Wet-only Sampler Research Articles

The Effect of Dust Transport on the Concentration of Chlorophyll-A in the Surface Layer of the Black Sea

This paper focuses on the atmospheric dust transport effect on the changes in chlorophyll-A concentration in the Black Sea surface layer. In order to assess the input of nutrients with atmospheric precipitations at the Crimean coast of the Black Sea, the collected samples were analyzed for the content of inorganic nitrogen, phosphates, and silicon. The samples were taken into a wet-only sampler and into a permanently open one, to assess the effect of dust on the nutrients concentration in dry depositions. Cases of multi-fold excess of the nutrients content in the open sampler collected precipitation over that in the wet-only sampler were identified. For such high concentration cases, the 7-day back-trajectories analyses was carried out using the model of the international network AERONET and the HYSPLIT model. The results of our research showed that the influx of nutrients with the atmospheric depositions can result in increasing of chlorophyll-A concentration in 11–36% in the surface layer of the Black Sea. After atmospheric depositions, concentration of phosphates in the surface layer can increase more than five times compared with the background concentration. The increase of silicon concentration can reach 30%. The influx of atmospheric precipitation containing significant amounts of nutrients into the bay can shifts the Redfield ratio compared with background value up to three times.

Bulk Atmospheric Mercury Fluxes for the Northern Great Plains, USA

Total atmospheric bulk mercury (Hg) concentration and deposition were measured from August 2008 to November 2010 at nine locations in the Northern Great Plains, USA using passive bulk mercury samplers. Monthly mercury concentrations ranged from 1.3 to 51.0 ng L−1 with an overall volume weighted mean of 12.9 ng L−1. Normalized daily Hg fluxes ranged from 0.43 to 110 ng m−2 day−1 with higher rates occurring during high precipitation months as rainfall during spring and summer. Annual deposition rates ranged from 5.82 to 9.21 μg m−2 year−1 and were comparable to studies performed at similar latitudes and to estimates from the Mercury Deposition Network (MDN). There was no significant difference (p > 0.05) between measured atmospheric mercury for one colocated bulk Hg sampler and an existing MDN wet-only sampler at Eagle Butte, South Dakota, demonstrating measurement unity between the two sampling techniques in this geographic area.

Atmospheric dry and wet nitrogen deposition on three contrasting land use types of an agricultural catchment in subtropical central China

Atmospheric emissions of reactive nitrogen (N) species are at high levels in China in recent years, but few studies have employed N deposition monitoring techniques that measure both dry and wet deposition for comprehensive evaluation of the impacts of N deposition on ecosystems. In this study, to quantify the total N deposition, both dry and wet N depositions were monitored using denuder/filter pack systems, passive samplers and wet-only samplers at three sites with different land use types (forest, paddy field and tea field) in a 135-km2 catchment in subtropical central China from September 2010 to August 2011. At the three sampling sites, the annual mean concentrations of total N (the sum of NH4+, NO3− and DON) in rainwater were 1.2–1.6 mg N L−1, showing small variation across sites. Annual mean concentrations of total N (the sum of NH3, NO2, HNO3, particulate NH4+ and NO3−) in the air were 13–18 μg N m−3. High NH3 concentrations in the air were observed at the agricultural sites of tea and paddy fields, indicating significant NH3 emissions from N fertiliser application; and high NO2 concentrations were found at the upland sites of forest and tea field, suggesting high NO emissions from soils due to high N deposition or high N fertiliser input. The annual total N deposition for the three sites of paddy field, tea field and forest was estimated as 22, 34 and 55 kg N ha−1 yr−1, in which the dry N deposition components contributed to 21%, 36% and 63% of the annual total N deposition, respectively. The annual deposition of reduced N species was 1.1–1.8 times of the annual deposition of oxidised N species. To minimise the adverse effects of atmospheric N deposition on natural/semi-natural ecosystems, it is crucial to reduce the reactive N emissions from anthropogenic activities (e.g., N fertiliser application, animal production and fossil fuel combustion) in subtropical central China.

