Agricultural Pesticide Use Estimates for the USGS National Water Quality Network, 1992-2014: Version 2

The National Water Quality Network (NWQN) for Rivers and Streams includes 113 surface-water river and stream sites monitored by the U.S. Geological Survey (USGS) National Water Quality Program (NWQP). The NWQN represents the consolidation of four historical national networks: the USGS National Water-Quality Assessment (NAWQA) Project, the USGS National Stream Quality Accounting Network (NASQAN), the National Monitoring Network (NMN), and the Hydrologic Benchmark Network (HBN). The NWQN includes 22 large river coastal sites, 41 large river inland sites, 30 wadeable stream reference sites, 10 wadeable stream urban sites, and 10 wadeable stream agricultural sites. In addition to the 113 NWQN sites, 3 large inland river monitoring sites from the USGS Cooperative Matching Funds program are also included in the NWQN to be consistent with previous USGS studies of nutrient transport in the Mississippi-Atchafalaya River Basin. This data release provides estimated agricultural pesticide use for 83 NWQN watersheds for 116 pesticide compounds from 1992-2014. Pesticide use was not estimated for the 30 wadeable stream reference sites, or for 3 large river coastal sites (07381590, "Wax Lake Outlet at Calumet, LA3"; 07381600, "Lower Atchafalaya River at Morgan City, LA2"; or 15565477, "Yukon River at Pilot Station, AK"). Use was not estimated for reference sites because pesticides are not monitored at reference water-quality sampling sites. Pesticide use data are not available for Alaska and thus no data is available for the Yukon River site. The other two coastal sites (07381590 and 07381600) where use was not estimated are outflow distributaries into the Gulf of Mexico. This data release provides use estimates for the same pesticide parent compounds sampled in water and analyzed by USGS, National Water Quality Laboratory (NWQL), Schedule 2437: http://wwwnwql.cr.usgs.gov/USGS/catalog/index.cfm. Pesticide use data are not available for degradate compounds or for compounds not used in agricultural applications. County-level pesticide use estimates and methods for making the estimates are available on the USGS Pesticide National Synthesis Project (PNSP) page: https://water.usgs.gov/nawqa/pnsp/usage/maps/, https://dx.doi.org/doi:10.5066/F7NP22KM. County-level estimates are based on farm surveys of pesticide use. Two estimates, EPEST_LOW_KG and EPEST_HIGH_KG, provide a range of values of pesticide use and differ in how they treated situations where surveys were done but pesticide use was not reported for a particular pesticide-by-crop combination. The HIGH method tends to spread estimated use over a larger geographic area. EPEST_LOW_KG annual-use totals can be greater than EPEST_HIGH_KG totals when the LOW method of estimation concentrates the use to a particular area while the HIGH method spreads the use over a larger area. Details on the difference between the two estimates are explained on the PNSP page. There is uncertainty in both the HIGH and LOW estimates that is difficult to quantify. A user should become familiar with the two methods to decide which estimate is best for a specific application. To obtain estimates for NWQN watersheds county-level estimates were proportionally allocated to agricultural land within each NWQN watershed. Zero values indicate that pesticide use was estimated for that watershed but that the total use for the watershed was less than 0.1 kg. Null values indicate that use was not estimated because there was not enough farm survey data available to make an estimate for that particular compound in that watershed. Place holder rows were kept for all compounds and years regardless of whether an estimate was made so that users know which compounds were included in the estimation process. Version 2 of this data release includes pesticide use estimates for glyphosate and glufosinate. These compounds were sampled in water along with Schedule 2437 compounds but were analyzed by USGS, Organic Geochemistry Research Laboratory (OGRL), Glyphosate, AMPA, and Glufosinate Method (LCGY): https://ks.water.usgs.gov/lcgy. In addition, duplicate pesticide use values, inadvertently included in the previous version, for site 07144100 "Little Arkansas River near Sedgwick, KS" were deleted. Two compound names, "cis-Permethrin" and "Paraoxon-ethyl", which were labelled incorrectly in the previous version, were changed to "Permethrin" and "Parathion" respectively in Version 2. The total count of pesticide compounds, including glyphosate and glufosinate, for which use is estimated is 116. In the previous version the number of compounds for which use was estimated was listed incorrectly as 110. Data from this release are presented at the USGS Tracking Water Quality page: http://cida.usgs.gov/quality/rivers/home (Deacon and others, 2015). Use estimates provided here are for the corresponding watersheds and general time period provided in the data release by Deacon and others (2016). Deacon, J.R., Lee, C.J., Norman, J.E., and Reutter, D.C., 2016, Nutrient and pesticide data collected from the USGS National Water Quality Network and previous networks, 1980-2015, U.S. Geological Survey data release, https://dx.doi.org/10.5066/F7BK19GZ Deacon, J.R., Lee, C.J., Toccalino, P.L., Warren, M.P., Baker, N.T., Crawford, C.G., Gilliom, R.G., and Woodside, M.D., 2015, Tracking water-quality of the Nation’s rivers and streams, U.S. Geological Survey Web page: http://cida.usgs.gov/quality/rivers, https://dx.doi.org/doi:10.5066/F70G3H51.

