Surface Area Basis Research Articles

Effective stress profiles and seepage flows beneath glaciers and ice sheets

AbstractThe resistance to sliding and the extent of till deformation beneath soft-bedded glaciers depend on the spatially averaged level of effective stress , which is controlled by the distribution of water pressure at the bed. Major subglacial conduits that facilitate large-scale water transport are expected to be predominantly aligned with the direction of maximum hydraulic gradient, which is normally parallel to the slope of the glacier surface. When the basal heat flow promotes net melting or freezing, seepage transport can enable water exchange between these conduits and the rest of the basal surface area. For a simple glacier geometry with subglacial conduits that are aligned parallel to a uniform slope, the seepage transport is driven primarily by gradients in effective stress. Balance equations determine how varies with conduit spacing and the heat-flow regime. Considerations of thermodynamic equilibrium require that ice penetrates the pore space at high effective stress. Even when the glacier base experiences net melting, for a given heat-flow regime there are limits on the conduit spacing that can be attained before a finite till layer becomes partially frozen throughout. During net freezing, the resistance to flow through partially frozen sediments limits the steady-state conduit spacing. The partially frozen zone can actually be restricted to smaller thicknesses when the freezing rate is greater.

Macrophage Responses to Silica Nanoparticles are Highly Conserved Across Particle Sizes

Concerns about the potential adverse health effects of engineered nanoparticles stems in part from the possibility that some materials display unique chemical and physical properties at nanoscales which could exacerbate their biological activity. However, studies that have assessed the effect of particle size across a comprehensive set of biological responses have not been reported. Using a macrophage cell model, we demonstrate that the ability of unopsonized amorphous silica particles to stimulate inflammatory protein secretion and induce macrophage cytotoxicity scales closely with the total administered particle surface area across a wide range of particle diameters (7-500 nm). Whole genome microarray analysis of the early gene expression changes induced by 10- and 500-nm particles showed that the magnitude of change for the majority of genes affected correlated more tightly with particle surface area than either particle mass or number. Gene expression changes that were particle size-specific were also identified. However, the overall biological processes represented by all gene expression changes were nearly identical, irrespective of particle diameter. Direct comparison of the cell processes represented in the 10- and 500-nm particle gene sets using gene set enrichment analysis revealed that among 1009 total biological processes, none were statistically enriched in one particle size group over the other. The key mechanisms involved in silica nanoparticle-mediated gene regulation and cytotoxicity have yet to be established. However, our results suggest that on an equivalent nominal surface area basis, common biological modes of action are expected for nano- and supranano-sized silica particles.

Studies of NO−Char Reaction Kinetics Obtained from Drop-Tube Furnace and Thermogravimetric Experiments

Four coal chars were prepared in a flat flame flow reactor (FFR), which can simulate the temperature and gas composition of a real pulverized coal combustion environment. The pore structure of chars was measured by mercury porosimetry and nitrogen adsorption, and the Hg and Brunauer−Emmett−Teller (BET) surface areas were obtained. The kinetics of NO−char was studied in a drop-tube furnace (DTF) and thermogravimetric analyzer (TGA). In the TGA experiments, the random pore model (RPM) was applied to describe the NO−char reactions and obtain the intrinsic kinetics. By presenting the data of DTF and TGA experiments on the same Arrhenius plot, it can be concluded that TGA is an available tool to study the kinetics of a high-temperature NO−char reaction. With respect to the DTF experiments, in comparison to the BET surface area, the Hg surface area is a better basis for normalizing the reactivity of different coal chars because of less scatter in the measured values, better agreement with TGA experimental data, and more stable values during the process of reaction. Moreover, by comparing the Hg surface area of chars before and after reactions, it is believed that the Hg surface area basis is more appropriate for high-rank coal chars. The determined kinetic rate constants are in good agreement with other data in the literature, and a new rate constant expression is proposed.

