EFFECTS OF RAIN pH, SOIL ORGANIC MATTER, CATION EXCHANGE CAPACITY AND TOTAL LEAD CONTENT IN SHOOTING RANGE SOIL ON THE CONCENTRATION OF LEAD IN LEACHATE

Abstract

Leaching of lead (Pb) from the shooting range soil may contaminate water resource if rain pH decreases and soil has a low cation exchange capacity (CEC). Over exposure of Pb may cause brain injury and death. In this study, leaching of Pb from shooting range soil was simulated with column leaching test using artificial rain at pH 4 and 7. Soil physico-chemical parameters (i.e. pH, organic matter (OM), and CEC) were determined, and its' correlation with Pb concentrations in soil (Soil Pb) and leachate (Leachate Pb) were studied using Pearson's correlation. Compare to control soil, shooting range soil has higher contents of Pb (12,163 -17,278 mg/kg, dry weight basis) and sand (64 -68 %). The CEC value of shooting range soil (193 cmol/kg at pH 7) is lower than those in control soil (85 -140 cmol/kg at pH 7), possibly due to low contents of clay and OM. There is positive correlation between Soil Pb and Leachate Pb variable pair (r = 0.94; p = 0.06); while Soil OM and Leachate Pb variable pair has a negative correlation (r = -0.94; p = 0.06). In conclusion, the combination of high soil Pb content, low CEC, and low rain pH increases leaching of Pb from shooting range soil.Keywords: lead shots, heavy metal, groundwater, acid rain, sorption Abstrak Larut lesap Pb daripada tanah lapang sasar boleh mencemarkan sumber air jika nilai pH hujan menurun dan tanah mempunyai keupayaan pertukaran kation (CEC) yang rendah. Pendedahan Pb yang keterlaluan boleh menyebabkan kecederaan otak dan kematian. Dalam kajian ini, larut lesap Pb dari tanah lapang sasar telah disimulasikan dengan ujian larut lesap turus menggunakan air hujan tiruan pada pH 4 dan 7. Parameter tanah (iaitu, pH, jirim organik (OM), dan CEC) telah ditentukan, dan dikaji korelasinya dengan kepekatan Pb di dalam tanah dan larut resap dengan menggunakan korelasi Pearson. Berbanding dengan tanah kawalan, kandungan Pb (12163 -17278 mg/kg, secara berat kering) dan pasir (64 -68 %) pada tanah lapang sasar adalah lebih tinggi. Nilai CEC tanah lapang sasar (193 cmol/kg pada pH 7) adalah lebih rendah daripada tanah kawalan (85 -140 cmol/kg pada pH 7), mungkin disebabkan oleh kandungan rendah tanah liat dan jirim organik. Terdapat hubungan yang positif antara pasangan pemboleh ubah Pb tanah dan Pb larut lesap (r = 0.94; p = 0.06); manakala pasangan pemboleh ubah jirim organik tanah dan Pb larut lesap mempunyai korelasi negatif (r = -0,94; p = 0.06). Kesimpulannya, gabungan faktor-faktor seperti kandungan Pb yang tinggi di dalam tanah, nilai CEC tanah yang rendah dan nilai pH hujan yang rendah boleh meningkatkan risiko larut lesap Pb dari tanah lapang sasar.Kata kunci: peluru plumbum, logam berat, air bawah tanah, hujan berasid, jerapan