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UV-visible spectroscopy has been shown to be a useful technique for determining dissolved organic carbon (DOC) concentrations. However, at present we are unaware of any studies in the literature that have investigated the suitability of this approach for tropical DOC water samples from any tropical peatlands, although some work has been performed in other tropical environments. We used water samples from two oil palm estates in Sarawak, Malaysia to: i) investigate the suitability of both single and two-wavelength proxies for tropical DOC determination; ii) develop a calibration dataset and set of parameters to calculate DOC concentrations indirectly; iii) provide tropical researchers with guidance on the best spectrophotometric approaches to use in future analyses of DOC. Both single and two-wavelength model approaches performed well with no one model significantly outperforming the other. The predictive ability of the models suggests that UV-visible spectroscopy is both a viable and low cost method for rapidly analyzing DOC in water samples immediately post-collection, which can be important when working at remote field sites with access to only basic laboratory facilities.

A dynamic multi-media model that includes temperature-dependency for partitioning and degradation was developed to predict the behaviour of petroleum hydrocarbons during biopiling at low temperature. The activation energy (Ea) for degradation was derived by fitting the Arrhenius equation to hydrocarbon concentrations from temperature-controlled soil mesocosms contaminated with crude oil and diesel. The model was then applied to field-scale biopiles containing soil contaminated with diesel and kerosene at Casey Station, Antarctica. Temporal changes of total petroleum hydrocarbons (TPH) concentrations were very well described and predictions for individual hydrocarbon fractions were generally acceptable (disparity between measured and predicted concentrations was less than a factor two for most fractions). Biodegradation was predicted to be the dominant loss mechanism for all but the lightest aliphatic fractions, for which volatilisation was most important. Summertime losses were significant, resulting in TPH concentrations which were about 25% of initial concentrations just 1 year after the start of treatment. This contrasts with the slow rates often reported for hydrocarbons in situ and suggests that relatively simple remediation techniques can be effective even in Antarctica.

The influence of biochar (5%) on the loss, partitioning and bioaccessibility of (14)C-isoproturon ((14)C-IPU) was evaluated. Results indicated that biochar had a dramatic effect upon (14)C-IPU partitioning: (14)C-IPU extractability (0.01 M CaCl2) in biochar-amended treatments was reduced to2% while, (14)C-IPU extractability in biochar free treatments decreased with ageing from 90% to 40%. A partitioning model was constructed to derive an effective partition coefficient for biochar:water (KBW of 7.82 × 10(4) L kg(-1)). This was two orders of magnitude greater than the apparent Kfoc value of the soil organic carbon:water (631 L kg(-1)). (14)C-radiorespirometry assays indicated high competence of microorganisms to mineralise (14)C-IPU in the absence of biochar (40.3 ± 0.9%). Where biochar was present (14)C-IPU mineralisation never exceeded 2%. These results indicate reduced herbicide bioaccessibility. Increasing IPU application to ×10 its recommended dose was ineffective at redressing IPU sequestration and its low bioaccessibility.

The marine fate and pelagic food chain transfer of three cyclic volatile methyl siloxanes (cVMS: D4, D5 and D6) was explored in the Inner Oslofjord, Norway, using two dynamic models (the Oslofjord POP Model and the aquatic component of ACC-HUMAN). Predicted concentrations of D4, D5, and D6 in the water column were all less than current analytical detection limits, as was the predicted concentration of D4 in sediment (in agreement with measured data). The concentrations predicted for D5 and D6 in sediment were also in broad agreement with measured concentrations from the Inner Oslofjord. Volatilisation was predicted to be the most important loss mechanism for D5 and D6, whereas hydrolysis was predicted to dominate for D4. Concentrations of all three compounds in sediment are controlled by burial below the active mixed sediment layer. The marine food web model in ACC-HUMAN predicted “trophic dilution” of lipid-normalised cVMS concentrations between zooplankton and herring (Culpea harengus) and between herring and cod (Gadus morhua), principally due to a combination of in-fish metabolism and reduced gut absorption efficiency (as a consequence of high KOW). Predicted D5 concentrations in herring and cod agree well with measured data from the inner fjord, particularly when measured concentrations in zooplankton were used to set the initial dissolved-phase aqueous concentrations. Predicted concentrations of D4 and D6 in fish were over- and under-estimated by the model – possibly due to extrapolation of the metabolism rate constant from D5.

