US EPA

814087 

Journal Article 

Lead accumulation in Westlake Longjing tea: non-edaphic genesis as revealed by regional scale estimate 

Jiachun Shi; Gang Wang; Yan He; Jianjun Wu; Jianming Xu 

2010 

Yes 

Journal of Soils and Sediments
ISSN: 1439-0108
EISSN: 1614-7480 

10 

5 

933-942 

10 

English 

10.1007/s11368-010-0189-3 

WOS:000278741300017 

Longjing (Dragon Well) tea from the West Lake region of Hangzhou, China, is one of the highest quality green teas prized for drinking and is often called the national drink of China. However, the ever-increasing accumulation of lead (Pb) in Westlake Longjing tea has been continually reported in the recent decades, while the exact Pb sources still remain unclear. Our purpose is to investigate the key factors that account for the concentration increase of Pb accumulated in Longjing tea based on a broad regional scale. Eighty-one young tea leaves and corresponding soil and air samples where the tea plants grow in and around, respectively, were collected from three typical Longjing tea gardens for illustrating the sources of Pb that accumulated in Longjing tea. The sampling lines were arranged with the proximity to the traffic area. Pb concentrations in the tea leaves and soil and air samples were determined, respectively. Wash procedures were also conducted to trace the removable possibility and rates of Pb in young tea leaves. Simple statistical analysis and spatial geostatistics were further applied for the investigation of the potential relationship of Pb levels among young tea leaves and the relevant soil and air samples. The regional differences and seasonal variation of Pb concentration were found for young tea leaves, with the order of Longwu > Meijiawu > Longjing and spring > summer ( p < 0.05), respectively. The significant positive correlation was found only for the Pb concentration between young tea leaves and air samples ( r = 0.34, p < 0.01). The results from wash experiment showed that a substantial portion of Pb in young tea leaves could be removed by wash, and the removable rates of Pb showed an obvious decrease with the increasing distance from the traffic area in Longwu and Meijiawu. A similar geographic distribution tendency of Pb between young tea leaves and air was also revealed by further geographic spatial analysis taking Longwu as a case. The significant correlations and similar distribution tendency of Pb concentration between young tea leaves and air suggested that atmospheric deposition could be an important, even predominant, source for Pb accumulated in Longjin tea. This non-edaphic contribution was further validated in wash experiment and testified to be distance dependent on the proximity to the main traffic area. This might be attributed to the large rough pubescent surface of tea leaves which are conducive to foliar deposition and/or absorption of Pb. The lack of correlations between young tea leaves Pb and soil Pb indicated that the contribution of soil Pb would be limited (especially near the traffic area where the influence of atmospheric Pb was dominant) and might be attributed to the low bioavailability of Pb in soils and finite uptake and transport of Pb from roots to shoots. Meanwhile, the higher Pb concentration in spring teas (compared with summer teas) might be due to the long growth period that allowed for a long time interception of Pb by young tea leaves through atmospheric deposition. The Pb that rooted in air was suggested as the main source accounting for the accumulation of Pb in Longjing Tea of the tested tea gardens. This non-edaphic contribution of atmospheric deposition was distance dependent on the proximity to the main traffic area. For alleviating the accumulation and elevation of Pb amount in Longjing Tea, efforts should be made especially during the period of spring tea growth. The additional wash procedure was also recommended before the tea leaf processing in factories. 

CHINA;GREEN tea;TEA -- China;LEAD -- Environmental aspects;GEOLOGY -- Statistical methods;AGRICULTURAL pollution 

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