Aerosol and precipitation chemistry measurements in a remote site in Central Amazonia: the role of biogenic contribution

Abstract. In this analysis a 3.5 years data set of aerosol and precipitation chemistry, obtained in a remote site in Central Amazonia (Balbina, (1°55' S, 59°29' W, 174 m a.s.l.), about 200 km north of Manaus) is discussed. Aerosols were sampled using stacked filter units (SFU), which separate fine (d < 2.5 μm) and coarse mode (2.5 μm < d < 10.0 μm) aerosol particles. Filters were analyzed for particulate mass (PM), Equivalent Black Carbon (BCE) and elemental composition by Particle Induced X-Ray Emission (PIXE). Rainwater samples were collected using a wet-only sampler and samples were analyzed for pH and ionic composition, which was determined using ionic chromatography (IC). Natural sources dominated the aerosol mass during the wet season, when it was predominantly of natural biogenic origin mostly in the coarse mode, which comprised up to 81% of PM10. Biogenic aerosol from both primary emissions and secondary organic aerosol dominates the fine mode in the wet season, with very low concentrations (average 2.2 μg m-3). Soil dust was responsible for a minor fraction of the aerosol mass (less than 17%). Sudden increases in the concentration of elements as Al, Ti and Fe were also observed, both in fine and coarse mode (mostly during the April-may months), which we attribute to episodes of Saharan dust transport. During the dry periods, a significant contribution to the fine aerosols loading was observed, due to the large-scale transport of smoke from biomass burning in other portions of the Amazon basin. This contribution is associated with the enhancement of the concentration of S, K, Zn and BCE. Chlorine, which is commonly associated to sea salt and also to biomass burning emissions, presented higher concentration not only during the dry season but also for the April–June months, due to the establishment of more favorable meteorological conditions to the transport of Atlantic air masses to Central Amazonia. The chemical composition of rainwater was similar to those ones observed in other remote sites in tropical forests. The volume-weighted mean (VWM) pH was 4.90. The most important contribution to acidity was from weak organic acids. The organic acidity was predominantly associated with the presence of acetic acid instead of formic acid, which is more often observed in pristine tropical areas. Wet deposition rates for major species did not differ significantly between dry and wet season, except for NH4+, citrate and acetate, which had smaller deposition rates during dry season. While biomass burning emissions were clearly identified in the aerosol component, it did not present a clear signature in rainwater. The biogenic component and the long-range transport of sea salt were observed both in aerosols and rainwater composition. The results shown here indicate that in Central Amazonia it is still possible to observe quite pristine atmospheric conditions, relatively free of anthropogenic influences.

Wet deposition and scavenging efficiency of gaseous and particulate phase polycyclic aromatic compounds at a central European suburban site

Abstract The concentration of 15 3–6-ring polycyclic aromatic hydrocarbons (PAHs) in atmospheric precipitation was monitored over 18 months in the years 2006–2008, using an automatic wet-only sampler at a suburban site in Brno, Czech Republic. The PAH concentration in rainwater varied between 2.8 and 571 ng L−1 and the volume weighted mean was 93 ng L−1 with fluoranthene, pyrene, phenanthrene and benzo(b)fluoranthene contributing most. The contribution of particle-associated PAH (sum of 15) to the wet deposition flux was by average 51%, 82% in summer and 47% in winter. The median total (gas and particulate) scavenging ratios, Wt (m3 L−1), varied between 450 for acenaphthene and 3.1 × 104 for fluoranthene. Estimates of the scavenged fraction in the column of air subject to precipitation suggest that typically only a few percent or less of the airborne PAHs are washed out during a precipitation event. The contribution of particle scavenging to total PAH scavenging varied between 7 and 98% among events. Its median was 41%. Scavenging efficiency seems to be influenced by mass size distribution. It is concluded that wet deposition of PAHs is less efficient than dry deposition.