The behaviour of cyclic volatile methyl siloxanes (cVMS) in lakes was explored using a fugacity-based steady-state non-equilibrium multimedia fate and transport model (a modified version of QWASI). Three substances were investigated: Octamethylcyclotetrasiloxane (D4), Decamethylcyclopentasiloxane (D5) and Dodecamethylcyclohexasiloxane (D6) in two contrasting North American lakes: Lake Ontario and Lake Pepin (a natural shallow lake on the Mississippi river between Minnesota and Wisconsin). Values for the principal partition coefficients and the hydrolysis rate constant were adjusted for the mean annual temperatures of each lake. Hydrolysis rate constants were also adjusted for the fraction of chemical calculated to be in the freely dissolved phase. Half-lives in sediment were calculated from partitioning theory, assuming hydrolysis can occur only in the dissolved phase. Best estimates of substance-specific emissions were obtained by combining current per capita approximations of usage and fraction lost to domestic waste water, the population of the lake catchment and cVMS removal in waste water treatment. Concentrations were generally lower and chemical residence times longer in Lake Ontario than in Lake Pepin, owing to greater depth, a higher hydraulic retention time and a higher degree of dilution. Overall persistence in Lake Pepin is significantly influenced by the high rate of sediment burial assumed in the model, as well as by a relatively high rate of water discharge. Despite the many similarities of the compounds considered, the dominant loss mechanisms vary significantly and are not the same in each lake system. This highlights the pitfalls of subjective evaluation of chemical fate and illustrates the important role which models have to play in providing a quantitative framework for assessing chemical behaviour objectively under the influence of a complex and interacting set of factors.

Pesticide losses to water can present problems for environmental management, particularly in catchments where surface waters are abstracted for drinking water supply. The relative role of different transfer pathways (spray drift, spills, overland flow and leaching from soils) is often uncertain, and there is a need for experimental observation and modelling to ensure that processes are understood under a range of conditions. Here we examine the transport of propyzamide and carbetamide in a small (15.5 ha) headwater sub-catchment dominated by an artificially drained field with strongly undulating topography (topographic gradients >1:10). Specifically, we explore the validity of the "field-scale lysimeter" analogy by applying the one dimensional mathematical model MACRO. Although one dimensional representation has been shown to be reasonable elsewhere, the scale and topography of the monitored system challenge many of the underlying assumptions. MACRO considers two interacting flow domains: micropores and macropores. The effect of subsurface drains can also be included. A component of the outflow from the main drain was identified as originating from an upslope permeable shallow aquifer which was represented using a simple groundwater model. Predicted herbicide losses were sensitive to drain spacing and the organic carbon to water partition coefficient, K(OC). The magnitude of the peak water and herbicide transport and their timing were simulated satisfactorily, although model performance was poor following a period of one month when snow covered the ground and precipitation was underestimated by the rain gauge. Total herbicide loads were simulated adequately by MACRO, suggesting that the field-scale lysimeter analogy is valid at this scale, although baseflow contributions to flow needed to be accounted for separately in order to adequately represent hydrological response.

Summary This paper compares the fluvial flux of nitrate at the UK’s tidal limit with an estimate of losses from the terrestrial biosphere at the point of entry to the river system to estimate in-stream losses across the UK’s entire river network between 1925 and 2007. These estimates were used to support interpretation of the current trend in the fluvial flux of nitrogen from the UK, and to give an assessment of the fluvial component of the total nitrogen budget of UK. The release of nitrate to the point at which it enters the stream network is estimated, using a Monte-Carlo framework, from a description of annual soil N mineralisation and immobilisation combined with an export coefficient model. Long-term records of land use (including – agricultural, forestry and urban uses); livestock; human population and atmospheric deposition are used. The study shows that: (i) The flux of nitrate from UK soils in the period since 1925 varied between 420 and 1463 ktonnes N yr −1 , with two peaks, one in 1944 and one in 1967. The first of these peaks was caused by mineralisation of soil organic matter following radical land use change in the 1940s, and the second was a multifactorial response to land use change and agricultural intensification in the 1960s. (ii) The current trend in N release from soils appears to be downward but the current fluvial flux at the tidal limit is slowly increasing. It is possible that in the near future nitrate–N losses at the tidal limit will, in some years, exceed N losses from soils implying a net N gain into the fluvial network. This apparent gain can be explained by the breakthrough of high nitrate groundwater into surface waters. (iii) The predicted export from UK soils at source as water enters the stream network implies that the UK will soon become a net source of total reactive N species, as the capacity for in-stream removal becomes exhausted by the ingress of N-rich groundwater to the river system.

