Nitrate, phosphate and boron content in wastewater for crop irrigation in Mezquital Valley, Hidalgo

Introduction: Mexico City generates an approximate volume of wastewater of 57 m3 s-1, the wastewater is conduct by the drainage network: main channel-west interceptor-central emitter, and conducted to Hidalgo State, during it course, an important volume is poured into irrigation channels and is used for crop irrigation in the Mezquital Valley.Method: in this study, nitrate (NO3-), phosphate (PO4-3) boron (B3+) and chloride (Cl-) content in 188 wastewater samples was determined. The objective was to assessment the risk of toxicity by specific ions (B3+ and Cl-) and the nutrients content (N, P, K, Ca y Mg) in wastewater used for crop irrigation.Results: the nitrate (NO3-) concentration was very heterogeneous (CV=59.83 %) and this was attributed to the lixiviation of nitrogen fertilizers. The maximum phosphate (PO4-3) value was 65.7 mg L-1, and its concentration was attributed to the discharge of household wastewater. The boron concentration (B3+) was less than 1.88 mg L-1. The risk of toxicity due to the use of wastewater in irrigation may cause a decrease the yield of sensitive crops, such as beans.Conclusion: untreated wastewater used in irrigation in Mezquital Valley, may cause toxicity problems in some crops; the nitrate and phosphate concentrations in wastewater of the Mexico City-Mezquital Valley drainage network were high, and these were attributed to the discharges of domestic and industrial wastewaters and to agricultural drainage, high concentrations of nitrate and phosphate represent a risk for aquatic organisms due to pollution and the possible eutrophication of water bodies. The risk of toxicity by B3+ and Cl-can have a negative effect on the germination and yield of bean crops.