Long-Term Performance of a Solar-Powered Small Automatic Rainwater Collector and Its Application to Acid Deposition Monitoring in the Southeast Mountainside of Mt. Fuji

The performance of a solar-powered small automatic rainwater collector was investigated, which was developed with an emphasis on small-size, lightweight, and inexpensive for use in a wet deposition monitoring network in a mountainous area. It was studied at Tarobo, which is located at the southeast mountainside (1300 m a.s.l.) on Mt. Fuji, during four years from July 2005 to September 2009. The rainfall amounts estimated by the automatic rainwater collector corresponded to those observed by a rain gauge verified by Japan Meteorological Agency. A comparison of the rainwater chemistry by the automatic rainwater collector with that by a commercially available wet-only sampler indicates that the automatic rainwater collector is available for use in wet deposition monitoring in mountainous areas. The mean annual wet deposition fluxes of H+, NH4+, NO3−, and SO42− at Tarobo were 48.9, 35.0, 38.0 and 69.4 meq/m2/y during three years from 2006 to 2008, respectively, and were higher than those at remote sites in Japan, particularly NO3− deposition. The concentration of acidic substances at Tarobo was nearly equal to those at remote sites in Japan, so it is expected for Tarobo to be in use for a remote site of an acid-deposition monitoring network in Japan because of easy access to Tarobo.

Measurement of dry deposition to bulk precipitation collectors using a novel flushing sampler

Bulk precipitation samplers, which are continuously open, also sample gases and particles deposited on the funnel surface. Wet-only samplers, which open only during precipitation, avoid this problem, but can be bulky (leading to disruption of air flow and droplet collection) and need electrical power. We describe here a simple battery-powered modification to a standard bulk sampler that allows the separate measurement of deposition to the funnel surface and wet deposition by washing the funnel surface when precipitation is detected. Comparison of this design with a standard bulk sampler over 3 months at a site in eastern Scotland showed that dry deposition to the funnel surface contributed around 20% of sulfate, 20-30% of nitrate and 20-40% of ammonium ions. There was also a significant loss of ammonium and nitrate in the modified sampler, presumably in the tubing, even though a biocide had been added to the sample bottles. This observation has implications for bulk samplers of similar design, with a sample bottle at ground level. Deposition of sea salts and calcium was greater to the flushing collectors than to the bulk collectors, implying that regular cleaning of funnel surfaces with 10% methanol solution subtly alters the capture efficiency for larger particles.

Impacts of sulfur dioxide from Miyakejima on precipitation chemistry in Japan

Precipitation chemistry data of Japanese Acid Deposition Survey (JADS) by Japan Ministry of the Environment was analyzed to evaluate the influence of SO 2 emitted from the volcano of Miyakejima located in the Pacific Ocean 200 km south of Tokyo. Precipitation samples were collected with wet-only samplers on a daily basis at eight sites over Japan. The sampling periods (1997–2005) were divided into three periods in consideration of the start of the eruption, August 2000: 1997–1999 (Period A), 2000–2002 (Period B), 2003–2005 (Period C). The influence was evaluated in terms of the ratio before-to-after the eruption, B/A and C/A. The B/A ratios for mean nss-SO 4 2− concentration ranged from 1.1 to 2.3. The average pH decreased at most sites in Period B. The ratios for annual deposition were the same level as those of the concentration. The influence was also assessed for daily concentration and deposition at Tanzawa and Tsukuba, the two closest sites to Miyakejima. The cumulative frequency distributions of the daily nss-SO 4 2− concentration shifted to higher concentration for both sites in Period B. Daily pH cumulative frequency distributions shifted to lower values at both sites in Period B. The monthly fraction, nss-SO 4 2−/(nss-SO 4 2− + NO 3 −), increased immediately after the eruption onset. The eruption was found to have influenced concentrations and deposition of nss-SO 4 2− and pH on a national scale, and the sites closest to Miyakejima showed the largest influence.

