Background, aim, and scope At tropical latitudes, and especially on the semi-arid coasts of the Brazilian Northeast, the rainfall regime governs the
water quality of estuaries due to the pronounced difference between the rainy and dry seasons. These changes may be responsible
for seasonal changes in bioavailability of mercury (Hg) and other pollutants to the estuarine and coastal biota. Mercury bioaccumulates
along estuarine–marine food chains usually result in higher concentrations in tissues of top predators and posing a risk to
both marine mammals and humans alike. The Goiana River Estuary (7.5° S) is a typical estuary of the semi-arid tropical regions
and supports traditional communities with fisheries (mollusks, fish, and crustacean). It is also responsible for an important
part of the biological production of the adjacent coastal waters.
Materials and methods
Trichiurus lepturus (Actinopterygii: Perciformes) is a pscivorous marine straggler. Fish from this species (n = 104) were captured in a trapping barrier used by the local traditional population and using an otter trawl net along the
main channel of the low estuary during two dry seasons (D1 = November, December 2005, January 2006; D2 = November, December
2006, January 2007) and the end of a rainy season (R = August, September, October 2006). Fish muscle samples were preserved
cold and then freeze-dried prior to analysis of its total mercury (Hg-T) contents. Total mercury was determined by cold vapor
atomic absorption spectrometry (CV-AAS) with sodium borohydride as a reducing agent.
Results The studied individuals (n = 104) were sub-adult (30–70 cm, 71 ind.) and adult fish (>70 cm, 33 ind.). Weight (W) (204.1 ± 97.9 g, total biomass = 21,229.7 g)
and total length (TL) (63.1 ± 10.1 cm, range 29.5–89.0 cm) presented a significant (p < 0.05) correlation. Two-way ANOVA (n = 81) showed that TL and W had significant differences (p < 0.05) among seasons, being higher in D1 than in D2 and R, respectively. Moreover, season vs. month interaction were detected
for the variables length and weight. For the variable weight was detected significant difference for the factor month (p < 0.05). It suggests that the fish enter the estuary at the end of the rainy season and increase in length and weight during
the time they spend in the estuary. Fish from this estuary are shown to be fit for human consumption (125.3 ± 61.9 μgHg-T
kg–1 w.wt.; n = 104). Fish mercury contents increased with size and weight. Correlations between TL and Hg-T (r = 0.37286) and between W and Hg-T (r = 0.38212) were significant (p < 0.05). Dryer months showed higher mercury concentrations in fish (D1 773.4 ± 207.5 μgHg-T kg–1 d.wt., n = 27; D2 370.1 ± 78.8 μgHg-T kg–1 d.wt., n = 27; R 331.2 ± 138.5 μgHg-T kg–1 d.wt., n = 27). The variable mercury concentration showed differences in relation to the factor season (p < 0.05), where fish captured during the first dry season showed the highest concentration of mercury. The correlation between
Hg-T and rainfall (Rf) showed a negative correlation (r = –0.56; p < 0.05).
Discussion The main likely source of mercury to this estuary is diffuse continental run off, including urban and industrial effluents.
Since concentration of mercury in fish tissue is negatively correlated to rainfall, but positively correlated with fish length
and weight, it suggests that fish growth in this estuary results in mercury uptake and concentration on the fish tissue. In
the dry season of 2005–2006, when rainfall remained below the historic average, fish bioaccumulated significantly more mercury
than in the dry season 2006–2007, when rainfall was within the predictable historic average. It is suggested that less rainfall,
and consequently less particulate matter and less primary production in the estuary, make mercury more available to the higher
levels of the estuarine food chain. In the case of higher rainfall, when river flow increases and water quality in the estuary
is reduced, mercury probably is quickly exported associated to the particulate matter to the adjacent coastal waters where
it then disperses. This species is a potential routine bioindicator for mercury contamination of the biota, but so far was
used only with a limited number of individuals and contexts.
