Ecotoxicity assessment of aged petroleum sludge using a suite of effects-based end points in earthworm Eisenia fetida.

Laboratory investigations were conducted to test the toxicity of aged petroleum sludge collected from Shengli Oil Field, the second largest oilfield in China, to earthworm Eisenia fetida. Various end points were measured in the earthworms, including mortality, growth, cocoon output, juvenile production, and avoidance behavioral response, to determine their comparative sensitivity for assessing harmful effects of petroleum-hydrocarbon-contaminated soil. The results showed that all these assays responded in a concentration-dependent manner, and two chronic end points, juvenile production and cocoon output, as well as avoidance behavioral response appeared to be sensitive end points for detecting toxicity of petroleum-hydrocarbon-contaminated soil. Comparatively, juvenile production exhibited similar sensitivity to avoidance behavior response, both of which were more sensitive than cocoon output, while mortality and adult growth were proposed as the least sensitive parameters. It was suggested that large amounts of petroleum sludge deposited in Shengli Oil Field may pose a potential threat to the local ecosystem, and the utility of multiple effects-based end points in earthworm E. fetida is useful to facilitate ecological risk assessments in hydrocarbon-contaminated sites.

Removal of Cd, Pb, Zn, Cu in smelter soil by citric acid leaching.

Soil washing has been verified as a feasible technology for source reduction for contaminated soil with heavy metals. We conducted batch and column leaching experiments to investigate the removal of Cd, Pb, Cu and Zn from smelter soil by citric acid. The removal efficiency of heavy metals by batch leaching reached a maximum (89.1% Cd, 26.8% Pb, 41.7% Zn, 14.2% Cu) at a concentration of 0.1 M and a pH of 5. Citric acid also removed 91.3%, 11.1%, 39.2% and 11.1% of Cd, Pb, Zn, and Cu respectively after column leaching. Citric acid mainly removed exchangeable, carbonate bound and oxide bound Cd, Pb, Cu and Zn fractions. Vertical distributions of Cd, Cu and Zn similarly increased with increasing soil depth. Chestnut shells were applied to the recovery of citric acid from the waste eluent, which removed 84.4%, 97.5%, 74.6%, 70.3% of Cd, Pb, Zn, and Cu, respectively, due to chestnut shell chelation. Fresh and regenerated citric acid was used in batch leaching of heavy metal-contaminated soil, and they showed similar ability to extract heavy metals.

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With the rapid urbanization and industrial structure adjustment in China, many contaminated sites have been left for remediation. It is essential to develop and implement ecological risk assessment (ERA) before remediating contaminated sites at a large scale as well as sequential management. In this review, we discussed the key problems in ecological risk assessment of soils in contaminated sites focusing on scientific principles, frameworks, techniques, and approaches, including 1) the site-specific framework, 2) uncertainty of conceptual model, 3) toxic mechanisms of combined contamination in soil, 4) screening of assessment endpoints, and 5) development of assessing approaches and frameworks. Then, two perspectives were addressed: the toxicological mechanism of soil combined pollution including bioavailability of contaminants in soil and their joint effect is the scientific problem in ecological risk assessment of soil in contaminated site; and weight of evidence approach based on USEPA four-step approach and EU Tier approach is applicable for ecological risk assessment in field conditions. Future studies should focus on: 1) the coordination of ecological risk assessment (ERA) framework and risk management framework, 2) conceptual mo-del, 3) process-based reactive transport models for exposure evaluation, 4) ecotoxicological mechanism of combined contamination in site soil, and 5) high ecological level endpoints. The aim of this review was to provide theoretical base and framework for the establishment of local guideline of ecological risk assessment in China.

[Size Distribution Characteristics and Inhalation Exposure of Particle-Bound PAHs in an Industrial City].

