Noktasal kaynaklardan kirlenmiş topraklarda saha durum ve risk analizi = Field situation and risk analysis in soils contaminated from point sources

Abstract

Toprak kirliliği, ekolojik dengeyi, çevre ve insan sağlığını tehdit eden en önemli faktörlerden biridir. Toprak kalitesinin değerlendirilmesi, kirlilik şüphesi bulunan ya da kirlendiği bilinen sahaların yönetimi, kirliliğin boyutunun belirlenmesi, sahanın temizleme işlemlerine ihtiyaç olup olmadığının belirlenmesi gibi süreçlerde insan sağlığı risk analizi değerlendirmelerinden faydalanılmaktadır. Bu değerlendirmede kirleticilerin maruz kalan alıcılarda yol açabileceği kanser dışı sağlık sağlık etkileri Tehlike İndeksi (HI) hesaplanarak değerlendirilir. Bu çalışmanın amacı; noktasal kaynaklı kirlilik şüphesi olan endüstriyel bir sahada arsenik (As), nikel (Ni) ve toplam krom (T.Cr) konsantrasyonlarının belirlenmesi, kirleticilerin alıcılara ulaşmasında etkili taşınım yollarının tespit edilmesi ve bu kirleticilere maruz kalacak potansiyel yetişkin popülasyonunda kanser dışı sağlık riskinin değerlendirilmesidir. Bu amaçla sahada 4 kontrol noktası ile 2 referans noktasında 2 m ve 4 m olmak üzere iki ayrı derinlikten toprak numuneleri, 3 adet gözlem kuyusu ve 1 adet referans kuyusundan 10 m derinlikten su örnekleri alınarak As, Ni, Toplam Cr konsantrasyonları belirlenmiştir. Kontrol noktalarında 2 m derinlikten alınan toprak örneklerinde en yüksek As, Ni, T.Cr konsantrasyonları sırası ile 19,8 mg/kg, 72,5 mg/kg, 69.2 mg/kg, 4 m derinlikten alınan toprak örneklerinde ise 18,7 mg/kg, 54,4 mg/kg, 57.2 mg/kg olarak belirlenmiştir. Kontrol noktalarında elde edilen ölçüm sonuçları (ÖD) kirlilikten etkilenmediği varsayılan referans noktalarından alınan örneklerden elde edilen sonuçlar (RD) ile oranlanmıştır. Tüm noktalar için ÖD/RD<25 olduğu, ancak 1-25 arasında olan değerler bulunduğu tespit edilmiştir. Tespit edilen kirletici konsantrasyonları ilgili kirleticiler için belirlenmiş olan sınır değerler ile karşılaştırılmıştır. Kirleticilerin sahadaki potansiyel alıcılara taşınmasında etkili olabilecek taşınım yolları belirlenmiş ve her bir taşınım yolu ile maruz kalınan kirletici miktarları hesaplanmıştır. Her üç kirletici için de kirleticilerin suyun içilmesi yoluyla alınmasının en fazla maruziyete neden olduğu görülmüştür. Maruz kalınan kirleticilerin alıcılarda yol açabileceği kanser dışı sağlık riski değerlendirmesi için HI değerleri hesaplanmıştır. Hesaplanan toplam HI değerlerinin 1,23E-02-1,57E-02 arasında ve toplam HI<1 olduğu belirlenmiştir. Toplam HI< 1 olması sahadaki kirleticilere maruz kalınmasından dolayı kanser dışı olumsuz sağlık etkilerinin beklenmediğini işaret etmektedir.

