Determination of soluble salts in soil samples from

Determination of soluble salts in soil samples from Cyprus Dr Irene Christoforou

Outline n n n n n Introduction Sampling Ion Chromatography Method Development Estimates of Reproducibility, Limits of Detection (LOD) and Limits of Quantification (LOQ) Distributions of Fluorides Distributions of Chlorides Distributions of Nitrates Distributions of Sulfates Conclusions

Introduction n Soil comprises the loose top layer of our planet's crust and contains a mixture of rock particles, organic matter, bacteria, air and water. Minerals, nutrients Ions in solution Heat, cold, wind, rain, hail, ice Frost Spontaneous weathering Mechanical weathering Oxides of iron & alumina Silica Clays Parent material Fine parent material Chemical weathering Acids, moisture Carbonates

Introduction n n Plants and crops are dependent on soil for the supply of water, nutrients and as a medium for growing. This dependence makes soil one of the most fundamental components for supporting life on the planet. The term soluble salts refers to the inorganic soil constituents (ions) that are loosely bound to the matrix of soil and therefore can be dissolved in the water with relative ease. The levels of soluble salts in the soil are important since high concentrations are considered an environmental stress and constitute a limiting factor for agriculture. Furthermore some of the most important soil threats, such as salinisation and desertification are closely linked with increased concentrations of soluble salts. Therefore, the determination of soluble salts in soils is crucial for the estimation of soil condition in relation to several soil threats and soil contamination.

Introduction n This study as a part of the compilation of the Geochemical Atlas of Cyprus project, aims to provide a detailed geochemical “snap shot” of the distribution and abundance of soluble salts in Cyprus soil. For the purpose of this project an in-house method was developed for the extraction of soluble salts, following an optimized procedure. The dissolved anions (F-, Cl-, NO 3 -, SO 42 -) were determined by liquid chromatography.

Introduction Circum-Troodos Sedimentary Sequence (calcarenites, siltstones, carbonates) Keryneia Terrane (allochthonous massive and recrystallised limestones, dolomites and marbles) Mamonia Terrane (igneous, sedimentary, metamorphic rocks) Quaternary Troodos Ophiolite Complex & Arakapas Transform Sequence pillow lavas mafic units ultramafic unit

Sampling Method n n n 5502 Top Soil Samples. Sampling density - one site per 1 km 2. Troodos - reduced to one site per 2. 2 km 2. Areas not under the effective control of the Government of the Republic of Cyprus

Sampling Method n n n Sample locations - determined by GPS. The surface was cleared of recent organic debris. Top soil samples (0– 25 cm depth). All samples were sieved to <2 mm. Samples delivered and archived at the GSD. 400 g Sample, <2 mm 300 g GSD archive 100 g UNSW Steel Mill 5 g SS 2 g TC, TS, TOC 10 g XRF Majors

Ion Chromatography Eluent Data Processing Pump Conductivity Detector Guard Separator Suppressor Column Trace Instrument Shimadzu Eluent 1. 8 m. M of Na 2 CO 3 1. 7 m. M of Na. HCO 3 Flow Rate 1 m. L/min Separator column 250 mm. L x 4. 0 mm Shim-pack IC-SA 2 Guard column Shim-pack IC-SA 2(G) Injection volume 50 μL Detector CDD-10 Asp suppressed conductivity

Method Development Concentration of calibration solutions 1. 000 ± 0. 002 g/L Low concentration range for F -, Cl-, NO 3 -, SO 42 - 0. 05 -10 mg/L High concentration range for Cl - 20 -75 mg/L High concentration range for SO 42 - 10 -50 mg/L Squared correlation coefficient R 2 > 0. 99

Method Development Sample Preparation: n sieving < 2 mm mesh size n milling Experimental n 5 g sample / 200 ml DW n 120 minutes shaking n filtration (ashless filter paper) n conductivity measurement n filtration (0. 45 μm membrane filter) n liquid chromatography Samples of conductivity greater than 600μS/cm or with anion concentrations exceeding the calibration range were diluted. Control: CYP-A , a calcareous sediment collected from an outcrop of Pakhna.