Atmospheric Deposition of Reactive Nitrogen on Turf Grassland in Central Japan: Comparison of the Contribution of Wet and Dry Deposition

The atmospheric deposition of reactive nitrogen on turf grassland in Tsukuba, central Japan, was investigated from July 2003 to December 2004. The target components were ammonium, nitrate, and nitrite ions for wet deposition and gaseous ammonia, nitric and nitrous acids, and particulate ammonium, nitrate, and nitrite for dry deposition. Organic nitrogen was also evaluated by subtracting the amount of inorganic nitrogen from total nitrogen. A wet-only sampler and filter holders were used to collect precipitation and the atmospheric components, respectively. An inferential method was applied to calculate the dry deposition velocity of gases and particles, which involved the effects of surface wetness and ammonia volatilization through stomata on the dry deposition velocity. The mean fraction of the monthly wet to total deposition was different among chemical species; 37, 77, and 1% for ammoniacal, nitrate-, and nitrite-nitrogen, respectively. The annual deposition of inorganic nitrogen in 2004 was 47 and 48 mmol m−2 yr−1 for wet and dry deposition, respectively; 51% of atmospheric deposition was contributed by dry deposition. The annual wet deposition in 2004 was 20, 27, and 0.07 mmol m−2 yr−1, and the annual dry deposition in 2004 was 35, 7.4, and 5.4 mmol m−2 yr−1 for ammoniacal, nitrate-, and nitrite-nitrogen, respectively. Ammoniacal nitrogen was the most important reactive nitrogen because of its remarkable contribution to both wet and dry deposition. The median ratio of the organic nitrogen concentration to total nitrogen was 9.8, 17, and 15% for precipitation, gases, and particles, respectively.

The status of wet deposition of nitrogen compounds in an intensive dairy farming area in central Japan

(pp. 47–52) The wet deposition of nitrogen compounds in the intensive dairy farming area and its environs in the northern part of the Kanto region in central Japan was investigated from April 2003 to April 2005. Open-bulk samplers were used to collect open-bulk precipitation, which approximates the sum of wet and dry deposition. Furthermore, wet-only samplers were applied to collect the precipitation for every 1 mm in a rainfall, termed the wet sample. The concentrations of total nitrogen and ammonium ions in the open-bulk precipitation were high in the central part of the dairy farming area and low in the remote mountainous area more than 15 km away the concentrations were generally high during winter and spring, and low during summer and autumn. There was a large difference in the annual deposition of nitrogen between the farming area and the surrounding area. The annual deposition of nitrogen in the farming area was significantly high compared to the values of existing data in Japan and Europe. The concentrations of respective nitrogen compounds in the wet sample, which accounted for 40 of the total rainfalls events, were notably high at the beginning of precipitation and rapidly decreased by 8 mm of continuous precipitation. The nitrogen concentrations at the beginning of precipitation were high in the farming area, and relatively low in the surrounding area. It was thought that the cause of the large wet deposition in the farming area was due to ammonia emissions, mainly from cattle manure produced at dairy farms. The factors of the seasonal changes were considered to be the frequency and the amount of precipitation, and the change in ammonia emissions from manure management performed by dairy farmers.

Precipitation Chemistry and Wet Deposition in Kruger National Park, South Africa

The chemical composition, as well as the sources contributing to rainwater chemistry have been determined at Skukuza, in the Kruger National Park, South Africa. Major inorganic and organic ions were determined in 93 rainwater samples collected using an automated wet-only sampler from July 1999 to June 2002. The results indicate that the rain is acidic and the averaged precipitation pH was 4.72. This acidity results from a mixture of mineral acids (82%, of which 50% is H2SO4) and organic acids (18%). Most of the H2SO4 component can be attributed to the emissions of sulphur dioxide from the industrial region on the Highveld. The wet deposition of S and N is 5.9 kgS⋅ha−1⋅yr−1 and 2.8 kgN⋅ha−1⋅yr−1, respectively. The N deposition was mainly in the form of NH4 +. Terrigenous, sea salt component, nitrogenous and anthropogenic pollutants have been identified as potential sources of chemical components in rainwater. The results are compared to observations from other African regions.

