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991.
Nineteen years (1980–1998) of precipitation chemistry data from a site in Alaska are examined for trends using a least squares general linear model. The annual concentrations of SO2– 4 show a significant decreasing trend at 0.001 level and the annual change in concentration is —0.012mg 1–1 yr–1. The annual concentrations of NO – 3 show an increasing tendency non‐significant. The annual base cation concentrations show a clear significant decreasing trend at 0.001 level and the decrease is —0.009mg 1–1 yr–1. Ca2+ concentrations exhibit a significant decreasing trend at 0.001 level and the annual change of concentration is —0.003 mg 1–1 yr–1. Mg2+ and Na+ concentrations show a significant decreasing trend at 0.01 level and the annual change is —0.001 mg1–1 yr–1 for Mg2+ and —0.004 mg1–1 yr–1 for Na+. K+ concentrations are characterised by a decreasing trend, significant at 0.05 level. K+ concentrations have decreased —0.002mg1–1 yr–1. The strongest rates of concentration decline for base cations, Ca2+, Mg2+, K+ and Na+ occurred in fall and winter season. The annual values of pH show a decreasing trend non‐significant. The values of pH oscillate between 5.1 and 5.6 during the period considered. 相似文献
992.
E. Alonso Alvarez M. Callejón Mochón J.C. Jiménez Sánchez L. Moreno López 《毒物与环境化学》2013,95(1-2):55-63
The application of the electrochemical speciation of heavy metals in tracking groundwater is presented. Three fractions interchangeable, associated to the organic materials and associated to the matter in suspension of the metals Zn, Cd, Pb and Cu by means of the anodic stripping voltammetry were determined. The parameters of the determination were: electrodeposition potential ‐1.2 V, time of deaerating with nitrogen 300 s, time of the electrolysis 90 s (with stirring) and the rest time 40 s. The core of this work was to determine the validity of this scheme of electrochemical speciation in the pursuit of the follow‐up of groundwater pollution caused by heavy metals after the breakdown of the mining raft at the River Guadiamar Basin (Andalusia, Spain). 相似文献
993.
The annual averages (1986–1997) of pH are analysed for the most important European Monitoring and Evaluation Programme stations in Europe. The first objective is to discover the different temporal patterns and trends for the pH. To do this, a cluster analysis is developed. The trends are analysed by linear regression for the annual averages. In general, the pH shows an increasing trend significant at 0.05 level and the annual change ranging from +0.01 to +0.05 pH‐units per year for the different clusters obtained. The second objective is to examine the spatial variability of pH in precipitation through the use of principal component analysis. Six statistically significant modes of variability are obtained for the pH which represent the 84.5% of the total variance. 相似文献
994.
Reversed phase thin layer chromatography (RPTLC) has been investigated for the estimation of octanol/water partition coefficients (P), an important parameter for the prediction of the environmental behaviour of organic chemicals. A strong correlation between P derived from the traditional octanol/water system and RPTLC has been established over five orders of magnitude. RPTLC data are likewise correlated to results obtained by high performance chromatography (HPLC). Due to the low costs, simplicity and separation power RPTLC is especially suited for the investigation and screening of mixtures of compounds before more complicated tests are involved. Results from a round robin test on the determination of partition coefficients by HPLC, RPTLC and the batch method indicate the simplicity and accuracy of the RPTLC technique. Applications of the RPTLC‐technique on technical products and industrial waste waters are described. 相似文献
995.
We studied the reproductive cycle of the sea urchin Arbacia lixula in a subtidal population from northeast Spain over four years using a gonadosomatic index (GSI) and gonad histology. Our results show that the GSI of A. lixula follows a seasonal cycle which peaks in May–July and attains its lowest values in October–November every year. The time course of the GSI matched closely the photoperiod cycle. We also found a remarkable inter-annual variability in the maximum value of GSI, which correlated with mean water temperature during the gonad growth period (winter and spring). Gonad histology was also in agreement with a single gametogenic cycle per year in this species. We explored the application of circular statistics to present and analyse gonadal development data, which allowed us to adequately handle the high intra-individual variability detected, with several developmental stages commonly found within the same gonad. The picture that emerged is one of a gametogenic timing driven by photoperiod, while the amount of reproductive output is determined by temperature. This is coherent with the tropical origin of the species and lends support to recent warnings about an increase in the abundance of this species in the Mediterranean as a result of global warming, with associated increased impact potential in sublittoral communities. 相似文献
996.
997.
