美国和五大湖双边共同关注区域的白肚燕(双色树燕)雏鸟的有机污染状况

白肚燕,又名双色树燕,栖居于五大湖流域中27个双边共同关注区域(AOCs),从2010年到2014年对其进行了污染物暴露风险评估,以协助管理者和监管者评估五大湖AOCs的污染状况。本文比较了AOCs和附近非AOCs雏鸟体内污染物浓度的差异。AOCs白肚燕雏鸟尸体中多氯联苯(PCB)和多溴联苯醚的含量分别为30%和33%,低于非AOCs的平均浓度。AOCs白肚燕雏鸟胃含物中多环芳烃(PAH)浓度和血浆中全氟化合物浓度分别为67%和64%,也低于非AOCs的平均浓度。但是与已有生殖效应记载的高PCB污染区相比,有些AOCs雏鸟尸体内的PCBs浓度只是存在小幅升高。一些AOCs食物中PAHs的浓度足够高以致引起可测量的生理响应。在AOCs中,全氟化合物全氟辛烷磺酸在血浆中的最高浓度出现在Raisin河(密歇根州,美国;几何平均数330 ng/mL),但远低于预估毒性的参考值(1 700 ng/mL)。之前有研究报道雏鸟胃含物中PAH和PCB的浓度以及尸体中PCBs的含量与沉积物中污染物的含量显著相关,从而可加强白肚燕在评估沉积物污染生物有效性方面的应用。
精选自Thomas W. Custer, Christine M. Custer, Paul M. Dummer, Diana Goldberg, J. Christian Franson, Richard A. Erickson. Organic contamination in tree swallow (Tachycineta bicolor) nestlings at United States and binational Great Lakes areas of concern. Environmental Toxicology and Chemistry: Volume 36, Issue 3, pages 735–748, July 2017. DOI: 10.1002/etc.3598
详情请见http://onlinelibrary.wiley.com/wol1/doi/10.1002/etc.3598/full
     

Effect of the allelochemicals from the macrophyte Egeria densa on the competitive interactions of pelagic and littoral cladocerans

Macrophytes release allelochemicals, which affect pelagic cladocerans such as Daphnia. Using population growth experiments, we analysed the effects of allelochemicals from the macrophyte Egeria densa on the interaction between Daphnia mendotae and three littoral cladocerans (Diaphanosoma birgei, Macrothrix triserialis and Simocephalus mixtus). We found that allelochemicals from E. densa increased the abundance of all the tested cladocerans in spite of the presence of a competitor. This effect was stronger (nearly three to four times higher than in controls) for D. birgei and M. triserialis in the absence of D. mendotae. Independent of the presence of allelochemicals, S. mixtus, but not D. birgei and M. triserialis, reduced the abundance of D. mendotae as compared to controls. The rate of population increase (r) per day was significantly elevated due to the presence of Egeria’s allelochemicals (from 0.07–0.16?d^?1 without allelochemicals against 0.12–0.24?d^?1 with allelochemicals). In our competition experiments, the rates of population increase of the cladocerans were lower than those in single-species cultures when cultured in the absence of allelochemicals. However, in the presence of allelochemicals this trend was not consistent. Thus, the positive effects of Egeria’s allelochemicals over the cladoceran populations may enhance the grazing pressure on phytoplankton.     

