USDA-ARS Environmental Microbial and Food Safety Laboratory, Beltsville, Maryland, USA
Department of Environmental Science and Technology, University of Maryland College Park, Maryland, USA.
Appl Environ Microbiol. 2018 Jan 17;84(3). doi: 10.1128/AEM.01876-17. Print 2018 Feb 1.
Fecal contamination of water sources is an important water quality issue for agricultural irrigation ponds. concentrations are commonly used to evaluate recreational and irrigation water quality. We hypothesized that there may exist temporally stable spatial patterns of concentrations across ponds, meaning that some areas mostly have higher and other areas mostly lower than average concentrations of To test this hypothesis, we sampled two irrigation ponds in Maryland at nodes of spatial grids biweekly during the summer of 2016. Environmental covariates-temperature, turbidity, conductivity, pH, dissolved oxygen, chlorophyll , and nutrients-were measured in conjunction with concentrations. Temporal stability was assessed using mean relative differences between measurements in each location and averaged measurements across ponds. Temporally stable spatial patterns of concentrations and the majority of environmental covariates were expressed for both ponds. In the pond interior, larger relative mean differences in chlorophyll corresponded to smaller mean relative differences in concentrations, with a Spearman's rank correlation coefficient of 0.819. Turbidity and ammonium concentrations were the two other environmental covariates with the largest positive correlations between their location ranks and the concentration location ranks. Tenfold differences were found between geometric mean concentrations in locations that were consistently high or consistently low. The existence of temporally stable patterns of concentrations can affect the results of microbial water quality assessment in ponds and should be accounted for in microbial water quality monitoring design. The microbial quality of water in irrigation water sources must be assessed to prevent the spread of microbes that can cause disease in humans because of produce consumption. The microbial quality of irrigation water is evaluated based on concentrations of as the indicator organism. Given the high spatial and temporal variability of concentrations in irrigation water sources, recommendations are needed on where and when samples of water have to be taken for microbial analysis. This work demonstrates the presence of a temporally stable spatial pattern in the distributions of concentrations across irrigation ponds. The ponds studied had zones where concentrations were mostly higher than average and zones where the concentrations were mostly lower than average over the entire observation period, covering the season when water was used for irrigation. Accounting for the existence of such zones will improve the design and implementation of microbial water quality monitoring.
水源粪便污染是农业灌溉池塘水质的一个重要问题。 浓度通常用于评估娱乐和灌溉水的质量。我们假设池塘之间可能存在 浓度的时空稳定空间格局，这意味着某些区域的浓度通常较高，而其他区域的浓度通常较低。为了验证这一假设，我们在 2016 年夏季，在马里兰州的两个灌溉池塘的空间网格节点上，每两周进行一次采样。与 浓度一起测量了环境协变量-温度、浊度、电导率、pH 值、溶解氧、叶绿素和养分。使用每个位置测量之间的平均相对差异和池塘平均测量来评估时间稳定性。两种池塘都表达了 浓度和大多数环境协变量的时空稳定空间格局。在池塘内部，叶绿素 测量的相对平均差异较大， 浓度的相对平均差异较小，Spearman 秩相关系数为 0.819。浊度和铵浓度是另外两个与位置等级和 浓度位置等级之间具有最大正相关的环境协变量。在位置上，几何平均 浓度相差十倍，这些位置要么一直较高，要么一直较低。在灌溉水源中， 浓度的存在可能会影响池塘中微生物水质评估的结果，因此在微生物水质监测设计中应考虑到这一点。必须评估灌溉用水源的水的微生物质量，以防止因食用农产品而导致的可引起人类疾病的微生物传播。灌溉水的微生物质量是根据 作为指示生物的浓度来评估的。鉴于灌溉水中 浓度的时空变异性很高，因此需要就微生物分析所需的采样地点和时间提出建议。这项工作证明了在灌溉池塘中 浓度的分布存在时空稳定的空间模式。研究的池塘有几个区域，在整个观测期间，这些区域的 浓度通常高于平均水平，而其他区域的浓度通常低于平均水平，涵盖了用于灌溉的季节。考虑到这些区域的存在，将提高微生物水质监测的设计和实施。
