Grafting of (2-methacryloyloxyethyl) trimethyl ammonium chloride onto chitosan through gamma-radiation in acidic aqueous solutions was achieved for production of a novel flocculant. The grafted copolymer was characterized by Fourier-transform infrared, X-ray powder diffraction and thermogravimetric analysis. The effects of reaction parameters, such as total absorbed dose, dose rate, monomer concentration and temperature, on grafting percentage were investigated. The flocculation capacities of the grafted copolymer were evaluated with 0.25% (w/v) kaolin suspensions using the standard jar test. The results demonstrate the superiority of the grafted copolymer over chitosan as a flocculant. 相似文献
Acid volatile sulfide (AVS) has been regarded as an important factor controlling metal bioavailability in anoxic sediments, but its effect on metal accumulation under natural conditions is poorly understood. Here, a field study of the influence of AVS on metal accumulation by Limnodrilus sp. in a heavily polluted river is provided. Most of the study area was subject to anaerobic and strongly reducing conditions, and the concentration of trace metals in surface sediments was high, as were the concentration of AVS and simultaneously extracted metals (SEM; average AVS?=?20.3 μmol g?1, average ∑SEM5?=?9.42 μmol g?1; ∑SEM5 refers to the sum of SEMCd, SEMCu, SEMPb, SEMNi, and SEMZn). Only a few species and small quantities of benthic invertebrates were found, and Limnodrilus sp. was dominant. There was no correlation between trace metal accumulation and (SEM-AVS), and in stations where (SEM-AVS) <0, the absolute value of bioaccumulation was high (average ∑BIO5?=?4.07 μmol g?1; ∑BIO5 refers to the sum of BIOCd, BIOCu, BIOPb, BIONi, and BIOZn), indicating that there was no relationship between (SEM–AVS) and metal accumulation in Limnodrilus sp. This was likely because Limnodrilus sp. ingest sediment particles as their main food source, so pore water metals play a minor role in their bioaccumulation (BIO) of materials. However, ∑BIO5 was significantly correlated with ∑SEM5 (r?=?0.795, p?<?0.01), revealing that the large number of sulfide-bound metals (SEM) in sediments may play an important role in metal accumulation in Limnodrilus sp., which can assimilate sulfide-associated metals by the help of the digestive fluids in the digestive systems. 相似文献
Technological innovation is one of the potential engines to mitigate environmental pollution. However, the implementation of new technologies sometimes fails owing to socioeconomic constraints from different stakeholders. Thus, it is essential to analyze constraints of environmental technologies in order to build a pathway for their implementation. In this study, taking three technologies on rural sewage treatment in Hangzhou, China as a case study, i.e., wastewater treatment plant (WTP), constructed wetland (CW), and biogas system, we analyzed how socioeconomic constraints affect the technological choices. Results showed that socioeconomic constraints play a key role through changing the relative opportunity cost of inputs from government as compared to that of residents to deliver the public good—sewage treatment—under different economic levels. Economic level determines the technological choice, and the preferred sewage treatment technologies change from biogas system to CW and further to WTP along with the increase of economic level. Mismatch of technological choice and economic level results in failures of rural sewage treatment, e.g., the CW only work well in moderately developed regions in Hangzhou. This finding expands the environmental Kuznets law by introducing the coproduction theory into analysis (i.e., inputs from both government and residents are essential for the delivery of public goods and services such as good environmental quality). A match between technology and socioeconomic conditions is essential to the environmental governance.