Changes in bird‐migration patterns associated with human‐induced mortality

Many bird populations have recently changed their migratory behavior in response to alterations of the environment. We collected data over 16 years on male Great Bustards (Otis tarda), a species showing a partial migratory pattern (sedentary and migratory birds coexisting in the same breeding groups). We conducted population counts and radio tracked 180 individuals to examine differences in survival rates between migratory and sedentary individuals and evaluate possible effects of these differences on the migratory pattern of the population. Overall, 65% of individuals migrated and 35% did not. The average distance between breeding and postbreeding areas of migrant individuals was 89.9 km, and the longest average movement of sedentary males was 3.8 km. Breeding group and migration distance had no effect on survival. However, mortality of migrants was 2.4 to 3.5 times higher than mortality of sedentary birds. For marked males, collision with power lines was the main cause of death from unnatural causes (37.6% of all deaths), and migratory birds died in collisions with power lines more frequently than sedentary birds (21.3% vs 6.3%). The percentage of sedentary individuals increased from 17% in 1997 to 45% in 2012. These results were consistent with data collected from radio‐tracked individuals: The proportion of migratory individuals decreased from 86% in 1997–1999 to 44% in 2006–2010. The observed decrease in the migratory tendency was not related to climatic changes (temperatures did not change over the study period) or improvements in habitat quality (dry cereal farmland area decreased in the main study area). Our findings suggest that human‐induced mortality during migration may be an important factor shaping the migration patterns of species inhabiting humanized landscapes.     

Southwestern corn borer damage to maize: Influence of plant age at time of larval infestation

A maize (Zea mays L.) hybrid was infested with 30 southwestern corn borer [Diatraea grandiosella (Dyar)] larvae per plant at 4, 5, 6, 7 or 8 weeks after planting in a three-year study conducted at Mississippi State, Mississippi. Visual ratings of leaf feeding damage were highest when plants were infested 5 weeks after planting. Plant height increased linearly with the age of plants at infestation. Height of infested plants was significantly less than uninfested plants only when infestations were made 4 weeks after planting. The relationship between age of plants at infestation and yield was curvilinear. Yields were significantly reduced at all infestation times; however, the least yield reduction occurred when plants were infested 6 weeks after planting. To evaluate resistance to southwestern corn borer damage, infestation at 4 or 5 weeks after planting appeared to be most satisfactory. Yield reductions following infestation at 7 and 8 weeks after planting indicated that, when infestations are late, leaf feeding damage ratings alone may not be satisfactory indicators of plant damage.     

Excitation–emission matrices applied to the study of urban effluent discharges in the Chubut River (Patagonia, Argentina)

Natural and contaminated waters of the final reaches of the Chubut River (Patagonia, Argentina) were studied to obtain information about river organic matter and effects of domestic and industrial discharges (fishery effluents and sewages). Fluorescence Excitation–Emission Matrices (EEMs) were obtained from samples only filtered (0.45 μm) and diluted, if necessary, to avoid the inner filter effect. In addition, physicochemical parameters were measured to know the quality of the water and the effluents. Results show that EEMs allow a rapid and simple control of the effluents from fisheries and domestic sewage in Chubut River estuary, necessary to take management decisions.     

Iron, cadmium, and chromium in seagrass (Thalassia testudinum) from a coastal nature reserve in karstic Yucatán

The management of protected areas in karstic regions is a challenge because flooded cave systems form there and provide underground hydrological conducts that may link different zones. As a consequence, affectations to the protected areas can possibly occur as a consequence of human activities in remote areas and may therefore pass undetected. Thus, the monitoring of possible contaminants in these regions is becoming imperative. In this work, we analyze the concentration of essential (iron) and non-essential metals (cadmium and chromium) in the seagrass Thalassia testudinum that grows in Yalahau Lagoon, located in a near-to-pristine protected area of the Yucatán Peninsula, close to the rapidly developing touristic belt of the Mexican Caribbean. Salinity and silicate patterns show that Yalahau is an evaporation lagoon, where groundwater discharge is important. High iron (>400 μg/g), cadmium (>4 μg/g), and chromium (≈1 μg/g) concentrations were found in the area of highest groundwater input of the lagoon. High levels (5.1 μg/g) were also found near the town dump. In the rest of the sampling sites, metal concentrations remained near to background levels as estimated from other works. Temporal changes of concentrations in the seagrass tissues show also a local input and an input from the groundwater that could provoke an environmental problem in the Yalahau Lagoon in the near future.     