Kasim Cemal Guven Erdoğan Okuş Sayhan Topcuoğlu Nur Esen Rezzan Küçükcezzar Emine Seddigh 《毒物与环境化学》2013,95(3-4):435-440
The paper reports heavy metal accumulation in algae collected at four stations and in sediments at three stations on the Black Sea coast of Turkey. The metals analysed are Cd, Co, Cr, Cu, Fe, Pb, Sb and Zn. The metal content of algae increased generally (with some exceptions) from 1991 till 1993 in ?ile and Sinop. In the sediments Sb in ?ile, As in Riva, Fe, Zn in Sinop are high. According to these findings the metal pollution increased in Turkish area of the Black Sea during the years investigated. 相似文献
998.
999.
Antoine Carlier Bénédicte Ritt Clara F. Rodrigues Jozée Sarrazin Karine Olu Jacques Grall Jacques Clavier 《Marine Biology》2010,157(11):2545-2565
Cold seep communities in the Mediterranean Sea have only been discovered two decades ago, and their trophic ecology has been
the subject of very few studies. We investigated the benthic food web of two deep chemosynthesis-based ecosystems on the Napoli
and Amsterdam mud volcanoes (MVs) in the eastern Mediterranean Sea (~2,000 m depth). Seeping methane has been detected at
the surface of both MVs during pioneering cruises and has been hypothesised to be assimilated by benthic fauna as observed
in other oceans’ margins. Given the extreme oligotrophic character of the eastern Mediterranean Sea, we a priori expected
that chemosynthetic food sources, especially methane-derived carbon (MDC), played a major trophic role in these deep seep
communities relative to what has been observed in other seep systems worldwide. We aimed at unravelling the trophic relationships
on Napoli and Amsterdam MVs through the analysis of carbon, nitrogen and sulphur isotopes both in the dominant benthic invertebrates
including the small endofauna (300 μm < size < 1 cm) and in the sedimented organic matter. In particular, we assessed the
fraction of MDC in the tissue of several heterotrophic and symbiotic species. Low mean δ34S and δ13C values (0.4 ± 4.8‰ and −31.6 ± 5.7‰, respectively) obtained for mega- and macrofauna suggested that the investigated benthic
food webs are virtually exclusively fuelled by carbon of chemosynthetic origin. A few grazer invertebrates (δ34S up to 11‰) depart from this trend and could complement their diet with sedimented and decayed phytoplanktonic organic matter.
Faunal δ13C values indicated that the oxidation of sulphur is likely the predominant energetic pathway for biosynthesis on both MVs.
Nevertheless, mytilid bivalves and small capitellid, ampharetid and spionid polychaetes were 13C-depleted (δ13C < −37‰) in a way indicating they assimilated a significant portion of MDC. For these later heterotrophic species, MDC ranged
between 21 and 31% (lower estimates) and 97 and 100% (upper estimates). However, our results highlighted that the origin of
assimilated carbon may be complex for some symbiotic species. The vestimentiferan tubeworm Lamellibrachia sp., which exclusively depends on its sulphur-oxidising endosymbionts, showed a ~20‰ inter-individual δ13C variability on a very small spatial scale (<1 m) at the summit of Napoli MV. This mostly reflects the variable isotopic
composition of pore-water-dissolved inorganic carbon (DIC) and evidenced that tubeworms (and subsequently their endosymbionts)
uptake DIC derived from multiple methane oxidation processes in varying proportions. The lower and upper MDC estimates for
the vestimentum of Napoli’s individuals were 11–38 and 21–73%, respectively. Finally, data on trophic ecology of Napoli and
Amsterdam MVs clearly corroborate previous geophysical results evidencing the spatial heterogeneity of Mediterranean MV environmental
conditions. 相似文献
1000.
In aquatic environments, many prey rely on chemosensory information from injured (alarm cues) or stressed conspecifics (disturbance
cues) to assess predation risk. Alarm cues are considered as a sign of higher risk than disturbance cues. These cues could
be used by prey to learn potential new predators. In this study, we tested whether Iberian green frog tadpoles (Pelophylax perezi) exhibited antipredator responses to alarm and disturbance cues of conspecifics and whether tadpoles could associate new
predators with alarm or disturbance cues. Tadpoles reduced their activity in the presence of disturbance cues, but only weakly
when compared with their response to alarm cues. Also, tadpoles learned to recognize new predators from association with alarm
or disturbance cues. However, the period of retention of the learned association was shorter for disturbance than alarm cues.
Our results indicate that tadpoles are able to modify their antipredatory behavior according to (1) the degree of risk implied
by the experimental cues (2) their previous experience of chemical cues of the predator. 相似文献