Recent EU legislation is directed to reverse the upward trends in the concentrations of agricultural pollutants in groundwater. However, uncertainty of the groundwater travel time towards the screens of the groundwater quality monitoring networks complicates the demonstration of trend reversal. We investigated whether trend reversal can be demonstrated by relating concentrations of pollutants in groundwater to the time of recharge, instead of the time of sampling. To do so, we used the travel time to monitoring screens in sandy agricultural areas in the Netherlands, determined by 3H/3He groundwater dating. We observed that concentrations of conservative pollutants increased in groundwater recharged before 1985 and decreased after 1990. Thereby, we demonstrated trend reversal of groundwater quality. From this research we concluded that 3H/3He dating can be used to facilitate (re)interpretation of existing groundwater quality data. The presented approach is widely applicable in areas with unconsolidated granular aquifers and large agricultural pressures on groundwater resources. Groundwater age dating reveals trends and trend reversal in groundwater quality.

As part of the Endis-Risks project, the current study describes the occurrence of the chlorotriazine pesticides atrazine, simazine and terbutylazine in water, sediment and suspended matter in the Scheldt estuary (B-Nl) from 2002 to 2005 (3 samplings a year, 8 sampling points). Atrazine was found at the highest concentrations, varying from 10 to 736 ng/l in water and from 5 up to 10 ng/g in suspended matter. Simazine and terbutylazine were detected at lower concentrations. Traces of the targeted pesticides were also detected in sediments, but these were below the limit of quantification. As part of an ecotoxicological assessment, we studied the potential effect of atrazine on molting of Neomysis integer (Crustacea:Mysidacea), a resident invertebrate of the Scheldt Estuary and a proposed test organism for the evaluation of endocrine disruption. Following chronic exposure (3 weeks), atrazine did not significantly affect mysid molting at environmentally relevant concentrations (up to 1 μg/l). The water of the Scheldt estuary and its associated suspended solids are contaminated with chlorotriazines at concentrations that do not affect mysid molting.

Photosynthetic stimulation and stomatal conductance (Gs) depression in Quercus ilex leaves at a CO2 spring suggested no down-regulation. The insensitivity of Gs to a CO2 increase (from ambient 1500 to 2000 μmol mol-1) suggested stomatal acclimation. Both responses are likely adaptations to the special environment of CO2 springs. At the CO2-enriched site, not at the control site, photosynthesis decreased 9% in leaves exposed to 2x ambient O3 concentrations in branch enclosures, compared to controls in charcoal-filtered air. The stomatal density reduction at high CO2 was one-third lower than the concomitant Gs reduction, so that the O3 uptake per single stoma was lower than at ambient CO2. No significant variation in monoterpene emission was measured. Higher trichome and mesophyll density were recorded at the CO2-enriched site, accounting for lower O3 sensitivity. A long-term exposure to H2S, reflected by higher foliar S-content, and CO2 might depress the antioxidant capacity of leaves close to the vent and increase their O3 sensitivity. Very high CO2 concentrations did not compensate for the effects of O3 on holm oak photosynthesis.

Human activity is changing air quality and climate in the US Pacific Northwest. In a first application of non-metric multidimensional scaling to a large-scale, framework dataset, we modeled lichen community response to air quality and climate gradients at 1416 forested 0.4 ha plots. Model development balanced polluted plots across elevation, forest type and precipitation ranges to isolate pollution response. Air and climate scores were fitted for remaining plots, classed by lichen bioeffects, and mapped. Projected 2040 temperatures would create climate zones with no current analogue. Worst air scores occurred in urban-industrial and agricultural valleys and represented 24% of the landscape. They were correlated with: absence of sensitive lichens, enhancement of nitrophilous lichens, mean wet deposition of ammonium >0.06 mg l-1, lichen nitrogen and sulfur concentrations >0.6% and 0.07%, and SO2 levels harmful to sensitive lichens. The model can detect changes in air quality and climate by scoring re-measurements. Lichen-based air quality and climate gradients in western Oregon and Washington are responsive to regionally increasing nitrogen availability and to temperature changes predicted by climate models.

Multivariate statistical techniques are efficient ways to display complex relationships among many objects. An attempt was made to study the data of trace elements in groundwater using multivariate statistical techniques such as principal component analysis (PCA), Q-mode factor analysis and cluster analysis. The original matrix consisted of 17 trace elements estimated from 55 groundwater samples colleted in 27 wells located in a coastal area in Shenzhen, China. PCA results show that trace elements of V, Cr, As, Mo, W, and U with greatest positive loadings typically occur as soluble oxyanions in oxidizing waters, while Mn and Co with greatest negative loadings are generally more soluble within oxygen depleted groundwater. Cluster analyses demonstrate that most groundwater samples collected from the same well in the study area during summer and winter still fall into the same group. This study also demonstrates the usefulness of multivariate statistical analysis in hydrochemical studies. Multivariate statistical analysis was used to investigate relationships among trace elements and factors controlling trace element distribution in groundwater.

