STiR coffee and tea magazine

Volume 4, Number 3

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STiR tea & coffee industry international 53 Illustration of a tea plantation's underlying geochemistry. a) Plantation with pristine element cycles between rocks, soils and tea plants. b) Plantation with high levels of heavy metals within rocks and tea leaves. c) Plantation with depleted amounts of elements within rocks, soils and leaves. Google Earth illustration modified by Dr. Markus Heidak The results showed as many as 60 dif- ferent elements within tea leaves, includ- ing macro- and micro-nutrients such as iron (Fe), potassium (K), calcium (Ca), manganese (Mn), and, heavy metals such as lead (Pb), cadmium (Cd), and, mercury (Hg) as well as rare earth elements such as cerium (Ce), neodymium (Nd), and gado- linium (Gd). Sufficient amounts of these nutrients are crucial for strong and healthy plant growth, but the concentrations of heavy metals should be kept as low as possible due to their detrimental effects on hu- mans and the environment. The toxicological health effects on humans through the consumption of rare earth elements are not entirely known but major tea import countries have speci- fied thresholds for elements such as lead, cadmium and mercury which may not be exceeded. Sampling demonstrated there are no distinct differences between organic or non-organic plantations. The natural plantations contained sufficient and nor- mal amounts of elements. They can be described in the chart at right (Fig. 3a) as plantations with pristine element cycles between rock, soils, and tea bushes. Areas with enriched amounts of min- erals showed that rocks affected the tea plants by releasing different chemical elements into the soils which were then taken up into the leaves. There was a clear correlation between rocks containing heavy metals (e.g. Pb, Cd, Hg) in polluted areas where leaves showed an uptake of heavy metal (Fig. 3b). Levels of up to 6.75 ppm of lead (Pb) were found in the leaves when high levels (up to 255 ppm) were found in the anal- ysed rocks. This can have a significant impact on export. The European Community, for example, has specified a Pb limit value of 0.2 ppm for all crops including teas (green, black, white). Therefore, teas from those sampling areas are neither eligible for consumption nor for export to the EU. The same correlation was seen in rocks containing rare earth elements and leaves, and was recognizable for increased nutrients as well. In regions with strongly weathered rocks, where elements have already been released and washed out. Our sampling showed depleted element levels in the soils and in the leaves (Fig. 3c). In these areas adding fertilizer is unavoidable to keep yields constant. These results cannot be generalized for all tea plantations worldwide since there are also other parameters that steer the availability and the uptake of elements (e.g. climate, soil pH). Therefore, the geo- logical condition of each plantation has to be individually examined. The research study showed that in terms of quality control and food security, plantations should not only focus on the applied pesticides and fertilizers but also on geological and geochemical informa- tion. The study demonstrates that an analy- sis of rocks should taken into account in order to cultivate consistent tea quality, to prevent natural contamination (e.g. heavy metals), to reduce the amounts of applied fertilizers and to cultivate tea more cost efficient and sustainable. Dr. Markus Heidak is a geologist and geo- chemist with offices in Dubai, UAE.

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