Atmospheric particulate matter was collected during the heating period and the non-heating period of a typical steel industrial process in Northeast China to study the following:① the size-depended distribution and enrichment characteristics of polycyclic aromatic hydrocarbons (PAHs); ② the deposition concentrations of PAHs of different particle sizes in various organs of the human respiratory system; and 3 the risk from human respiratory exposure. The 14 priority PAHs in the samples were determined by high-performance liquid chromatography (HPLC), and respiratory exposure assessment was conducted by combining the atmospheric particle size fractionation sampling technique with an internal deposition model. The results showed that the PAH concentrations during the heating periods (743.9 ng·m-3) were higher than those during the non-heating periods (169.0 ng·m-3). Most PAH contributions (86.3%-89.9%) were related to fine particles with a diameter ≤ 2.06 µm; medium and low molecular weight PAHs showed two concentration peaks in 1.07-2.06 µm and 7.04-9.99 µm range, respectively. In contrast, high molecular weight PAHs showed a unimodal peak in 1.07-2.06 µm range. Four-ring PAHs accounted for 40% of the total PAHs concentrations. With respect to human exposure, 53.3% and 55.3% of the granular PAHs were deposited in the lungs during the heating and non-heating periods, respectively. The incremental lifetime cancer risk (R) of particulate PAHs in the population was calculated using the concentration in the human respiratory system and the total concentration associated with the particulate matter. The R values for adults ranged between 1.3×10-5 and 2.9×10-5 during the heating period, and between 3.1×10-6 and 6.0×10-6 during the non-heating period. The R values for children during the heating period ranged between 1.0×10-5 and 2.3×10-5, and between 2.4×10-6 and 4.8×10-6 during the non-heating period. The results indicated that particle size greatly affected the concentrations of particles deposited in the respiratory system and the level of carcinogenic risk. The combination of the grading sampling technique and the respiratory system settlement model can effectively avoid the over-evaluation of human respiratory exposure.

[Soil Pollution Characteristics and Ecological Risk Assessment of As at a Large-scale Arsenic Slag-contaminated Site].

A large-scale arsenic slag-contaminated site was selected to determine soil pollution characteristics and the degree of ecological risk of a large-scale contaminated site. In this study, 184 site soil samples, 101 agricultural soil samples, and 14 arsenic slag samples were collected and the pollution characteristics and ecological risk of As were evaluated using multivariate statistics, geostatistics, and the geoaccumulation and potential ecological risk index methods. The results show that the average As contents in site soil, agricultural soil, and arsenic slag are 1333.0, 358.1, and 17316.1 mg·kg-1, respectively. The degree of contamination of As exceeds the national standard Ⅲof the environmental soil quality. The results of the vertical and three-dimensional distributions of contamination show that As is accumulated to different extents in different strata. The accumulation in the site surface soil is the most serious. The As concentrations in site soil samples are higher than that in agricultural soil samples. The potential ecological risk index method shows that all mean potential ecological risk indexes exceed 100 in different strata. Moreover, the percentage of samples in site and agricultural soils at medium pollution level ratios is 58.21% and 61.39%, respectively, illustrating that the As pollution of soil samples from this contaminated site and surrounding farm areas is serious.

[Spatial distribution prediction of surface soil Pb in a battery contaminated site].

In order to enhance the reliability of risk estimation and to improve the accuracy of pollution scope determination in a battery contaminated site with the soil characteristic pollutant Pb, four spatial interpolation models, including Combination Prediction Model (OK(LG) + TIN), kriging model (OK(BC)), Inverse Distance Weighting model (IDW), and Spline model were employed to compare their effects on the spatial distribution and pollution assessment of soil Pb. The results showed that Pb concentration varied significantly and the data was severely skewed. The variation coefficient of the site was higher in the local region. OK(LG) + TIN was found to be more accurate than the other three models in predicting the actual pollution situations of the contaminated site. The prediction accuracy of other models was lower, due to the effect of the principle of different models and datum feature. The interpolation results of OK(BC), IDW and Spline could not reflect the detailed characteristics of seriously contaminated areas, and were not suitable for mapping and spatial distribution prediction of soil Pb in this site. This study gives great contributions and provides useful references for defining the remediation boundary and making remediation decision of contaminated sites.

[Statistical characteristic analysis of soil PAHs in a coking contaminated site of China].

Statistical characteristic analysis of pollutants in contaminated sites can help identify the origin, generation, and spatial variation of different pollutants, and can reduce the uncertainty of site survey data. Taking a large and abandoned contaminated coking site of China as the object, 114 surface (0-50 cm) soil samples were collected, with the statistical and spatial characteristics of 16 priority PAHs (sigmaPAHs) analyzed. The descriptive statistical analysis indicated that the sigmaPAH levels varied significantly, and the data were severely skewed. The correlation matrix (CM) and principal component analysis (PCA) showed that the extracted first two principal components (PCs) could effectively represent the whole site pollution data. Four pollutants, i. e., Baa, Bbf&Bkf, Bap, and Inp, were selected for trend analysis and spatial local variance analysis. In the east-west and north-south directions of the site, the pollution showed a low-high-low trend. The variation coefficient of pollution for the site was higher in the central, northwest, and southwest regions, while lower in the other regions.