Comparative field study on precipitation, throughfall, stemflow, fog water, and atmospheric aerosol and gases at urban and rural sites in Japan

Precipitation collected by a wet-only sampler (WP), precipitation collected by a filtering-type bulk sampler (BP), throughfall (TF), stemflow (SF), fog water (FW), and atmospheric aerosol and gases were collected at two sites with different site classifications: an urban site (Mt. Rokko) and a rural site (Mt. Awaga) to investigate canopy–atmosphere interactions and to study the chemistry of precipitation in forested areas located in different atmospheric conditions. Compared to those at the rural site, the monthly volume-weighted pH values at the urban site were not significantly ( p > 0.05) different for WP, higher ( p < 0.05) for BP, not significantly ( p > 0.05) different for TF, lower ( p < 0.01) for SF, and lower ( p < 0.01) for FW. The order of mean pH values at the urban site was FW < SF < WP < TF < BP. In contrast, the order at the rural site was FW < SF < BP < WP < TF. Concentrations of chemical species at the urban site were higher than those at the rural site in all samples and all chemical species. In particular, higher NO 3 − concentrations at the urban site were observed in all samples. The amount of dry deposition on leaves at the urban site was approximately 1.17 times larger than that at the rural site. The monthly net TF (= TF − BP) in autumn seemed to be larger than that in summer; this trend was remarkable in K +. The monthly NO 3 − deposition in the net TF was larger at the urban site than at other parameters and at the rural site. The concentrations of chemical species in aerosol and gases that were measured near the central part of Kobe City were ca. 3.4 times higher than those in the rural area. Mt. Rokko borders the central part of the city, which caused the concentrations at Mt. Rokko to be higher than those at Mt. Awaga. The deposition amounts at Mt. Rokko were larger than those at Mt. Awaga, which probably can be attributed to the higher concentrations of chemical species in atmospheric aerosol and gases.

Atmospheric deposition of polycyclic aromatic hydrocarbons on the Lake Balaton, Hungary

The concentration of polycyclic aromatic hydrocarbons (PAHs) in atmospheric precipitation and aerosol samples was monitored on the Lake Balaton to examine the seasonal variations and depositions. Samples were collected at Tihany located on the north part of the Lake Balaton between April 2002 and April 2003. Aerosol particles were sampled on quartz fiber filters using low volume sampler (1.2 m 3/h). For the determination of the size distribution of PAHs, aerosol was collected on aluminium foils by an eight-stage Berner-type low-pressure impactor (31.2 m 3/h, cutoff diameters: 0.0625–8 μm). The dry deposition velocities on water surface as a function of the particle diameter were estimated. The collection of rain and snow samples was performed by an automatic wet-only sampler. The seasonal mean concentration of the ΣPAHs in precipitation was found as 149, 96, 586, and 1136 ng/l in spring, summer, autumn, and winter, respectively. In the atmospheric aerosol samples, the seasonal mean concentration of the ΣPAHs varied from 3.2, 1.7, 6.2, and 31 ng/m 3 in spring, summer, autumn, and winter, respectively. It was found that PAHs generally showed the maximum concentration in the 0.25- to 1.0-μm size range in every season. Wet (280 μg/m 2×year) and dry (70 μg/m 2×year) deposition rates were calculated, and pollution loading of PAHs from the atmosphere to the Lake Balaton was obtained as 170 kg/year of wet and 40 kg/year of dry deposition.

Precipitation Chemistry in Semi-Arid Areas of Southern Africa: A Case Study of a Rural and an Industrial Site

Experimental data on the precipitation chemistry in the semi-arid savanna of South Africa is presented in this paper. A total of 901 rainwater samples were collected with automatic wet-only samplers at a rural site, Louis Trichardt, and at an industrial site, Amersfoort, from July 1986 to June 1999. The chemical composition of precipitation was analysed for seven inorganic and two organic ions, using ion chromatography. The most abundant ion was SO4 2 − and a large proportion of theprecipitation is acidic, with 98% of samples at Amersfoort and 94% at LouisTrichardt having a pH below 5.6 (average pH of 4.4 and 4.9, respectively). This acidity results from a mixture of mineral and organic acids, with mineral acids being the primary contributors to the precipitation acidity in Amersfoort, while at Louis Trichardt, organic and mineral acids contribute equal amounts of acidity. It was found that the composition of rainwater is controlled by five sources: marine, terrigenous, nitrogenous, biomass burning and anthropogenic sources. The relative contributions of these sources at the two sites were calculated. Anthropogenic sources dominate at Amersfoort and biomass burning at Louis Trichardt. Most ions exhibit a seasonal pattern at Louis Trichardt, with the highest concentrations occurring during the austral spring as a result of agricultural activities and biomass combustion, while at Amersfoort it is less pronounced due to the dominance of relatively constant industrial emissions. The results are compared to observations from other African regions.

