Remediation of Persistent Organic Pollutants (POPs) in Two Different Soils

Persistent organic pollutants (POPs) are a set of chemicals that are toxic, persist in the environment for long periods of time, and biomagnify as they move up through the food chain. The most widely used method of POP destruction is incineration, which is expensive and could result in undesirable by-products. An alternative bioremediation technology, which is cheaper and environ-mentally friendly, was tested during this experiment. Two different soil types containing high and low organic matter (OM) were spiked with 100 mg/kg each of pyrene and Aroclor 1248 and planted with three different species of grasses. The objective of the study was to determine residue recovery levels (availability) and potential effectiveness of these plant species for the remediation of POPs. The results showed that recovery levels were highly dependent on the soil organic matter content—very low in all treatments with the high OM content soil compared to recoveries in the low OM soil. This indicates that availability, and, hence, biodegradability of the contaminants is dependent on the organic matter content of the soil. Moreover, the degree of availability was also significantly different for the two classes of chemicals. The polyaromatic hydrocarbon (PAH) recovery (availability) was extremely low in the high organic matter content soil compared to that of the polychlorinated biphenyls (PCBs). In both soil types, all of the plant species treatments showed significantly greater PCB biodegradation compared to the unplanted controls. Planting did not have any significant effect on the transformation of the PAHs in both soil types; however, planting with switchgrass was the best remedial option for both soil types contaminated with PCB.

Distribution of organic and reduced sulfur forms in marsh soils of coastal Louisiana

Soil samples from a Louisiana Barataria Basin brackish marshes were fractionated into acid-volatile sulfides (AVS), HCl-soluble sulfur, elemental sulfur, pyrite sulfur, ester-sulfate sulfur, and carbon-bonded sulfur. Inorganic sulfur composed 13% of total sulfur in brackish marsh soil with HCl-soluble sulfur representing 63–92% of the inorganic sulfur fraction. AVS represented less than 1% of the total sulfur pool. Pyrite sulfur and elemental sulfur together accounted for 8–33% of the inorganic sulfur pool. Organic sulfur, in the forms of ester-sulfate sulfur and carbon-bonded sulfur, was the most dominant pool representing the majority of total sulfur in brackish marsh. Results were compared to values reported for fresh and salt marshes. Reported inorganic sulfur fractions were greater in adjacent marshes, constituting 24% of total sulfur in salt marsh, and 22% in freshwater marshes. Along a salinity gradient, HCl-soluble sulfur represented 78–86% of the inorganic sulfur fraction in fresh, brackish, and salt marsh. Organic sulfur in the forms of ester-sulfate sulfur and carbon-bonded sulfur was the major constituent (76–87%) of total sulfur in all marshes. Reduced sulfur species, except elemental sulfur, increased seaward along the salinity gradient. Accumulation of reduced sulfur forms through sedimentation processes was significant in marsh energy flow in fresh, brackish and salt marshes.

秸秆还田对灌溉玉米田土壤反硝化及N_2O排放的影响

运用乙炔抑制技术研究了不同施氮水平下秸秆还田对灌溉玉米田土壤反硝化反应和氧化亚氮(N2O)排放的影响。结果表明,土壤反硝化速率及N2O的排放受氮肥施用、秸秆处理方式及其交互作用的显著影响。与秸秆燃烧相比,不施氮或低施氮水平时,秸秆还田可刺激培养初期反硝化反应速率及N2O排放,增加培养期间N2O平均排放通量;高施氮水平时,秸秆还田可降低反硝化反应速率及反硝化过程中的N2O排放。秸秆还田可降低反硝化中N2O/N2的比例。

Effects of multiple environmental factors on CO2 emission and CH4 uptake from old-growth forest soils

National Key Research and Development Program [2010CB833502]; National Natural Science Foundation of China [30600071, 40601097, 30590381, 30721140307]; Knowledge Innovation Project of the Chinese Academy of Sciences [KZCX2-YW-432, O7V70080SZ, LENOM07LS-01

Probabilistic modelling of soil moisture dynamics of irrigated cropland in the North China Plain

A probabilistic soil moisture dynamic model is used to estimate the soil moisture probability distribution and plant water stress of irrigated cropland in the North China Plain. Soil moisture and meteorological data during the period of 1998 to 2003 were obtained from an irrigated cropland ecosystem with winter wheat and maize in the North China Plain to test the probabilistic soil moisture dynamic model. Results showed that the model was able to capture the soil moisture dynamics and estimate long-term water balance reasonably well when little soil water deficit existed. The prediction of mean plant water stress during winter wheat and maize growing season quantified the suitability of the wheat-maize rotation to the soil and climate environmental conditions in North China Plain under the impact of irrigation. Under the impact of precipitation fluctuations, there is no significant bimodality of the average soil moisture probability density function.

Evaluation of a sequential extraction for the speciation of thorium in soils from Baotou area, Inner Mongolia

Sequential extraction procedures were widely applied for speciation of radioactive elements. In this study, the sequential extraction procedure developed by Martinez-Aguirre was employed for quantification of different chemical forms of thorium in the soil. The total amount of thorium in contaminated soil was much higher by four-fold than the local background value. The soil properties affect the amount of thoriurn and distribution of fractions in contaminated soil. Results showed that the proportion of thorium in soils from Baotou was found as the residual fraction (F5 + F6) > absorbed fraction (F3), coprecipitated fraction (F4) > carbonates fraction (172) and exchangeable fraction (F1) that could be available to plants. The recovery, calculated by ratio of the sum of the six fractions to the pseudo-total content of thorium, was in the range from 96% to 110%. A comparison was carried out between the sequential extraction and the single extraction to evaluate the selectivity of the extractants. It was found that the amount of thorium of absorbed fraction (H) was higher in the single extraction than that estimated in the sequential extraction, possibly duo to transform of the labile form. While for non-residual fraction analysis, the single extraction scheme was a desirable alternative to the sequential extraction procedure.

Determination of rare and rare earth elements in soils and sediments by ICP-MS using Ti(OH)(4)-Fe(OH)(3) co-precipitation preconcentration

A method was developed for the determination of trace and ultratrace amounts of REE. Cd. In. Tl. Th. Nb, Ta. Zr and Hf in soils and sediments. With NaOH-Na2O2 as the flux. Ti(OH)(4)-Fe(OH)(3) co-precipitation as the preconcentration technique and inductively coupled plasma mass spectrometry (ICP-MS) for measurement, the whole procedure was concise and suitable for batch analysis of multi-element solutions. An investigation was carried out of the Ti(OH)(4)-Fe(OH)(3) co-precipitation system, and the results obtained showed that the natural situation of Ti tightly coexisting with Nb. Ta, Zr and Hf in geological samples plays a very important role in the complete co-precipitation of the four elements. The accuracy of this procedure was established using six Chinese soil and sediment certified reference materials (GSS and GSD). and the relative errors between the found and certified values were mostly below 10%.