Half-life In Soil Research Articles

Response to comment on “Identification of substances with potential for long-range transport as possible substances of very high concern”

In his comment on our article “Identification of substances with potential for long-range transport as possible substances of very high concern” [1], Sierra Rayne identified several substances, which might lead to another classification as indicated by us. We agree with Dr. Rayne that one substance ethanol, 2,2′,2′′-nitrilotris-, compound with (chlorometyl)oxirane (1:1) (CAS No. 68141-08-02) is significantly ionized in most aquatic systems. He further claimed that some compounds have been classified as persistent although they are rapidly hydrolyzed. We clearly described in the methods section of our article that we used the fugacity module of the EPI Suite for estimating degradation half-lives in air, water, sediment, and soil (p. 3154). The latter three half-lives are determined using the BIOWIN estimation program. “If a compound is susceptible to abiotic hydrolysis under environmental conditions, ... then the user must manually enter the value into the Fugacity, Half-life Selection option.” (EPI Suite, fugacity help file). We developed an automatic screening procedure for a large substance list without manually entered values and evaluated “the screening results for the identified 11 compounds...to underline that estimated parameters of the technically identified substances can be confirmed...” (p. 3159). We thank Dr. Rayne for checking the substances on their hydrolytic degradation potential, which is very helpful to prioritizing chemicals as possible substances of very high concern.

Assessment of PBTs in the European Union: a critical assessment of the proposed evaluation scheme with reference to plant protection products

A number of international and national programs classify substances that are persistent (P or very P), bioaccumulative (B or very B), toxic (T), or have the potential for long-range transport. The oldest of these programs is the Stockholm Convention on Persistent Organic Pollutants. More recent programs address persistent, bioaccumulative, and toxic (PBT) properties for chemicals in general (Registration, Evaluation, Authorisation and Restriction of Chemicals, REACH; EC 253/2011) and plant protection products (PPPs) (EC 1107/2009). However, these programs used different criteria for categorization. We critically assessed the criteria and process used in the categorization of PPPs and noted that EC1107/2009, in contrast to the Stockholm Convention or REACH, offers no process for carrying out a further, more refined assessment of those pesticides that are identified as having PBT properties. Thus, in contrast to REACH, few basic screening criteria are used for final-step management decisions. Guidance on the selection of data is not provided, and the criteria used are unclear. For example, no guidance is given as to how the half-lives in soil, water, and sediment should be derived and the term ‘half-life’ is not clearly defined. Large amounts of useful data on environmental and toxicological properties are available for PPPs but most of this is not used in the categorization, for example, photolysis in water, water-sediment, and on soil, important environmental degradation processes particularly relevant to pesticides. The criteria for bioaccumulation and toxicity appear to be focused only on aquatic ecosystems and do not address the terrestrial compartment which is particularly relevant for pesticides and potentially relevant for PBT considerations. The categorization process under EC 1107/2009 could be made more efficient and reduce false negatives and positives if a formal weight of evidence approach was applied to multiple lines of evidence. This paper presents these ideas and how they can be incorporated into the framework for categorization to better classify plant protection products in terms of persistence, bioaccumulation, and toxicity.

