Pesticides in ground water in the united states: Monitoring,modeling, and risks from the U.S. perspective

Abstract

Scientific and regulatory interest in ground water contamination by pesticides increased significantly in 1979. This was prompted by findings of the nematicide 1,2‐dibromo‐3‐chloropropane (DBCP) and the nematicide/insecticide aldicarb (Temik®) in ground water in several states. Since that time, at least 130 pesticides and pesticide metabolites have been detected in ground water in over 150 studies, but detection frequencies are 4–10% nationally. Detection frequencies of pesticides over Health Advisory Levels are generally lower. Screening‐level models and detailed computer simulation models are useful for risk assessments and regulatory decisions. Attenuation Factor, CMLS, PRZM2, GLEAMS, and LEACHM are all useful models.     

Water Planning and Hydro-Climatic Change in the Murray-Darling Basin,Australia

More than a third of humanity lives in regions with less than 1 million liters of fresh water per person per year. Population growth will increase water demand while climate change in arid and semi-arid areas may reduce water availability. The Murray-Darling Basin in Australia is a region where water reform and planning have been used to reduce consumptive extraction to better sustain river ecosystems under climate variability. Using actual data and previously published models that account for climate variability and climate change, the trade-off between water extractions and water essential to the long-term ecological function of river systems is analysed. The findings indicate that better water planning and a more complete understanding of the effects of irrigation on regional climate evapotranspiration could: (1) increase the overall benefits of consumptive and non-consumptive water use; (2) improve riparian environments under climate variability; and (3) be achieved with only small effects on the profits and gross value of food and fiber production.     

扬水曝气器的水质改善功能及提水、充氧性能研究

扬水曝气器是水源水质改善设备,应用于湖泊水库水源地,抑制藻类生长,控制底泥污染物释放,取得了良好的效果.建立了扬水曝气器上升流速数学模型,用于模拟计算扬水曝气器的提水能力.建立了扬水曝气器曝气室的充氧能力数学模型.在实验室实测了扬水曝气器上升流速及其对水体的充氧过程,实测值与模拟计算值吻合较好,验证了提水、充氧能力数学模型.     

N:P ratios,light limitation,and cyanobacterial dominance in a subtropical lake impacted by non-point source nutrient pollution

A long-term (28-year) data set was used to investigate historical changes in concentrations of phosphorus (P), nitrogen (N), N:P ratios, and Secchi disk transparency in a shallow subtropical lake (Lake Okeechobee, Florida, USA). The aim was to evaluate changes in the risk of N2-fixing cyanobacterial blooms, which have infrequently occurred in the lake's pelagic zone. Predictions regarding bloom risk were based on previously published N:P ratio models. Temporal trends in the biomass of cyanobacteria were evaluated using phytoplankton data collected in 1974, 1989-1992, and 1997-2000. Concentrations of pelagic total P increased from near 50 microg l-1 in the mid-1970s to over 100 microg l-1 in the late 1990s. Coincidentally, the total N:P (mass) ratio decreased from 30:1 to below 15:1, and soluble N:P ratio decreased from 15:1 to near 6:1, in the lake water. Published empirical models predict that current conditions favor cyanobacteria. The observations confirm this prediction: cyanobacteria presently account for 50-80% of total phytoplankton biovolume. The historical decrease in TN:TP ratio in the lake can be attributed to a decreased TN:TP ratio in the inflow water and to a decline in the lake's assimilation of P, relative to N. Coincident with these declines in total and soluble N:P ratios, Secchi disk transparency declined from 0.6 m to near 0.3 m, possibly due to increased mineral turbidity in the lake water. Empirical models predict that under the turbid, low irradiance conditions that prevail in this lake, non-heterocystous cyanobacteria should dominate the phytoplankton. Our observations confirmed this prediction: non-N2-fixing taxa (primarily Oscillatoria and Lyngbya spp.) typically dominated the cyanobacteria community during the last decade. The only exception was a year with very low water levels, when heterocystous N2-fixing Anabaena became dominant. In the near-shore regions of this shallow lake, low N:P ratios potentially favor blooms of N2-fixing cyanobacteria, but their occurrence in the pelagic zone is restricted by low irradiance and lack of stable stratification.     