Soil pollution is one of the most important factors that threaten ecological balance, environment and human health. Pollution in soils is not only limited to terrestrial ecosystems, but can also be transported to different points by factors such as atmospheric transport, precipitation and flows, and can also pollute surface and groundwater resources. This situation also makes the prevention and correct management of soil pollution a necessity for the sustainable use of water resources. Soil quality is one of the most important factors in terms of plant development. Therefore, it is of great importance to improve soil quality and prevent pollution in order to ensure agricultural productivity, the quality of produced agricultural products and food safety. Various diffuse or point sources can cause soil pollution. Industrial activities and accidents occurring during these activities are one of the most important causes of soil pollution. Especially heavy metal pollution in industrial areas is a concern for the reasons such as their resistance to microbial or chemical degradation and their ability to be transported through the food chain. In order to protect human and environmental health, increase human welfare, and prevent economic losses that soil pollution may cause, soil pollution must first be prevented through preventive actions. In cases of pollution cannot be prevented, in order to control, manage, remediate the pollution correctly with scientifically based approaches, it is important to identify the polluting sources, determine the extent of the pollution, determine whether cleaning operations are needed, and in areas where pollution is suspected, to clarify the pollution situation of the site. Human health risk assessment offers significant advantages in all these processes. Human health risk assessment analysis are used in processes such as the assessment of soil quality, management of contaminated or suspected contaminated, determination of the extent of pollution, and determination of whether the site requires cleaning operations. Cleaning processes of contaminated soils may be multi-component, complex, quite time-consuming, labor-intensive and costly. Using human health risk assessment in the soil pollution management process can contribute to more effective use of time, labor and economic resources. Revealing the suitability of soils for their current or planned future use through human health risk assessment studies can support the sustainable use of resources. Particularly in areas used or planned to be used for agricultural production, it can help prevent the transport of pollutants through the food chain. xx In the health risk assessment, it is accepted that the target pollutants cause cancer and non- cancerogenic health risks in potential exposed receptors. Different formulas are used to calculate the health risks in these two groups. The non- cancerogenic health effects that pollutants may cause in exposed receptors are evaluated by calculating the Hazard Index (HI). In this evaluation, the chemical intake to be exposed over a certain period of time is divided by the reference chemical intake developed for a similar period of time. Receptors can be exposed to the pollutants mainly ingestion, inhalation, and dermal contact pathways. For the calculation of HI, the exposure amounts first be determined for the exposure pathways. Calculated values are compared with reference values. When calculating the non-cancerogenic health risks that may occur as a result of receptors being exposed to more than one chemical, the amounts to be exposed to each chemical through each exposure are calculated. Then, the total hazard index is calculated by adding up the values for each chemical. Total HI>1 indicates that adverse non- cancerogenic health effects due to exposure to examined pollutants can be expected. The aim of this study is to determine arsenic, nickel and total chromium concentrations in an industrial site with suspected point source pollution, to identify exposure pathways, and calculate the hazard index (HI) to estimate non-cancerogenic health risk in the exposed adult population. For this purpose soil samples collected from two different depths. Soil samples were taken from 2 m and 4 m depth at 4 control points (T1, T2, T3, T4) and 2 reference points (RT1, RT2). Water samples collected from 3 observation wells (S1, S2, S3) and 1 reference well (RS) at 10 m depth. Reference points are areas thought to be unaffected by pollution. Arsenic (As), nickel (Ni), total chromium (T.Cr) concentrations were determined in all samples. The highest As, Ni, total Cr concentrations in the soil samples taken from 2 m depth at control points were determined as 19,8 mg/kg, 72,5 mg/kg, 69.2 mg/kg, respectively and 18,7 mg/kg, 54,4 mg/kg, 57.2 mg/kg, respectively in the samples taken from 4 m depth. The measurement results obtained at the control points (ÖD) were compared with the results of the samples taken from the reference points (RD). ÖD/RD is used to determine the decision to be made regarding the field. If ÖD/RD≤1, related site does not require monitoring. If ÖD/RD >25, the site is considered contaminated and requires cleaning. If 1<ÖD/RD<25, second stage evaluation process including site and pollution characterization, generic risk assessment, and site-specific risk assessments is needed. In this study, it was determined that ÖD/RD<25 for all points, but there were values between 1-25. The detected pollutant concentrations were compared with the limit values determined for the relevant pollutants. Pathways that may be valid in transporting pollutants to potential receptors in the field were determined, and pollutant intake amounts for each pathways were calculated.In this study for all three pollutants, ingestion of pollutants through drinking water was found to cause the highest exposure. HI values were calculated to assess the non-cancer health risk that exposed pollutants may cause in receptors. It was determined that the calculated total HI values were between 1,23E-02-1,57E-02 and total HI<1. A total HI < 1 indicates that non-cancerogenic adverse health effects are not expected due to exposure to contaminants at the site.