Oxygen Evolution Behavior of PTFE-F-PbO 2 Electrode in H 2SO 4 Solution

F-PbO 2 electrode and polytetrafluoroethylene (PTFE) doped F-PbO 2 electrode (PTFE-F-PbO 2) were prepared on a plexiglas sheet substrate by a series of procedure including chemical and electrochemical depositions. The electrochemical activities of these two electrodes for oxygen evolution (OE) reaction were examined by electrochemical tests. In comparison with F-PbO 2, PTFE-F-PbO 2 electrode exhibited larger active surface area and higher oxygen vacancy deficiency, which resulted in its higher electrocatalytic activity for OE. In addition, both exchange current density and activation energy of the electrodes for OE were calculated in terms of active surface area. The values of exchange current density and activation energy in 0.5 mol·L −1 H 2SO 4 aqueous solution were 1.125×10 −3 mA·cm −2 and 18.62 kJ·mol −1 for PTFE-F-PbO 2, and 8.384×10 −4 mA·cm −2 and 28.98 kJ·mol −1 for F-PbO 2, respectively. Because these values are calculated on the basis of the active surface areas of the electrodes, the enhanced activity of PTFE-F-PbO 2 can be attributed to an increase in oxygen vacancy deficiency of PbO 2 due to doping by PTFE. The influence of PTFE adulteration on the activity of PbO 2 film electrode for OE was investigated in detail in this study.

Juvenile Rhus glabra leaves have higher temperatures and lower gas exchange rates than mature leaves when compared in the field during periods of high irradiance

We sought to test the hypothesis that stomatal development determines the timing of gas exchange competency, which then influences leaf temperature through transpirationally driven leaf cooling. To test this idea, daily patterns of gas exchange and leaflet temperature were obtained from leaves of two distinctively different developmental stages of smooth sumac (Rhus glabra) grown in its native habitat. Juvenile and mature leaves were also sampled for ultrastructural studies of stomatal development. When plants were sampled in May-June, the hypothesis was supported: juvenile leaflets were (for part of the day) from 1.4 to 6.0 degrees C warmer than mature leaflets and as much as 2.0 degrees C above ambient air temperature with lower stomatal conductance and photosynthetic rates than mature leaflets. When measurements were taken from July to October, no significant differences were observed, although mature leaflet gas exchange rates declined to the levels of the juvenile leaves. The gas exchange data were supported by the observations that juvenile leaves had approximately half the number of functional stomata on a leaf surface area basis as did mature leaves. It was concluded that leaf temperature and stage of leaf development in sumac are strongly linked with the higher surface temperatures observed in juvenile leaflets in the early spring possibly being involved in promoting photosynthesis and leaf expansion when air temperatures are cooler.

Treating children with acute lymphoblastic leukemia and Down syndrome: Pharmacokinetics provides insight into vincristine therapy

Treating children with acute lymphoblastic leukemia and Down syndrome: Pharmacokinetics provides insight into vincristine therapy

Solar Light Induced Photocatalytic Degradation of Pollutants over Titania Pillared Zirconium Phosphate and Titanium Phosphate

Titania pillared zirconium phosphate (ZrP) and titanium phosphate (TiP) were prepared by intercalating Ti (IV) isopropoxide sol in the interlayers of the mono sodium form of the corresponding metal phosphate. The sol-intercalated samples were activated at various temperatures and characterized by XRD, UV–vis DRS, FTIR, BET-surface area, BJH-pore size distribution and acid sites measurement. Basal spacing and surface area analyses revealed that highest amount of pillaring has taken place with 2 and 4 wt.% titania loading for ZrP and TiP, respectively. The photocatalytic degradation of 4-nitrophenol (4-NP), phenol, methylene blue (MB) and hexavalent chromium (Cr (VI)) was studied in aqueous solution over the neat as well as pillared materials under solar irradiation. Catalytic activity tests revealed that hexavalent chromium (Cr (VI)) and 4-nitrophenol (4-NP) were completely degraded under acidic conditions, whereas, the same was observed in almost neutral conditions for phenol and methylene blue (MB) over 0.6 g/L of catalyst.

