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611.
研究聚丙烯酸钠(PAAS)溶液的超滤行为,考察各操作参数对膜通量(J)和截留系数(R)的影响,结果表明,J随运行时间延长衰减不明显,随压差增大呈线性递增,随温度升高而增大,pH高于5时J基本不变;R随压差增大或温度升高均下降,随pH增大而增大。建立膜阻力(rf)模型,研究影响rf的主要因素,发现,rf随压差增大而增大,随温度升高而减少,pH低于5时rf随pH增大而迅速下降。研究PAAS溶液浓缩过程,当体积浓缩因子为16时,J衰减明显,截留液PAAS浓度(Cr)呈线性递增,渗透液PAAS浓度(Cp)在较长时期内基本不变,至浓缩后期,Cp轻微下降。以去离子水对浓缩液予以洗涤,随着洗涤液体积增大,Cr轻微下降,Cp逐渐趋于零。 相似文献
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Gillis PL 《Environmental pollution (Barking, Essex : 1987)》2011,159(6):1702-1708
Chloride concentrations in surface waters have increased significantly, a rise attributed to road salt use. In Canada, this may be a concern for endangered freshwater mussels, many with ranges limited to southern Ontario, Canada’s most road-dense region. The acute toxicity of NaCl was determined for glochidia, the mussel’s larval stage. The 24 h EC50s of four (including two Canadian endangered) species ranged from 113-1430 mg Cl L−1 (reconstituted water, 100 mg CaCO3 L−1). To determine how mussels would respond to a chloride pulse, natural river water (hardness 278-322 mg CaCO3 L−1) was augmented with salt. Lampsilis fasciola glochidia were significantly less sensitive to salt in natural water (EC50s 1265-1559 mg Cl L−1) than in reconstituted water (EC50 285 mg L−1). Chloride data from mussel habitats revealed chloride reaches levels acutely toxic to glochidia (1300 mg L−1). The increased salinization of freshwater could negatively impact freshwater mussels, including numerous species at risk. 相似文献
614.
土壤盐分含量(SSC)是评价土地退化和肥力水平的重要指标,实现SSC状态和空间分异的快速准确监测对区域环境的优化管理极为关键。选取潍北平原为研究区,野外采集233处土壤样品并获取同时相Sentinel-2多光谱影像,进一步将特征光谱波段和构建的最优光谱指数作为输入自变量,测试得到的SSC实测值为因变量,最后将空间关联函数引入到随机森林中去建立基于空间关联随机森林算法的SSC遥感估算模型,完成区域尺度上的SSC反演估算与空间制图。结果表明:影像的B3、B8和B11是SSC的特征波段,通过波段比值变换能够增强卫星光谱信号对SSC的吸收响应,筛选得到的最优光谱指数分别为RI34(波段3和波段4的反射率比值)、RI711(波段7和波段11的反射率比值)、ND611(波段6和波段11的反射率归一化值)和D45(波段4和波段5的反射率差值);仅用特征波段或最优光谱指数来构建模型不能取得满意的SSC估算精度,空间关联随机森林模型的SSC估算精度要高于随机森林模型;在将上述特征波段和最优光谱指数共同输入空间关联随机... 相似文献
615.
Cecilia Cullen Daniel B. Abrams Devin H. Mannix Walton R. Kelly 《Journal of the American Water Resources Association》2023,59(3):539-553
Winter deicers are a major source of chloride contamination to shallow aquifers in northern latitudes. In the greater Chicago area of northeast Illinois, chloride has been accumulating for decades and in many places now exceeds the United States Environmental Protection Agency secondary standard of 250 mg/L. MODFLOW-NWT and MT3D-USGS were used to simulate the accumulation of chloride with 30 years of data in the shallow aquifer of Will County in northeast Illinois. This aquifer is composed of unconsolidated sediments, largely from glacial deposits, overlying a fractured dolomite bedrock. To calibrate to observed heads and chloride, the model needed refined geologic features, higher chloride concentrations on cells representing commercial or industrial lands, lower chloride concentrations on cells representing roads, and point source areas to speed chloride's emergence in the aquifer. These point sources are locally significant and could represent different anthropogenic or geologic features, such as municipal stormwater infrastructure. Future simulations indicate that chloride is not at steady state in the shallow aquifer and wells are at risk of exceeding the secondary standard if winter deicing applications are not reduced. It may take decades for the full impacts of reduced deicing rates to be observed in wells, owing to the long residence time of water in the aquifer. This transient model calibration was possible because of the 30-year dataset collected by communities and government agencies. 相似文献
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617.
ABSTRACTThis study investigated the potential influence of three organic ameliorators (peat, biochar and leonardite) on salts and nutrients in salt-affected soils during intermittent leaching. Results showed that nearly 90% of salt was removed from columns in the leaching process and sodium adsorption ratio (SAR) of the soil after leaching was reduced by 67.3% (control, CK), 62.9% (peat), 70.1% (biochar) and 55.0% (leonardite). Total N loss declined by 26.2% (peat), 11.7% (biochar) and 55.5% (leonardite) compared with CK in the process of leaching. The maintaining N (NH4+ and NO3?) of soil after leaching was 8.25, 7.31, 11.31 and 14.48?mg/kg for CK, peat, biochar and leonardite treatments. Final P loss was 0.47, 0.31, 0.54, 0.27?mg/column in leaching for CK, peat, biochar and leonardite treatments. Soluble P of soil after leaching was measured as 6.95 (CK), 5.62 (peat), 8.52 (biochar) and 3.33 (leonardite) mg/kg. Leaching could remove the salt effectively but with nutrient loss in the process. The findings of this study suggest that organic ameliorators (biochar, peat or leonardite) play an important role in retaining nutrients during leaching as well as supplying nutrients after leaching to offer practical assistance for the amendment of salt-affected soil in the Yellow River Delta. 相似文献
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619.
Microcosm investigations of stormwater pond sediment toxicity to embryonic and larval amphibians: variation in sensitivity among species 总被引:2,自引:0,他引:2
Snodgrass JW Casey RE Joseph D Simon JA 《Environmental pollution (Barking, Essex : 1987)》2008,154(2):291-297
Stormwater ponds have become common features of modern development and often represent significant amounts of open space in urbanized areas. Although stormwater ponds may provide habitat for wildlife, factors responsible for producing variation in wildlife use of ponds have received limited attention. To investigate the role of variation in species tolerances of pollutants in structuring pond-breeding amphibian assemblages, we exposed species tolerant (Bufo americanus) and not tolerant (Rana sylvatica) of urbanization to pond sediments in laboratory microcosms. Pond microcosms had elevated sediment metal levels and chloride water concentrations. Among R. sylvatica embryos, exposure to pond sediments resulted in 100% mortality. In contrast, B. americanus embryos and larvae experienced only sublethal effects (i.e., reduced size at metamorphosis) due to pond sediment exposure. Our results suggest variation in pollutant tolerance among early developmental stages of amphibians may act in concert with terrestrial habitat availability to structure amphibian assemblages associated with stormwater ponds. 相似文献
620.