Sand as a relevant fraction in geochemical studies in intertidal environments

Soil and sediment samples from several intertidal environment exposed to different types of contamination were studied to investigate the importance of grain size in relation to the capacity of the substrates to retain trace metals. The unfractionated samples (referred to as bulk samples) were separated into the following grain/size fractions: fine–coarse sand (2?0.100 mm), very fine sand (0.100?0.050 mm), silt (0.050?0.002 mm), and clay (0.002 mm). The sample into its fractions was carried out was in a glove box under high-purity N₂ atmosphere in order to minimize any alterations to the samples. The bulk samples were characterized in terms of physicochemical properties such as pH, redox potential, and grain size. The total organic carbon (TOC), total sulfur (S), iron (Fe) pyrite, Fe, and manganese (Mn), and trace metals lead (Pb), mercury (Hg), chromium (Cr), and nickel (Ni) were analyzed in the bulk samples and in each fraction. The sand fractions were also examined by scanning electron microscopy (SEM). Comparisons of the above parameters were made between fractions and between each fraction and the corresponding bulk sample. The fine–coarse sand fraction contained high levels of the primary elements of the geochemical processes that occur in marine sedimentary environments such as TOC, total Fe, Mn, and S. The net concentrations of these four elements were higher in the fine-coarse sand fraction than in the very fine sand fraction and were similar to the net concentrations in the silt and clay fractions. Detailed SEM analysis of the sand coarse fraction revealed the presence of Fe and aluminum oxyhydroxide coatings in the oxic layers, whereas the framboidal pyrites and coatings observed in the anoxic layers were Fe sulfides. The presence of the various coatings explains why the trace metal concentrations in the sand fine–coarse fraction were similar to those in the clay fraction and higher than those in the very fine sand fraction. The present results highlight the importance of the sand fraction, which is generally disregarded in geochemical and environmental studies of sedimentary layers.     

Biofilm thickness measurement using an ultrasound method in a liquid phase

In this report, the development of an online, noninvasive, measurement method of the biofilm thickness in a liquid phase is presented. The method is based in the analysis of the ultrasound wave pulse-echo behavior in a liquid phase reproducing the real reactor conditions. It does not imply the removal of the biomass from the support or any kind of intervention in the support (pipes) to detect and perform the measurements (non-invasiveness). The developed method allows for its sensor to be easily and quickly mounted and unmounted in any location along a pipe or reactor wall. Finally, this method is an important innovation because it allows the thickness measurement of a biofilm, in liquid phase conditions that can be used in monitoring programs, to help in scheduling cleaning actions to remove the unwanted biofilm, in several application areas, namely in potable water supply pipes.     

Fractionation of heavy metals and assessment of contamination of the sediments of Lake Titicaca

Chemical weathering is one of the major geochemical processes that control the mobilization of heavy metals. The present study provides the first report on heavy metal fractionation in sediments (8–156 m) of Lake Titicaca (3,820 m a.s.l.), which is shared by the Republic of Peru and the Plurinational State of Bolivia. Both contents of total Cu, Fe, Ni, Co, Mn, Cd, Pb, and Zn and also the fractionation of these heavy metals associated with four different fractions have been determined following the BCR scheme. The principal component analysis suggests that Co, Ni, and Cd can be attributed to natural sources related to the mineralized geological formations. Moreover, the sources of Cu, Fe, and Mn are effluents and wastes generated from mining activities, while Pb and Zn also suggest that their common source is associated to mining activities. According to the Risk Assessment Code, there is a moderate to high risk related to Zn, Pb, Cd, Mn, Co, and Ni mobilization and/or remobilization from the bottom sediment to the water column. Furthermore, the Geoaccumulation Index and the Enrichment Factor reveal that Zn, Pb, and Cd are enriched in the sediments. The results suggest that the effluents from various traditional mining waste sites in both countries are the main source of heavy metal contamination in the sediments of Lake Titicaca.