排序方式： 共有7条查询结果，搜索用时 15 毫秒
1
1.
Loska Krzysztof Cebula Jan Pelczar Jacek Wiechuła Danuta Kwapuliński Jerzy 《Water, air, and soil pollution》1997,93(1-4):347-365
In this paper, the contamination degree of the Rybnik Reservoir with cadmium, copper and nickel was analyzed. Quality of the water from the reservoir was determined by drawing comparisons between the metal content in the water and both the officially permitted levels (contamination factor) and levels of metals occurring in the water of non-contaminated areas (enrichment factor). Contamination of bottom sediment with chosen metals was analyzed with reference to the metal content in mudstone (geoaccumulation index, enrichment factor, contamination factor). Trends towards changing the metal content in the bottom sediment was analyzed by determining the enrichment factor of the surface layer of the bottom sediments in relation to a deeper layer. Enrichment of the bottom sediments with metals coming from the water was also determined. 相似文献
2.
We examine the impact of differences in state‐level higher education policies on location choices of undocumented immigrants in the U.S. using six years of available data over the period 2000 to 2012. The effect of greater access to higher education on the percentage of undocumented migrants residing in a state is positive, suggesting the existence of a “higher public education magnet” effect. Among states with favorable higher education policies, undocumented migrants prefer those states with larger networks, despite the likelihood of greater competition for admission to public institutions of higher education. However, undocumented migrants are reluctant to locate in states that have both large networks and unfavorable educational policies. This is possibly because the fear of attracting additional restrictive regulations dominates the positive cost‐saving effect of large networks. 相似文献
3.
Changes of chemical forms of metallic zinc and zinc sulfide during the composting process of municipal solid waste in oxygen conditions have been determined. Speciation of zinc was carried out by means of sequential extraction. It has been found that contamination of the waste with Zn is dangerous to the environment because zinc accumulates in bioavailable forms - organically bound and carbonate. Zinc sulfide remains mainly in a less mobile sulfide form. The composting process increases the mobility of zinc insignificantly. 相似文献
4.
5.
Turek Marian Korolewicz Teofil Ciba Jerzy Cebula Jan 《Water, air, and soil pollution》2002,135(1-4):311-323
Total content of zinc and other metals has been assayed in thesludge that remained after leaching zinc-bearing smelting losswith sulfuric acid. The paper also presents zinc speciationcarried out by means of the sequential extraction by Rudd and an analysis of chemical forms of zinc. It has been found thatzinc occurs mainly in the mobile, bioavailable, soluble form and in the moderately mobile, carbonate form. The speciationcarried out showed that zinc occurred in the sludge in the following forms (mg kg-1): sulfate 143 000, oxide 79 000,metallic 68 200, siliceous 35 500, sulfide 20 800 and ferrate18 500. Preparatory extraction of zinc from the sludge usingwater, sodium salt of ethylenediaminetetraacetic acid (EDTA)and acetic acid has also been conducted. 相似文献
6.
D A Wink K S Kasprzak C M Maragos R K Elespuru M Misra T M Dunams T A Cebula W H Koch A W Andrews J S Allen 《Science (New York, N.Y.)》1991,254(5034):1001-1003
Nitric oxide (NO), a multifaceted bioregulatory agent and an environmental pollutant, can also cause genomic alterations. In vitro, NO deaminated deoxynucleosides, deoxynucleotides, and intact DNA at physiological pH. That similar DNA damage can also occur in vivo was tested by treating Salmonella typhimurium strain TA1535 with three NO-releasing compounds, including nitroglycerin. All proved mutagenic. Observed DNA sequence changes were greater than 99% C----T transitions in the hisG46 (CCC) target codon, consistent with a cytosine-deamination mechanism. Because exposure to endogenously and exogenously produced NO is extensive, this mechanism may contribute to the incidence of deamination-related genetic disease and cancer. 相似文献
7.
Abstract. Total concentrations of heavy metals in soils were measured before and after the catastrophic floods of 1997, which devastated most districts within the commune of Racibórz in southern Poland. The assays covered lead, zinc, cadmium, chromium, nickel and copper. Analyses on soil samples taken in 2002, after the floods, were compared with those of 1992, taken as part of regular monitoring. There was an increase in the mean concentrations of heavy metals as a consequence of the flooding. Only a small part of this increase may be due to changes in the method of analysis between the two dates. The mean concentrations of heavy metals after flooding did not exceed the permissible levels for Polish soils. Permission was therefore granted to continue using much of the flooded land for farming. However, the investigations located a number of places where heavy metals were above permissible levels. Some of these were a consequence of the floods, but others were considered to be due to contamination from previous industry. Where high concentrations were found, land was excluded from agricultural use. 相似文献
1