水环境中的微塑料：环境危害的本证和反证及主要研究空白

科学界与公众对微塑料(microplastics, MPs)的污染越来越重视。我们对文献进行了系统综述,以评价MPs对环境危害的证据权重。我们发现MPs在地表水和沉积物中均有存在。主要以珠状组成为主的碎片和纤维只是检测到的MP形态中的一小部分。检测出的MPs环境浓度很低,与能够影响生物分子水平上的毒性终点、以及摄食、繁殖、生长、组织炎症和死亡率的浓度有数量级的差别。MPs作为疏水性有机化合物的携带者使其在生物体中富集的作用很弱。现有数据表明MPs对环境造成的危害并不明显。实验室毒性实验中使用的MPs与环境中检测到的MPs在颗粒形态、尺寸范围和浓度等方面都有差距。研究中环境介质的选择少受关注。我们亟需开展更高质量的整体监测和更多实际环境效应的研究。只有这样,我们才能够全面表征MPs的环境风险,以便制定实施真正改善环境质量的管控措施。 精选自Emily E. Burns, Alistair B.A. Boxall. Microplastics in the aquatic environment: Evidence for or against adverse impacts and major knowledge gaps. Environmental Toxicology and Chemistry,2018,37:2776–2796.
详情请见 https://doi.org/10.1002/etc.4268
     

Testing the ecotoxicology of vegetable versus mineral based lubricating oils: 1. Degradation rates using tropical marine microbes

Vegetable-derived lubricants (VDL) might be more biodegradable than mineral-derived lubricants (MDL) due to the absence of high molecular weight aromatics, but this remains largely untested in tropical conditions. In this laboratory study, the degradation rates of 2-stroke, 4-stroke and hydraulic VDLs were compared with their MDL counterparts in the presence of mangrove and coral reef microbial communities. While MDLs were comprised largely of unresolved saturated and some aromatic hydrocarbons, their VDL counterparts contained, potentially more degradable, fatty acid methyl esters. Degradation of some VDL was observed by day 7, with the 2-stroke VDL markedly consumed by mangrove microorganisms and the hydraulic VDL degraded by both microorganism communities after this short period. All of the VDL groups were significantly more degraded than the comparable MDLs mineral oil lubricants over 14 days in the presence of either mangrove or coral reef microbial communities. In general the mangrove-sourced microorganisms more efficiently degraded the lubricants than reef-sourced microorganisms.     

Organochlorines, including chlordane compounds and their metabolites, in peregrine-falcon, prairie-falcon, and clapper-rail eggs from the USA

Four compounds present in technical chlordane (trans- and cis-nonachlor, and tentatively MC-2 and MC-5) and three metabolites of chlordane (heptachlor epoxide, oxychlordane, and U-4) were identified by GC/MS in peregrine-falcon (Falco peregrinus anatum) eggs. Levels of Heptachlor epoxide, oxychlordane, trans- and cis-chlordane, trans- and cis-nonachlor, MC-2, and MC-5 were quantified by GC/ECD in peregrine-falcon eggs from the US east coast, Colorado, and California; and in prairie-falcon (Falco mexicanus) and light-footed-clapper-rail (Rallus longirostris levipes) eggs from California. The eggs were collected between 1986 and 1989. Oxychlordane, heptachlor epoxide, trans- and cis-nonachlor, MC-2, and MC-5 were detected in every egg analyzed. Heptachlor, trans-, and cis-chlordane were either not detected, or present at low levels in the eggs. The highest Sigmachlordane levels were found in the East Coast peregrine-falcon eggs at a geometric mean (geom. mean) concentrations of 1800 microg/kg (ppb); the lowest levels of Sigmachlordane were found in the prairie-falcon eggs at a concentration of 120 microg/kg (geom. mean). Of the technical chlordane compounds measured, MC-2 bioaccumulated to the greatest degree. SigmaDDT levels in the falcons ranged from 11 000 microg/kg (geom. mean) in the Colorado samples to 8800 microg/kg (geom. mean) in the East Coast and California peregrines. SigmaDDT levels in the rail eggs were 3000 microg/kg (geom. mean). The highest SigmaPCB levels were found in the East Coast peregrine-falcon eggs at a concentration of 14 000 microg/kg (geom. mean); the lowest levels of SigmaPCB were found in the prairie-falcon eggs at a concentration of 350 microg/kg (geom. mean).     