Field intercomparison of precipitation measurements performed within the framework of the Pan European Intensive Monitoring Program of EU/ICP Forest

A 6-month field intercomparison study on precipitation measurements was performed at Schagerbrug near the west coast in the Netherlands. Twenty bulk sampling systems and two wet-only samplers were evaluated on accuracy, sampling strategy and performance under field conditions. Bulk precipitation fluxes of NO 3 −, NH 4 +, H + and Kjeldahl-N generally could be determined with a greater accuracy than bulk precipitation fluxes of SO 4 2−, Na +, Cl −, Mg 2+, Ca 2+, Alkalinity and H +. Bulk precipitation fluxes of K + generally had the lowest accuracy. Only 20% of the sampling systems differed less than 10% from the best estimate, whereas most systems (60%) differed more than 20% from the best estimate. The inaccuracy induced by the sampling system appeared to be much larger than that resulting from the analysis of the samples by different laboratories as determined by ring-tests.

Difference between filtering-type bulk and wet-only data sets based on site classification

In order to clarify the limitations and the effectiveness of filtering-type bulk sampler, a study on precipitation collected by filtering-type bulk and wet-only samplers was performed. At an urban site, there was a statistically significant difference between the filtering-type bulk and wet-only samples at a 1% significance level in the pH and major chemical components. At a suburban site, pH, NH 4 +, and nss-Ca 2+ showed a difference at a 1% significance level and NO 3 − at a 5% significance level, but nss-SO 4 2− did not show any difference even at a 5% significance level. At a rural site, although there was a difference in nss-Ca 2+ at a 1% significance level and in pH at a 5% significance level, nss-SO 4 2−, NO 3 −, and NH 4 + did not show any difference. The attributions of the deposition of gaseous compounds and particulate matter in a filtering-type bulk sampler were estimated to be 32% (nss-SO 4 2−), 46% (NO 3 −), 36% (NH 4 +), and 75% (nss-Ca 2+) at an urban site, 14% (nss-SO 4 2−), 16% (NO 3 −), 27% (NH 4 +), and 42% (nss-Ca 2+) at a suburban site, and 16% (nss-SO 4 2−), 17% (NO 3 −), 19% (NH 4 +), and 47% (nss-Ca 2+) at a rural site. The degree of pollution at a sampling site should be taken into account when using a data set collected with filtering-type bulk samplers.

Wet Deposition of Trace Metals in Singapore

The concentrations of 12 trace metals (Al, Cd, Cr, Cu, Co, Fe,Mn, Ni, Pb, Zn, V, and Ti) in wet depositions are reported. Eighty four rainwater samples were collected using an automated wet-only sampler in Singapore for one year (2000) and subjected to chemical analysis using ICP-MS. Based on the volume-weighted meanconcentrations measured, the trace metals were classified into three groups: Al and Fe with an average concentration of largerthan 15 μg L-1, Cr, Cu, Mn, Ni, Pb, Zn, V, and Ti withconcentrations between 1 and 10 μg L-1, and finally Co and Cd with concentrations lower than 1 μg L-1. Elementenrichment factors were calculated to distinguish between naturaland anthropogenic sources. The calculation of crustal enrichmentfactors with Al as the reference element indicated that while Ti,Fe and Mn originated from crustal sources, the remaining trace metals (Cd, Cr, Co, Cu, Ni, Pb, Zn and V) were mainly derived from anthropogenic sources. The removal of the trace metals from the atmosphere by precipitation was influenced by the rainfall amount as well as pH. The magnitude of the measured average annual wet deposition fluxes of Al, Fe, and combustion-generatedelements such as V, Ni, and Cu is higher than that reportedfor other sites outside Singapore, owing to abundant rainfallthroughout the year in this region.

