**5.3 Pb content in rice**

The results of the Pb analysis of rice based on the age of the paddy fields can be seen in **Table 9**. The data show that the highest and lowest Pb content was found in 80- and 20-year-old rice fields, namely, 3.11 and 2.35 mg kg−1. The Pb content has exceeded the critical limit set by WHO, which is 2 mg kg−1. The Pb content in grain from paddy fields in Pati, Central Java, and Wonosobo highlands ranged from 0.23 to 1.23 mg kg−1 [54] and 0.28–1.32 mg kg−1 [60]. In the present study, the concentration of Pb was found to be higher in roots than in shoots and grains [19].

The relationship between the Pb content of rice with time follows an exponential pattern. The mathematical equations as a function of time are Ln (Y) = 2.06 + 0.005 x and R<sup>2</sup> = 0.928, where Y = Pb in rice (mg kg−1) and x = age of land cultivation (year).


### **Table 8.**

*Soil Cd content and percentage increase based on the age of use of paddy fields [5].*

*Heavy Metals in Indonesian Paddy Soils DOI: http://dx.doi.org/10.5772/intechopen.109027*


**Table 9.**

*Pb levels in rice based on the age of use of paddy fields [5].*

### **5.4 Cd content in rice**

Cadmium can affect enzyme activity in plants, leading to lower photosynthesis. Therefore, growth and development, including germination, root elongation, and leaf expansion, can be decreased [65–67]. The Cd analysis of rice based on the age of the paddy fields can be seen in **Table 10**. It shows that the highest and lowest Cd content is found in rice fields aged 80 and 20 years, namely, 0.29 and 0.15 mg kg−1. The content of Cd in 80-year-old rice fields has exceeded the critical limit set by WHO, which is 0.24 mg kg−1. In the shoots, the concentration was higher than that in roots and grains [19]. Jarvis et al. [68] reported that Cd was easily taken up by plants and transported to different parts, but it is nonessential and has no beneficial effects on plants.

The relationship between the Cd content of rice with time follows an exponential pattern. The mathematical equations as a function of time are Ln (Y) = 0.11 + 0.011 x and R<sup>2</sup> = 0.934, where Y = Cd in rice (mg kg−1) and x = age of land use cultivation (year).

The high content of Pb and Cd was caused by the content in the soil and the low fertility of paddy fields. Lowland rice plants can absorb dissolved Pb and Cd in the soil and accumulate them in large quantities from their tissues. The elements contained in plant tissue in the vegetative phase will be translocated to fruit during vegetative growth. Aprilia and Purwani [69] added that heavy metals Pb and Cd are more easily absorbed by plant roots in the form of Pb2+ and Cd2+ ions. Munaf [70] explained that the accumulation of Pb and Cd in plant tissues derived from the absorption of roots could be influenced by several factors. These include the solubility properties of compounds in soil solution, pH, organic C content, cation exchange capacity (CEC), and clay content.


### **Table 10.**

*Cd content in rice based on the age of use of paddy fields [5].*