Aminopyralid Residue Impacts on Potatoes and Weeds

Aminopyralid is used in Alaska to control certain invasive weed species; however it appears to have an extended soil half-life in interior Alaska resulting in carry-over injury in potatoes. Field studies at three experiment stations in Delta Junction, Fairbanks, and Palmer, Alaska were established to determine the dose–response of weeds and above and below ground potato growth to soil-applied aminopyralid (0, 8, 15, 31, 62, and 123 g ae ha−1) . Both prostrate knotweed and narrowleaf hawksbeard were susceptible to aminopyralid. At Delta Junction and Fairbanks, visual injury of potatoes greater than 25 % was observed at 15 g ae ha−1 aminopyralid, whereas at Palmer visual injury was greater than 40 % at 8 g ae ha−1, the lowest rate tested. Potato tuber production was reduced by aminopyralid at rates of 15 g ae ha−1 and above at both Delta Junction and Palmer. Sub-samples of potato tubers from Delta Junction and Palmer were analyzed for aminopyralid content and grown out to determine if aminopyralid in tubers would reduce subsequent growth. The aminopyralid concentration in potato tubers increased with increasing field application rates, with 30 ppb extracted from tubers grown at the highest application rate (123 g ae ha−1). All plants grown from daughter tubers except from control plots in Palmer exhibited injury symptoms. The number of emerged shoots, and shoot height decreased with increasing aminopyralid concentrations in the tuber, with injury rates greater than 70 % at 8 g ae ha−1.

The investigation on lambda-cyhalothrin dissipation under field conditions

The soil dissipation of lambda-cyhalothrin was investigated in Changchun (Jilin), Tongzhou (Beijing), Yangling (Shanxi), Xiaoxiang (Anhui), and Danzhou (Hainan) in China under field conditions; and the dissipation on maize, soybean, tomato, cabbage and apple was investigated under field conditions as well. The declining rates of lambda-cyhalothrin in soil were relatively faster in the initial days. The half-lives in soil were in the range of 1.56 to 5.30 days in the five locations. Significantly lower degradation rate was observed on the apple whose half-lives were 10.3 days and 17.7 days in Beijing and Anhui, respectively. The half-lives of cabbage, maize, soybean and tomato were in the ranges of 1.32 to 2.74 days in Beijing and 2.07 to 3.80 days in Anhui. Lambda-cyhalothrin was less transported in the plants and could be detected in the eatable parts of maize, soybean and tomato. It could be in the cabbage, maize plant and apple.

Buffer strip effect on terbuthylazine, desethyl-terbuthylazine and S-metolachlor runoff from maize fields in Northern Italy

The effectiveness of a 6 m wide vegetative buffer strip for reducing runoff of S-metolachlor, terbuthylazine and desethyl-terbuthylazine was studied in 2007–2008 in Northern Italy. Two cultivated fields, with and without the buffer strip, were compared. Residues of the chemicals were investigated in runoff water collected after runoff events and their dissipation in the soil was studied. The highest concentration of the chemicals in water occurred in samples collected from the unbuffered field at the first runoff events. Losses of terbuthylazine and S-metolachlor in runoff waters were particularly high in 2007 (2.6% and 0.9% of the amount applied, respectively). Soil half-life of terbuthylazine and S-metolachlor ranged between 12.1 and 8.9 days and 16 and 7 days, respectively. The presence of desethyl-terbuthylazine was related to parent compound degradation. The buffer strip allowed an important reduction of chemical content in water (>90%), in particular during the first runoff events.

Dissipation and Residues of Rimsulfuron in Potato and Soil Under Field Conditions

The analytical method for the residue analysis of a sulfonylurea herbicide, rimsulfuron, and its dissipation in soil and potato plants under field conditions were studied. Rimsulfuron residues were determined by Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method and ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS). Mean recoveries ranged from 74.6 % to 106.2 % with relative standard deviations (RSDs) of 2.0 %-13.8 % at three different spiking levels for each different matrix. The limits of detection (LOD) of rimsulfuron were ranged from 0.3 to 1.4 μg/kg, while the limits of quantification (LOQ) ranged from 0.9 to 4.3 μg/kg in different matrixes. The dissipation dynamics of rimsulfuron in the field trials in Shandong and Zhejiang Province were investigated. The half-lives in potato seedlings were 4.1 days in Shandong and 4.3 days in Zhejiang, both with a dissipation rate of 90 % about 7 days after application. The half-lives in soil were 6.0 days in Shandong and 6.6 days in Zhejiang, and with a dissipation rate of 90 % over 28 days. The terminal residues in potato and soil were not detectable. The fact that all the terminal residues were below the maximum residue level (0.1 mg/kg) set by Japan and 0.05 mg/kg set by EU. Hence it was safe for the use of this pesticide and the results also could give a reference for maximum residue limits setting of rimsulfuron in potato in China.

