The vapor phase organics (VPOs) in the air of Beijing, Langfang and Tianjin were detected by a capillary gas chromatography and GC/MS during the winter and the summer separately. The tentatively identified compounds include alkanes, cyclic hydrocarbons, alkenes, aromatics, acids, alcohols, aldehydes, ketones, esters, halocarbons and so on. The numbers of VPOs found are 118 in Beijing, 83 in Lang-fang and 65 in Tianjin in the winter, and 56, 39 and 72 in the summer respectively. Based on the data of some representative compounds determined quantitatively by GC and GC/MS, a profile of organic pollution in the air of the three cities is presented. 相似文献
In this paper, the drinking water biotic safety of particles and bacteria attached to fines in activated carbon process was investigated by actual treatment process and advanced treatment pilot trial with granular activated carbon. In the experiment, the particles were detected by IBR particle calculating instrument, the activated carbon fines were counted on the basis of the most probable number (MPN) with a microscope, the total number of bacteria was analyzed between the conventional agar culture medium and the one with R2A, and the bacteria attached to activated carbon fines was resolved by the homogenization technique. The experimental results showed that the average total number of particles was 205 CNT/mL in the activated carbon effluent during a filter cycle, of which the number of particles with sizes > 2 μm was 77 CNT/mL more than the present particle control criterion of the American drinking water product standard (50 CNT/mL). The backwash of low density and long duration lowered particle number in the effluent. The MPN of activated carbon fines in the effluent was between 400 and 600 CNT/L, which accounted for less than 5‰ of the total particles from activated carbon filtration for a poor relative level (R2 = 0.34). The microorganisms in activated carbon effluent consisted mostly of heterotrophic bacillus and the total bacteria number was five times as high as that of the inflow, i.e. the effluent from sand filter. The actual bacteria number may be truly indicated by the detection technique with R2A culture medium compared with the traditional agar cultivation. The inactivation efficiency of bacteria attached to activated carbon fines was less than 40% under 1.1 mg/L of chlorine contacting for 40 min. Results showed that the particles and bacteria attached to activated carbon fines may influence drinking water biotic safety, and that the effective control measures need to be further investigated. 相似文献
Pteris vittata was the first terrestrial plant known to hyperaccumulate arsenic (As). However, it is unclear how As hyperaccumulation influences nutrient uptake by this plant. P. vittata fern was grown in soil spiked with 0-500 mg As kg(-1) in the greenhouse for 24 weeks. The concentrations of essential macro- (P, K, Ca, and Mg) and micro- (Fe, Mn, Cu, Zn, B and Mo) elements in the fronds of different age were examined. Both macro- and micronutrients in the fronds were found to be within the normal concentration ranges for non-hyperaccumulators. However, As hyperaccumulation did influence the elemental distribution among fronds of different age of P. vittata. Arsenic-induced P and K enhancements in the fronds contributed to the As-induced growth stimulation at low As levels. The frond P/As molar ratios of 1.0 can be used as the threshold value for normal growth of P. vittata. Potassium may function as a counter-cation for As in the fronds as shown by the As-induced K increases in the fronds. The present findings not only demonstrate that P. vittata has the ability to maintain adequate concentrations of essential nutrients while hyperaccumulating As from the soil, but also have implications for soil management (fertilization in particular) of P. vittata in As phytoextraction practice. 相似文献
Organophosphate pesticides (OPPs) are one type of the most massively used pesticides and ubiquitously detected in aquatic environments, which may pose potential risks to the aquatic organisms and human health. In the present study, the spatiotemporal distribution and potential risks of OPPs were investigated in overlying water and surficial sediments from urban waterways of Guangzhou. For all studied sites, in general, four target OPPs (i.e., malathion, chlorpyrifos, terbufos, and diazinon) were present in the overlying water, with malathion and chlorpyrifos as major components. Higher concentrations of the four OPPs were found for the water and sediments collected in the dry season compared to the wet season, possibly because of the dilution effect of heavy rains. The results of Pearson’s analyses and principal coordinate analyses (PCoA) suggested similar sources for target OPPs in the water and sediments across the Guangzhou urban waterways. Potential ecological risks of the OPPs to three representative taxons (algae, aquatic invertebrates, and fish) were evaluated via toxic units (TUs) and risk quotients (RQs), while risk assessment on human health was performed using hazard index (HI). Although TU results showed no acute risks to the aquatic organisms in the overlying water and surface sediments, RQ results of the mixture showed high risks to the aquatic invertebrate and fish in all water samples. Individual HI values and cumulative HI values were on the order of 10?6–10?3 for children and adults, suggesting no potential risks to either children or adults through drinking and bathing.