid Rain↗
PubMed2001

Chorology of New Caledonian palms and possible evidence of Pleistocene rain forest refugia.

The distribution of the 36 palm species of New Caledonia is studied in relation to several parameters: elevation, rainfall, geological substrate, phytogeographical sectors and vegetation types. The climate (thermal gradient and rainfall) appears to be the principal factor influencing the distribution of palms, the substrate effect being subordinate to the climatic pattern. Nearly all palm populations are included within the 1,500 mm isoline. Maximum levels of species richness and endemism are located in four areas receiving more than 3,000 mm of annual rainfall. We interpret these areas as former Pleistocene refugia of lowland rain forest based on three lines of evidence: 1) all locally endemic lowland palm species and genera are restricted to these areas; 2) local endemics occur on east-facing slopes receiving the highest rainfall and most likely to have sustained rain forests during the driest periods; and 3) several pairs of sister species are disjunct between the southeastern and northeastern high rainfall areas.

Climate↗
PubMed2001

Haloacetates in fog and rain.

Atmospheric haloacetates can arise from photochemical degradation of halogenated hydrocarbons and from direct anthropogenic emissions. Furthermore, there is also evidence of natural sources although these are quantitatively uncertain. As haloacetates are highly soluble in water, hydrometeors are most significant for their deposition. Fogwater (96 samples) and rainwater samples (over 100 samples) were collected from July 1998 to March 1999 at an ecological research site in northeastern Bavaria, Germany. They were analyzed for monofluoroacetate (MFA), difluoroacetate (DFA), trifluoroacetate (TFA), monochloroacetate (MCA), dichloroacetate (DCA), trichloroacetate (TCA), monobromoacetate (MBA), and dibromoacetate (DBA). The major inorganic ions were also determined. High concentrations of up to 11 microg/L MCA, 5 microg/L DCA, 2 microg/L TCA, and 2 microg/L TFA were found in fogwater associated with westerly winds. Backward trajectories were calculated to determine the origin of the air masses. MBA and DBA have highest concentrations in fogwater advected with air originating from the Atlantic, suggesting the marine origin of these two compounds. All analyzed substances show higher average concentrations in fog than in rain. Estimates of the deposition of haloacetates suggest that the contribution of fog may be more important than rain for the total burden of a forest ecosystem.

Acetates↗
PubMed2005

Organic complexation of Fe(II) and its impact on the redox cycling of iron in rain.

More than 80% of the iron(II) present in a dilute (pH 4.5) H2SO4 solution was oxidized by hydrogen peroxide (3 microM) in 24 h, whereas in rainwater Fe(II) remained stable for days indicating that a complexed form of Fe(II) exists in rainwater that protects it against oxidation. When a rain sample was irradiated for 2 h with simulated sunlight, there was a 57 nM increase in Fe(II) resulting from photoreduction of organic Fe(III) complexes. Once irradiation ceased, the photoproduced Fe(II) rapidly oxidized back to its initial concentration of 32 nM prior to irradiation, but not to zero. These photochemical studies demonstrate that during the daytime when sunlight is present there are dynamic interconversions between complexed and uncomplexed Fe(II) and Fe(III) species in rainwater. During the night, after the photochemically produced Fe(II) is reoxidized to Fe(III), virtually all remaining Fe(II) is complexed by ligands which resist further oxidation. Rain samples oxidized under intense UV light lost their ability to stabilize Fe(II), suggesting the ligands stabilizing Fe(II) are organic compounds destroyed by UV-irradiation. Additional UV-irradiation studies demonstrated that on average 25% of the Fe-complexing ligands in rainwater are extremely strong and cannot be detected by spectrophotometric analysis using ferrozine. The stability of organically complexed Fe(II) has important implications for the bioavailability of rainwater-derived Fe in the surface ocean.

Biological Availability↗
PubMedDate not supplied

The effect of seed mass and gap size on seed fate of tropical rain forest tree species in guyana.

For eleven tree species, differing in seed mass, germination success (emergence success for two small-seeded species) and the causes of failure to germinate were studied in the forest understorey and in logging gaps in the tropical rain forests of Guyana. In the forest understorey, germination success increased with seed mass. However, as gap size increased the difference between smaller and larger seeded species diminished because germination success of smaller-seeded species increased slightly, while that of larger-seeded species decreased dramatically. The negative effect of gap size on germination success of larger-seeded species was caused by an increased risk of desiccation with gap size, which was a far more important seed mortality agent for larger than for smaller-seeded species. Generally, seeds of smaller-seeded species suffered more from insect predation and were removed at higher rates than larger-seeded species. On the other hand, larger-seeded species were eaten more by mammals than smaller-seeded species. It is concluded that logging can result in shifts in the species composition in the tropical rain forests of Guyana which are dominated by species with large seeds, since germination success of larger-seeded species is dramatically reduced in large logging gaps.

Germination↗
PubMed1993

Malaria in a rural area of Sierra Leone. II. Parasitological and related results from pre- and post-rains clinical surveys.