Describing the environmental fate of diuron in a tropical river catchment

The use of the herbicide diuron on sugarcane fields along the river catchments of the Great Barrier Reef (GBR) in Australia is an issue of concern due to high levels of diuron reported in the GBR lagoon, and has recently led to a restriction on the use of diuron during the 2011/12 wet season. An important question in this context is how much diuron is mobilised from the agricultural area by strong rainfall and floods in the wet season and transferred to the GBR lagoon. We have set up a multimedia chemical fate model for a tropical catchment to describe the fate of diuron within the Tully River catchment, Queensland, Australia. The model includes highly variable rainfall based on meteorological data from the Tully River catchment and a flood water compartment on top of the agricultural soil that is present during times for which floods were reported. The model is driven by diuron application data estimated for the Tully River catchment and is solved for time-dependent diuron concentrations in agricultural soil and seawater. Model results show that on average 25% of the diuron applied every year is transferred to the GBR lagoon with rainwater and flood water runoff. Diuron concentrations estimated for the seawater range from 0.1ng/L to 12ng/L and are in good agreement with concentrations measured in the GBR lagoon. The uncertainty of the diuron concentrations estimated for seawater is approximately a factor of two and mainly derives from uncertainty in the diuron degradation half-life in soil, properties of the soil compartment such as organic matter content, and the speed of the seawater current removing diuron dissolved in seawater from the seawater compartment of the model.

Dissipation of Propanil and 3,4 Dichloroaniline in Three Different Rice Management Systems

This study focused on the dissipation of propanil and 3,4 dichloroaniline (3,4 DCA) over time in the soil, field water, inlet water, and outlet water of paddy fields under three management systems: conventional water seeding (CON), conventional water seeding with supplied liquid manure (LMA), and dry seeding (DRY). Propanil dissipation in water was also investigated under laboratory conditions. The field study was conducted from 2004 to 2006 at Vercelli, northern Italy. Propanil and 3,4 DCA showed rapid dissipation in water and soil environments both in the field and in the laboratory. Under controlled conditions, chemical hydrolysis was not detected for either compounds for up to 100 d at pHs of 5, 7, and 9. In the laboratory, the half-life of propanil in irrigation water was 1.1 d; its half-life in soil was routinely measured at <1.0 d (between 0.17 and 1.77 d). 3,4 DCA was found to persist much longer. Measured in all three study years at 50 d after treatment, its concentration ranged between 44 μg kg (CON) and 140 μg kg (DRY). Propanil and 3,4 DCA concentrations in paddy water were particularly high in samples collected at 4 d (2004) and 2 d (2005) after treatment. Maximum concentrations were 54.4 μg L (CON) for propanil (2005) and 113.7 μg L (LMA) for 3,4 DCA (2004). The concentrations of propanil and 3,4 DCA in inlet water were never above 1.1 and 0.3 μg L, respectively, whereas the highest concentration of each compound in outlet water was in samples collected first after treatment in 2005 and 2006. Both chemicals dissipated rapidly in all the soil-water environments but displayed no important differences among the three management systems. In conclusion, propanil and 3,4 DCA did not persist longer in paddy fields. A risk of water network contamination by these compounds may occur only early after herbicide spraying. A water-holding period after herbicide spraying may reduce this risk.