Conclusions Fish from the Goiana River estuary can still be safely consumed by the local population. However, any further contamination
of this resource might lead to total mercury levels above the recommended limits for pregnant women and small children. The
proposed heavy dependency of total mercury levels in fish on water quality indicates that land use and water quality standards
must be more closely watched in order to guarantee that best possible practices are in place to prevent bioaccumulation of
mercury and its transfer along the food chain. Human interventions and climatic events which affect river water flow are also
playing a role in the mercury cycle at tropical semi-arid estuaries.
Recommendations and perspectives
T. lepturus is largely consumed by coastal populations of tropical and sub-tropical countries all over the world. It is also consumed
by a number of marine mammals over which we have a strong conservation interest. This species is also a link among different
ecosystems along the estuarine ecocline. Therefore, knowledge of its degree of contamination might contribute to public health
issues as well as marine conservation actions. Studies on mercury and other contaminants using this species as bioindicator
(cosmopolitan, readily available) could help elucidating mechanisms through which pollutants are being transferred not only
through the food chain, but also from estuarine–coastal–open waters. In addition, using the same species in marine pollution
studies, especially as part of a mosaic of species, allows for wide range comparisons of marine food chain contamination. 相似文献
Surface waters located in intensive agricultural areas are more vulnerable to the pesticides contamination, which is a major concern if the water is intended to be used for human consumption. The aim of this study was to evaluate the presence and the distribution of pesticides in the Alqueva reservoir, an important source of water supply (South of Portugal), considering their representativeness in the agricultural practice of the area. For the analysis of pesticides risk impact we used the environmental quality standards in the field of water policy proposed recently by the European Commission. The pesticides belonging to the classes of phenylureas, triazines, chloroacetanilides, organophosphorous and thiocarbamates were analysed by on-line solid phase extraction-liquid chromatography-tandem mass spectrometry. The pesticides more frequently detected were atrazine, simazine, diuron and terbuthylazine. The highest levels of these pesticides were registered in spring, after pesticides treatment, namely in olive-tree and vine crops. The priority pesticides atrazine and diuron reached values above the annual average proposed in the European Union Legislation. The herbicide atrazine reached values that surpassed the proposed maximum allowable concentration (2 000 ng L? 1). The sampling stations most affected by these pesticides were Sra. Ajuda, Lucefecit and Alcarrache, located in the northern part of the reservoir, closer to Spain where the agricultural activity is more intensive. 相似文献
The presence of metals in the Antarctic environment is principally a natural phenomenon caused by geochemical characteristics of the region, although some anthropogenic activities can increase these natural levels. Antarctic penguins present several of the characteristics of useful sentinels of pollution in Antarctica such as they are long-lived species situated at the top of food web. The concentrations of Al, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Cd, and Pb were determined by inductively coupled plasma–mass spectrometry in samples of liver, kidney, muscle, bone, feather, and stomach contents of gentoo, chinstrap, and Adélie penguin (12 adults, five juveniles) from carcasses of naturally dead individuals collected opportunistically in the Antarctic Peninsula area. The obtained results showed that accumulation and magnification of several elements can be occurring, so that Cd and Se reached levels potentially toxic in some specimens. The presence of human activities seems to be increasing the presence of toxic metals such as Mn, Cr, Ni, or Pb in penguins. 相似文献
Platinum group metal (PGM) refining processes produce large quantities of wastewater, which is contaminated with the compounds that make up the solvents/extractants mixtures used in the process. These compounds often include solvesso, beta-hydroxyxime, amines, amides and methyl isobutyl ketone. A process to clean up PGM refinery wastewaters so that they could be re-used in the refining process would greatly contribute to continual water storage problems and to cost reduction for the industry. Based on the concept that organic compounds that are produced biologically can be destroyed biologically, the use of biological processes for the treatment of organic compounds in other types of waste stream has been favoured in recent years, owing to their low cost and environmental acceptability. This review examines the available biotechnologies and their effectiveness for treating compounds likely to be contained in precious metal extraction process wastewaters. The processes examined include: biofilters, fluidized bed reactors, trickle-bed bioreactors, bioscrubbers, two-phase partitioning bioreactors, membrane bioreactors and activated sludge. Although all processes examined showed adequate to excellent removal of organic compounds from various gaseous and fewer liquid waste streams, there was a variation in their effectiveness. Variations in performance of laboratory-scale biological processes are probably due to the inherent change in the microbial population composition due to selection pressure, environmental conditions and the time allowed for adaptation to the organic compounds. However, if these factors are disregarded, it can be established that activated sludge and membrane bioreactors are the most promising processes for use in the treatment of PGM refinery wastewaters. 相似文献
Land taken by artificial surfaces has an impact on the quality of life and ecosystems. To reduce possible negative impacts of land take, the European Commission proposed setting a milestone objective for 2020 in terms of future rates of land take.