Cation Exchange at the Mineral−Water Interface: H3O+/K+ Competition at the Surface of Nano-Muscovite

This article describes a (39)K nuclear magnetic resonance (NMR) spectroscopic study of K+ displacement at the muscovite/water interface as a function of aqueous phase pH. (39)K NMR spectra and T 2 relaxation data for nanocrystalline muscovite wet with a solid/solution weight ratio of 1 at pH 1, 3, and 5.5 show substantial liquid-like K+ only at pH 1. At pH 3 and 5.5, all K+ appears to be associated with muscovite as inner- or outer-sphere complexes, indicating that H(3)O+ does not displace basal surface K+ beyond the (39)K detection limit under these conditions. In our pH 1 mixture, only approximately 1/3 of the initial basal surface K+ population is located more than 3-4 A from the surface. (29)Si and (27)Al MAS NMR spectra and SEM images show no evidence of dissolution during the (39)K experiments, consistent with the liquid-like (39)K fraction originating from displaced basal surface K+. Assuming no muscovite dissolution or interlayer exchange, the K+/H(3)O+ ratio relevant to the solution/surface exchange equilibrium is controlled by the total amount of K+ on the surface and H(3)O+ in solution (K+(surf)/H(3)O+(aq)). These parameters, in turn, depend on the basal surface area, solution pH, and the solid/solution ratio. The results here are consistent with significant displacement of surface K+ only under conditions where the initial K+(surf)/H(3)O+(aq). ratio is less than approximately 1. Computational molecular models of the muscovite/water interface should account for both K+ and H(3)O+ in the near-surface region.

Activated carbon nanotubes-supported catalyst in fuel cells

The electrochemical property of platinum loaded on activated carbon nanotubes (Pt/ACNTs) was investigated by cyclic voltammograms (CVs) recorded in H 2SO 4 and H 2SO 4/CH 3OH aqueous solutions, respectively. Compared to 0.0046 A/cm 2 of Pt-loaded on pristine carbon nanotubes (Pt/CNTs) with a S BET of 164 m 2/g and 0.0042 A/cm 2 of conventional carbon black (Pt/C, Vulcan XC-72) with a S BET of ∼250 m 2/g, a better electrochemical activity (a high current density of 0.0070 A/cm 2 for weak-H 2 adsorption/desorption) of the Pt/ACNTs with high specific surface area ( S BET) of 830–960 m 2/g was obtained. Furthermore, the highest current density of 0.079 A/cm 2 at 0.65 V in anodic sweep was observed during the methanol oxidation. On the basis of Pt size, utility ratio, and electro-active specific surface area (EAS), the Pt/ACNTs with a high Pt-loading of 50 wt.% exhibited the best electrochemical activity. The present ACNTs may be an excellent support material for electrochemical catalyst in proton exchange membrane and direct methanol fuel cells.

Phase I/II study of metronomic chemotherapy using S-1 and irinotecan in patients with advanced colorectal cancer (KSCOG CR-01)