Enantioselective Damage of Diclofop Acid Mediated by Oxidative Stress and Acetyl-CoA Carboxylase in Nontarget Plant Arabidopsis thaliana

Diclofop-methyl (DM) is a widely used chiral herbicide, which rapidly hydrolyzes to its major metabolite diclofop acid (DC) after application. With a carbon chiral center, DC not only is an important ingredient of herbicidal activity, but also has a long half-life in soil. Studies so far have only considered the activity of racemic DM in target organisms, and the enantioselective toxicity in nontarget plants of DM and DC has yet to be explored. In this study, the enantioselective phytotoxicity of DC mediated by oxidative stress and the key enzyme ACCase in the fatty acid synthesis system on the model plant Arabidopsis thaliana was investigated. Significant differences between the two enantiomers were observed in phytotoxicity including growth inhibition, oxidative damage and alteration of key genes expression of ACCase, with R-DC showing greater toxicity to Arabidopsis thaliana than S-DC. The results of molecular docking showed that there was a stronger affinity between R-DC and the target enzyme carboxyltransferase domain of ACCase, likely leading to the enantioselective phytotoxicity of DC. This study suggested that chirality of both parent compounds and metabolites should be considered to improve our understanding of the environmental fate and risks of chiral pesticides.

Behavior of pesticide residues in agricultural soil and adjacent River Kuywa sediment and water samples from Nzoia sugarcane belt in Kenya

An inventory survey conducted to determine pesticide usage in a sub-catchment of the Nzoia sugarcane belt found a variety of pesticides used in the sub-catchment, which are reported in this paper. Analysis of soil samples from seven fallow experimental field plots left uncultivated for various periods from 3 to 96 months after cultivation with pesticide application indicated persistence of high concentrations of pesticide residues in the soil, with estimated soil half-lives (in years) ranging from 0.72 to 57.75 for organochlorines and from 1.13 to 8.25 for herbicides. The mean water concentrations (in μg/L) of the pesticide residues in River Kuywa, which flows through the Nzoia Nucleus Estate sugarcane farms, ranged from 0.12 (lindane) to 1.36 (p,p′-DDT) for organochlorines and from 0.14 (atrazine) to 1.75 (diuron) for herbicides during the heavy rains period in August 2008 while the mean sediment concentrations (in μg/g) ranged from 0.28 (lindane) to 1.87 (endrin) for organochlorines and 0.39 (hexazinone) to 4.61 (alachlor) for herbicides. The mean concentrations of residues in water during the light rain period in December 2008 ranged from 0.17 (p,p′-DDT) to 0.71 (aldrin) for organochlorines and 0.01 (atrazine) to 1.74 (alachlor) for herbicides while the sediment concentrations ranged from 0.38 (p,p′-DDT) to 1.145 (aldrin) for organochlorines and 0.74 (atrazine) to 1.98 (alachlor) for herbicides. Although DDT, aldrin, dieldrin, and endrin were not reported in the survey, their presence in the fallow experimental field plot soils and in River Kuywa water and sediment could indicate previous application, lack of recorded data or illegal usage since 1997 when they were banned. Notably, the concentrations of alachlor, diuron, cypermethrin, and hexazinone in the water column were substantial indicating their extensive usage and residual persistence in the sub-catchment, with subsequent wash-off and leaching into River Kuywa. The concentration levels of some of the individual pesticides exceeded the EU limit requirements for drinking water and indicated potential risk to humans and cattle if the water is used without treatment.