Phospholipid fatty acid (PLFA) analysis is an informative method for characterising and quantifying changes in the phenotypic profile of the soil microbial community when soils are exposed to chemical toxicants and other xenobiotics. However, where such materials are lipophilic, a range of non-polar compounds can be co-extracted with PLFAs and can consequently mask PLFA chromatograms. We found this to be the case with the lipophilic anti-microbial compound triclosan, which can enter the soil via the addition of sewage sludge. A simple method of washing soil in solvent prior to extraction was developed in order to remove triclosan without altering the relative abundance of PLFAs. Three contrasting soils were spiked with 500 mg kg −1 of triclosan before being washed with methanol (MeOH), dichloromethane (DCM), hexane or aqueous solutions of these solvents. PLFAs were then extracted and analysed. All treatments were found to remove triclosan effectively, allowing all peaks to be identifiable. Whilst the polar solvents MeOH and DCM significantly altered the relative abundance of extracted fatty acids in most of the soils tested, soil washing with a small quantity of hexane was able to remove triclosan whilst best preserving the fidelity of the PLFA profiles.

Summary A model of catchment-scale nitrate transport is presented for a small, rural headwater basin (Alton Pancras: 2 ) in Dorset, UK, for the period 1930–2007. Estimates of annual nitrogen (N) loading were based on parish land-use data, held in the UK’s National Archives, and previously reported figures of typical UK N loadings from livestock, fertiliser, ploughing of permanent pasture, atmospheric deposition, biological fixation and crop uptake. Loading calculations were performed within an uncertainty framework to allow for the reliance on literature data sources. Loading calculations show that all significant sources must be included not just fertiliser application which, at most, contributes 50% of N input in any given year. A simple algorithm was used to transform estimated catchment N loading (1930–2007) into a river nitrate response (observed data: 1980–2004). This assumed N-loads were delayed by some catchment mean travel time (MTT), t a , attenuated according to a Peclet number, P e , converted into solute concentrations by a factor, α , to increase some initial baseline river concentration, C b . Simple graphical translation of estimated catchment N loading to the river concentration data suggested a MTT of around 37 years. As P e → ∞ , the transport model simplified to a linear relationship between catchment N load and river nitrate concentration response lagged by the MTT. Hence, the model results suggest that, in this catchment, advection is the dominant mechanism for transport of diffuse pollution from land to river: there is little or no dispersion present. The MTT ( t a ) was then reconsidered using an estimated distribution of unsaturated zone depths in the Alton Pancras catchment. Conclusions suggest that, in modelling of long-term nutrient transport, a detailed source term is of much greater importance than a complex hydrogeological model. Implications of epistemic uncertainty, long-term prediction and management of diffuse agricultural pollution are discussed.

Anaerobic digestion (AD) is becoming increasingly popular for treating organic waste. The methane produced can be burned to generate electricity and the digestate, which is high in mineral nitrogen, can be used as a fertiliser. In this paper we evaluate potential losses of ammonia via volatilisation from food waste anaerobic digestate using a closed chamber system equipped with a sulphuric acid trap. Ammonia losses represent a pollution source and, over long periods could reduce the agronomic value of the digestate. Observed ammonia losses from the experimental system were linear with time. A simple non-steady-state partitioning model was developed to represent the process. After calibration, the model was able to describe the behaviour of ammonia in the digestate and in the trap very well. The average rate of volatilisation was approximately 5.2 g N m −2 week −1 . The model was used to extrapolate the findings of the laboratory study to a number of AD storage scenarios. The simulations highlight that open storage of digestate could result in significant losses of ammonia to the atmosphere. Losses are predicted to be relatively minor from covered facilities, particularly if depth to surface area ratio is high.