This paper describes a methodology to model the impacts of the 2020 land-take milestone proposed in the RERM in the European Union 27 MS. An integrated modelling framework was configured to assess the spatial impact of two land-take scenarios: a ‘Reference’ scenario, which is driven by demographic and economic trends, and a ‘Target 0’ scenario that follows the 2020 land-take milestone proposed in the RERM. We conclude that the implementation of the 2020 land-take milestone, by reducing future land take in Europe, will foster more efficient use of land (less land taken for the same activity levels) and minimise negative impacts on non-artificial land uses. 相似文献
The use of pesticides to increase agricultural production can result in the contamination of the environment, causing changes in the genetic structure of organisms and in the loss of biodiversity. This practice is also inducing changes in the rainforest ecosystem. In this work, a Pseudomonas aeruginosa isolated from a preservation soil area of the Brazilian Amazon Forest, without usage of any pesticide, was evaluated for its potential to degrade atrazine. This isolate presented all responsible genes (atzA, atzB, atzC, atzD, atzE, and atzF) for atrazine mineralization and demonstrated capacity to use atrazine as a nitrogen source, having achieved a reduction of 44 % of the initial concentration of atrazine after 24 h. These results confirm gene dispersion and/or a possible contamination of the area with the herbicide, which reinforces global concern of the increase and intensive use of pesticides worldwide. 相似文献
Parvulastra exigua, a species that lacks a dispersive larva, is paradoxically one of the most widely distributed and abundant sea stars in Australia.
The potential that self-fertilization and successful development of self-generated progeny might contribute to population
maintenance in this species was investigated through induction of spawning in isolated individuals collected from five populations
near Sydney, New South Wales (34°S, 151°E), during the spawning period (August–October 2010, 2011). Evidence of selfing differed
significantly among the five populations but the level of selfing within individual egg masses did not. Overall, there was
a mean of 8.9% fertilization in egg masses with embryos. Some clutches developed to the juvenile stage while others arrested
development before hatching. The presence of miniscule testis tissue in gonads that appeared to be ovaries indicated that
hermaphroditism may be more common in some populations than indicated by anatomy. Mixed mating (selfing + outcrossing), pseudocopulation
during egg laying and developmental success of self-fertilized embryos may contribute to the ecological success of P. exigua. These might influence population genetic structure and would facilitate establishment of founder populations by a small
number of migrants. 相似文献
The present study evaluated the mutagenic potential of surface water from the Lucrecia dam. The Tradescantia-micronucleus (Trad-MCN) test and CBMN assay in human peripheral blood lymphocytes were applied, corresponding to an in vivo and in vitro system, respectively. Heavy metals and some physicochemical properties were also measured. Water samples were collected in November 2009 (dry season) and May 2010 (rainy season) at three different points. Results of both assays for raw water showed positive responses for the points analyzed when compared to the negative control. The CBMN assay showed that diluted water was still able to induce a significant increase in micronucleus frequency. For both assays, the highest mean MN was observed in the dry season. Chemical analyses detected an increase in heavy metal levels at the sampling points and in the different seasons. These findings indicate the presence of genotoxins, such as heavy metals, in the water, which may be affecting the entire ecosystem, as well as human health. More prolonged monitoring is recommended in order to better characterize this public water supply. 相似文献