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.

The beneficial uptake of nutrients by wetland plants is countered to some extent by nutrient release back into the aquatic environment due to vegetative die-back. This current study examined whether Leersia oryzoides, a common wetland plant, exhibits luxury uptake of nutrients from simulated farm runoff. The study also tested whether with subsequent decomposition, these nutrients are released back into the water column. When exposed to elevated (>2 mg/L N and P) runoff, L. oryzoides assimilated significantly higher concentrations of nitrogen (p < 0.001) and phosphorus (p < 0.001) in above-ground biomass as compared to non-enriched treatments (<0.05 mg/L N and P). Subsequently, senescence of enriched above-ground biomass yielded significantly higher concentrations of phosphorus (2.19 ± 0.84 mg P/L). Using L. oryzoides as our model, this study demonstrates nitrogen and phosphorus sequestration during the growing season and release of phosphorus in the winter. Release of sequestered nutrients during plant senescence.

The urban landscape is comprised of many land uses, none more intensively managed than turfgrass; however, quantification of nutrient losses from specific land uses within urban watersheds, specifically golf courses is limited. Nitrate (NO3-N) and dissolved reactive phosphorus (DRP) were measured on a golf course in Austin, TX, USA from April 1, 1998 to March 31, 2003. NO3-N and DRP concentrations measured in storm flow were significantly greater exiting the course compared to those entering the course. Significant differences were also measured in baseflow NO3-N concentrations. The measured loading from the course was 4.0 kg NO3-N ha 1 yr 1 (11% of applied) and 0.66 kg DRP ha 1 yr 1 (8% of applied). The resulting concentrations contributed by the course were 1.2 mg L 1 NO3-N and 0.2 mg L 1 DRP. At these levels, NO3-N poses minimal environmental risk. However, the DRP concentration is twice the recommended level to guard against eutrophication

To determine the source of dissolved inorganic nitrogen (N) in runoff, approx. 35 kg N enriched with the stable isotope 15N (2110[per thousand] δ15N) was added to a mature coniferous forested catchment for one whole year. The total N input was approx. 50 kg ha-1 year-1. The enrichment study was part of a long-term whole-catchment ammonium nitrate addition experiment at Gårdsjön, Sweden. The 15N concentrations in precipitation, throughfall, runoff and upper forest floor were measured prior to, during, and 3-9 years following the 15N addition. During the year of the 15N addition the δ15N level in runoff largely reflected the level in incoming N, indicating that the leached NO3- came predominantly from precipitation. Only 1.1% of the incoming N was lost during the year of the tracer addition. The cumulative loss of tracer N over a 10-year period was only 3.9% as DIN and 1.1% as DON. 15N tracer addition showed that initially the main source of NO3- in runoff was N from atmospheric deposition.

The phytotoxic risk of ambient air pollution to local vegetation was assessed in Selangor State, Malaysia. The AOT40 value was calculated by means of the continuously monitored daily maximum concentration and the local diurnal pattern of O3. Together with minor risks associated with the levels of NO2 and SO2, the study found that the monthly AOT40 values in these peri-urban sites were consistently over 1.0 ppm·h, which is well in exceedance of the given European critical level. Linking the O3 level to actual agricultural crop production in Selangor State also indicated that the extent of yield losses could have ranged from 1.6 to 5.0% (by weight) in 2000. Despite a number of uncertainties, the study showed a simple but useful methodological framework for phytotoxic risk assessment with a limited data set, which could contribute to appropriate policy discussion and countermeasures in countries under similar conditions. There is a large potential of phytotoxic risk on vegetation in Selangor State, Malaysia.

The monitoring of a spring and seven piezometers in the 3 km2 Brévilles agricultural catchment (France) over five and a half years revealed considerable spatial and temporal variability in the concentrations of atrazine and its metabolite deethylatrazine (both systematically quantified at the outlet spring): maximum 0.97 and 2.72 μg L-1, mean 0.19 and 0.59 μg L-1, respectively. Isoproturon, the pesticide applied in the greatest amount, was detected in only 10 of the 133 samples. These observations can only partly be explained by land use and intrinsic pesticide properties. Geochemical measurements and tritium dating showed the importance of the stratification of the sandy saturated zone and the buffer function of the unsaturated limestone. Principal component analysis on 39 monthly data series of atrazine, deethylatrazine, nitrate, chloride and piezometric levels revealed a temporal structuring of the data possibly reflecting the existence within the aquifer of two different reservoirs with time-variable contributions. We present an integrated approach combining geochemistry and hydrogeology that leads to a better understanding of the spatial and temporal fluctuations of the pesticide concentrations in groundwater of a pilot agricultural catchment.