[Heterogeneous characteristic of PAHs' spatial distribution in a large coking site of China].

A large coking contaminated site was selected to study the PAHs' spatial distribution probability in surface-soil (0-50 cm) through the indicator kriging of the non-parametric geostatistics, and the map of probability distribution with a contaminant target was plotted over the entire site. Results indicated that the indicator semivariograms were stable after the conversion of sample data, but the poor correlation of spatial samples was observed due to the spatial variability. In this site, the distribution of the contamination probability of four PAHs' showed a similar characteristic, and the areas with a probability of more than 45% were mainly distributed in production process workshops for coking, gas purification, tar products etc, of the central, northwest and southeast site with serious contamination, while the areas with a probability of less than 45% were mainly distributed in coal preparation, gas purification workshops of the southwest and northeast site. Based on the above analysis results, we can draw a conclusion that the forecast probability results are consistent with the occurrence and distribution of pollution sources, which is important for defining the remediation boundary and calculating the contaminated soil volume.

[Bioremediation of petroleum hydrocarbon-contaminated soils by cold-adapted microorganisms: research advance].

Cold-adapted microorganisms such as psychrotrophs and psychrophiles widely exist in the soils of sub-Arctic, Arctic, Antarctic, alpine, and high mountains, being the important microbial resources for the biodegradation of petroleum hydrocarbons at low temperature. Using the unique advantage of cold-adapted microorganisms to the bioremediation of petroleum hydrocarbon-contaminated soils in low temperature region has become a research hotspot. This paper summarized the category and cold-adaptation mechanisms of the microorganisms able to degrade petroleum hydrocarbon at low temperature, biodegradation characteristics and mechanisms of different petroleum fractions under the action of cold-adapted microorganisms, bio-stimulation techniques for improving biodegradation efficiency, e. g., inoculating petroleum-degrading microorganisms and adding nutrients or bio-surfactants, and the present status of applying molecular biotechnology in this research field, aimed to provide references to the development of bioremediation techniques for petroleum hydrocarbon-contaminated soils.

[Health risk analysis of VOC/SVOC contaminated soil in an abandoned chemical plant].

Environmental health risk of contaminated soil in a typical abandoned industry was analyzed based on the full field investigation according to the site assessment procedure of American Society for Testing and Material (ASTM). Parameters were modified with the combination of Chinese crowd character and site specifics. Results indicated that the site was mainly contaminated with volatile and semi-volatile organic compounds in soil profiles. And the contents of carbon tetrachloride, tetrachloroethylene, pentachloroethane, hexachlorobutadiene, hexachloroethane and hexachlorobenzene in soil samples were exceeded the national environmental standard. These contaminants ranked the carcinogenic risks and hazard quotients more than 10(-2) and 1 in some locations with the exposure by oral ingestion, dermal contact and inhalation. Contaminants in this site had resulted in the high health risks to the residents and surrounding communities. The risk should be reduced to the health acceptable level by the treatment and remediation before further development for residential and commercial utilization.

[Comparison on desorptive behavior of cadmium in phaeozem and burozem].

Desorptive behavior of Cd2+ was comparatively studied by the batch method on the two typical soils in northeast China. The results indicated that the two soils exhibit statistically significant sorption-desorption hysteresis. Phaeozem has a longer hysteresis period than the Burozem. The desorptive behavior of Cd2+ in the two tested soils was a rapid reactions, which could account for 90% of the Cd2+ equilibrium desorption within the first 30 min. Compared with the total adsorption, the desorptive percentage of the adsorped Cd2+ in the phaeozem and burozem was in a low extent, which was ranged within rate of 9.0% and 15.1% respectively. The desorptive rates of Cd2+ in the soils were increased with the higher concentrations of Cd2+ in the treatments, and decreased with the increasing desorptive amount and time. Soil properties had no significant effect on the desorptive rate decreasing. Freundlich equation was the optimal model to describe the desorptive isotherm of Cd2+, while the Elovich equation was the best model to describe Cd2+ desorption kinetics in the two soils.