engleski

Agriculture Impact on Groundwater Quality

Intensive agriculture is putting great pressure on the environment and therefore it is vital to rationalize its inputs, and to control and monitor the impact agricultural activities have on soil, water, and air, in order to achieve sustainability. For better understanding of the impact that conventional agricultural practices have not only on soil, but on water resources as well, two main objectives were established. The first one is to measure concentrations of nitrate (NO3-) and sulfate (SO42-) in lysimeter and drainpipe waters related to different nitrogen fertilization levels. The second one is to identify organic pollutants that potentially originate from used agrochemicals. The results of two-year investigating period (2014-2015) are presented in this study. The experimental field was established in Potok near Popovača on distric Stagnosols. The research contained ten treatments with four replications where different nitrogen fertilizer levels were applied: 1. Control (no fertilization), 2. N0 + P + K, 3. N100 + P + K, 4. N150 + P + K, 5. N200 + P + K, 6. N250 + P + K, 7. N250 + P + K + phosphogypsum, 8. N250 + P + K + zeolitic tuff + CaCO3, 9. N300 + P + K, and 10. Black fallow – tillage only. Phosphorous (P) and potassium (K) levels were constant, 120 and 180 kg/ha respectively. Each treatment area included two drainpipes (placed at the depth of 120 cm) and one lysimeter (at the depth of 80 cm) from which water samples were taken when discharge appeared. During the investigated period, 24 water samples for inorganic (13 from lysimeters and 11 from drainpipes) and 16 for organic substances analysis (six in 2014 and two in 2015 from lysimeters ; five in 2014 and three in 2015 from drainpipes) were taken. The concentrations of NO3- and SO42- were determined by suppressed ion chromatography (Dionex ICS-1000 system) using IonPac AS17-C separation column fitted with IonPac AG17 guard column. The gradient flow analysis was conducted using KOH as an eluent solution (10-30-10 mmol). Ultra-high performance liquid chromatography (UHPLC) coupled to time-of-flight mass spectrometry (Q- TOF/MS) was used for non-target screening and quantification of organic substances. This allowed the search of the entire spectrum of various organic compounds and their quantification at high resolution (> 10000 FWHM, full width half maximal), with accurate mass accuracy (< 1 ppm) and satisfactory sensitivity in fullacquisition mode. Research results indicated that NO3- content in both lysimeters and drainpipes increased with rising doses of N fertilizer. In the investigated period the daily concentration varied from 0.52–265 mg/L in both lysimeters and drainpipes, depending on the treatment, precipitation and agrotechnical measures. Higher average concentrations for each treatment were observed in water samples from drainpipes (up to 126 mg/L), which are placed deeper in the soil (120 cm) confirming that nitrates do not bond with soil particles and are leached into groundwater. Daily SO4 2- concentrations varied from 1-302 mg/L. As expected, the maximum average concentrations were recorded in treatment 7 with added phosphogypsum (184 mg/L in lysimeters and 105 mg/L in drainpipes), while the average concentrations on all other treatments were low (< 20 mg/L). Non-target screening revealed more than 400 different organic substances (agrochemicals, hormones, opioids, antibiotics and various other drugs) in water samples. The correlation with applied plant protection products was not observed. The focus of this study was three herbicides: atrazine, simazine, and isoproturon. Atrazine and simazine have been banned in Croatia since 2004, while isoproturon is still used. The average annual concentrations of atrazine, simazine and isoproturon in water from lysimeters in 2014 were 1.40, 0.20 and 0.21 μg/L, respectively. In drainpipes the concentrations were 0.44, 0.20 and 0.04 μg/L, respectively. The average annual concentration of atrazine, simazine and isoproturon in lysimeters in 2015 was 4.69, 8.70 and 0.78 μg/L, respectively. In drainpipes the concentrations were 0.82, 3.82 and 1.66 μg/L, respectively. Due to the fact that atrazine and simazine have not been used in Croatia since 2004 and there have been no records of isoproturon use in the investigated area since 1997, it can be assumed that these compounds persist in the environment for a considerable length of time.

ion chromatography, UHPCL Q-TOF/MS, groundwater quality

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