We intensively surveyed the concentrations of chemical species in aerosols and gases using a four-stage filter-pack method at a site in Japan facing the Sea of Japan in winter with 6-h sample intervals. A few chloride species emitted anthropogenically were detected, and the HCl (g) concentration was quite low. The number of chloride species artifacts was also low. The HNO₃ (g) concentration was significantly higher when the monitored air mass passed over the Korean Peninsula compared to when it did not pass over the Korean Peninsula. In addition, the HNO₃ (g) concentration was significantly higher when the air mass arrived at the monitoring site by passing the route at lower latitude than the latitude of the monitoring site. On the other hand, the SO₂ (g) concentration showed no change between various trajectories of the air mass. The [Formula: see text] (p)/non-seasalt- (nss-) [Formula: see text] (p) ratio was intermediate between the compositions of (NH₄)₂SO₄ and NH₄HSO₄ when the air mass passed over the Korean Peninsula, whereas it was intermediate between NH₄HSO₄ and H₂SO₄ when the air mass did not pass over the Korean Peninsula. We detected the transboundary transport of sulfur dioxide with high time-resolution monitoring at two separate monitoring points: the current monitoring site and Oki Island.

Within the European monitoring network (EMEP, http://www.emep.int) several different sampling procedures for measuring the main air components have been applied. This has contributed to systematic concentration differences and a comparability problem. Since 1997 co-located experiments in 15 countries have been carried out to quantify these differences. In addition, three major measurement campaigns were organized by EMEP between 1985 and 1991. Differences among results depend on the concentration level and methods used. The decrease in SO₂ concentrations over the last twenty years has placed greater demands on the methodology. Absorbing solutions methods for SO₂, (H₂O₂ and tetrachloromercurate (TCM)) typically have higher detection limits than the reference method, which uses KOH impregnated filters. The TCM method also has problems with negative interference, especially in summertime. UV fluorescence monitors have in a few cases proven to give good results, but interferences, detection limit and poor maintenance can be problems. For NO₂, many countries are using the TGS absorption solution method, which has a higher detection limit than the reference method using NaI impregnated glass sinters. The Salzmann method gives unreliable results at concentrations below 1 μgN/m³, and even at higher concentrations the uncertainty is rather unsatisfactory. The chemiluminescence monitor with molybdenum converters tends to systematically overestimate NO₂ concentrations, possibly because zero-drift problems and the non-specific response to NO₂. Particulate sulphate measurements in general have lower bias and uncertainties than gas and other aerosol measurements.

Field study at the Cervenohorske sedlo (1,013 m a.s.l.) (Hruby Jesenik Mountains, the Czech Republic, Central Europe) during 1999-2002 has been conducted in order to analyse the chemistry of rain/snow water using bulk and throughfall collector and fog/cloud water using modified passive Grunow collector. Fog water input to coniferous forest (Picea abies) was quantified using canopy balance method. For all samples pH, and the concentrations of [graphic removed] , Ca²⁺, K⁺, Mg²⁺, Na⁺, Cl-, [graphic removed] , and [graphic removed] were measured. The volume-weighted mean pH value varied from 4.92 to 5.43 in open bulk precipitation, from 4.30 to 4.71 in throughfall and from 4.66 to 5.23 in fog water. The fog droplets generally contain higher ion concentrations than rainwater. The related enrichment factors lie between 1.1 and 10.7 for the relevant species. The fog samples exhibit higher concentrations of [graphic removed] and [graphic removed] as compared to the bulk samples during 2000-2002. [graphic removed] are 5.7-10.7 times more concentrated in fog water and [graphic removed] are 3.4-7.2 times more concentrated in fog water. These differences may result from the height and characteristics of formation of the droplets. Based on canopy balance method, the annual fog water inputs were estimated to be 22 and 19% of rain and snow annual amounts in 1999 and 2000, respectively. For [graphic removed] , [graphic removed] , and [graphic removed] , the contribution of fog deposition in total (bulk + fog) deposition is estimated as 54, 47, and 42%, respectively.

The SO₄-S and NO₃-N concentrations and pH in bulk precipitation, throughfall, stemflow and soil water for the 1994-2004 period were studied in pine forests in Latvia (Rucava and Taurene Integrated Monitoring stations). The SO₄-S and NO₃-N concentrations decreased over the study period, simultaneously with a decrease of acidity in precipitation. The changes were more evident in the western part of Latvia, probably due to declining long-range air pollution from West Europe. The trend of decreasing sulphate concentrations and increasing pH in precipitation were not followed by respective changes in soil water. In the upper soil horizon sulphate ion concentrations and acidity increased in soil water. Over the observation period, nitrate concentrations also showed an increasing trend in soil water at Rucava and Taurene, but these changes were not statistically significant.