Adsorption of Lead Ions by Linde type F(K) Zeolite

The Test was to examine the adsorption property of Pb(II) irons by Linde type F (K) zeolite. The zeolite was synthesized by fly ash. The adsorbent dosage, pH, reaction temperature and reaction time were investigated. The adsorption isotherm and adsorption kinetics equation were studied. The results showed the adsorbent dosage, pH, reaction temperature and reaction time had significant effects on the adsorption of Pb(II) irons. The removal rate was improved with the increasing of zeolite dosage. The saturated adsorption capacity was decreased gradually. The adsorption of Pb(II) irons tended to saturate when initial pH was 6. With the increasing of temperature, the equilibration time of adsorption was shorter. Langmuir isotherm was more applicable to explain the monolayer adsorption procedure of Pb(II) on Linde type F(K) zeolite. For adsorption kinetics, pseudo-second order model showed better calculation results

Effects of microplastic biofilms on nutrient cycling in simulated freshwater systems

Microplastic surfaces could be colonized by microorganisms and form biofilms in aquatic ecosystem, which can participate in the nitrogen (N) and phosphorus (P) cycles. In this work, polypropylene squares were deployed in a pond for 30 clays for microplastic biofilms colonization and then were transported to indoor microcosms at an environmental relevant level to study their effects on N and P cycling. Results showed that microplastic biofilms could accelerate ammonia and nitrite oxidation as well as denitrification. Presence of microplastic biofilms accumulated P temporarily and increased alkaline phosphatase activities (APA) in the system. Later in the experiment, disintegration of matured biofilms released N and P into the water. Mass balance calculation suggested possible N input caused by biological nitrogen fixation. Our results demonstrated that microplastics associated biofilms have the ability to alter the N and P cycling processes in aquatic system. However, additional works are required to further quantify the extent of such impact. (C) 2020 Elsevier B.V. All rights reserved

Dual Function Behavior of Carbon Fiber-Reinforced Polymer in Simulated Pore Solution

The mechanical and electrochemical performance of carbon fiber-reinforced polymer (CFRP) were investigated regarding a novel improvement in the load-carrying capacity and durability of reinforced concrete structures by adopting CFRP as both a structural strengthener and an anode of the impressed current cathodic protection (ICCP) system. The mechanical and anode performance of CFRP were investigated in an aqueous pore solution in which the electrolytes were available to the anode in a cured concrete structure. Accelerated polarization tests were designed with different test durations and various levels of applied currents in accordance with the international standard. The CFRP specimens were mechanically characterized after polarization. The measured feeding voltage and potential during the test period indicates CFRP have stable anode performance in a simulated pore solution. Two failure modes were observed through tensile testing. The tensile properties of the post-polarization CFRP specimens declined with an increased charge density. The CFRP demonstrated success as a structural strengthener and ICCP anode. We propose a mathematic model predicting the tensile strengths of CFRP with varied impressed charge densities

Sinking of floating plastic debris caused by biofilm development in a freshwater lake

Plastic pollution has been increasingly reported in both marine environment and inland waters, but their fate is not well understood. Several studies have showed that the surface of plastic debris can be colonized by microbes, leading to the sinking of floating plastic debris in marine environment. In this work, development of biofilm on polypropylene sheet (squares with a side length of 5 and 10 mm) and their buoyancy changes were studied in a freshwater lake in four seasons. Results showed that biofilm development have different growth rate and distinct algae composition in different seasons, which are mainly related to the difference in temperature, nutrient levels, and suspend solids in lake water. Biofilm development was much quicker on small plastics in all seasons. At the end of the experiment, all plastics lost buoyancy in summer while only a small portion lost buoyance in other seasons. Sinking of the floating plastics can be attributed to the development of biofilm and the trapped minerals. Our results demonstrated that biofilm development can cause the sinking of floating plastics in fresh lakes but the time required to lose buoyance can differ seasonally. Floating plastics will remain in water for a longer time in cold season but sink in a short time in warm season. Future research is required to determine the influence of plastic types and shapes, and quantitative relation between environmental variables and the sinking behavior of the fouled plastics should be established for a better prediction of their fate in the freshwater environment. (C) 2019 Elsevier Ltd. All rights reserved

Sources and distribution of microplastics in China's largest inland lake - Qinghai Lake

Microplastic pollution was studied in China&#39;s largest inland lake Qinghai Lake in this work. Micro plastics were detected with abundance varies from 0.05 x 10(5) to 7.58 x 10(5) items km(-2) in the lake surface water, 0.03 x 10(5) to 0.31 x 10(5) items km-2 in the inflowing rivers, 50 to 1292 items m(-2) in the lakeshore sediment, and 2 to 15 items per individual in the fish samples, respectively. Small microplastics (0.1-0.5 mm) dominated in the lake surface water while large microplastics (1-5 mm) are more abundant in the river samples. Microplastics were predominantly in sheet and fiber shapes in the lake and river water samples but were more diverse in the lakeshore sediment samples. Polymer types of microplastics were mainly polyethylene (PE) and polypropylene (PP) as identified using Raman Spectroscopy. Spatially, microplastic abundance was the highest in the central part of the lake, likely due to the transport of lake current. Based on the higher abundance of microplastics near the tourist access points, plastic wastes from tourism are considered as an important source of microplastics in Qinghai Lake. As an important area for wildlife conservation, better waste management practice should be implemented, and waste disposal and recycling infrastructures should be improved for the protection of Qinghai Lake. (C) 2018 Elsevier Ltd. All rights reserved.</p

The hydro-fluctuation belt of the Three Gorges Reservoir: Source or sink of microplastics in the water?

Reservoirs can be an important environmental compartment for microplastic pollution. Previous investigations have found that surface waters and sediments in the Three Gorges Reservoir (TGR) have had high microplastic abundance, and the Xiangxi River, which is one of the largest primary tributaries of the TGR, has had much higher microplastic abundance than several marine and freshwater systems in China. A strip of land on the bank of the reservoir area, which is called the hydro-fluctuation belt (HFB), is periodically exposed due to the special hydrodynamic conditions in the TGR The HFB may be an important source and/or sink of microplastics in TGR. In this study, microplastic occurrence in sediments from the Xiangxi River HFB was investigated to reflect the local microplastic pollution status and to evaluate its potential to serve as a source/sink of microplastics in the TGR Seven sampling sites were selected, and sediments within the HFB and above the belt were collected in summer when the water level was low. The results showed that the microplastic abundance ranged from 0.55 +/- 0.12 x 10(3) to 14.58 +/- 5.67 x 10(3) particles m(-2), which was one to two orders of magnitude higher than that in sediments from the Xiangxi River in our previous study (80-846 particles m(-2)). Statistical analysis revealed that the microplastic abundance within the HFB was significantly higher than that of the area above the HFB. The results indicate that the HFB can be an important microplastic sink when the water level is low, and the belt can turn into a potential source when the water level is high. Cluster analysis was applied to reveal the characteristics of the microplastics collected at different sites, and the results suggest that the cluster analysis may be a useful tool in elucidating the source and fate of microplastics. (C) 2019 Elsevier Ltd. All rights reserved