The study uses measured and calculated data on airborne pollutants, particularly nitrogen (ranges between 28 to 43 kg N*ha-1*yr-1) and sulphur (10 to 18 kg SO4-S*ha-1*yr-1), in order to assess their long-term (1992 to 2005) effects on bryophytes at the UN-ECE Integrated Monitoring site 'Zöbelboden' in Austria. Bryophytes were used as reaction indicators on 20 epiphytic plots using the IM monitoring method and on 14 terrestrial plots using standardised photography. The plots were recorded in the years 1992, 1993, 1998, and 2004/2005. Most species remained stable in terms of their overall population size during the observed period, even though there were rapid turnover rates of a large percentage of species on all investigated plots. Only a few bryophytes (Hypnum cupressiforme, Leucodon sciuroides) responded unambiguously to N and S deposition. Nitrogen deposition had a weak but significant effect on the distribution of bryophyte communities. However, the time shifts in bryophyte communities did not depend on total deposition of N and S. Bryophytes show ambiguous response to airborne pollutants during 14 years of monitoring in a forest ecosystem.

A Biotic Ligand Model was developed predicting the effect of cobalt on root growth of barley (Hordeum vulgare) in nutrient solutions. The extent to which Ca2+, Mg2+, Na+, K+ ions and pH independently affect cobalt toxicity to barley was studied. With increasing activities of Mg2+, and to a lesser extent also K+, the 4-d EC50Co2+ increased linearly, while Ca2+, Na+ and H+ activities did not affect Co2+ toxicity. Stability constants for the binding of Co2+, Mg2+ and K+ to the biotic ligand were obtained: log KCoBL = 5.14, log KMgBL = 3.86 and log KKBL = 2.50. Limited validation of the model with one standard artificial soil and one standard field soil showed that the 4-d EC50Co2+ could only be predicted within a factor of four from the observed values, indicating further refinement of the BLM is needed. Biotic Ligand Models are not only a useful tool to assess metal toxicity in aquatic systems but can also be used for terrestrial plants.

Residence time-dependent distribution patterns of hexachlorobenzene (HCB) and dichlorodiphenyltrichloroethane (DDT) among different soil organic matter fractions of three Chinese soils were investigated. Soil organic matter (SOM) was fractionated into fulvic acid (FA), humic acid (HA), bound-humic acid (BHA), lipid, and insoluble residue (IR) fractions using methyl isobutyl ketone (MIBK) method. Results revealed that as the residence time prolonged, the amounts of HCB and DDT in the FA, HA and BHA fractions decreased, while those in the lipid and IR fractions increased. One- and two-compartment first order, and one- and two-parameter pore-diffusion kinetic models were used to describe the mobility of HCB and DDT from the FA, HA and BHA fractions. The results suggest that excellent agreements were achieved between the experimental data and fits to the two-compartment first order kinetic model (R2 > 0.97). The transfer rates of HCB and DDT followed the order FA > HA > BHA. HCB and DDT tend to transfer from FA, HA and BHA fractions to lipid and IR fractions with increasing residence time.

In industrial barrens adjacent to a nickel-copper smelter at Monchegorsk, the Kola Peninsula, root colonisation in Deschampsia flexuosa by arbuscular mycorrhizal (AM)-type of hyphae was lower than in unpolluted forests (60.9 vs. 80.4%), while Olpidium-colonisation showed a marginally significant decline, and dark septate endophytic (DSE) hyphal colonisation was not affected. We detected an interactive effect of pollution and a neighbouring tree on DSE hyphal colonisation: at the highly polluted sites, colonisation was lower in D. flexuosa growing near trees, whereas at sites with low pollution the presence of the neighbouring tree had no effect on colonisation. High numbers of intracellular DSE sclerotia in the industrial barrens (13.3 vs. 3.4%) may indicate a survial strategy in an unfavourable environment and a dispersal strategy into a more favourable environment. While lower root colonisation by AM fungi has been also earlier reported in graminoids for heavy metal contamination, the results on other ubiquitous fungi colonising D. flexuosa roots are more novel. Severe pollution decreased root colonisation by some fungal groups; neighbouring trees decreased root colonisation by dark septate endophytic fungi in highly polluted sites.

The United States and Canada currently use exposure-based metrics to protect vegetation from O3. Using 5 years (1999-2003) of co-measured O3, meteorology and growth response, we have developed exposure-based regression models that predict Populus tremuloides growth change within the North American ambient air quality context. The models comprised growing season fourth-highest daily maximum 8-h average O3 concentration, growing degree days, and wind speed. They had high statistical significance, high goodness of fit, include 95% confidence intervals for tree growth change, and are simple to use. Averaged across a wide range of clonal sensitivity, historical 2001-2003 growth change over most of the 26 M ha P. tremuloides distribution was estimated to have ranged from no impact (0%) to strong negative impacts (-31%). With four aspen clones responding negatively (one responded positively) to O3, the growing season fourth-highest daily maximum 8-h average O3 concentration performed much better than growing season SUM06, AOT40 or maximum 1 h average O3 concentration metrics as a single indicator of aspen stem cross-sectional area growth. A new exposure-based metric approach to predict O3 risk to North American aspen forests has been developed.