In situ soil water extraction: a review

The knowledge of the composition and fluxes of vadose zone water is essential for a wide range of scientific and practical fields, including water-use management, pesticide registration, fate of xenobiotics, monitoring of disposal from mining and industries, nutrient management of agricultural and forest ecosystems, ecology, and environmental protection. Nowadays, water and solute flow can be monitored using either in situ methods or minimally invasive geophysical measurements. In situ information, however, is necessary to interpret most geophysical data sets and to determine the chemical composition of seepage water. Therefore, we present a comprehensive review of in situ soil water extraction methods to monitor solute concentration, solute transport, and to calculate mass balances in natural soils. We distinguished six different sampling devices: porous cups, porous plates, capillary wicks, pan lysimeters, resin boxes, and lysimeters. For each of the six sampling devices we discuss the basic principles, the advantages and disadvantages, and limits of data acquisition. We also give decision guidance for the selection of the appropriate sampling system. The choice of material is addressed in terms of potential contamination, filtering, and sorption of the target substances. The information provided in this review will support scientists and professionals in optimizing their experimental set-up for meeting their specific goals.     

Assessment of vegetation stress using reflectance or fluorescence measurements

Current methods for large-scale vegetation monitoring rely on multispectral remote sensing, which has serious limitation for the detection of vegetation stress. To contribute to the establishment of a generalized spectral approach for vegetation stress detection, this study compares the ability of high-spectral-resolution reflectance (R) and fluorescence (F) foliar measurements to detect vegetation changes associated with common environmental factors affecting plant growth and productivity. To obtain a spectral dataset from a broad range of species and stress conditions, plant material from three experiments was examined, including (i) corn, nitrogen (N) deficiency/excess; (ii) soybean, elevated carbon dioxide, and ozone levels; and (iii) red maple, augmented ultraviolet irradiation. Fluorescence and R spectra (400-800 nm) were measured on the same foliar samples in conjunction with photosynthetic pigments, carbon, and N content. For separation of a wide range of treatment levels, hyperspectral (5-10 nm) R indices were superior compared with F or broadband R indices, with the derivative parameters providing optimal results. For the detection of changes in vegetation physiology, hyperspectral indices can provide a significant improvement over broadband indices. The relationship of treatment levels to R was linear, whereas that to F was curvilinear. Using reflectance measurements, it was not possible to identify the unstressed vegetation condition, which was accomplished in all three experiments using F indices. Large-scale monitoring of vegetation condition and the detection of vegetation stress could be improved by using hyperspectral R and F information, a possible strategy for future remote sensing missions.     

Using surfactant-modified clays to determine sorption mechanisms for a representative organic base, quinoline

Sorption of a representative ionizable nitrogen heterocycle, quinoline (pKa = 4.92), was investigated to determine the relative contributions of the neutral and protonated species to the overall process. Batch sorption experiments were conducted on surfactant-modified clays that were synthesized from the exchange of hexadecyltrimethylammonium cations for resident sodium cations on a specimen smectite (Swy-2) at 0, 60, 80, and 100% of the clay's cation exchange capacity (CEC). Hexadecyltrimethylammonium exchange creates highly effective organic partitioning domains within the clay interlayers in proportion to their coverage on the exchange complex. The fractionally exchanged clays, therefore, provided discrete exchange and organic partitioning domains for the protonated and neutral species of quinoline. Data were described by a combined Langmuir-linear isotherm that permitted independent characterization of both sorption components. Results indicated that cationic sorption dominated but that the neutral species can contribute substantially given sufficient organic carbon content relative to the CEC and at pH above the pKa of quinoline. The data obtained in this study for quinoline demonstrated that the combined isotherm (including cation exchange and hydrophobic partitioning terms) describes sorption data and compares favorably with the purely empirical Freundlish isotherm.     

