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. 2021 Jun 23;129(6):067004. doi: 10.1289/EHP7813

Figure 4.

Figure 4A is an area graph titled Nitrate, groundwater recharge plotting Probability, nitrate nitrogen greater than 10 milligrams per liter begin superscript negative 1 ends superscript, ranging from 0.0 to 0.6 in increments of 0.2 (y-axis) across area of fields with nutrient management plan within 229 meters of well in hectares, ranging from 0 to 15 in increments of 5 (x-axis). Figure 4B is an area graph titled Nitrate, no recharge plotting Probability, nitrate nitrogen greater than 10 milligrams liter begin superscript negative 1 ends superscript, ranging from 0.0 to 0.3 in unit increments (y-axis) across bedrock depth in meters, ranging from 0 to 60 in increments of 20 (x-axis). Figure 4C is an area graph titled Coliforms, groundwater recharge plotting Probability coliform detection, ranging from 0.0 to 0.8 in increments of 0.2 (y-axis) across Bedrock depth in meters, ranging from 0 to 50 in increments of 10 (x-axis). Figure 4D is an area graph titled Coliforms, no recharge plotting Probability coliforms detection, ranging from 0.0 to 0.5 in unit increments (y-axis) across distance to manure storage, ranging from 0 to 6000 in increments of 2000 (x-axis).

Detection probabilities for NO3-N>10mg/L and coliform bacteria in private wells regressed (log-binomial) on key risk factors during groundwater recharge and no recharge periods. Coefficients and p-values are reported in Table 4. Black line: estimated probability of detection. Dashed lines: 95% pointwise confidence limits. Covariates in the multivariable models were fixed at their median values for the purpose of plotting. Fields with NMPs likely receive manure and inorganic fertilizer inputs. Note: NMP, nutrient management plan.