Các yếu tố dấu vết: kim loại nặng và vi chất dinh dưỡng GIỚI THIỆU nguyên tố vi lượng cần thiết trong một lượng nhỏ bằng cách thực vật hoặc động vật. Một số trong số này đã được xác định trong khi những người khác có thể vẫn còn chưa biết. Kim loại nặng là một nhóm các nguyên tố được tìm thấy trong bảng tuần hoàn với trọng lượng phân tử tương đối cao (mật độ 5,0 mg/m3) và, khi được đưa vào cơ thể, có thể tích lũy trong các bộ phận cơ thể cụ thể. Ashworth (1991). | CHAPTER 4 Trace Elements Heavy Metals and Micronutrients INTRODUCTION Trace elements are required in small amounts by plants or animals. Some of these have been identified while others may still be unknown. Heavy metals are a group of elements found in the periodic table with a relatively high molecular weight density mg m3 and when taken into the body can accumulate in specific body organs. Ashworth 1991 argues that the term heavy metals is a misnomer because at least two elements arsenic and selenium are not metals. The trace elements often referred to as heavy metals that have been regulated are arsenic As cadmium Cd copper Cu lead Pb mercury Hg molybdenum Mo nickel Ni selenium Se and zinc Zn . Chromium Cr was regulated in the first draft of the 503 regulations issued in 1993. In 1995 Cr was deleted. In this chapter the term trace elements will be used except where the literature specifically uses the term heavy metals. Micronutrients are those essential trace elements that are needed in relatively small quantities for growth of plants animals or humans. The eight plant micronutrients are boron B copper Cu iron Fe manganese Mn molybdenum Mo nickel Ni selenium Se and zinc Zn Mortvedt et al. 1991 . Elements such as nitrogen N phosphorus P potassium K calcium Ca and magnesium Mg are referred to as macronutrients because they are required in large amounts by plants. The elements cobalt Co iodine I Cu Fe Mn Mo Se and Zn are trace elements essential for animal nutrition Miller et al. 1991 . Several other elements arsenic boron bromine cadmium lithium nickel lead silicon tin and vanadium have more recently been proposed as essential to some animal species Van Campen 1991 . Van Campen identifies eight essential trace elements for human nutrition Cu Cr Fe I Mn Mo Se and Zn. The heavy metals indicated in the USEPA and state regulations are trace elements that can be harmful to the environment humans animals and plants. Consequently both regulations and literature .