不确定性水质模型及其研究进展

水环境是一个充满不确定性因素的复杂巨系统,研究这些不确定性的变化有利于提高人们对水环境分析的认识和做出更切合实际的决策.详细、清晰地评述了不确定性水质模型研究的必要性、研究的方法和国内外研究进展等,并针对此类模型研究与应用过程中普遍存在的一些问题、主要表现和成因进行了分析与论述,最后结合目前的研究热点指出了今后不确定性水质模型发展的3个重要方向.     

可视化黄浦江水环境数学模型系统设计与开发

随着信息技术的高速发展,传统的水环境数学模型与数据库技术、GIS技术、可视化编程工具紧密结合,水环境数学模型的可视化是其发展的一个重要趋势,也是开发水环境决策支持系统和水环境数学模型商业软件的重要基础。对可视化水环境数学模型的设计框架进行了初步探讨,并结合自主开发的可视化黄浦江二维水环境数学模型系统,介绍可视化水环境数学模型的设计与开发。     

Measurements and modelling of the ozone deposition velocity to concrete tiles,including the effect of diffusion

A range of models were fitted to the experimental time-dependent curves for the deposition velocity of O₃ to concrete floor tile samples. The models included modified Langmuir isotherms assuming adsorption of O₃ on the material surfaces and models assuming direct reaction on and diffusion of O₃ into the material from the air. The best fit was obtained with a simple two-parameter model assuming direct reaction of O₃ with adsorbed surface water and direct diffusion of O₃ into the material from the air. However, models assuming an additional second-order reaction of O₃ with an adsorbed surface species with a given start mass gave improved curve fit in the first 500 min. Applying the best model to experimental data obtained over the whole air humidity range resulted in markedly lower equilibrium deposition velocities than those measured after 48 h. The modelling gave a deposition velocity minimum in the 50–70% relative air humidity range in agreement with observations. The deposition velocity minimum could be explained with a reduced constant for the reaction of O₃ with water or OH⁻ ions on the surface.     

Use of satellite imagery to assess the trophic state of Miyun Reservoir, Beijing, China

The objective of this research is to explore an appropriate way of monitoring and assessing water quality by satellite remote sensing techniques in the Miyun reservoir of Beijing, China. Two scene Thematic Mapper images in May and October of 2003 were acquired and simultaneous in situ measurements, sampling and analysis were conducted. Statistical analysis indicates that satellite-based normalized ratio vegetation index (NRVI) and in situ measured water chlorophyll a (Chl-a) concentration have very high correlation. Two linear regression models with high determination coefficients were constructed for NRVI and Chl-a of sample points. According to the modified trophic state index map, water quality in the western section of Miyun reservoir was consistently higher than in the eastern section during the two months tested. The trophic grade of the eastern reservoir remained mesotrophic with a tendency for eutrophication.     

Spatial and temporal organic and heavy metal pollution at Mai Po Marshes Nature Reserve,Hong Kong

An intensive monthly sampling of water and sediments from 12 sites over 8 months covering wet and dry seasons at Mai Po Marshes Nature Reserve was conducted during June 1997-February 1998. Major organic (C, N and P) and heavy metal pollutants (Cd, Cr, Cu, Ni, Pb, Zn) water and sediment samples were examined. The results showed that Mai Po Marshes were severely polluted by organic matter and heavy metals, and the water from Deep Bay appeared to be the source of pollution. Up to 13-55% chance that the sediments of Mai Po Marshes were classified as moderately to seriously metal contaminated materials, according to the guideline set by Hong Kong Government. Empirical models describing organic matter and heavy metal spatial and seasonal dynamics in the water and sediments were formulated, based on data analysis. During wet season (June-October), more than 58% variations of total P can be explained by ortho-P in water, while ammonia-N explained up to 90% variations of total Kjeldahl nitrogen in water. Throughout the whole sampling period (June-February), there were significant correlations (p<0.01) between total organic C in water. pH in the sediments and salinity in water appeared to be important factors determining heavy metal mobility in sediments, while potential metal release from the sediments is a concern when any oxidizing processes such as flooding or dredging are imposed on sediments.     

湍流扩散方程数学解析的探讨

本文讨论了水流场中平流、分子扩散、湍流扩散、离散作用所引起的扩散物质质量通量的数学解析以及几种水质数学模型的应用条件。     

面向城市水系环境需水的再生水空间配置——以深圳市宝安区为例

以深圳市宝安区为例,探讨以再生水满足城市水系环境需水的方法.应用一维恒定与非恒定水质模型计算了4种补水水质方案下该区10条主要河流的环境需水量,从水量平衡角度提出全区再生水BOD5的平均值,并进一步分析了补水水质与河流环境需水量的关系.结合该区水系与污水处理系统空间位置,提出3种再生水的空间配置方法.结果表明:茅洲河和...     