2535 Background: The antiangiogenic efficacy of chemotherapy would seem to be optimized by administering comparatively lower dosages of drugs on a more frequent (daily, several times a week, or weekly) or continuous schedule, with no extended interruptions, sometimes referred to as ‘metronomic’ chemotherapy. This phase I/II study determine the recommended dose (RD), the efficacy and safety of the metronomic chemotherapy using oral fluoropyrimidine S-1 plus weekly irinotecan (CPT-11) in patients with previously untreated advanced or recurrent colorectal cancer. Methods: Patients received first-line chemotherapy comprising S-1 80 mg/m(2)/day given on days 3 to 7, 10 to 14, and 17 to 21 with escalating doses of CPT-11 (from 40 mg/m(2)) administered intravenously on day 1, 8, and 15 of a 28-day cycle. Eligibility criteria were standard. Patients were assigned on the basis of body surface area (BSA) to receive one of the following oral doses of S-1 twice daily: 40 mg (BSA < 1.25 m(2)), 50 mg (BSA ≥ 1.25 to < 1.50 m(2)), or 60 mg (BSA ≥ 1.50 m(2)). The RD was defined as the dose at which ≥ 50% of six patients experienced a skip of CPT-11 or S-1 during cycle 1 within the MTD. Results: The 60 mg/m (2) dose level was established as the RD of CPT-11 and expanded to 45 patients in whom treatment was generally well tolerated with a 92% in CPT-11 and a 95% in S-1 as dose intensity. One patient had complete response, and 21 had partial responses. The overall response rate was 48.9% (95% confidential interval, 33.7%-64.2%). Median progression-free survival was 7.6 months. The rates of grade 3 or 4 toxicity were as follows: neutropenia, 8.9%; anemia, 4.4%; anorexia, 6.7%; and diarrhea, 4.4%. Conclusions: Metronomic chemotherapy using S-1 and irinotecan is an effective, less toxic, and convenient regimen in patients with advanced colorectal cancer. Our findings suggest that this metronomic chemotherapy is a promising regimen, offering benefits in terms of safety and survival as compared with conventional regimens in patients with advanced colorectal cancer. No significant financial relationships to disclose.

Interaction of the Phospholipid Head Group with Representative Quartz and Aluminosilicate Structures: An Ab initio Study

Silica dust particles in the form of quartz (but not kaolin) have been hypothesized to promote pulmonary diseases such as silicosis. The hypothesis is that quartz and kaolin have a comparable membranolytic potential on a specific surface area basis, and they have a comparable cytotoxic potential for lavaged pulmonary macrophages. Suppression of the cytotoxic activity occurs when these dust particles are treated with dipalmitoylphosphatidylcholine (DPPC), a common phospholipid component of the lung pulmonary surfactant. However, the enzyme phospholipase A2 is known to digest the phospholipid component more readily in the presence of quartz than kaolin. Since surface silanol (Si-OH) and aluminol (Al-OH) groups may interact differently with the phospholipid, an understanding of the selective removal of phospholipid by PLA2 may explain in vivo differences in cytotoxicity between quartz and kaolin. To develop some insight into this phenomenon, the interaction between a phospholipid and silica particles was examined by performing ab initio DFT calculations on clusters constructed with small (one or two silica tetrahedral units) representative parts of the silicate surface and the phospholipid head group. The clusters consisted of a phospholipid head group or functional groups from the head group complexed with Si(OSiH 3) 3OH, Al(OSiH 3) 3OH (-) or Al(OSiH 3) 3OH 2. Fully optimized geometries of the complexes were used to determine binding energies, -OH vibrational frequency shifts, and NMR chemical shieldings. Results indicate that interaction of the protonated aluminol group (Al-OH 2 (+)) with the phosphate portion of the head group is strongest, while interaction of the -OH 2 (+) group with the trimethyl-choline moiety of the head group is weakest. The presence of the choline moiety increased the magnitude of the -OH vibrational frequency shifts, and the shifts were significantly larger in complexes with protonated aluminol groups relative to silanol complexes. Analysis of ChelpG atomic charges shows that a net transfer of charge occurs from the silica unit to the head group within the complexes.