The contribution of ice cover to sediment resuspension in a shallow temperate lake: possible effects of climate change on internal nutrient loading

The effect of ice cover on sediment resuspension and internal total P (Tot-P) loading was studied in the northern temperate Kirkkoj?rvi basin in Finland. The gross sedimentation and resuspension rates were estimated with sediment traps during ice-cover and ice-free periods. After ice break, the average gross sedimentation rate increased from 1.4 to 30.0 g dw m(-2) d(-1). Resuspension calculations showed clearly higher values after ice break as well. Under ice cover, resuspension ranged from 50 to 78% of the gross sedimentation while during the ice-free period it constituted from 87 to 97% of the gross sedimentation. Consequently, the average resuspension rate increased from 1.0 g dw m(-2) d(-1) under ice-cover to 27.0 g dw m(-2) d(-1) after thaw, indicating the strong effect of ice cover on sediment resuspension. To estimate the potential effect of climate change on internal P loading caused by resuspension we compared the Tot-P loading calculations between the present climate and the climate with doubled atmospheric CO2 concentration relative to the present day values (ice cover reduced from current 165 to 105 d). The annual load increased from 7.4 to 9.4 g m(-2). In conclusion, the annual internal Tot-P loading caused by resuspension will increase by 28% in the Kirkkoj?rvi basin if the 2xCO2 climate scenario comes true.     

Relationships between soil and runoff phosphorus in small Alberta watersheds

Field-scale relationships between soil test phosphorus (STP) and flow-weighted mean concentrations (FWMCs) of dissolved reactive phosphorus (DRP) and total phosphorus (TP) in runoff are essential for modeling phosphorus losses, but are lacking. The objectives of this study were (i) to determine the relationships between soil phosphorus (STP and degree of phosphorus saturation (DPS)) and runoff phosphorus (TP and DRP) from field-sized catchments under spring snowmelt and summer rainfall conditions, and (ii) to determine whether a variety of depths and spatial representations of STP improved the prediction of phosphorus losses. Runoff was monitored from eight field-scale microwatersheds (2 to 248 ha) for 3 yr. Soil test phosphorus was determined for three layers (0 to 2.5 cm, 0 to 5 cm, and 0 to 15 cm) in spring and fall and the DPS was determined for the surface layer. Average STP (0 to 15 cm) ranged from 3 to 512 mg kg(-1), and DPS (0 to 2.5 cm) ranged from 5 to 91%. Seasonal FWMCs ranged from 0.01 to 7.4 mg L(-1) DRP and from 0.1 to 8.0 mg L(-1) TP. Strong linear relationships (r2=0.87 to 0.89) were found between the site mean STP and the FWMCs of DRP and TP. The relationships had similar extraction coefficients, intercepts, and predictive power among all three soil layers. Extraction coefficients (0.013 to 0.014) were similar to those reported for other Alberta studies, but were greater than those reported for rainfall simulation studies. The curvilinear DPS relationship showed similar predictive ability to STP. The field-scale STP relationships derived from natural conditions in this study should provide the basis for modeling phosphorus in Alberta.     

Changes in microbial biomass parameters of a heavy metal-contaminated calcareous soil during a field remediation experiment

Soil microbial biomass parameters give useful information about the restoration degree and quality of contaminated soils. These parameters were studied in a field experiment where the effect of two organic amendments on the bioavailability of heavy metals in an agricultural soil and on their accumulation in Beta vulgaris and Beta maritima was assessed. The soil was a calcareous Xeric Torriorthent and the total metal levels were (mg kg(-1)): 2706 Zn, 3235 Pb, and 39 Cu. The treatments were: fresh cow manure, olive husk, and inorganic fertilizer as a control. Two successive crops (B. vulgaris and B. maritima) were grown on the treated and untreated plots. The soil was sampled before each planting and after each harvest over a 15-mo period. Biomass C and N increased in all plots, especially in the organically amended ones. The ratio CO(2)-C/biomass C decreased in olive husk and manure-treated plots, in comparison with the control, and also during the experiment, suggesting a beneficial effect of the organic amendments. In olive husk-treated plots a significant increase in the ratio of biomass C/total organic carbon (TOC) with time was observed. This indicated a reduction of heavy metal stress on the microbial population. The amendments showed, in general, a beneficial effect on soil quality and fertility, while microbial biomass parameters were found to be useful indicators of the evolution of the remediation processes.     