The contribution of advective fluxes to net ecosystem exchange in a high-elevation, subalpine forest

The eddy covariance technique, which is used in the determination of net ecosystem CO2 exchange (NEE), is subject to significant errors when advection that carries CO2 in the mean flow is ignored. We measured horizontal and vertical advective CO2 fluxes at the Niwot Ridge AmeriFlux site (Colorado, USA) using a measurement approach consisting of multiple towers. We observed relatively high rates of both horizontal (F(hadv)) and vertical (F(vadv)) advective fluxes at low surface friction velocities (u(*)) which were associated with downslope katabatic flows. We observed that F(hadv) was confined to a relatively thin layer (0-6 m thick) of subcanopy air that flowed beneath the eddy covariance sensors principally at night, carrying with it respired CO2 from the soil and lower parts of the canopy. The observed F(vadv) came from above the canopy and was presumably due to the convergence of drainage flows at the tower site. The magnitudes of both F(hadv) and F(vadv) were similar, of opposite sign, and increased with decreasing u(*), meaning that they most affected estimates of the total CO2 flux on calm nights with low wind speeds. The mathematical sign, temporal variation and dependence on u(*) of both F(hadv) and F(vadv) were determined by the unique terrain of the Niwot Ridge site. Therefore, the patterns we observed may not be broadly applicable to other sites. We evaluated the influence of advection on the cumulative annual and monthly estimates of the total CO2 flux (F(c)), which is often used as an estimate of NEE, over six years using the dependence of F(hadv) and F(vadv) on u(*). When the sum of F(hadv) and F(vadv) was used to correct monthly F(c), we observed values that were different from the monthly F(c) calculated using the traditional u(*)-filter correction by--16 to 20 g C x m(-2) x mo(-1); the mean percentage difference in monthly Fc for these two methods over the six-year period was 10%. When the sum of F(hadv) and F(vadv) was used to correct annual Fc, we observed a 65% difference compared to the traditional u(*)-filter approach. Thus, the errors to the local CO2 budget, when F(hadv) and F(vadv) are ignored, can become large when compounded in cumulative fashion over long time intervals. We conclude that the "micrometeorological" (using observations of F(hadv) and F(vadv)) and "biological" (using the u(*) filter and temperature vs. F(c) relationship) corrections differ on the basis of fundamental mechanistic grounds. The micrometeorological correction is based on aerodynamic mechanisms and shows no correlation to drivers of biological activity. Conversely, the biological correction is based on climatic responses of organisms and has no physical connection to aerodynamic processes. In those cases where they impose corrections of similar magnitude on the cumulative F(c) sum, the result is due to a serendipitous similarity in scale but has no clear mechanistic explanation.     

Seasonal variation in male-female competition,cooperation and selfish hoarding in a monogamous songbird

Both cooperation and conflict between the sexes are commonplace in monogamous mating systems. However, little is known about how cooperation and competition varies seasonally in monogamous species that maintain permanent territories. We presented territorial pairs of male and female New Zealand robins (Petroica australis) with a large supply of insect prey at monthly intervals for 2 years. Behavioural observations after food presentation were then made to quantify seasonal and sexual differences in aggressive interactions over prey, prey acquisition rates, mate provisioning, offspring provisioning, selfish food hoarding and cache retrieval. Data were used to evaluate sex-specific behavioural strategies of mediating competition for food. Results showed that males aggressively excluded females from experimental food sources year-round. Females only accessed food sources when males left them unattended. Consequently, females acquired fewer prey than males. After controlling for differences in prey acquisition, both sexes consumed similar amounts of prey in the non-breeding season. Even though males aggressively excluded females from accessing food sources directly, males fed large amounts of prey to females during the breeding season. Both sexes provisioned young at similar rates. Males cached less prey than females in the breeding season but more prey than females in the non-breeding season. Females showed similar caching intensities year-round. Although males tried to defend their hoards, females frequently retrieved male-made caches. Overall, results showed that although New Zealand robins cooperate to raise offspring during the breeding season, conflict between the sexes occurs year-round. Males and females display different behavioural strategies to gain access to experimental food sources, which appear to lessen male–female competition for food and evenly distribute food resources between the sexes.     