Properties and distribution of sediment in the Salton Sea, California: an assessment of predictive models

The Salton Sea is the largest lake, on a surface area basis, in California (939 km2). Although saline (>44 g/l) and shallow (mean depth approximately 9.7 m), it provides valuable habitat for a number of endangered species. The distribution of sediments and their properties within the Salton Sea are thought to have significant influence on benthic ecology and water quality. Sediment properties and their distribution were quantified and compared with predicted distributions using several sediment distribution models. Sediment samples (n = 90) were collected using a regular staggered-start sampling grid and analyzed for water content, organic carbon (C), calcium carbonate, total nitrogen (N), total phosphorus (P), organic phosphorus, and other properties. Water content, total N, and total and organic P concentrations were all highly correlated with organic C content. The organic C concentration showed a non-linear increase with depth, with low organic C contents (typically 1–2%) present in sediments found in depths up to 9 m, followed by a strong increase in organic C at greater depths (to about 12% at 15 m depth). The models of Hakanson, Rowan et al., Blais and Kalff, and Carper and Bachmann yielded very different predicted critical depths for accumulation (10.5–22.8 m) and areas of accumulation (0–49.5%). Hakanson’s dynamic ratio model more reasonably reproduced the observed zone of elevated organic C concentrations in the Salton Sea than either exposure- or slope-based equations. Wave theory calculations suggest that strong winds occurring less than 1% of the time are sufficient to minimize accumulation of organic matter in sediments that lie at depths less than 9 m in this system.

Phase II Study of a Combination of Irinotecan and S-1 in Patients with Advanced Gastric Cancer (OGSG0002)

Background/Aims: To investigate the efficacy and safety of the combination therapy of irinotecan (CPT-11) plus S-1 in patients with advanced gastric cancer at the dose recommended by a previous phase I study. Methods: A total of 23 patients received 80 mg/m² of CPT-11 on days 1 and 15, and S-1 at a dose level set on the basis of the body surface area (BSA): 40 (BSA <1.25 m²), 50 (BSA ≧1.25 to <1.5 m²) or 60 mg (BSA ≧1.5 m²) b.i.d. was given from days 1–21. Results: The overall response rate was 47.8% (11 of 23, 95% confidence interval, CI: 27.4–68.2%). The median time to progression (TTP) was 210 days (95% CI: 145–322 days) and the median survival time was 394 days (95% CI: 241–484 days). The incidence of grade 3 or 4 hematological and non-hematological toxicity was 17.4 and 8.7%. The most common hematological toxicity was anemia and the most common non-hematological toxicity was diarrhea. Conclusion: The combination therapy of CPT-11 and S-1 provided prolonged TTP with low toxicity, and the results warrant a further phase III study to define the efficacy in improvement of survival in patients with advanced gastric cancer.

A compact and inexpensive mobile weighing device for water relations studies of container-grown trees

A low-cost mobile load cell-based weighing device is described for use in experiments that involve measuring water use by container-grown trees. The relatively lightweight (~30 kg) mobile weighing device was constructed from strong, corrosion-resistant materials readily available from commercial sources. The device has a total weighing capacity of 500 kg on the basis of rated capacity of 250 kg from each of two load cells and a maximum resolution of 0.020 kg. On the basis of a soil surface area of 825 cm2 for the containers used in the proving study, this sensitivity corresponded to an equivalent water depth of 0.23 mm.

Influence of synthesis condition on pore structure of Al pillared clays and supported Pd catalysts for deep oxidation of benzene

Alumina pillared clays (Al-PILC) were impregnated with Ce and Pd, and then studied as catalysts in the deep oxidation of benzene of low concentration (130–160 ppm). The influence of synthesis conditions on pore structure of Al-PILC was investigated, and also the relationship between structure of the supports and catalytic properties in benzene oxidation of the catalysts was studied. The supports and catalysts were characterized by X-ray powder diffraction, N 2 adsorption, atomic force microscopy, transmission electron microscopy, and temperature programmed reduction techniques. The results showed that pillaring caused a strong increase in basal spacing ( d 001), surface area, micropore volume ( V mic) and mesopore surface area ( A mes). Doping with Ce on Al-PILC yielded a super structure and a reduction in V mic and A mes. Activity tests showed that optimized synthesis conditions of pillaring solution and doping with Ce can obviously improve the activity of Pd/Al-PILC catalysts. The optimized structure of the supports can strengthen the interaction between CeO 2 and Al-PILC, improve the dispersion of Pd particles and increase the active sites, which enhances the catalytic activity of catalysts for the deep oxidation of low concentration of benzene.

