Correlations between physicochemical properties of PAHs and their distribution in soil, moss and reindeer dung at Ny-Ålesund of the Arctic

Concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) in soil, moss and reindeer dung collected at Ny-Ålesund of the Arctic were measured to investigate their accumulation trends and distribution in the three compartments. Compared with the other regions, the proportions of 2 + 3 ring PAHs to the total PAHs were higher, whereas the proportions of 5 + 6 ring PAHs were lower in the three compartments at Ny-Ålesund. Significant log/log-linear relationship was observed between the sub-cooled liquid vapor pressure and the soil/moss quotient (Q_SM). The relation was similar to the relationship between the gas/particle partition coefficient (K_P) and of PAHs, implying Q_SM would be a “mirror image” of K_P. Excellent log/log-linear relationships were observed between Q_SM and K_OA as well as between the moss/dung quotient (Q_MD) and K_OW. The results presented here indicate the physicochemical properties are suitable for characterizing the distribution of PAHs in soil, moss and reindeer dung.     

Sorption kinetic characteristics of polybrominated diphenyl ethers on natural soils

Sorption kinetic characteristics of BDE-28 and BDE-47 on five natural soils with different organic carbon fractions were investigated, and could be satisfactorily described by a two (fast and slow)-compartment first-order model with the ratio of rate constants ranged from 9 to 94 times. The fast compartment made a dominant contribution (71% ∼ 94%) to the total sorption amount in the whole process, and accounted for over 90% of the increase in the total sorption amount at initial 5 h. The influence of the slow compartment on the increase in the total sorption amount became principal (above 90%) in the subsequent stage approximately from 9 h or 25 h to the apparent equilibrium at 265 h. The results proposed the different sorption behaviors of the mathematically classified compartments for BDE-28 and BDE-47, which may correspond to the different soil components, such as soil organic fractions with amorphous and condensed structures, respectively.     

Long-term depletion of calcium and other nutrients in eastern US forests

Both harvest removal and leaching losses can deplete nutrient capital in forests, but their combined long-term effects have not been assessed previously. We estimated changes in total soil and biomass N, Ca, K, Mg, and P over 120 years from published data for a spruce-fir site in Maine, two northern hardwood sites in New Hampshire, central hardwood sites in Connecticut and Tennessee, and a loblolly pine site in Tennessee. For N, atmospheric inputs counterbalance the outputs, and there is little long-term change on most sites. For K, Mg, and P, the total pool may decrease by 2%–10% in 120 years depending on site and harvest intensity. For Ca, net leaching loss is 4–16 kg/ha/yr in mature forests, and whole-tree harvest removes 200–1100 kg/ha. Such leaching loss and harvest removal could reduce total soil and biomass Ca by 20%–60% in only 120 years. We estimated unmeasured Ca inputs from rock breakdown, root-zone deepening, and dry deposition; these should not be expected to make up the Ca deficit. Acid precipitation may be the cause of current high leaching of Ca. Although Ca deficiency does not generally occur now in acid forest soils, it seems likely if anthropogenic leaching and intensive harvest removal continue.     

土壤侵蚀信息系统的结构设计

本文介绍了黄土地区土壤侵蚀信息系统的建造原理与方法。分析探讨了土壤侵蚀各因子计算机自动提取的算法，以及土壤侵蚀预测模型的构造方法，并用灰色控制系统的原理确定了模型的参数。并以山西省离石县王家沟流域羊道沟为例进行了试验研究。     

Effect of soil texture on surfactant-based remediation of hydrophobic organic-contaminated soil

Surfactants may be used in remediation of subsoil and aquifer contaminated with hydrophobic compounds. The objectives of this study were to examine the effect of soil texture on hydrophobic organic contaminant (HOC; toluene, or 1,2,4-trichlorobenzene [TCB]) removal from six soils and to evaluate the optimal composition of soil texture for maximum HOC removal using aqueous surfactant solution. Selected surfactants were 4% (vol/vol) sodium diphenyl oxide disulfonate (DOSL) and 4% (wt/vol) sodium lauryl sulfate (LS). Toluene and TCB were selected as the lighter-than-water nonaqueous phase liquid (LNAPL) and denser-than-water nonaqueous phase liquid (DNAPL) model substances, respectively. Soil types used for this study were Ottawa sand and five Iowa soils (Fruitfield, Keomah, Crippin, Webster, and Galvar). The greatest recovery of toluene and TCB in batch tests was 73% and 84%, respectively, which was obtained with DOSL surfactant in Ottawa sand. The toluene removal of 95% in column tests has been achieved in the Ottawa sand and three Iowa soils (Fruitfield, Keomah, Crippin) with DOSL after effluent volume of 3750 ml (about 32 pore volume) passed. TCB removal of 98% in column tests has been achieved in Ottawa sand and three Iowa soils (Fruitfield, Keomah, Crippin) with DOSL after effluent volume of 2500 ml (about 21 pore volume) passed. These results were related with soil texture (clay content 30%), clay mineralogy (kaolinite and smectite), as a function of transported pore volume.     

Predicting RUSLE (Revised Universal Soil Loss Equation) Monthly Erosivity Index from Readily Available Rainfall Data in Mediterranean Area

Summary Seasonal rainerosivity is important in the structure and dynamics of Mediterranean ecosystems. The present paper contributes to the quantitative assessment of RUSLE's monthly erosion index in a data-scarce Mediterranean region. Therefore, a regionalized relationship for estimating monthly erosion index (EI_30-month) from only three rainfall parameters has been obtained. Knowledge of the seasonal and annual distribution of erosivity index, permit soil and water conservationists to make improved designs for erosion control, water harvesting or small hydraulic structures. Although a few long data sets were used in the analysis, validation with established monthly erosivity index values from other Italian locations, suggest that the model presented (r² = 0.973) is robust. It is recommended to monthly erosivity estimates when experimental data-scarce rainfall become available.     