Method Development F(ppm) Cl(ppm) NO 3(ppm) SO 42(ppm) 12 12 Mean 0. 163 1. 722 0. 454 2. 938 SD 0. 030 0. 240 0. 033 0. 156 LOD 0. 09 0. 72 0. 10 0. 47 LOQ 0. 27 2. 16 0. 30 1. 40 Anion F(ppm) Cl(ppm) NO 3(ppm) SO 42(ppm) 151 151 MEAN 0. 245 3. 307 0. 556 3. 289 SD 0. 080 1. 242 0. 104 0. 408 RSD 0. 327 0. 376 0. 186 0. 124 %CVR 32. 7 37. 6 18. 6 12. 4 Anion N N

Distribution of Fluorides n n n n Fluorine is the most abundant halogen in the earth’s crust. It is the most electronegative element and binds metals forming complexes, which are adsorbed readily to the soil and plants. Fluorine is phytotoxic, causing damage in vegetation, wildlife and humans. Fluorine as an element in soil has a world average value of 200 -300 mg/kg. The main natural source of inorganic fluorides in soil is the parent rock. During weathering, some fluoride minerals are rapidly broken down. Fertilizer application is the main nongeogenic source of fluoride ions and fluorapatite is an important calcium- and fluoride-containing mineral used as a source of phosphates in the fertilizer industry. Phosphate fertilizers are manufactured from rock phosphates, which generally contain around 3. 5% of fluorine. Fluoride applied through fertilizer tends to have high residence time within the soil matrix particularly in soils of high clay content, high organic carbon content, high amorphous aluminium species or low p. H.

Distribution of Fluorides F - fluoride 34 E Ion chromatography LODreproducibility: 10 mg/kg average value: 18. 7 mg/kg highest value: 3536 mg/kg 33 E Top soil Keryneia Lefkosia (0 – 25 cm) Areas not under the effective control of the Government of the Republic of Cyprus Ammochostos Polis 35 N Ayia Napa Pafos Lemesos F- (mg/kg) 500 25 22 20 19 18 16 14 12 11 8

Distribution of Chlorides n n n The mantle, the crust and the oceans are three main reservoirs of earth chlorine with only the oceanic chlorine being readily mobile. Since parent materials in general contain only minor amounts of chloride, little of this nutrient arises from weathering. Most of the chloride presents in soils arrives from rainfall, marine aerosols, volcanic emissions, irrigation waters, and fertilizers. Chloride accumulates primarily in soil under arid conditions where leaching is minimal and where chloride moves upward in the soil profile in response to evapotranspiration. Near the ocean, soils have high levels of chloride. High chloride ion concentrations in soil, above geogenic concentrations, are often considered as a salinisation problem world wide and occur in warm and dry locations where soluble salts precipitate from water and accumulate in the soil.

Distribution of Chlorides Clchloride 34 E Ion chromatography LODreproducibility: 149 mg/kg average value: 809. 3 mg/kg highest value: 664778 mg/kg 33 E Top soil Keryneia Lefkosia (0 – 25 cm) Areas not under the effective control of the Government of the Republic of Cyprus Ammochostos Polis 35 N Ayia Napa Pafos Lemesos Cl- (mg/kg) 2, 000 450 350 270 230 200 180 160 140 120 80

The Nitrogen Cycle http: //www. physicalgeography. net

Distribution of Nitrates n n n Nitrate ions mainly originate from anthropogenic origins and constitute a very clear descriptor for characterising agricultural land use. The main source of nitrates is the application of synthetic fertilizers or manure to fields. Potential anthropogenic source of nitrates is the leakage from domestic septic fields, municipal sewage systems and livestock facilities. Excess nitrates in soil increases the risk of contamination of ground or surface waters causing eutrophication (increasing algae growth, degrading habitat for aquatic organisms) and adverse effects on human health. Nitrate vulnerable zones (NVZ) have been designated by the Cyprus government through studies (Geological Survey Department, 2000) in an effort to comply with the Nitrate Directive (91/676/EEC). The Directive has the objectives of reducing water pollution caused or induced by nitrates from agricultural sources and preventing further pollution.