Higher-tier environmental risk assessments on "down-the-drain" chemicals in river networks can be conducted using models such as GREAT-ER (Geography-referenced Regional Exposure Assessment Tool for European Rivers). It is important these models are evaluated and their sensitivities to input variables understood. This study had two primary objectives: evaluate GREAT-ER model performance, comparing simulated modelled predictions for LAS (linear alkylbenzene sulphonate) with measured concentrations, for four rivers in the UK, and investigate model sensitivity to input variables. We demonstrate that the GREAT-ER model is very sensitive to variability in river discharges. However it is insensitive to the form of distributions used to describe chemical usage and removal rate in sewage treatment plants (STPs). It is concluded that more effort should be directed towards improving empirical estimates of effluent load and reducing uncertainty associated with usage and removal rates in STPs. Simulations could be improved by incorporating the effect of river depth on dissipation rates.

In many parts of the world clothes are washed near to or in rivers and streams. Little information is available on resulting concentrations of detergent ingredients or on any potential effects caused. In this study, the fate of a commonly used anionic surfactant, linear alkylbenzene sulphonate (LAS) was investigated in a reach of the Balfour River (Eastern Cape Province, South Africa) which was regularly used as a site for laundry activity. Samples of river water were collected upstream of the main washing site and at a number of locations downstream on several occasions in winter and summer. Sediment samples were also collected and analysed. In addition, a household survey was conducted to ascertain the amount of detergent used and the distribution of washing practices. The results of the survey suggested that the use of riverside locations for laundry activities was seasonal. Most washing tended to be done at home during the winter with riverside sites used more frequently during the summer months. The monitoring data showed that LAS concentrations in water were very variable. They were occasionally high in the immediate vicinity of the laundry site (up to 342 microg L(-1)) but were generally very low (

It is useful to have available a variety of catchment-scale water quality models that range in complexity, spatial resolution and data requirements. In a previous paper [Warren, C., Mackay, D., Whelan, M., Fox, K., 2005. Mass balance modelling of contaminants in river basins: a flexible matrix approach. Chemosphere 61, 1458-1467] a series of simple to intermediately complex mass balance models was presented which can be used for tiered exposure assessments in river basins. The connectivity of the segments is expressed using a matrix that permits flexibility in application, enabling the model to be re-segmented and applied to different catchments as required. In this paper, the intermediate models, QWASI matrix-rate constant (QMX-R) and QWASI matrix-fugacity (QMX-F) are used to estimate concentrations of linear alkylbenzene sulfonates (LAS) in the rivers Aire and Calder, UK, and of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the Fraser River basin, Canada. The results compare satisfactorily with monitoring data, suggesting that these QWASI-based models for exposure and risk assessment may be applicable under data-limited conditions. The use of QWASI-based models for regulatory purposes in an evaluative river system is also discussed with reference to assessments of para-dichlorobenzene (pDCB), trichloroethylene (TCE), bis(2-ethylhexyl) phthalate (DEHP) and toluene. It is shown that multi-media QWASI model predictions can be usefully depicted graphically on chemical space diagrams and used to highlight regions in which advection, partitioning to sediments and volatilization may be important determinants of chemical fate in river systems.

Summary The performance of the SWAT-2000 model was evaluated using stream flow at the outlet of the 142 ha Colworth catchment (Bedfordshire, UK). This catchment has been monitored since October 1999. The soil type consists of clay loam soil over stony calcareous clay and a rotation of wheat, oil seed rape, grass, beans and peas is grown. Much of the catchment is tile drained. Acceptable performance in hydrological modelling, along with correct simulation of the processes driving the water balance were essential first requirements for predicting contaminant transport. Initial results from SWAT-2000 identified some necessary modifications in the model source code for correct simulation of processes driving water balance. After modification of the code, hydrological simulation, crop growth and evapotranspiration (ET) patterns were realistic when compared with empirical data. Acceptable model performance (based on a number of error measures) was obtained in final model runs, with reasonable runoff partitioning into overland flow, tile drainage and base flow.