Terbuthylazine and other triazines in Italian water resources

The concern on the presence of pesticides in Italian water resources historically broke out around 1980 after severe episodes of ambient, raw water and drinking water contamination due to some herbicides, atrazine (ATR), its metabolites desethylatrazine (DEA) and deisopropylatrazine (DIA), simazine, cyanazine, bentazone, molinate, which affected mainly the maize, grain and rice producing floodplains and karst areas of the northern Regions. Due to the risks of human exposure, in the early 1990 the use of atrazine was banned in Italy and was replaced by terbuthylazine (TERB). In a few years, TERB became a chemical of concern, together with its main metabolite desethylterbuthylazine (DET), because of alerting detections in surface and groundwater resources. Up to now, the risk of contamination of water resources by TERB, DET, DEA and, in some extent ATR, is of relevance in Italy due to their present and past wide employment in agriculture, the discharges or seepages in particularly vulnerable areas, their unfavorable intrinsic properties, e.g. poor sorption and high persistence, their mobility by drift, leaching and runoff in vadose zones, aquifers and surface water. So, unsurprisingly, results from national monitoring of ambient water and raw water indicate that TERB, DET, DEA and residual ATR, despite its withdrawal, are detected at remarkable frequencies and, sometimes, at levels higher than pesticide quality standards under the Italian Decrees for the protection of surface water (specifically, raw waters doomed at the drinking water abstraction), groundwater and drinking water (tap water), that is 0.1–0.5μg/l for individual pesticides and for total pesticides, respectively, including relevant metabolites. On the other hand, in these last years, the control measures in drinking water production adopted by the waterworks Companies and the regional and central health Authorities, also in the view of the recent WHO approaches under the Water Safety Plans, ensure that levels of any pesticide residue (also involving TERB, DET, DEA, ATR) in finished tap water meet parametric values for pesticides. Therefore, in these last years, no derogation to the parametric values for drinking water has been required. The aim of this paper is to contribute to widen the knowledge on the water impact of these important water pollutants giving sound details on present usages, levels and frequencies of detection in water bodies in Italy, on their key chemiodynamic properties, e.g. soil half-lives (DT50) and soil to organic carbon partition (Koc) available in the open literature, particularly for TERB metabolites, and some details on legal provision adopted at the national level. In fact, a more effective protection of water supplies, particularly against TERB and DET, has been pursued in the late 2000s by the Italian Health Ministry through the adoption of consistent provisions aimed at mitigating emissions of TERB in routine agricultural activities, and by the Italian Ministry of the Environment through the adoption of specific Environmental Quality Standards for TERB and its metabolite DET, ATR, SIM for the protection of surface waters.

Persistence of the Fluoroquinolone Antibiotic Difloxacin in Soil and Lacking Effects on Nitrogen Turnover

The environmental risks caused by the use of fluoroquinolone antibiotics in human therapeutics and animal husbandry are associated with their persistence and (bio)accessibility in soil. To assess these aspects, we administered difloxacin to pigs and applied the contaminated manure to soil. We then evaluated the dissipation and sequestration of difloxacin in soil in the absence and presence of plants within a laboratory trial, a mesocosm trial, and a field trial. A sequential extraction yielded antibiotic fractions of differing binding strength. We also assessed the antibiotic's effects on nitrogen turnover in soil (potential nitrification and denitrification). Difloxacin was hardly (bio)accessible and was very persistent under all conditions studied (dissipation half-life in bulk soil, >217 d), rapidly forming nonextractable residues. Although varying environmental conditions did not affect persistence, dissipation was accelerated in soil surrounding plant roots. Effects on nitrogen turnover were limited due to the compound's strong binding and small (bio)accessibility despite its persistence.

Evaluation of environmental fate of acetamiprid in the laboratory

The acetamiprid, a nenicotinoid insecticide, is a popular crop protection agent used in fields as well as in protected cultivation. A laboratory experiment was conditions to study the effect of light, moisture, and pH on the persistence of acetamiprid in water and soil. Dissipation half-lives of acetamiprid in water at pH4, 7, and 9 were 6.2, 7.3, and 5.1days, respectively, and 4.3days under UV and sunlight conditions. Half-life in soil at three concentrations, 0.1, 1.0, and 10μgg(-1) under different moisture regimes varied from 21.5-22.8, 15.6-22.4, 10.0-15.8days, respectively, indicating that acetamiprid dissipated faster in submerged soil as compared to field capacity moisture and dry conditions. The leaching study showed that the possibility for leaching of acetamiprid to ground water is extremely low under normal condition of average rainfall due to compact nature soil in the field. Acetamiprid poses low risks to the ecosystem because of their rapid dissipation and low-bound residues in the environment.