Aggregating high-priority landscape areas to the parcel level: an easement implementation tool

Landscape characteristics and parcel ownership information are often collected on different spatial scales leading to difficulties in implementing land use plans at the parcel level. This study provides a method for aggregating highly resolute landscape planning information to the parcel level. Our parcel prioritization model directly incorporates a Land Trust's conservation goals in the form of a compromise programming model. We then demonstrate the use of our approach for implementation decisions, including parcel selection under a budget constraint and the estimation of a total conservation budget necessary to meet specific conservation goals. We found that these cost constraints significantly alter the composition of the 'best' parcels for conservation and can also provide guidance for implementation. The model's results were integral to a local Land Trust's ability to further define and achieve their goals.     

The disposal of a lime water treatment residue on soil and spoil material from a coalmine: a glasshouse investigation

Eragrostis tef (Zucc.), Cenchrus ciliaris L., and Digitaria eriantha Steud. were grown in a soil (Psammentic Haplustalf) and spoil material from a coalmine both treated with a lime water treatment residue (WTR) at rates of 0, 50, 100, 200, and 400 g kg(-1). The yield of the grasses, from the sum of the three harvests, and concentrations of B, Ca, Cu, K, Fe, Mg, Mn, N, Na, P, and Zn in foliage from the second harvest were determined. The yield of grasses grown in the soil decreased exponentially as WTR application increased. The yields of C. ciliaris, D. eriantha, and E. tef (in the 400 g kg(-1) WTR treated soil) decreased by 74.4, 78.7, and 59.8%, respectively, when compared with the control treatments. In the spoil, the yield of E. tef and D. eriantha decreased by 13.6% and and D. eriantha by 23.9%, while an increase was observed for C. ciliaris (45.4%), at the highest WTR application rate. No relationship existed between yield of E. tef and WTR application rate when grown in the spoil, while a weak negative linear relationship (p < 0.05) was found for D. eriantha and a positive linear relationship existed for C. ciliaris. Magnesium concentrations of the grasses were positively correlated to WTR application rate. Grasses grown in the soil had higher Na concentrations, while those grown in the spoil typically had higher B, N, and Zn concentrations. The decreases in yield were attributed to nutrient deficiencies (notably Zn), induced by high WTR application rates that led to high substrate pH. Disposal of high rates of WTR on the mine materials was not recommended.     

Response to environmental flows in the lower Tarim River, Xinjiang, China: ground water

In China's west since the 1950s large-scale ecosystem degeneration has occurred through water diversions for agricultural purposes. Since 2000, 1038 x 10(6) m(3) of water have been released into the Tarim River with the result that water reached the terminal Taitema Lake for the first time in 30 years. This environmental flow raised water-table levels along 350 km of the river. To assess the response of the water-table, a comparison "pristine" site is compared with downstream monitored sites. The results show huge changes in water-table levels. The study verifies that the water-table is extremely responsive to environmental flows, that strong internal similarities exist along the length of the river, and that the effect on the water-table and hence likely riparian vegetation recovery can be tentatively predicted. The actual impacts of the restoration strategy are less than those originally expected politically, socially and within the scientific community. We make recommendations on more effective release strategies.     

On the relationship between set-out rates and participation ratios as a tool for enhancement of kerbside household waste recycling

Although the use of kerbside recycling facilities by householders is often key to the reduction of materials disposed of to landfill, the quantitative assessment of householders' recycling behaviour is problematic. This study introduces a method to diagnose recycling behaviour by assessing kerbside scheme use in terms of the set-out of recyclate containers compared to the proportion of households participating in recycling (participation ratio). Application of numerical behaviour models demonstrated that kerbside recycling in sampled regions of the UK tends to be consistent with householders using kerbside schemes more frequently than would be observed with random patterns of use that are uniform amongst all householders. When aggregated to collection rounds, householders' modal recycling behaviour tended towards either non-participation or frequent participation. We propose that initiatives to enhance kerbside recycling should employ such quantitative assessments of recycling behavioural modes to inform and guide promotional and educational strategies. A conceptual model for prioritizing campaigns to promote recycling at the kerbside on the basis of identifiable and quantifiable patterns of householder recycling behaviour is presented.