Catalytic Ozonation of Propanal Using Wood Fly Ash and Metal Oxide Nanoparticle Impregnated Carbon

Catalytic ozonation of propanal at ambient temperatures (23-25 degrees C) was investigated by varying propanal and ozone concentrations and catalyst type. The catalysts tested included wood fly ash (WFA), magnetically separated ash, synthetic hematite and magnetite, and metal oxide nanoparticle impregnated activated carbon and peanut hull char. A power law model independent of ozone concentration for WFA (r(w), moles g(-1) s(-1)) and magnetite (r(m)) were, respectively, r(w) = k'(w) C(R(0.89)) and r(m) = k'(m)C(R(1.55)), where kw, and k'(m) were 2.36 x 10(-6) g(-1) s(-1) (moles)(-0.11) (m3)(0.89) and 6.5 x 10(-4) g(-1) s(-1) (moles)(-0.55) (m3)(1.55), respectively (5-15 ppmv). Magnetite and hematite present in the WFA were theorized to be the primary active sites, since magnetically separated WFA had a significantly higher reaction rate (approximately 12x, mol m(-2) s(-1)) than that of WFA. X-ray diffraction analysis demonstrated a qualitative increase in magnetite and hematite in the magnetically separated ash, and synthetic magnetite and hematite had reaction rates >80x and 200x that of WFA or activated carbon (surface area basis). Supercritical deposition of hematite on/in peanut hull char successfully generated a porous, pelleted catalystfrom an agricultural residue capable of oxidizing propanal at rates 12x activated carbon and similar to commercially available catalysts (per mass basis). Water vapor significantly increased the propanal reaction rate when using wood fly ash and activated carbon.

Uptake and Storage of PCBs by Plant Cuticles

The uptake kinetics and storage of PCBs by isolated cuticles and cuticular waxes from Hedera helix, Prunus laurocerasus, and Ilex aquifolium were studied. Small chambers were used, allowing variation in plant uptake parameters to be studied by having the same air boundary layer in each chamber. During the 64 day study tri- and tetrachlorinated biphenyls generally reached equilibrium in waxes but not in whole cuticles. Differences between species were observed. Higher chlorinated PCB congeners did not approach equilibrium in either sample type. Although PCBs showed higher affinity for waxes than whole cuticles, the latter dominated the total uptake capacity on a surface area basis, because of the large amount of nonwax cuticular components. Mass transfer coefficients (MTCs) for PCB uptake (into both cuticles and waxes) indicated partition dependence up to log octanol/air partition coefficients (K(OA)) of 8.5-10, depending on species and sample type. For cuticles, higher MTCs occurred at the beginning of the experiment than later. This was not seen in reconstituted waxes, a difference which may be explained by the dispersion of intracuticular waxes within cuticles. For more lipophilic compounds, uptake appeared to be limited by diffusion processes, which may be influenced by plant physiology. Leaf surface area is, therefore, likely to control the ability of vegetation to scavenge these compounds from the air in many field situations.

The dependence of hematite site-occupancy standard state triple-layer model parameters on inner-layer capacitance