Degradation of Fentrazamide Herbicide in Soil Under Aerobic Condition

Dissipation of fentrazamide in soil under aerobic conditions was studied. Fentrazamide was extracted with 0.1 N HCl: acetone (1:1 v/v) followed by partition and cleanup. Separation was done on ODS-II column with mobile phase acetonitrile: water (70:30 v/v). Recovery varied from 74.51 % to 90.10 % percent in soil. Dissipation followed first order kinetics with monophasic pattern. Half life in soil was 9.02 days. Calibration curves were linear over the range of 0.05-1.00 μg mL(-1) and RSD was 1.82 %. LOD and LOQ were 0.002 and 0.005 μg g(-1) for soil. No residues in soil and crop were observed at harvest.

Structure–toxicity relationship of chloroacetanilide herbicides: Relative impact on soil microorganisms

The research was carried out to ascertain the effect of three chloroacetanilide herbicides, alachlor, butachlor and pretilachlor on soil microbial biomass growth and activity. Laboratory experiments were performed in a silty clay loam soil to relate changes of soil enzymatic activity to the herbicide persistence under laboratory condition up to 42 days at three application rates. The results showed that all the three herbicides caused enhancement of dehydrogenase activity. Higher concentrations of herbicide resulted in enhancement of the enzymatic activity. In addition, a similar trend was observed in β-glucosidase and acid phosphatase activity, although urease activity decreased upon incubation for 42 days as compared with initial soil incubation values. Based on the extent of impact for dehydrogenase activity in soil, the order was pretilachlor>alachlor>butachlor; whereas in case of urease activity, the order changed to pretilachlor>butachlor>alachlor. The soil half-lives of alachlor, butachlor and pretilachlor respectively, were 9.3, 12.7 and 7.3 days, which could be accounted for in terms of their respective chemical structures, as well as variable adsorption, degradation, differential effects of the agents on soil microbes. Soil management practices and the differing physicochemical properties of the herbicides may contribute to their rates of decay in soil.

Sustainability, certification, and regulation of biochar

Biochar has a relatively long half-life in soil and can fundamentally alter soil properties, processes, and ecosystem services. The prospect of global-scale biochar application to soils highlights the importance of a sophisticated and rigorous certification procedure. The objective of this work was to discuss the concept of integrating biochar properties with environmental and socioeconomic factors, in a sustainable biochar certification procedure that optimizes complementarity and compatibility between these factors over relevant time periods. Biochar effects and behavior should also be modelled at temporal scales similar to its expected functional lifetime in soils. Finally, when existing soil data are insufficient, soil sampling and analysis procedures need to be described as part of a biochar certification procedure.

Dissipation and Residues of Flumetsulam in Wheat and Soil

A residue analytical method for the determination of flumetsulam in wheat and soil was developed using gas chromatography with electron capture detector (GC-ECD). The limit of detection of the analytical method was 0.001 ng, and the limit of quantification was 0.005, 0.01 mg/kg for soil and wheat grain, respectively. The mean recoveries from soil and wheat ranged from 83.85 % to 107.2 % with average relative standard deviation ranging from 1.87 % to 8.09 %. The method was successfully applied to determine the residual level and dissipation rate of flumetsulam in the soil and wheat. The half-life in soil was 23.1 days with a dissipation rate of 69 % over 35 days. At harvest time, the residue levels of flumetsulam in wheat grain and soil from high dosage plot were 0.031 and 0.045 mg/kg, respectively. The flumetsulam residues could not be detected from low dosage plot. Direct confirmation of the analyte in real samples was achieved by GC-ECD.