The prevalence of Plasmodium falciparum in a cohort of over 900 nought to seven-year-old children living in a rural area of Sierra Leone was found to be approximately 61%, both before and after the rainy season. Plasmodium malariae rates measured in the same children were approximately 12%, and P. ovale rates averaged about 1%. Spleen rates averaged 44% for the two surveys; the age prevalence spleen profiles closely matched those for P. falciparum. The overall gametocyte rates for both P. falciparum and P. malariae were roughly one fifth of the prevalence rates for the asexual parasites. However, whilst there was no difference between the P. falciparum gametocyte rates at the two surveys, the P. malariae rate was significantly higher post-rains when compared with the pre-rains result. Spleen size did not increase with increased parasite density. There was a statistically significant difference between the geometric mean P. falciparum trophozoite densities of febrile and afebrile children both before and after the rainy season, but there was little seasonal difference in the means for the febrile children or in those for the afebrile children. Antimalaria antibody levels, measured by ELISA and IFAT, showed no significant differences at either survey. The levels found were high for all age groups, indicating that exposure to malaria begins at birth. Our results indicate that, in the area studied, malaria is hyperendemic and is probably transmitted perennially.

Animals↗
PubMed2001

Whither acid rain?

Acid rain, the environmental cause célèbre of the 1980s seems to have vanished from popular conscience. By contrast, scientific research, despite funding difficulties, has continued to produce hundreds of research papers each year. Studies of acid rain taught much about precipitation chemistry, the behaviour of snow packs, long-range transport of pollutants and new issues in the biology of fish and forested ecosystems. There is now evidence of a shift away from research in precipitation and sulfur chemistry, but an impressive theoretical base remains as a legacy.

Acid Rain↗
PubMed2006

Movement trajectories and habitat partitioning of small mammals in logged and unlogged rain forests on Borneo.

1. Non-volant animals in tropical rain forests differ in their ability to exploit the habitat above the forest floor and also in their response to habitat variability. It is predicted that specific movement trajectories are determined both by intrinsic factors such as ecological specialization, morphology and body size and by structural features of the surrounding habitat such as undergrowth and availability of supportive structures. 2. We applied spool-and-line tracking in order to describe movement trajectories and habitat segregation of eight species of small mammals from an assemblage of Muridae, Tupaiidae and Sciuridae in the rain forest of Borneo where we followed a total of 13,525 m path. We also analysed specific changes in the movement patterns of the small mammals in relation to habitat stratification between logged and unlogged forests. Variables related to climbing activity of the tracked species as well as the supportive structures of the vegetation and undergrowth density were measured along their tracks. 3. Movement patterns of the small mammals differed significantly between species. Most similarities were found in congeneric species that converged strongly in body size and morphology. All species were affected in their movement patterns by the altered forest structure in logged forests with most differences found in Leopoldamys sabanus. However, the large proportions of short step lengths found in all species for both forest types and similar path tortuosity suggest that the main movement strategies of the small mammals were not influenced by logging but comprised generally a response to the heterogeneous habitat as opposed to random movement strategies predicted for homogeneous environments. 4. Overall shifts in microhabitat use showed no coherent trend among species. Multivariate (principal component) analysis revealed contrasting trends for convergent species, in particular for Maxomys rajah and M. surifer as well as for Tupaia longipes and T. tana, suggesting that each species was uniquely affected in its movement trajectories by a multiple set of environmental and intrinsic features.

Animals↗
PubMed1984

Acid rain and soil.

A summary of important chemical properties of soil is given and the way in which acid rain may affect these properties is discussed. Acid rain may suppress microbiological decomposition and nitrification processes, thus influencing the nutrient status of soils. It has also been found that soil organic matter is less soluble in more acid solutions. Changed nutrient availability patterns are predicted in a low pH environment and enhanced leaching of essential elements from the soil exchange complex has been observed. Increased solubility of potentially toxic elements such as aluminium may also occur from soils which have been exposed to acidified rainfall.

Acids↗
PubMed2006

A cross-sectional study of the prevalence of intensity of infection with Schistosoma japonicum in 50 irrigated and rain-fed villages in Samar Province, the Philippines.