河流与溪流国家水质网络（National Water Quality Network, NWQN）由美国地质调查局（U.S. Geological Survey, USGS）国家水质计划（National Water Quality Program, NWQP）负责监测，包含113个地表水河流与溪流监测点位。该网络整合了4个历史国家监测网络：美国地质调查局国家水质评估（National Water-Quality Assessment, NAWQA）项目、美国地质调查局国家溪流质量核算网络（National Stream Quality Accounting Network, NASQAN）、国家监测网络（National Monitoring Network, NMN）以及水文基准网络（Hydrologic Benchmark Network, HBN）。NWQN的监测点位具体分类为：22个大型河流沿海点位、41个大型河流内陆点位、30个可涉水溪流参照点位、10个可涉水溪流城市点位以及10个可涉水溪流农业点位。

除上述113个NWQN点位外，本次数据集还纳入了美国地质调查局合作匹配资金项目的3个大型内陆河流监测点位，以与此前美国地质调查局关于密西西比-阿查法拉亚河流域养分输运的研究保持一致。

本数据集发布提供了1992-2014年间83个NWQN流域的116种农药化合物的农业农药使用量估算值。未对30个可涉水溪流参照点位，以及3个大型河流沿海点位（07381590，“路易斯安那州卡尔梅特的蜡湖出水口（Wax Lake Outlet at Calumet, LA3）”；07381600，“路易斯安那州摩根城下阿查法拉亚河（Lower Atchafalaya River at Morgan City, LA2）”；15565477，“阿拉斯加州试点站育空河（Yukon River at Pilot Station, AK）”）开展农药使用量估算。参照点位未进行使用量估算的原因是参照水质采样点位未开展农药监测。育空河点位因阿拉斯加州无农药使用相关数据，因此无对应估算值。另外两个未开展使用量估算的沿海点位（07381590与07381600）为注入墨西哥湾的分流河道。

本数据集发布提供了与美国地质调查局国家水质实验室（National Water Quality Laboratory, NWQL）Schedule 2437方案中在水体中采样并分析的相同农药母体化合物的使用量估算值，相关方案链接为：http://wwwnwql.cr.usgs.gov/USGS/catalog/index.cfm。降解产物化合物以及非农业应用场景使用的化合物，无对应农药使用量数据。

县级尺度的农药使用量估算方法及结果可在美国地质调查局农药国家综合项目（Pesticide National Synthesis Project, PNSP）页面获取，链接为：https://water.usgs.gov/nawqa/pnsp/usage/maps/，https://dx.doi.org/doi:10.5066/F7NP22KM。县级估算值基于农药使用农场调查数据生成。本次发布提供两种估算值：EPEST_LOW_KG与EPEST_HIGH_KG，二者给出了农药使用量的取值范围，差异在于对“开展了调查但未报告特定农药-作物组合使用量”场景的处理方式不同。HIGH方法倾向于将估算使用量分摊至更大的地理区域；当LOW估算方法将使用量集中于特定区域，而HIGH方法将使用量分摊至更大区域时，EPEST_LOW_KG的年度使用总量可能高于EPEST_HIGH_KG。两种估算值的差异细节可在PNSP页面查询。HIGH与LOW两种估算方法均存在难以量化的不确定性，使用者应熟悉这两种方法，以选择适配特定应用场景的估算值。

为获取NWQN流域的农药使用量估算值，需将县级尺度估算值按比例分配至每个NWQN流域内的农业用地。零值表示该流域已开展农药使用量估算，但流域总使用量低于0.1千克；空值表示因缺乏足够的农场调查数据，无法对该流域内的特定化合物进行使用量估算。无论是否生成估算值，均保留所有化合物和年份的占位符行，以便使用者了解估算过程中纳入的化合物种类。

本次数据集发布的版本2包含草甘膦（glyphosate）与草铵膦（glufosinate）的农药使用量估算值。这两种化合物与Schedule 2437方案中的化合物一同在水体中采样，但由美国地质调查局有机地球化学研究实验室（Organic Geochemistry Research Laboratory, OGRL）采用草甘膦、氨基甲基膦酸（AMPA）及草铵膦分析方法（LCGY）进行分析，相关方法链接为：https://ks.water.usgs.gov/lcgy。此外，版本2删除了前一版本中意外包含的点位07144100 “堪萨斯州塞奇威克附近的小阿肯色河（Little Arkansas River near Sedgwick, KS）”的重复农药使用量值；前一版本中错误标注的顺式氯菊酯（cis-Permethrin）与乙基对氧磷（Paraoxon-ethyl）两个化合物名称，在版本2中分别更正为氯菊酯（Permethrin）与对硫磷（Parathion）。纳入草甘膦与草铵膦后，可估算使用量的农药化合物总数为116种；前一版本中可估算使用量的化合物数量被错误列为110种。

本数据集发布的数据可在美国地质调查局全国河流水质追踪页面查看：http://cida.usgs.gov/quality/rivers/home（Deacon等人，2015）。本文提供的使用量估算值对应Deacon等人（2016）发布的数据集中的流域与大致时间段。

参考文献：
1. Deacon, J.R., Lee, C.J., Norman, J.E., Reutter, D.C., 2016, 1980-2015年美国地质调查局国家水质网络及既往网络采集的养分与农药数据集，美国地质调查局公开数据集，https://dx.doi.org/10.5066/F7BK19GZ
2. Deacon, J.R., Lee, C.J., Toccalino, P.L., Warren, M.P., Baker, N.T., Crawford, C.G., Gilliom, R.G., Woodside, M.D., 2015, 美国全国河流水质追踪，美国地质调查局官方网页：http://cida.usgs.gov/quality/rivers，https://dx.doi.org/doi:10.5066/F70G3H51