Summary Distributed models used in hydrological modelling, have many parameters. To get useful results from the model, every parameter is required to have a sensible value. Usually a calibration is undertaken to reduce the uncertainties associated with the estimation of model parameters. To ensure efficient calibration, a sensitivity analysis is conducted to identify the most sensitive parameters. This paper describes simple and efficient approaches for sensitivity analysis, calibration and identification of the best methodology within a modelling framework. For this study, the SWAT-2000 model was used on a small catchment of 141.5 ha in the Unilever Colworth estate, in Bedfordshire, England. Acceptable performance in hydrological modelling, and correct simulation of the processes driving the water balance were essential requirements for subsequent pesticide modelling. SWAT gives various options for both evapotranspiration and runoff modelling. Identification of the best modelling option for these processes is a pre-requisite to achieve these requirements. As a first step, a sensitivity analysis was conducted to identify the sensitive parameters affecting stream flow for subsequent application in stream flow calibration. Hydrological modelling has been carried out for the catchment for the period September 1999 to May 2002 inclusive using both daily and sub-daily rainfall data. The Hargreaves and Penman-Montieth methods of evapotranspiration estimation and the NRCS curve number (CN) and Green and Ampt infiltration methods for runoff estimation techniques were used, in four different combinations, to identify the combination of methodologies that best reproduced the observed data. In addition, as the initial calibration period, starting in September 1999, was substantially wetter than the following corresponding validation period, the calibration and validation periods are interchanged to test the impact of calibration using wet or dry periods.

When river water quality fluctuates over relatively short periods of time with respect to the sampling frequency, the collection of grab samples may be inappropriate for characterising average water quality. This paper presents the results of a water quality monitoring study carried out on a stretch of the river Lambro (northern Italy) dominated by a periodically overloaded sewage treatment works (STW) located near its upstream end. Water quality was strongly influenced by a pronounced diurnal cycle in pollutant loads caused by the regular emission of untreated waste water during periods of high domestic flow (daytime). Two different sampling techniques were employed: grab sampling and 24-h composite sampling using automatic samplers. Samples were collected at the plant overflow and at several sites along the river and analysed for two common ingredients of household detergents, linear alkylbenzene sulphonate (LAS) and boron (B) and for routine water quality variables. The results obtained show that: (1) The diurnal variability of point-source-derived chemical concentrations in the river downstream of the undersized STW increased with increasing removal efficiency in sewage treatment. (2) The shape of the diurnal concentration signal remained relatively intact for a considerable distance downstream of the STW for several water quality variables, suggesting that hydrodynamic dispersion plays a relatively minor role in controlling concentration patterns in this river. (3) In-stream degradation of LAS was consistent with first order kinetics with a rate constant of 0.05–0.06 h−1. (4) Grab sampling is a relatively inefficient methodology for capturing mean concentrations for rivers subjected to highly variable loads, especially when it is restricted to office hours. The inefficiency of grab sampling is more marked for substances (e.g. LAS) which are effectively removed during sewage treatment than for substances which are not. (5) For LAS, diurnal variability in the concentration signal decreases with distance downstream, making grab sampling an increasingly reliable methodology for estimating mean concentrations. (6) 24-h composite sampling is an efficient way of eliminating the effect of diurnal variations in load strength.

GREAT-ER (Geography-referenced Regional Exposure Assessment Tool for European Rivers) is a model system for predicting chemical fate and exposure in surface waters. The GREAT-ER approach combines a series of well-studied models (for sewers, waste water treatment plants and rivers) with spatial information managed by a GIS. A new version of GREAT-ER (version 2) has been developed which has a number of improved features compared to its predecessor. All components are now implemented as Free Software and make use of Free Software where possible. This simplifies the distribution, use and extension of the system and its components for scientific applications. In addition, two new platform-independent user interfaces have been developed. The first is a simplified web-based interface for easy access without installation and the second is a full-featured desktop version. The model system has been re-designed to increase its flexibility for the modification and extension of its component models. In addition, the file-based data storage system used in version 1 has been replaced by a database management system with a flexible Application Programming Interface (API). This makes it easier for users to share their results, using a new repository (also with web-based and desktop versions) serving as a central communication tool. The output from the new system has been successfully tested against the field-validated models in GREAT-ER 1.0.