Relatedness and environment affect traits associated with invasive and noninvasive introduced Commelinaceae.

Understanding the traits of invasive species may improve the ability to predict, prevent, and manage invasions. I compared morphological and performance traits of five congeneric pairs of invasive and noninvasive Commelinaceae across a factorial experiment using a range of water and nutrient availabilities. Invasive species had greater fecundity and vegetative reproduction than their noninvasive relatives. The invasive species also had higher relative growth rates, greater specific leaf area, and more plastic root-to-shoot ratios than noninvasive species. However, whether a trait was associated with invasiveness often depended on both environment and relatedness. Invasives had greater sexual and vegetative reproduction, higher specific leaf area, and greater relative growth rates than noninvasive congeners, but only in some environments. Differences between invasive and noninvasive taxa were greatest at high nutrient availabilities. These results suggest that studies of invasive species' traits must incorporate information on conditions under which the trait was measured. In addition, incorporating information on relatedness improved our ability to detect associations between species traits, such as specific leaf area and relative growth rate, and invasiveness, suggesting that such information may be required for a complete understanding of what makes a species invasive.     

The toxicity of titanium dioxide nanopowder to early life stages of the Japanese medaka (Oryzias latipes)

In this study, fertilized Japanese medaka (Oryzias latipes) embryos were exposed from fertilization to 5 d post-hatch using static non-renewal assays to aqueous suspensions of titanium dioxide nanoparticles (nTiO₂) ranging in nominal concentrations between 0 and 14 μg mL⁻¹. The average size of the nTiO₂ in the stock solution before addition to the test treatments was 87 nm (±14 nm). TiO₂ materials accumulated in a concentration dependent manner on the chorionic filaments of developing medaka embryos with evidence of pericardial edema occurring during embryo development. However, no significant (p > 0.05) increases in mortality relative to control treatments were observed for the nTiO₂ exposed embryos. A concentration dependent increase in cumulative percent hatch was observed at 11 d, indicating that exposure to increasing concentrations of nTiO₂ resulted in the premature hatch of medaka embryos. Post-hatch, a significant proportion of sac fry from the nTiO₂ exposure groups exhibited moribund swimming behavior and these individuals also experienced greater mortality at 15 d post-hatch. Combined, these results demonstrate that exposure to nTiO₂ can impact the development of early life stages of fish.     

Serum concentrations of chlorinated dibenzo-p-dioxins and dibenzofurans among former New Zealand trichlorophenol workers

This study examined serum levels of 2,3,7,8-substituted chlorinated dioxins and furans, and 15 PCBs for 346 New Zealand employees who worked at a site that manufactured 2,4,5-trichlorophenol (TCP) and 2,4,5-trichlorophenoxy acetic acid (2,4,5-T). Participants with potential TCP or 2,4,5-T exposures had mean lipid-adjusted 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) levels of 9.9 ng kg⁻¹ lipid compared to 4.9 ng kg⁻¹ for workers with no exposure at the site. Among exposed workers, we found evidence of differences in 2,3,7,8-TCDD levels by department and duties. Workers involved in an accidental release had the highest mean 2,3,7,8-TCDD levels, 37.9 ng kg⁻¹, followed by workers in the trichlorophenol plant, 23.4 ng kg⁻¹. Workers with potential intermittent exposures to 2,3,7,8-TCDD in construction, maintenance, mechanics, and transport had 2,3,7,8-TCDD levels above New Zealand background levels of 3.9 ng kg⁻¹, indicating workplace exposures. Among participants with work history indicating no 2,3,7,8-TCDD exposures, we observed some individuals with 2,3,7,8-TCDD levels above background levels. However, in most cases, these workers reported workplace exposures not recorded on their work histories or held other jobs with the potential for 2,3,7,8-TCDD exposures outside the plant. All other dioxin, furan, and PCB levels were similar among the exposed and unexposed workers.