Potentiometric acid–base titration data for three hematite samples that differed on the basis of specific surface area (17.4, 33, 83 m 2/g for hematite A, B, and C, respectively) was analyzed using the triple-layer model (TLM). The sensitivity of the TLM fits of the data to the choice of site density ( N s ) was evaluated from 1.5 to 22 sites/nm 2. In general, little dependence in the quality of fit was determined, irrespective of the value of N s . Values of the electrolyte adsorption equilibrium constants ( log K cation 0 and log K anion 0 ) steadily increased with decreasing N s . These constants are consistent with the commonly used 1.0 M standard state and when converted into comparable constants consistent with the site-occupancy standard state ( log K cation θ and log K anion θ ) a single value for each respective constant was determined. Values of the inner-layer capacitance ( C 1 ) were varied during these optimizations and increased with decreasing N s , particularly below 5 sites/nm 2. The optimized C 1 values exhibited an apparent inverse relationship with specific surface area (i.e., C 1 for hematite A > C 1 for hematite B > C 1 for hematite C). The magnitude of change in C 1 with respect to N s depended upon the magnitude of C 1 for each hematite as the higher the C 1 value, the greater was the change with respect to N s . These results suggest when the site-occupancy standard state parameters are used to predict constants at different site density values without re-regression of titration data that variations in C 1 should be accounted for, particularly for low specific surface area samples that have a high C 1 .

Adsorption of Polar and Nonpolar Organic Chemicals to Carbon Nanotubes

Understanding adsorptive interactions between organic contaminants and carbon nanotubes is critical to both the environmental application of carbon nanotubes as special adsorbents and the assessment of the potential impact of carbon nanotubes on the fate and transport of organic contaminants in the environment. The adsorption of organic compounds with varied physical-chemical properties (hydrophobicity, polarity, electron polarizability, and size) to one single-walled carbon nanotube (SWNT) and two multiwalled carbon nanotubes (MWNTs) was evaluated. For a given carbon nanotube, the adsorption affinity correlated poorly with hydrophobicity but increased in the order of nonpolar aliphatic < nonpolar aromatics < nitroaromatics, and within the group of nitroaromatics, the adsorption affinity increased with the number of nitrofunctional groups. We propose that the strong adsorptive interaction between carbon nanotubes and nitroaromatics was due to the pi-pi electron-donor-acceptor (EDA) interaction between nitroaromatic molecules (electron acceptors) and the highly polarizable graphene sheets (electron donors) of carbon nanotubes. Additionally, we attribute the stronger adsorption of nonpolar aromatics compared to that of nonpolar aliphatics to the pi-electron coupling between the flat surfaces of both aromatic molecules and carbon nanotubes. For tetrachlorobenzene, the bulkiest adsorbate, adsorption affinity (on a unit surface area basis) to the SWNT was much stronger than to the two MWNTs, indicating a probable molecular sieving effect.

Fine root biomass in relation to site and stand characteristics in Norway spruce and Scots pine stands

Variations in fine root biomass of trees and understory in 16 stands throughout Finland were examined and relationships to site and stand characteristics determined. Norway spruce fine root biomass varied between 184 and 370 g m(-2), and that of Scots pine ranged between 149 and 386 g m(-2). In northern Finland, understory roots and rhizomes (< 2 mm diameter) accounted for up to 50% of the stand total fine root biomass. Therefore, the fine root biomass of trees plus understory was larger in northern Finland in stands of both tree species, resulting in a negative relationship between fine root biomass and the temperature sum and a positive relationship between fine root biomass and the carbon:nitrogen ratio of the soil organic layer. The foliage:fine root ratio varied between 2.1 and 6.4 for Norway spruce and between 0.8 and 2.2 for Scots pine. The ratio decreased for both Norway spruce and Scots pine from south to north, as well as from fertile to more infertile site types. The foliage:fine root ratio of Norway spruce was related to basal area and stem surface area. The strong positive correlations of these three parameters with fine root nitrogen concentration implies that more fine roots are needed to maintain a certain amount of foliage when nutrient availability is low. No significant relationships were found between stand parameters and fine root biomass at the stand level, but the relationships considerably improved when both fine root biomass and stand parameters were calculated for the mean tree in the stand. When the northern and southern sites were analyzed separately, fine root biomass per tree of both species was significantly correlated with basal area and stem surface area per tree. Basal area, stem surface area and stand density can be estimated accurately and easily. Thus, our results may have value in predicting fine root biomass at the tree and stand level in boreal Norway spruce and Scots pine forests.