Dam reverse flow events influence limnological variables and fish assemblages of a downstream tributary in a Neotropical floodplain

We used a dam‐free tributary (the Baía River) in the upper Paraná River floodplain downstream of a major dam in the Paraná River, Brazil to investigate the effects of dam‐regulated reverse flow on limnological variables and fish. We tested the hypotheses that limnological variables in tributaries change based on flow direction and that fish assemblages respond to this variation. Sampling sites were determined considering flow direction (normal or reverse) and position (near or far from the river mouth). Limnological variables showed higher values for transparency, oxygen, pH, and electrical conductivity at sites near the mouth of the Baía River during reverse flow. Species richness and evenness differed significantly in relation to position, with higher values closer to the Paraná River. The average standard length of fish species was higher near the mouth of the Baía River and during the reverse flow period. No significant differences in species abundance were found. Reverse flow into the Baía River brought nutrient‐poor water from the dammed Paraná River, thereby altering the limnological variables. This flow condition impelled the entry of species with higher average standard lengths. However, increased species richness and low evenness were due to the increase in species dispersal rates under all flow conditions. Our results emphasize that the effects of dams can extend several kilometres into the floodplain, provide basic knowledge on the effects of major dams on downstream pristine tributaries, and highlight the need for further studies to understand the wider influences.     

老年人弥补性景观及其规划设计初探

中国已进入老龄化社会。随着养老方式的转变,户外环境将承担越来越多的“养老”功能。老年人对户外环境有各种特殊需求,需要大量弥补性景观。应在空间布局、交通组织、景观要素和服务设施等方面深入探讨老年人弥补性景观的规划设计要点。     

Recycling by injection and chrome plating of acrylonitrile–butadiene–styrene parts pickled in hydrochloric and nitric acids

Chrome-plated acrylonitrile–butadiene–styrene ( ABS) parts with defects in the metal layer were submitted to pickling with hydrochloric and nitric acids and recycled by injection in different proportions with neat ABS. For comparison, samples with neat ABS (ABSn) and ABS submitted to pickling (ABSp) were also injected. The influence of the pickled material on the samples properties was evaluated by chemical, thermal, and mechanical analysis. The injected samples were chrome by conventional process and evaluated by visual inspection, adhesion test, resistance to corrosion, and accelerated aging test, to evaluate the quality of the chrome finish. A gradual darkening of samples and formation of carbonyl groups with the increase in the pickled ABS concentration and little influence on the melt flow index were observed. The samples exhibited one thermal degradation stage similar to ABSn. The increase in the pickled ABS percentage caused a slight increase in glass-transition temperature of polybutadiene phase, and did not influence the tensile properties and hardness of samples, but decreased the impact resistance. After chrome plating, all samples were approved for visual inspection and metal layer adhesion test. Only the sample injected with pickled ABS was reproved in corrosion test, due to the oxidation of the chrome layer. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48372.