Fertilization can modify the non-target effects of pesticides on soil microbial communities

A three-month mesocosm experiment was performed to unravel interactions between pesticides (difenoconazole: fungicide, deltamethrin: insecticide, ethofumesate: herbicide) and fertilizers (NPK synthetic fertilizer, compost) regarding the potential non-target effects of pesticides on soil microbial communities. To this aim, pesticides and fertilizers were applied to soil at a rate of 5 mg active ingredient kg−1 DW soil and 185 mg N kg−1 DW soil, respectively. Soil sampling was done after 0, 7, 30, 60 and 90 days of incubation in order to determine pesticide degradation rates and microbial properties: enzyme activities, basal respiration, substrate-induced respiration, potentially mineralizable N, nitrification rate and denitrification potential. By the end of the incubation, difenoconazole, deltamethrin and ethofumesate in non-fertilized soils were degraded by 52, 85 and 93%, with half-lives of 86, 36 and 29 days, respectively. Compost application had a stimulatory effect on difenoconazole and deltamethrin degradation. NPK fertilization led to a 26% increase in ethofumesate half-life in soil. Difenoconazole and deltamethrin caused a short-term inhibitory effect on microbial activity in non-fertilized soils, but not in fertilized soils. A short-term antagonistic effect between NPK fertilization and deltamethrin or ethofumesate presence was found regarding their inhibitory effect on potentially mineralizable N. In compost-fertilized soils, pesticides (especially, ethofumesate) counteracted the stimulatory effect of compost on denitrification potential. Pesticides caused a slight negative effect on the capacity of soils to recycle nutrients that was counteracted at day 90 by the addition of compost, as reflected by the values of the treated-soil quality index. We concluded that fertilizers can modify both pesticide degradation rates and their non-target effects on soil microbial communities.

Dissipation studies of fentrazamide (YRC-2388) in soil under anaerobic condition

Dissipation of fentrazamide in soil and water under flooded (anaerobic) conditions was studied. Fentrazamide was applied to soil at 100 g ha(-1). Soil was extracted with 0.1 N HCl : acetone (1 : 1 v/v) followed by partition and cleanup with silica SPE. Separation was achieved in an ODS-II column with a mobile phase of acetonitrile : water (70 : 30 v/v) and detection at 214 nm. Recovery of fentrazamide varied from 75.2-90.4% and 89.9-97.8% in soil and water, respectively. Fentrazamide dissipated rapidly and fentrazamide residues were not detected after 100 and 35 days of application in soil and water, respectively. Half life in soil and water was 9.06 and 3.66 days, respectively. Dissipation followed monophasic first order kinetics pattern. No fentrazamide was detected in soil, rice grain and rice straw at harvest of crop. Calibration curves for quantification were linear and relative standard deviation (RSD) was 1.78%. LOD for instrument was 0.002 μg mL(-1) and LOQ for methods were 0.005 μg g(-1) for soil and water.

Propagation of Uncertainties in Soil and Pesticide Properties to Pesticide Leaching

In the new Dutch decision tree for the evaluation of pesticide leaching to groundwater, spatially distributed soil data are used by the GeoPEARL model to calculate the 90th percentile of the spatial cumulative distribution function of the leaching concentration in the area of potential usage (SP90). Until now it was not known to what extent uncertainties in soil and pesticide properties propagate to spatially aggregated parameters like the SP90. A study was performed to quantify the uncertainties in soil and pesticide properties and to analyze their contribution to the uncertainty in SP90. First, uncertainties in the soil and pesticide properties were quantified. Next, a regular grid sample of points covering the whole of the agricultural area in the Netherlands was randomly selected. At the grid nodes, realizations from the probability distributions of the uncertain inputs were generated and used as input to a Monte Carlo uncertainty propagation analysis. The analysis showed that the uncertainty concerning the SP90 is 10 times smaller than the uncertainty about the leaching concentration at individual point locations. The parameters that contribute most to the uncertainty about the SP90 are, however, the same as the parameters that contribute most to uncertainty about the leaching concentration at individual point locations (e.g., the transformation half-life in soil and the coefficient of sorption on organic matter). Taking uncertainties in soil and pesticide properties into account further leads to a systematic increase of the predicted SP90. The important implication for pesticide regulation is that the leaching concentration is systematically underestimated when these uncertainties are ignored.