Analysis of polar pesticides in rainwater in Denmark by liquid chromatography–tandem mass spectrometry

A new LC–MS–MS method for analysis of rainwater has been developed and validated for 53 pesticides, degradation products of pesticides and selected nitrophenols. The method was used to monitor the concentration of pesticides in rainwater at one location near Roskilde, Denmark from February 2000 to August 2000. Sampling was done in periods of up to 4 weeks using a cooled wet-only sampler. Water samples were extracted by solid-phase extraction on Oasis HLB columns. The analysis of the extracts was performed by LC–MS–MS with electrospray ionization. All samples were analysed in negative and in positive ionization mode, respectively for acidic and neutral compounds. All analyses were done in the selected reaction monitoring mode in order to obtain a better signal-to-noise ratio. The method has been validated for the following parameters: recovery, detection limit, uncertainty and linearity. Atrazine, terbuthylazine, isoproturon, mechlorprop and (2-methyl-4-chlorophenoxy)acetic acid were measured at concentrations above 0.100 μg/l, mainly during the period of agricultural use. Nitrophenols were measured at high concentrations all year with peaks in the cold season (February–March).

Input of pesticides by atmospheric deposition

Sampling and analytical methods were developed to examine the input of various pesticides on noncultivated areas of the FAM (Research Network on Agroecosystems) Research Station Scheyern. Off-target drift from pesticide application on nearby cultivated land, as well as input due to long-range atmospheric transport, were measured. The wet deposition was determined by a cooled wet-only sampler. Bulk samplers and specially designed samplers with glass-fiber surface were used for total deposition measurements. Analysis of pesticides was carried out using liquid/liquid or solid-phase extraction and high performance liquid chromatography-UV (HPLC-UV) or gas chromatography-nitrogen/phosphorus-sensitive detector/MS (GC-NPD/MS) detection. Obtained results demonstrated that for several compounds, total deposition, i.e. the sum of wet and dry deposition, was marginally higher than wet deposition alone. In contrast, total deposition data of pesticides having been applied near the sampling site exceeded wet deposition values by orders of magnitude. In addition to direct drift, determined as droplets depositing near pesticide application areas, an indirect drift represented by particle-associated or gaseous transport was observed, both of which contributed considerably to total deposition. Therefore, to determine the input of pesticides to nontarget areas in the close vicinity of pesticide application, direct and indirect drift, and background deposition must be considered.

Biological and chemical analysis of the toxic potency of pesticides in rainwater

A newly developed method for measuring the integrated esterase inhibiting potency of rainwater samples was applied in practice, and the results are compared to the toxic potency calculated from concentrations of 31 organophosphate (OP) and carbamate pesticides, out of a total of 66 chemically analyzed pesticides. In addition, the general toxic potency of the rainwater samples was evaluated in a microtiter luminescence assay with Vibrio fischeri bacteria. Rainwater samples were collected over four consecutive 14-day periods in both open and wet-only samplers. The esterase inhibiting potency of the open rainwater samples (expressed as ng dichlorvos-equivalents/l) corresponded well with the chemical analyses of the rainwater samples collected by both types of samplers ( r=0.83–0.86). By far, the highest esterase inhibiting potency was found in a sample collected in an area with intense horticultural activities in June, and was attributed to high concentrations of dichlorvos, mevinphos, pirimiphos-methyl and methiocarb. The esterase inhibiting potency of this sample was equivalent to a dichlorvos concentration of 1380 ng/l in the rainwater, which is almost 2000 times higher than the maximum permissible concentration (MPC) of dichlorvos set for surface water in Netherlands. Maximum individual concentrations of dichlorvos and pirimiphos-methyl even exceeded the EC 50 for Daphnia, suggesting that pesticides in rainwater pose a risk for aquatic organisms. Not all responses of the luminescence-assay for general toxicity could be explained by the analyzed pesticide concentrations. The bio-assays enable a direct assessment the toxic potency of all individual compounds present in the complex mixture of rainwater pollutants, even if they are unknown or present at concentrations below the detection limit. Therefore, they are valuable tools for prescreening and hazard characterization purposes.