Effects of land use and land cover, stream discharge, and interannual climate on the magnitude and timing of nitrogen, phosphorus, and organic carbon concentrations in three coastal plain watersheds.

In-stream nitrogen, phosphorus, organic carbon, and suspended sediment concentrations were measured in 18 subbasins over 2 annual cycles to assess how land use and land cover (LULC) and stream discharge regulate water quality variables. The LULC was a primary driver of in-stream constituent concentrations and nutrient speciation owing to differences in dominant sources and input pathways associated with agricultural, urban, and forested land uses. Stream discharge was shown to be a major factor that dictated not only the magnitude of constituent concentrations, but also the chemical form. In high discharge agricultural subbasins, where nitrate was the dominant nitrogen form, there was a negative correlation between discharge and nitrate concentration indicating groundwater inputs as the dominant pathway. In urban settings, however, nitrate was positively correlated with discharge, and, in forested subwatersheds, where dissolved organic nitrogen (DON) was the dominant nitrogen form, there was a positive correlation between discharge and DON, indicating washoff from the watershed as the dominant input pathway. Similarly, phosphorus concentrations were strongly regulated by LULC, discharge, and seasonality. This comparative study highlights that different mechanisms regulate different forms of nitrogen, phosphorus, and carbon, and thus field programs or water quality models used for regulatory purposes must assess these nutrient forms to accurately apply management plans for nutrient reductions.     

湖泊富营养化模型的研究进展

湖泊的富营养化是全球普遍关注的环境问题之一.湖泊的富营养化模型是防治、修复和治理湖泊富营养化的重要决策工具.按研究的侧重点不同,将湖泊富营养化模型分为简单回归模型、水质模型、生态模型和生态-水动力水质模型,并分别回顾了四类模型的研究进展.最后指出湖泊富营养化模型的发展趋势,强调不确定理论、3S技术、耦合模型是今后湖泊富营养化模型研究的重点,应在此基础上建立通用的模拟、预测、评价和优化模型,为湖泊富营养化管理提供科学依据.     

湖泊富营养化模型的研究进展

湖泊的富营养化是全球普遍关注的环境问题之一.湖泊的富营养化模型是防治、修复和治理湖泊富营养化的重要决策工具.按研究的侧重点不同,将湖泊富营养化模型分为简单回归模型、水质模型、生态模型和生态-水动力水质模型,并分别回顾了四类模型的研究进展.最后指出湖泊富营养化模型的发展趋势,强调不确定理论、3S技术、耦合模型是今后湖泊富营养化模型研究的重点,应在此基础上建立通用的模拟、预测、评价和优化模型,为湖泊富营养化管理提供科学依据.     

Inverse modeling of BTEX dissolution and biodegradation at the Bemidji, MN crude-oil spill site

The U.S. Geological Survey (USGS) solute transport and biodegradation code BIOMOC was used in conjunction with the USGS universal inverse modeling code UCODE to quantify field-scale hydrocarbon dissolution and biodegradation at the USGS Toxic Substances Hydrology Program crude-oil spill research site located near Bemidji, MN. This inverse modeling effort used the extensive historical data compiled at the Bemidji site from 1986 to 1997 and incorporated a multicomponent transport and biodegradation model. Inverse modeling was successful when coupled transport and degradation processes were incorporated into the model and a single dissolution rate coefficient was used for all BTEX components. Assuming a stationary oil body, we simulated benzene, toluene, ethylbenzene, m,p-xylene, and o-xylene (BTEX) concentrations in the oil and ground water, respectively, as well as dissolved oxygen. Dissolution from the oil phase and aerobic and anaerobic degradation processes were represented. The parameters estimated were the recharge rate, hydraulic conductivity, dissolution rate coefficient, individual first-order BTEX anaerobic degradation rates, and transverse dispersivity. Results were similar for simulations obtained using several alternative conceptual models of the hydrologic system and biodegradation processes. The dissolved BTEX concentration data were not sufficient to discriminate between these conceptual models. The calibrated simulations reproduced the general large-scale evolution of the plume, but did not reproduce the observed small-scale spatial and temporal variability in concentrations. The estimated anaerobic biodegradation rates for toluene and o-xylene were greater than the dissolution rate coefficient. However, the estimated anaerobic biodegradation rates for benzene, ethylbenzene, and m,p-xylene were less than the dissolution rate coefficient. The calibrated model was used to determine the BTEX mass balance in the oil body and groundwater plume. Dissolution from the oil body was greatest for compounds with large effective solubilities (benzene) and with large degradation rates (toluene and o-xylene). Anaerobic degradation removed 77% of the BTEX that dissolved into the water phase and aerobic degradation removed 17%. Although goodness-of-fit measures for the alternative conceptual models were not significantly different, predictions made with the models were quite variable.     

