Concentrations of nitrate and trace elements such as arsenic,cadmium,chromium,copper,manganese,nickel,lead,selenium,antimony and mercury in 18 different brands of bottled water were investigated.For comparison,samples of tap and well water from three different places of Tehran were also analyzed.UV/VIS spectrophotometer and Graphite Furnace Atomic Absorption Spectrometer were used for the analysis of nitrate and trace elements,respectively.Results obtained were compared to Iranian,World Health Organization(WHO)and Environmental Protection Agency(EPA)guideline for drinking water.Nitrate concentration in bottled,tap and well water samples were in maximum safe nitrate concentration of Iranian and WHO standards.However,70%of bottled water samples and one sample of tap water were below the standard level proposed by EPA and probably remedial action should be taken.Concentration levels of all analyzed elements investigated in all examined water samples were below the maximum contaminant level prescribed by Iranian,WHO and EPA regulations. 相似文献
Marine aquaculture in semi-enclosed bays can significantly influence nutrient cycling in coastal ecosystems. However, the impact of marine aquaculture on the dynamics of dissimilatory nitrate reduction processes (DNRPs) and the fate of reactive nitrogen remain poorly understood. In this study, the rates of DNRPs and the abundances of related functional genes were investigated in aquaculture and non-aquaculture areas. The results showed that marine aquaculture significantly increased the denitrification (DNF) and dissimilatory nitrate reduction to ammonium (DNRA) rates and decreased the rate of anaerobic ammonium oxidation (ANA), as compared with non-aquaculture sites. DNF was the dominant pathway contributing to the total nitrate reduction, and its contribution to the total nitrate reduction significantly increased from 66.72% at non-aquaculture sites to 78.50% at aquaculture sites. Marine aquaculture can significantly affect the physicochemical characteristics of sediment and the abundances of related functional genes, leading to variations in the nitrate reduction rates. Although nitrate removal rates increased in the marine aquaculture area, ammonification rates and the nitrogen retention index in the aquaculture areas were 2.19 and 1.24 times, respectively, higher than those at non-aquaculture sites. Net reactive nitrogen retention exceeded nitrogen removal in the aquaculture area, and the retained reactive nitrogen could diffuse with the tidal current to the entire bay, thereby aggravating N pollution in the entire study area. These results show that marine aquaculture is the dominant source of nitrogen pollution in semi-enclosed bays. This study can provide insights into nitrogen pollution control in semi-enclosed bays with well-developed marine aquaculture. 相似文献
ABSTRACT: Excessive nitrate‐nitrogen (nitrate) export from the Raccoon River in west central Iowa is an environmental concern to downstream receptors. The 1972 to 2000 record of daily streamflow and the results from 981 nitrate measurements were examined to describe the relation of nitrate to streamflow in the Raccoon River. No long term trends in streamflow and nitrate concentrations were noted in the 28‐year record. Strong seasonal patterns were evident in nitrate concentrations, with higher concentrations occurring in spring and fall. Nitrate concentrations were linearly related to streamflow at daily, monthly, seasonal, and annual time scales. At all time scales evaluated, the relation was improved when baseflow was used as the discharge variable instead of total streamflow. Nitrate concentrations were found to be highly stratified according to flow, but there was little relation of nitrate to streamflow within each flow range. Simple linear regression models developed to predict monthly mean nitrate concentrations explained as much as 76 percent of the variability in the monthly nitrate concentration data for 2001. Extrapolation of current nitrate baseflow relations to historical conditions in the Raccoon River revealed that increasing baseflow over the 20th century could account for a measurable increase in nitrate concentrations. 相似文献
In order to obtain a better understanding of the non-ideal detonation behaviour of ammonium nitrate based explosives, detonation velocities of ANFO (ammonium nitrate and fuel oil) prepared with different kinds of ammonium nitrate (AN) were measured in steel tubes. In this series of test six kinds of AN were used and the influence of the pore diameter, the pore volume and the particle diameter of the AN particle on the detonation velocity of ANFO was investigated.
It was found that the pore diameter and the pore volume had a strong influence on the detonation velocities of ANFO. In the case of ANFO samples which were prepared with AN that had the same pore diameter and the pore volume, when tested the highest detonation velocity (3.85 km/s) was observed when the smallest particle diameter (<0.85 mm) was used. This value corresponded to 75% of the ideal detonation velocity, which was theoretically predicted by the CHEETAH code with the JCZ3-EOS.
The 12 months aging showed the change of the detonation velocities of ANFO and the reaction of ANFO was influenced both by the physical and the chemical properties of AN particles and oil during the storage period. 相似文献