环境与自然资源保护统一立法的必要性

该文从理论基础和现实意义两个方面对环境与自然资源保护统一立法的必要性做了浅要分析。     

上海天然水中铀含量

一分析仪对上海市天然水体中的铀含量进行了１０年连续监测，并比较了不同水体的铀含量，描述了其分布及其变化情况。结果表明，上海天然水体中铀含量的范围为０．０５－０８９μｇ＝Ｌ，属我国天然水铀含量本底范围。     

Comparison between background concentrations of arsenic in urban and non-urban areas of Florida

Arsenic contamination is of great environmental concern due to its toxic effects as a carcinogen. Knowledge of arsenic background concentrations is important for land application of wastes and for making remediation decisions. The soil clean-up target level for arsenic in Florida (0.8 and 3.7 mg kg⁻¹ for residential and commercial areas, respectively) lies within the range of both background and analytical quantification limits. The objective of this study was to compare arsenic distribution in urban and non-urban areas of Florida. Approximately 440 urban and 448 non-urban Florida soil samples were compared. For urban areas, soil samples were collected from three land-use classes (residential, commercial and public land) in two cities, Gainesville and Miami. For the non-urban areas, samples were collected from relatively undisturbed non-inhabited areas. Arsenic concentrations varied greatly in Gainesville, ranging from 0.21 to approximately 660 mg kg⁻¹ with a geometric mean (GM) of 0.40 mg kg⁻¹, which were lower than Miami samples (ranging from 0.32 to 112 mg kg⁻¹; GM=2.81 mg kg⁻¹). Arsenic background concentrations in urban soils were significantly greater and showed greater variation than those from relatively undisturbed non-urban soils (GM=0.27 mg kg⁻¹) in general.     

Biophysical energy analyses of non-market values of the Ebro Delta

Non-market values were estimated with energy analysis under four land cover scenarios in the Ebro Delta, Spain. The market value of agriculture, the primary use value, is compared. Conversion of the natural landscape to agricultural fields has resulted in a drop in total annual non-market value from $721 million in the pristine scenario to $11 million in the present scenario. The market value of the agricultural crops has risen over time, from $10 million to almost $52 million, contributing the major portion of the total value of the Delta. However, the rate of return has decreased from the pristine to the present delta, indicating that more energy is required to produce a smaller output. Energy analyses reveal that one form of value—non-market value—is being traded for another—market value.     

Assessing microbial degradation of o-xylene at field-scale from the reduction in mass flow rate combined with compound-specific isotope analyses

In recent years, natural attenuation (NA) has evolved into a possible remediation alternative, especially in the case of BTEX spills. In order to be approved by the regulators, biodegradation needs to be demonstrated which requires efficient site investigation and monitoring tools. Three methods--the Integral Groundwater Investigation method, the compound-specific isotope analysis (CSIA) and a newly developed combination of both--were used in this work to quantify at field scale the biodegradation of o-xylene at a former gasworks site which is heavily contaminated with BTEX and PAHs. First, the Integral Groundwater Investigation method [Schwarz, R., Ptak, T., Holder, T., Teutsch, G., 1998. Groundwater risk assessment at contaminated sites: a new investigation approach. In: Herbert, M. and Kovar, K. (Editors), GQ'98 Groundwater Quality: Remediation and Protection. IAHS Publication 250, pp. 68-71; COH 4 (2000) 170] was applied, which allows the determination of mass flow rates of o-xylene by integral pumping tests. Concentration time series obtained during pumping at two wells were used to calculate inversely contaminant mass flow rates at the two control planes that are defined by the diameter of the maximum isochrone. A reactive transport model was used within a Monte Carlo approach to identify biodegradation as the dominant process for reduction in the contaminant mass flow rate between the two consecutive control planes. Secondly, compound-specific carbon isotope analyses of o-xylene were performed on the basis of point-scale samples from the same two wells. The Rayleigh equation was used to quantify the degree of biodegradation that occurred between the wells. Thirdly, a combination of the Integral Groundwater Investigation method and the compound-specific isotope analysis was developed and applied. It comprises isotope measurements during the integral pumping tests and the evaluation of delta13C time series by an inversion algorithm to obtain spatially integrated mean isotope values at the control planes. It was shown that the Rayleigh equation is applicable to spatially integrated mean isotope values in order to obtain the mean biodegradation between the consecutive control planes. All three approaches yielded consistently a 98-99% degradation of o-xylene.     