Distribution of Nitrates NO 3 nitrate Ion chromatography LODreproducibility: 12 g/kg average value: 68. 4 mg/kg highest value: 3001 mg/kg NO 3 - 34 E (mg/kg) 33 E Top soil Keryneia 220 150 100 80 70 55 40 32 26 22 15 (0 – 25 cm) Areas not under the effective control of the Government Lefkosia of the Republic of Cyprus Ammochostos Polis 35 N Ayia Napa Pafos Lemesos P ICP-MS Keryneia P Lefkosia Ammochostos Polis Larnaca Pafos Lemesos Ayia Napa (%) 0. 160 0. 100 0. 092 0. 085 0. 062 0. 055 0. 042 0. 035 0. 020 0. 010

Distribution of Sulfates n n Sulfate ions are made available from dissolution of sulfate salts from oxidation of sulfur-bearing minerals in soils all around the world. Among the sulfur-bearing minerals identified in sedimentary rocks, iron sulfide polymorphs, pyrite and marcasite, are the more common forms, of which pyrite is the most common. Oxidation of these sulfide groups releases sulfate phases into soils. The soils that contain iron sulfide minerals or their oxidation products are known as Acid Sulfate Soils (ASS). If the ASS are drained and exposed to air, the sulfides react with oxygen to form sulfuric acid which can create a variety of adverse impacts: killing vegetation and aquatic organisms, acidifying groundwater and water bodies, degrading concrete and steel structures to the point of failure.

Distribution of Sulfates SO 42 sulfate 34 E Ion chromatography LODreproducibility : 49 mg/kg average value: 160. 3 mg/kg highest value: 231701 mg/kg 33 E Top soil Keryneia Lefkosia (0 – 25 cm) SO 42(mg/kg) 750 300 180 140 120 100 80 65 55 45 30 Areas not under the effective control of the Government of the Republic of Cyprus Ammochostos Polis 35 N Ayia Napa Pafos Lemesos 100, 000 S XRF Keryneia S Lefkosia (mg/kg) Ammochostos Polis 10, 000 S XRF 1, 000 (mg/kg) 100 10 10 Larnaca SO 42 ion chrom 100 1, 000100, 000 (mg/kg) Pafos Lemesos Ayia Napa 6000 1500 1200 1000 900 800 700 500 400 300 200

Distribution of Soluble Salts Ffluoride Clchloride 34 E 33 E Top soil Keryneia (0 – 25 cm) Lefkosia Ammochostos Polis 35 N Ayia Napa Pafos Lemesos NO 3 nitrate Lemesos SO 42 sulfate 34 E 33 E Keryneia Top soil 34 E 33 E Keryneia (0 – 25 cm) Lefkosia Ammochostos Polis 35 N Ayia Napa Pafos Lemesos Top soil Lemesos

Conclusions n n n The soluble salt distribution maps provide the baseline values for every geological formation of the island of Cyprus and give sufficient information of soil contamination sides. The two salt lakes of the island are considered to be the main nonanthropogenic contamination sources resulting to enhance values of all the measured soluble salts and particularly those of the chlorides and sulfates. The soluble salt distribution maps confirms also the anthropogenic soil contamination with nitrates and sulfates due to fertilizers application and mining activity respectively. This study provides a basis for a number of future projects dealing with environmental monitoring and management. The observed soil contamination caused by mining activity gives also the opportunity to run several mine rehabilitation projects in Cyprus.