A novel and flexible approach is described for simulating the behaviour of chemicals in river basins. A number (n) of river reaches are defined and their connectivity is described by entries in an n x n matrix. Changes in segmentation can be readily accommodated by altering the matrix entries, without the need for model revision. Two models are described. The simpler QMX-R model only considers advection and an overall loss due to the combined processes of volatilization, net transfer to sediment and degradation. The rate constant for the overall loss is derived from fugacity calculations for a single segment system. The more rigorous QMX-F model performs fugacity calculations for each segment and explicitly includes the processes of advection, evaporation, water-sediment exchange and degradation in both water and sediment. In this way chemical exposure in all compartments (including equilibrium concentrations in biota) can be estimated. Both models are designed to serve as intermediate-complexity exposure assessment tools for river basins with relatively low data requirements. By considering the spatially explicit nature of emission sources and the changes in concentration which occur with transport in the channel system, the approach offers significant advantages over simple one-segment simulations while being more readily applicable than more sophisticated, highly segmented, GIS-based models.

A simple point-source water quality model was constructed to explore hypothetical scenarios of linear alkylbenzene sulphonate (LAS) load variability, chemical degradation kinetics, river discharge and river velocities within the context of planned water quality monitoring in the river Lambro, northern Italy. LAS is an anionic surfactant and a commonly used ingredient of household detergents. Input loads were derived from flow and concentration measurements at sewage treatment works (STW). River travel times are approximated using hydraulic geometry concepts based on existing records of stage, discharge and velocity measurements. The model proved to be especially useful in predicting the impact of overflows from an undersized STW near the top of the catchment on diurnal variations in water quality downstream. Probability density functions (pdf's) of LAS concentrations for a number of points on the river were approximated by running the model stochastically (using a Monte Carlo procedure) over independent frequency distributions of discharge, temperature and input load. The predicted concentration pdf's were then used to estimate the number of random grab and 24 h composite samples, which would be required in order to estimate mean concentrations with confidence. This is especially important in situations where the analysis is expensive and the sample budget is limited. The model results showed that grab sampling was not a viable strategy in the Lambro largely due to the very strong diurnal variability in concentrations induced by the STW overflow. This conclusion was corroborated by field data.

Spatial variability of throughfall depth and mineral ion composition was investigated in a Norway spruce (Picea abies (Karst) L.) plantation at the small plot scale. A regular array of 39 funnel collectors was set up on the forest floor and throughfall volume and concentrations of nitrate, ammonium, chloride, potassium and sulphate were measured on six sampling occasions over a period of 81 days in winter. Considerable spatial variability was found in the patterns of throughfall depth and ion concentrations but for each sampling period there were consistent features in the spatial patterns of these inputs. Throughfall depth increased significantly as a function of increasing distance from the nearest tree bole while ion load was negatively correlated with distance from the tree. The magnitude of the mean ion load for each period depended on mean throughfall depth. Throughfall depth and deposition of ions were also correlated with spatially referenced values of canopy interception capacity estimated using a deterministic model of the canopy hydrology above each collector. Although linear correlations between the canopy cover above each collector (estimated from image analysis of photographs) and the spatial patterns of throughfall volume, concentration and load were significant for only 17% of the time, least-squares fitting of quadratic equations (input vs cover with a maximum input at some intermediate value of cover) were significant for more than half of the cases examined. This study highlights the need for a better characterisation of canopy architecture in order to improve understanding of its role in affecting water and mineral ion deposition on the forest floor.