Inverse modeling of BTEX dissolution and biodegradation at the Bemidji, MN crude-oil spill site

The U.S. Geological Survey (USGS) solute transport and biodegradation code BIOMOC was used in conjunction with the USGS universal inverse modeling code UCODE to quantify field-scale hydrocarbon dissolution and biodegradation at the USGS Toxic Substances Hydrology Program crude-oil spill research site located near Bemidji, MN. This inverse modeling effort used the extensive historical data compiled at the Bemidji site from 1986 to 1997 and incorporated a multicomponent transport and biodegradation model. Inverse modeling was successful when coupled transport and degradation processes were incorporated into the model and a single dissolution rate coefficient was used for all BTEX components. Assuming a stationary oil body, we simulated benzene, toluene, ethylbenzene, m,p-xylene, and o-xylene (BTEX) concentrations in the oil and ground water, respectively, as well as dissolved oxygen. Dissolution from the oil phase and aerobic and anaerobic degradation processes were represented. The parameters estimated were the recharge rate, hydraulic conductivity, dissolution rate coefficient, individual first-order BTEX anaerobic degradation rates, and transverse dispersivity. Results were similar for simulations obtained using several alternative conceptual models of the hydrologic system and biodegradation processes. The dissolved BTEX concentration data were not sufficient to discriminate between these conceptual models. The calibrated simulations reproduced the general large-scale evolution of the plume, but did not reproduce the observed small-scale spatial and temporal variability in concentrations. The estimated anaerobic biodegradation rates for toluene and o-xylene were greater than the dissolution rate coefficient. However, the estimated anaerobic biodegradation rates for benzene, ethylbenzene, and m,p-xylene were less than the dissolution rate coefficient. The calibrated model was used to determine the BTEX mass balance in the oil body and groundwater plume. Dissolution from the oil body was greatest for compounds with large effective solubilities (benzene) and with large degradation rates (toluene and o-xylene). Anaerobic degradation removed 77% of the BTEX that dissolved into the water phase and aerobic degradation removed 17%. Although goodness-of-fit measures for the alternative conceptual models were not significantly different, predictions made with the models were quite variable.     

Parameter estimation for fractional dispersion model for rivers

The fractional dispersion model for natural rivers, extended by including a first order reaction term, contains four parameters. In order to estimate these parameters a fractional Laplace transform-based method is developed in this paper. Based on 76 dye test data measured in natural streams, the new parameter estimation method shows that the fractional dispersion operator parameter F is the controlling parameter causing the non-Fickian dispersion and F does not take on an integer constant of 2 but instead varies in the range of 1.4–2.0. The adequacy of the fractional Laplace transform-based parameter estimation method is determined by computing dispersion characteristics of the extended fractional dispersion model and these characteristics are compared with those observed from 12 dye tests conducted on the US rivers, including Mississippi, Red, and Monocacy. The agreement between computed and observed dispersion characteristics is found to be good. When combined with the fractional Laplace transform-based parameter estimation method, the extended fractional dispersion model is capable of accurately simulating the non-Fickian dispersion process in natural streams.     

天然河流的二维等效扩散模型

通过对天然河流流带的拉伸或压缩处理，使之成为处处流速和水深均相等的理想河流，在此基础上建立了等效二维扩散模型。文中对建模方法和参数计算方法作了详细的介绍。     

Mineralogical characteristics and photocatalytic properties of natural sphalerite from China

Different natural sphalerites have a range of photocatalytic properties that can potentially be exploited for environmental remediation purposes. To develop value in the exploitation of sphalerite, samples were collected from 19 ore deposits in China and characterized for their mineralogical and photocatalytic properties. X-ray diffraction (XRD) and electron probe micro analysis (EPMA) measurements indicated that all the natural sphalerites from various localities crystallized in cubic phases with various chemical compositions. The substitution of Fe for Zn ranged from 0.235% to 14.826% by weight, Mn from 0.004% to 4.868%, Cu from 0.009% to 5.529% and Cd from 0.133% to 1.576%. As Fe became more abundant, the color of natural sphalerite darkened, becoming almost black; and higher Fe content was associated with stronger visible light absorption. Photoluminescence spectra showed emission mainly related to S-vacancies and progressively decreasing fluorescence intensity with increasing Fe content. Tests of the photocatalytic degradation of methyl orange indicated that the sample with the highest Cd content but moderate Fe content had the highest photocatalytic activity. Specifically, the degradation of Methyl Orange (30 mg/L) attained 82.11% efficiency under visible light irradiation for 4 hr of natural sphalerite with 4.262% Fe and 1.576% Cd. Overall, the Fe content in sphalerite was found to contribute to the visible light absorption ability and the recombination rate of photo-generated electrons and holes, while substitution by Cd was observed to have a greater effect on the photocatalytic properties. These findings provide a scientific basis for the profitable utilization of base metal resources like sphalerite.