Comparison of PDFs, closure schemes and turbulence parameterisations in Lagrangian stochastic models

Six one-dimensional models, based on the Ito-type stochastic equation, are presented and compared. Four of these take into account up to the fourth order moment of vertical velocity fluctuations, and two up to the third order moment. Four models make use of a bi-Gaussian probability density function (PDF) and the other two are based on a Gram-Charlier series expansion truncated to the third or fourth order. All the models were run with a parameterisation of input turbulence (i.e. w², w³, and τ profiles). Concerning the fourth order moment w⁴, two different parameterisations were considered. Comparisons are made between ground-level concentrations, plume height and plume width observed in the Willis and Deardorff water tank experiments and those predicted by the different models here considered. The goal of this study was to find the models that give greater confidence in their applicability in dispersion studies and to verify the importance of considering the fourth order moment. The main conclusions are: simulation results largely depend on the turbulence parameterisation chosen; the Gram-Charlier PDF gives the best agreement with observations; some combinations of models and turbulence parameterisations perform well in simulating the shape of the ground-level concentration (g.1.c.) trend but fail in correctly simulating the form of the plume (plume height and vertical width); in the case of the Gram-Charlier PDF, the fourth order model reproduced the vertical plume width better than the third order one, whereas the two schemes yielded similar g.1.c. distributions.     

Re-evaluation of metal bioaccumulation and chronic toxicity in Hyalella azteca using saturation curves and the biotic ligand model

Bioaccumulation by Hyalella of all metals studied so far in our laboratory was re-evaluated to determine if the data could be explained satisfactorily using saturation models. Saturation kinetics are predicted by the biotic ligand model (BLM), now widely used in modelling acute toxicity, and are a pre-requisite if the BLM is to be applied to chronic toxicity. Saturation models provided a good fit to all the data. Since these are mechanistically based, they provide additional insights into metal accumulation mechanisms not immediately apparent when using allometric models. For example, maximum Cd accumulation is dependent on the hardness of the water to which Hyalella are acclimated. The BLM may need to be modified when applied to chronic toxicity. Use of saturation models for bioaccumulation, however, also necessitates the need for using saturation models for dose-response relationships in order to produce unambiguous estimates of LC50 values based on water and body concentrations. This affects predictions of toxicity at very low metal concentrations and results in lower predicted toxicity of mixtures when many metals are present at low concentrations.     

Regulation (EC) No. 1107/2009 and upcoming challenges for exposure assessment of plant protection products--Harmonisation or national modelling approaches?

In the new European Pesticide Regulation (EC) No. 1107/2009, the harmonisation of approaches for estimation of the environmental exposure of pesticides is considered a major goal. Several member states currently require their own models for the calculation of predicted environmental concentrations (PEC) in surface water. The variety of methods makes risk evaluations rather time-consuming for both notifiers and evaluating authorities. In the present study we compare surface water concentrations of 19 compounds using EU and country-specific models and risk assessment approaches to evaluate to which extent the resulting estimated exposure concentrations differ. Our results show that EU and country specific approaches and the resulting surface water concentrations differ considerably regarding basic model assumptions and assessment methods. The results indicate that the aimed harmonisation of risk assessment approaches within the EU will be difficult based on current models. New scenarios may help to achieve a harmonisation taking country-specific features into account.     

一维有限段模型在小清河河口水质预测中的应用

本文建立了小清河-维河口有限段水质模型,并运用该水质模型预测了拟建的东营乙烯工程对小清河感潮段的水质影响,所获得的预测结论为有关部门确定东营乙烯工程废水的排污去向提供了重要的科学依据。