We investigated variations in the biochemical composition and biodegradation of Scots pine (Pinus sylvestris) needles and litter on four soils with different cation exchange characteristics, ranging from 7 to 92% base saturation. Trends in cellulose, non-crystalline holocellulose concentrations (as measured by a trifluoracetic acid (TFA) hydrolysis technique) and ratios of lignin-to-cellulose and lignin-to-N in needles and litters varied significantly between sampling sites and reflected trends in soil base status under P. sylvestris stands. Although these relationships need to be tested rigorously on a more extensive sample set, clearly the biochemical quality of needles and litter within the same tree species is not uniform. Detailed analysis of the carbohydrate composition of TFA extracts from plant tissues showed that the ratios of selected hexoses (predominantly of microbial origin) to pentoses (mainly from plant cell wall constituents) were between 1 and 15 times lower in decomposing litter than needles. The hexose-to-pentose ratios also increased from 0.117:1 to 0.136:1 (as rhamnose+fucose-to-arabinose+xylose) and from 1.32:1 to 1.67:1 (as galactose+mannose-to-arabinose+xylose) with increasing base saturation of soils. It is concluded that the former ratio most clearly differentiated between the contrasting sites, whereas the latter ratio was more diagnostic of biotransformations during litter decomposition and associated development of microbial biomass. The study highlights a need to further clarify intraspecific differences in tree leaf and litter biochemistry in relation to soil characteristics and challenges the conventional definition of litter quality in terms of C-to-N or lignin-to-N ratio without consideration for the biochemical quality and spatial patterns of a “holocellulose” fraction. The determination of constituent carbohydrates in TFA extracts may provide a useful diagnostic for the potential decomposition of litter and the depolymerisation of structural carbohydrates.

The estimation of throughfall to forest systems is an important requirement for modelling the hydrology and chemistry of catchments and for understanding moisture dependent processes on the forest floor. Despite widespread recognition that throughfall is inherently variable, relatively few attempts have been made to account for any systematic influence canopy architecture may have over throughfall patterns. A simple Rutter-type interception model is developed here to include spatially distributed parameters which are related to variable canopy cover and interception capacity. Evaporation rates are approximated using the Penman-Monteith equation and canopy drainage is modelled using a negative exponential equation related to canopy wetness. The model was calibrated and validated using field observations of throughfall from a regular array of funnel collectors installed in a small plot in a Norway spruce ( Picea abies ) plantation in southwest England. The observed throughfall patterns had a strong systematic component which was strongly correlated with spatially distributed measured canopy cover and calibrated canopy capacity. The model was able to reproduce the broad trends in observed patterns of throughfall to the plot and was able to predict the cumulative total throughfall input to the plot over 77 days to within 2% of the measured input.

Intact Pinus sylvestris needles and litter from the soil surface were sampled from several stands in SW England growing on soils with different chemical characteristics. The intrinsic chemical and biochemical characteristics of needle and litter samples were measured. The total concentration of lignin, measured by proximate analysis, and the chemical characteristics of the lignin-polymer in P. sylvestris needles and litter, varied between soil types. Lignin concentrations increased from 180 to 316 mg litter g −1 with increasing soil base saturation, although no similar trends in the concentration of lignin in needles were observed. The total concentration of phenylpropanoid moieties, released on CuO-oxidation, increased from 65.6 to 96.1 mg lignin g −1 in needles and 35.3–83.6 mg lignin g −1 in litters, which followed a trend of increasing soil base saturation under P. sylvestris stands. The concentration of NaOH-extractable moieties in needles increased from 1.79 to 2.35 μg sample g −1 with soil base saturation, as did the acid to aldehyde ratios of phenylpropanoid moieties in NaOH-extracts from litters. We conclude that the quality of lignin in needles and litter, as measured by its phenylpropanoid characteristics, varied significantly in P. sylvestris stands. In the light of the evidence from other studies that phenylpropanoid moieties have significantly different rates of microbial decomposition, this aspect of lignin quality should be considered when modelling the rate of litter mass loss and organic matter accumulation in forest soils. Furthermore, we have shown that by combining the CuO-oxidation technique with a NaOH-extraction procedure, phenylpropanoid signatures of a ‘bound’ and a relatively ‘labile’ lignin derived fraction in needles and litters can be more accurately monitored. A more extensive study is required to clarify the apparent relationships between the soil chemical characteristics beneath stands and the quality of lignin in plant materials.