Cadmium, copper and lead levels in different cultivars of lettuce and soil from urban agriculture.

Urban agriculture plays an important role in sustainable food supply. However, because of the atmospheric pollution and soil contamination associated with urban areas, this activity may be of concern. In fact, contamination of soil with metals and the transference of contaminants to vegetables can represent health and safety risks associated with urban agriculture. The objective of this study was to evaluate the concentrations of selected trace metals (cadmium, copper and lead) in three lettuce cultivars produced in three different urban gardens in the metropolitan region of Belo Horizonte, Brazil and their respective soils. Samples of lettuce and soil were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) and graphite furnace atomic absorption spectrometry (AAS-GF), respectively, and their transfer coefficients were calculated. The methods were optimized and were fit for the purpose. Copper was the prevalent metal found in soils and lettuce, with an average of 27.9 ±â€¯13.9 and 0.608 ±â€¯0.157 mg kg-1 respectively, followed by lead (19.4 ±â€¯7.7 and 0.037 ±â€¯0.039 mg kg-1), and cadmium (0.16 ±â€¯0.03 and 0.009 ±â€¯0.005 mg kg-1). Cadmium presented the largest transfer coefficients, ranging from 0.34 to 1.84 with an average of 0.92 ±â€¯0.45, which may indicate a potential risk of accumulation in vegetables in the case of high soil contamination. A significant positive correlation was observed (p < 0.01) between cadmium in lettuce and in soil. Even though lead concentrations varied in the soils from the different urban areas, ranging from 11.88 to 30.01 mg kg-1, no significant difference (p < 0.05) was found among the lettuce, probably due to its low mobility (transfer coefficient = 0.02). The copper and cadmium levels found in lettuce indicate safe lettuce production in the three urban gardens.

Comparison between ordinary least squares regression and weighted least squares regression in the calibration of metals present in human milk determined by ICP-OES.

In this study we compared the use of ordinary least squares and weighted least squares in the calibration of the method for analyzing essential and toxic metals present in human milk by ICP-OES, in order to avoid systematic errors in the measurements used. Human milk samples were provided by maternity clinic Odete Valadares and digested by means of a high-performance microwave (MW) oven. Evaluation of plasma short and long-term stability was made using a solution of digested milk (1:50) with 2.0mgL(-1) Mg in HNO(3) 2% (v/v). The detection power resulted to be at or below the mugL(-1) level, whilst the precision expressed as relative standard deviation R.S.D. was almost always equal to or better than 3.3%. Certified reference material Infant Formula (NIST SRM 1846) was used to assess the accuracy of the proposed method, which proved to be accurate and precise. Recovery rates were in the range of 83-117%. Aqueous calibration was carried out for each element under study.