COMPARISON OF PROCESS‐BASED AND ARTIFICIAL NEURAL NETWORK APPROACHES FOR STREAMFLOW MODELING IN AN AGRICULTURAL WATERSHED1

ABSTRACT: The performance of the Soil and Water Assessment Tool (SWAT) and artificial neural network (ANN) models in simulating hydrologic response was assessed in an agricultural watershed in southeastern Pennsylvania. All of the performance evaluation measures including Nash‐Sutcliffe coefficient of efficiency (E) and coefficient of determination (R²) suggest that the ANN monthly predictions were closer to the observed flows than the monthly predictions from the SWAT model. More specifically, monthly streamflow E and R² were 0.54 and 0.57, respectively, for the SWAT model calibration period, and 0.71 and 0.75, respectively, for the ANN model training period. For the validation period, these values were ?0.17 and 0.34 for the SWAT and 0.43 and 0.45 for the ANN model. SWAT model performance was affected by snowmelt events during winter months and by the model's inability to adequately simulate base flows. Even though this and other studies using ANN models suggest that these models provide a viable alternative approach for hydrologic and water quality modeling, ANN models in their current form are not spatially distributed watershed modeling systems. However, considering the promising performance of the simple ANN model, this study suggests that the ANN approach warrants further development to explicitly address the spatial distribution of hydrologic/water quality processes within watersheds.     

Degradation of Monophenylheptamethylcyclotetrasiloxane and 2,6-cis-Diphenylhexamethylcycloterasiloxane in Londo Soil

The natural degradation of monophenylheptamethylcyclotetrasiloxane and 2,6-cis-diphenylhexamethylcyclotetrasiloxane in soil was evaluated under laboratory conditions. Both monophenyl and 2,6-cis underwent rapid degradation in dry soil generating the same products in varying proportions. During the first 24 hr, approximately 99% of the two materials underwent significant chemical transformations forming silanols of various structures, dimethyl cyclic siloxanes of the structure (Me₂SiO)x, and rearrangement products (geometrical isomers) of diphenylhexamethylcyclotetrasiloxane. Among the silanols, the following were identified as trimethylsilyl derivatives: HOSiMe₂OH, HOSiMePhOH, HOSiMe₂OSiMe₂OH, HOSiMePhOSiMe₂OH, HOSiMePhOSiMePhOH, HOSiMe₂OSiMe₂OSiMe₂OH, HOSiMePhOSiMe₂OSiMe₂OH, HOSiMe₂OSiMePhOSiMe₂OH, HOSiMePhSiMe₂OSiMePhOH, HOSiMePhOSiMePhOSiMe₂OH, HOSiMePhOSiMe₂OSiMe₂OSiMe₂OH, HOSiMe₂OSiMePhOSiMe₂OSiMe₂OH, HOSiMePhOSiMe₂OSiMePhOSiMe₂OH, HOSiMePhOSiMePhOSiMe₂OSiMe₂OH, HOSiMePhOSiMe₂OSiMe₂OSiMePhOH, HOSiMe₂OSiMePh-OSiMePhOSiMe₂OH. Derivatization was carried out using bis(trimethylsilyl)trifluoroacetamide. Gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry (atmospheric pressure chemical ionization) analyses were used to derive structures. Structures were confirmed by gas chromatography-mass spectrometry comparisons of synthetic standards. Degradation was slower in wet soil. Nevertheless, in 14 days, the chemical transformation was essentially found to be complete as soil was allowed to dry. Detection of phenol as one of the degradation products revealed the occurrence of carbon–silicon bond cleavage promoted by soil.     

Not by nutrients alone: a call to broaden the soil fertility initiative

The article discusses agricultural practices in sub-Saharan Africa, especially in terms of maintaining soil fertility. It disagrees with alarmist tendencies in the current debate, exaggerating the state of soil impoverishment in the African region. Nor does it subscribe to the idea that the remedy lies primarily in a massive influx of chemical fertilisers, especially phosphorus.
Instead, the article advocates a more balanced approach, where soil nutrient replenishment, as an improvement in natural capital, is but one part of the investment African agriculture needs. To achieve sustainable rural livelihoods, other forms of capital are also required, such as physical capital, i.e. infrastructure (roads, means of communication); financial capital in the form of credit and savings schemes; and human- and social capital, especially improved access to information and knowledge for farmers as well as improved local organisation and empowerment.
The article reviews nine case studies, taken from different climate zones in the region and representing different soil conditions. All case studies were projects using the participatory learning and action research (PLAR) method, which is discussed in detail.     

Survey of land degradation in New South Wales,Australia

A survey of land degradation was undertaken in New South Wales, Australia during 1987–1988. The aims of the survey were to assess the location, extent, and severity of ten forms of degradation and to present the data in map and statistical form. Sample points were located on a regular grid. The method was designed so that data could be acquired from aerial photographs, expert local knowledge, and limited field checking. Individual statewide maps were prepared for each form of degradation. Map data were shown in pixel form. Sheet and rill erosion and soil structure decline were confined mostly to lands used for cropping. Gully erosion was commonly found across the state, while mass movement was confined to steeper lands. There were three severe areas of dryland salinity; irrigation salinity was mapped in parts of the southern irrigation lands. Induced soil acidity was severe in some cropping and pasture lands. Absence of tree regrowth was a noticeable feature of lands used for cropping. The survey enabled community awareness of the problems of land degradation to be increased, in addition to assisting regional land managers in resource allocation. The survey also provided the basis for the future location of sites that could be used to monitor the trends in the status of land degradation.