BACKGROUND: Few studies have described heterogeneity in Schistosoma japonicum infection intensity, and none were done in Philippines. The purpose of this report is to describe the village-to-village variation in the prevalence of two levels of infection intensity across 50 villages of Samar Province, the Philippines. METHODS: This cross-sectional study was conducted in 25 rain-fed and 25 irrigated villages endemic for S. japonicum between August 2003 and November 2004. Villages were selected based on irrigation and farming criteria. A maximum of 35 eligible households were selected per village. Each participant was asked to provide stool samples on three consecutive days. All those who provided at least one stool sample were included in the analysis. A Bayesian three category outcome hierarchical cumulative logit regression model with adjustment for age, sex, occupation and measurement error of the Kato-Katz technique was used for analysis. RESULTS: A total of 1427 households and 6917 individuals agreed to participate in the study. A total of 5624 (81.3%) participants provided at least one stool sample. The prevalences of those lightly and at least moderately infected varied from 0% (95% Bayesian credible interval (BCI): 0%-3.1%) to 45.2% (95% BCI: 36.5%-53.9%) and 0% to 23.0% (95% BCI: 16.4%-31.2%) from village-to-village, respectively. Using the 0-7 year old group as a reference category, the highest odds ratio (OR) among males and females were that of being aged 17-40-year old (OR = 8.76; 95% BCI: 6.03-12.47) and 11-16-year old (OR = 8.59; 95% BCI: 4.74-14.28), respectively. People who did not work on a rice farm had a lower prevalence of infection than those working full time on a rice farm. The OR for irrigated villages compared to rain-fed villages was 1.41 (95% BCI: 0.50-3.21). DISCUSSION: We found very important village-to-village variation in prevalence of infection intensity. This variation is probably due to village-level variables other than that explained by a crude classification of villages into the irrigated and non-irrigated categories. We are planning to capture this spatial heterogeneity by updating our initial transmission dynamics model with the data reported here combined with 1-year post-treatment follow-up of study participants.

Adolescent↗
PubMed2001

[Species composition and diversity of soil mesofauna in the 'Holy Hills' fragmentary tropical rain forest of Xishuangbanna, China].

The species composition and diversity of soil mesofauna were examined in fragmented dry tropical seasonal rainforest of tow 'Holy Hills' of Dai nationality, compared with the continuous moist tropical seasonal rain forest of Nature Reserve in Xishuangbanna area. 5 sample quadrats were selected along the diagonal of 20 m x 20 m sampling plot, and the samples of litterfall and 0-3 cm soil were collected from each 50 cm x 10 cm sample quadrat. Animals in soil sample were collected by using dry-funnel(Tullgren's), were identified to their groups according to the order. The H' index, D.G index and the pattern of relative abundance of species were used to compare the diversity of soil mesofauna. The results showed that the disturbance of vegetation and soil resulted by tropical rainforest fragmentation was the major factor affecting the diversity of soil mesofauna. Because the fragmented forest was intruded by some pioneer tree species and the "dry and warm" effect operated, this forest had more litterfall on the floor and more humus in the soil than the continuous moist rain forest. The soil condition with more soil organic matter, total N and P, higher pH value and lower soil bulk density became more favorable to the soil mesofauna. Therefore, the species richness, abundance and diversity of soil mesofauna in fragmented forests were higher than those in continuous forest, but the similarity of species composition in fragmented forest to the continuous forest was minimal. Soil mesofauna diversity in fragmented forests did not change with decreasing fragmented area, indicating that there was no species-area effect operation in this forest. The pattern of relative abundance of species in these forest soils was logarithmic series distribution.

Animals↗
PubMed2004

[Toxicity of surfactant, acid rain and Cd2+ combined pollution to the nucleus of Vicia faba root tip cells].

The toxicity of Cd2+ and its combination with surfactant or simulated acid rain to Vicia faba root tip cell was studied by using micro-nucleus technique. The results showed that the formation of micro-nucleus in Vicia faba root tip cell was strongly induced by Cd2+ in its concentration of 0-10.0 mg.L-1. The micro-nucleus rate was 13.85@1000 at 6.0 mg.L-1Cd2+, 4.53@1000 at 0 mg.L-1Cd2+, and the pollution index (PI) was 3.06. The micro-nucleus ratio and PI decreased when the accompanied surfactant LAS was also presented or the pH values decreased to 4.5 or 3.5. In the meantime, many deformed nuclei and grains were observed in the root tip cells. The growth of the Vicia faba roots was restrained, and the root cells were not easy to be scattered. Therefore, the toxicity of Cd2+ was increased by its combination with surfactant or acid rain. The Cd2+ toxicity to Vicia faba cells at pH3.5 was stronger than that at pH4.5. When the mutation effect of contaminant with high concentration or with strong toxicity to plant cell was tested, the contaminant should be diluted for at least three times, and hence, the highest micro-nucleus ratio and pollution index (PI) could be found.

Acid Rain↗
PubMed2004

[Effect of acid rain on mercury leaching from forest yellow soil in Jinyun Mountain].

Forest yellow soil and arable yellow soil in Jinyun Mountain were collected to study the effect of simulated acid rain(adjusted to pH 2.0, 3.0, 4.0 and 5.0) on the Hg leaching from soils by the methods of static extraction and dynamic leaching. The results showed that in forest yellow soils, surface accumulation of Hg occurred, and the accumulated Hg was easier to be leached out than that in arable yellow soil by acid rain. The amount of leached Hg was the largest at pH 4.0. To abate the risk of Hg pollution in water bodies by the Hg leaching from this forest soil, the Mountain should be closed, and timber-felling should be forbidden.

Acid Rain↗